This specification forms an integral part with:
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Inspection Procedure for Medium/High Voltage Switchboards.
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Standard Specification for DC Units. (Only if a DC unit is part of the scope of supply.)
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Standard Specification for Medium Voltage Draw Out Motor Control Center. (Only if MV motorstarters panels are included the scope of supply, when Vendors standard design for these starters is different from the one of the circuitbreaker panels.)
Note:
For the MV switching device the expression ‘’Circuitbreaker’’ is used in this specification.
If an other switching device for an MV circuit is to be applied, as required by the job documents, and or if specifically referred to in this specification, the requirements as specified for a circuitbreaker in the relevant paragraph are applicable for all types of switching devices, taking into account the physical properties (as per applicable standard) of these devices.
The switches devices are, isolators, fault make - loadbreak switches, contactors and the circuitbreaker itself.
An MV link is not considered to be a switching device.
Table of Contents
1. General
2. Design
3. Control and Protection
4. Measurement Transformers, Indicators and Measurement Devices
5. Accessories
6. Test and Inspection
7. Shipment
8. Start-up Spares
9. Maintenance
10. Installation at site
11. Drawings and Data
12. Spare Part Recommendation
13. Certificates
1.1 Description
This specification gives the minimum technical requirements for the design, manufacture, supply, provision of documents, testing and inspection, packing, transport and delivery to site of completely assembled, fully functional Medium Voltage (MV) power distribution and motor control starters. The scope of supply is including all auxiliary components as described in the purchase order documents. The MV materials are to be installed in oil refineries, chemical plants, and or other industrial installations.
Detailed and additional information for each individual case shall be given in the relevant requisition.
1.2 Standards
The switchboards shall be in accordance with:
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The national standards as mentioned in the requisition,
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The IEC publications, in particular the IEC Standard Publication 298,
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The requirements of the power supplier.
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The requirements as laid down in the Purchase Order and or as specified in the requisition.
The issue of the standards as described above shall be the one as valid on the date of Issue 1 of the requisition.
1.3 Service Conditions
The switchboards shall be suitable for the site conditions as mentioned in the requisition and they shall withstand a corrosive chemical and refinery atmosphere, at a maximum ambient temperature of 40°C and a minimum ambient temperature of -10°C, unless otherwise specified.
The switchboards shall be suitable for indoor use.
If the altitudes of installation exceeds 1000 m, this will be indicated in the requisition.
If the area where the material is to be installed is exposed to earthquakes, this will be highlighted in the requisition.
1.4 Conflicting Requirements
In case of a conflict between the conditions and the documents mentioned above or between these and this specification, the severest requirement shall always govern.
In case of a conflict between this specification and the requisition,the requirements in the requisition shall govern.
1.5 Responsibilities
Purchaser is not committed to check Vendor’s documents like quotations, order confirmations, drawings, etc. Purchaser will review these in principle only. It will remain the fill responsibility of the Vendor to make the switchboard in accordance with this specification in a fully functional and workmanlike manner.
A deviation from this specification is only acceptable in case Vendor has specified in his quotation under, the heading ‘’Deviations from Specification’’ the requirements he cannot meet and Company has accepted the deviation(s) in writing before ordering or in the order.
A failure to do so shall be interpreted by purchaser as confirmation that the Vendor/manufacturer fully complies with the Purchase Order, the documents and with this specification.
1.6 Safety
The entire switchboard shall be designed for maximum safety.
Even in the case that this should require more provisions than prescribed by (local) law, it is Vendor’s responsibility to include these provisions to meet the safety requirement.
The switchboard shall comply with IEC 298 appendix AA.
The internal arc-proof withstand capability shall be guaranteed and proven, not only with the switching element truck in the test position but also during the movement of the truck to and from the engaged and the test position. Therefore manual operation of the truck moving mechanism shall only be possible with the switchboard closed.
Alternatively electrical movement of the truck is permitted, provided mechanical emergency operation is always possible.
Operation of the circuit breaker mechanical tripping and or closing (if specified) facilities shall also be possible with the switchboard closed. The openings for all manual operation shall not disturb the internal arc-proof integrity.
The switchboard shall contain a minimum of flammable materials. The flammable materials shall be selected such as to prevent any toxic fumes, such as Chlorine gas, in case of a fire.
The design and manufacturing shall comply with the IEC publications 298 and 466, for metal clad switchboards and control gear with removable switching devices.
In addition the following requirements shall be applicable:
2.1 Enclosure
2.1.1 The entire switchboard enclosure shall be free standing, be floor mounted and be designed to ensure maximum safety during all operation conditions, inspection and or maintenance activities.
2.1.2 It shall be possible to weld or to bolt the structure of the switchboard to steel beams, which are cast-in or are part of the station floor.
2.1.3 The switchboard shall have extension possibilities at both sides. Extension shall be possible without the need to drill holes in the connecting surfaces or in the structural frame.
2.1.4 The enclosure covering plates shall be fixed such that an internal explosion shall never cause any movement of these plates. Removable cover plates therefore shall be fixed with bolted connections only. Any other construction using ‘’hook on’’ or fixing by means of swivels is not acceptable.
2.1.5 All compartment doors and their components shall be capable of withstanding an internal explosion such that they do not open or that parts are flying off.
2.1.6 Corrosion Protection
2.1.6.1 The (sheet) steel materials shall be adequately treated against corrosion. Poor ventilated parts of the enclosure shall be plated, alternatively an electro powder coating system for all surfaces is acceptable.
2.1.6.2 Strong preference exists for an entirely plated enclosure design, with only the visible parts painted in the required color, alternatively a fully electro powder coated design is acceptable.
2.1.6.3 The external surface treatment system, shall be Vendors standard system, provided that adequate degreasing and cleaning of the materials to be treated is performed, the thickness and the composition of the layers shall be as prescribed in Vendors instructions for this type of material.
If Vendors standard external color is not acceptable, the color shall be according the RAL number as specified in the requisition.
2.2 Switchboard Foundation and the Station Floor
2.2.1 If specified in the requisition, Vendor shall supply all the materials, such as but not limited to the supports, the beams or frames, anchor bolts and shims, necessary for installation for each of the MV assemblies and the auxiliary equipment.
The structural steel that has to be poured in the floor must be ready for shipment to site, not later than two months after the ordering of the switchboard.
The final date of supply to the site, shall be checked with Company’s Construction Superintendent or his representative well in advance of the proposed date.
The structural steel and or the other provisions that have to be made in the floor for the MV equipment, shall be suitable for future extension, with at least two additional cubicles on each side of the switchboard, unless the requisition states differently.
2.2.2 If specified in the requisition, Vendor shall install and align all the above materials, the installation shall be such that the foundations are ready to accept the equipment.
All changes in the floor layout, required after the approval of Vendor foundation and floor plans, or if repeated levelling of the foundation of the switchboards etc. is required, due to Vendors misalignment, are fully for the account and the responsibility of Vendor.
2.2.3 Company shall only provide the following:
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The holes and pockets in the concrete floor as indicated on Vendor’s drawings.
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The pouring of concrete around Vendor’s structural steel (if required) after the alignment of this steel by Vendor.
The finished floor surface of the station is to be considered adequate for circuit breaker transport truck or trolley movement.
The transport wheels on the trucks and or trolleys shall be sized such that the maximum rolling weight imposed on the wheels shall not make tracks in front of the panel caused by repeated movements.
The dimensions and the material of the wheels shall be such that moving the assembly over for instance over a computer floor or a tiled one, shall not cause rattling of the circuitbreaker.
2.3 Switchboard
Except for openings necessary for wiring, plug-in devices and ventilation, the switchboard shall be completely metal enclosed and compartmented, according IEC 298, paragraph 5.10.2.1, without using the floor as part of the enclosure unless otherwise specified.
2.3.1 Degree of Protection
The degree of protection of the enclosure shall be IP 41. LV equipment behind open doors or covers shall have a degree of protection not less than IP 20, this last requirement is also applicable for voltages below 25 V AC or 60 V DC.
2.3.2 Ventilation
Ventilation in and outlets shall be so arranged or shielded that a straight wire of any diameter cannot be brought into a position which would reduce the insulation level of the main circuits below the rated level, or that direct contact with live parts is possible.
The ventilation openings may be closed with a wire mesh or the like, provided that the material it is of a mechanical strength matching to the surrounding steel.
The ventilation shall not depend upon openings in the substation floor.
2.3.3 Compartmenting
2.3.3.1 The circuit breaker compartment, the busbar compartment, the LV relaying compartment and the cable termination compartment, etc., shall be separated from each other by grounded metal partitions.
2.3.3.2 It shall be possible without any danger or special precautions to connect all load side cabling, with the circuit breaker in the disconnected position or with the starter unit in isolated position and the MV and LV busbars energized.
2.3.3.3 The compartmenting shall be so designed, that the separation between the adjacent busbar, and or circuit breaker/ starter, and or the cable termination compartment is retained when the circuit breaker or starter is withdrawn.
2.3.3.4 A soft rubber gasket shall be applied between the vertical sections of a busbar compartment.
2.3.3.5 LV components and the DIN rail mounted LV terminals shall be located in a separate LV compartment and they shall be accessible, without opening any compartment containing MV parts.
The access to LV wiring spaces, such as relay compartments shall be by means of hinged doors from the front.
2.3.4 LV Cable Channeling
It is acceptable that LV cabling destined for a LV control compartment, located above the circuit breaker compartment of the same vertical section, may run through this circuit breaker compartment. The LV cable run through the MV part shall be fully encapsulated with an earthed steel cover.
Cable runs through a non-related or a busbar compartment are not permitted, unless the cables run in a solid steel, fully closed conduit system, from the position of entrance into the switchboard directly into the relevant LV compartment, without the need of opening of other compartments.
2.3.5 Doors
2.3.5.1 Each door shall be constructed such that it is rigid enough such that fluttering shall not occur, this means that suitable bracing or reinforcing shall be provided, in particular if a door is used as equipment carrier.
2.3.5.2 The hinges of a door shall be selected such that they are capable of withstanding the occurring forces, for instance the weight of the equipped door and the related torques, but also the forces as occurring during an internal explosion.
2.3.5.3 All doors shall be equipped with a lockable latch, high doors shall have a dual latching system (espagnolette).
2.3.5.4 Each door shall have an opening limiter, such that when opened, access into the panel is normal or the switching unit can be removed, but that it is prevented that the door is jammed against adjacent equipment.
If the limiter allows opening only just over a 90 degree angle, it shall be possible to disable the limiter to permit further opening for service.
2.3.5.5 All doors, shall be grounded by means of a flexible, stranded cooper wire, connected to the stationary part of the switchboard. Earthing connections through the hinges are not acceptable.
2.3.5.6 All doors shall be provided with a soft, neoprene or identical, non-sticking, rubber gasket to prevent the entrance of dust.
2.3.5.7 If a door is equipped with an inspection window, for instance to observe the earthing knives, the window shall have a mechanical strength fully comparable to that of the enclosure. It shall be made of a multi-layered safety glass. However if the certified window construction is of plastic, e.g. Lexan, precautions shall be taken to prevent the build up of electrostatic charges, for instance by shielding with suitable earthed wire mesh on the inside of the window.
2.3.5.8 The switchboard shall have facilities to store on the inside of the door of each compartment the related control schematics. If space is not available to house this facility, Vendor shall provide separately a wall mounted cabinet to store the folded documents.
2.3.6 Shutters
Shutters shall be provided, to separate the busbar and the incoming or outgoing stationary MV contracts from the circuitbreaker compartment, when the circuitbreaker is withdrawn from its engaged position.
Both shutters shall be closed completely before the test position of the circuitbreaker is reached.
2.3.6.1 The shutters shall operate only by the movement of the truck, independent of the gravity force, both when moving from the test position to the engaged position or in the reversed direction. Springs may be applied to keep the shutter in its closed position.
The shutters shall be made of metal, the only exception may be for a shutter of an outgoing circuit side, but only if the outgoing side can not be subject to feedback through the powercable.
The shutters shall be mounted inside the switching compartment of the stationary part, installation inside the busbar compartment is not permitted.
2.3.6.2 The metal shutters shall have a good earthing connection to the earthbar, using a flexible connection which can not hamper the operating mechanism simply by its location.
2.3.6.3 The shutters for the busbar side, the incoming or the outgoing circuits which can be subject to feedback, shall be colored red, the outgoing circuit shutters shall be colored yellow.
2.3.6.4 In addition, self-adhesive plastic stickers giving a clear distinction between the live and outgoing only contracts shall be provided.
2.3.6.5 The shutters mechanisms shall be padlockable, both the busbar shutter and the order shutter shall have separate locking facilities.
2.3.7 Fixing of Equipment on Side Walls
It is not be acceptable that adjacent panels have to be opened to fasten screws and/or nuts, in particular when the side walls of the panels are used to mount certain equipment (for example limit switches or shutter operating mechanisms).
Mounting of limit switches, or the like, directly against a sheet steel partition is not acceptable. These devices shall be mounted on structural beams and be adjustable by means of slots to ensure a proper alignment.
2.3.8 Withdrawable Units
The circuit breakers shall be fully withdrawable from the front of the switchboard.
Detailed requirements for the circuit breakers and for contractors, if applied in the same panel design as a circuit breaker, are given below.
2.3.9 Explosion Exhaust System
2.3.9.1 An explosion exhaust system shall be incorporated, such that the gases resulting from the internal arcing always escape in a direction, away from the operator standing in front of switchboard, as described in IEC 298 Appendix AA.
The explosion exhaust system shall be proven by type tests, these tests shall have been performed by a laboratory accepted for instance by the KEMA. Copies of the test certificates shall be included in the quotation.
2.3.9.2 Each MV compartment shall have its own a relief facility. The relief facility shall be separately for the busbar, the switch compartment and the cable compartment.
The cross section of the relief flaps shall be large enough to ensure that there is no possibility of further pressure built up inside a compartment.
The relief flaps shall be reclosing automatically after functioning. The flaps shall be properly earthed, by means of a flexible connection to the stationary part.
2.3.9.3 If circuit breakers have an explosion pressure relief, a channel shall be constructed such that the hot ionized gases from the circuit breaker are directly conducted to the outside of the switchboard, without reaching any other compartments of the switchboard.
2.3.10 Explosion Relief Ducting
2.3.10.1 If the danger exists that gases of an internal explosion, released in the station space can harm the operator, for instance because of its limited dimensions, additional ducting shall be quoted for separately, to conduct the gases to the outside of the station. Vendor shall state when this facility is required, free height of ceiling, free space over and to the rear of the switchboard.
If this ducting is included in the purchase order, the entire construction of the ducting, including the rupture plates fitted in the frames to be mounted into the station wall(s) are part of the scope of supply.
Included is also the mechanical protections to be installed on the outside of walls of the station to protect the rupture plates. Drawings of the frames to be fixed in the walls shall be available together with the first foundation layouts.
2.3.11 Identification Plates etc. on the Outside of the Switchboard
Durable and removable identification plates shall be mounted on front of each panel.
Identification plates shall be write with black engravings. Warnings shall be in white in red. All plates shall be mounted on the fixed part of the switchboard.
2.3.11.1 The inscriptions and language shall be stated by purchaser.
2.3.11.2 A simple mimic diagram in black shall be provided on the switchboards front on each panel.
2.3.11.3 All outside nameplates shall be fixed with bolts and nuts, the inside nameplates may be durably glued.
2.3.11.4 Each panel shall be provided with a panel reference number, and the equipment number, panels having rear access or require operation of for instance of the earthswitch at the rear, both the panel and equipment number shall be repeated at rear side to prevent mistakes.
2.3.11.5 Warning symbols shall be attached on covers giving access to MV compartments. These symbols shall comply with the practice of the country of destination of the material.
2.3.11.6 Instruction plates according to the country of destination requirements shall be provided in the relevant language.
2.4 Busbar System
2.4.1 The entire busbar system shall be made of rigid electrolytic copper busbars.
2.4.2 The busbar system includes the connections to and from the horizontal conductors and the incoming and the outgoing cables, both to or from the fixed contacts of the switching device.
2.4.3 Part of the busbar system are also the connections to the Potential Transformers and the Service Transformers.
2.4.4 Aluminium busbars are only acceptable provided:
They are Vendors standard, and that they are specially shaped, different from the flat normal commercial available copper. Vendors busbar design is to be part of the type tested switchboard configuration. When applying aluminium busbars special attention shall be paid to design of the connections. Aluminium busbars shall be silver-plated.
2.4.5 All busbars shall be rated and dynamically braced for the current values during normal and shortcircuit conditions as indicated in the job documents.
2.4.6 The rating and bracing of busbars or power wiring protected by MV fuses in starter unit may take into consideration the current rupturing capacity of the fuse, this is only applicable for the wiring in series with the MV fuses.
2.4.7 The requisition shall indicate if non-insulated or insulated busbars are required.
In any case Vendor shall quote alternatively, if Vendor’s standard is an insulated busbar system or as an option for the insulated version.
Insulated busbars shall be quoted for if they are Vendor’s standard design. If insulated busbars are an option of Vendor’s design, Vendor shall also quote for the insulated version.
Vendor shall in any case give details in his technical description, attached to the quotation, of the busbar system as quoted for and of the alternative if any.
2.4.8 The busbar insulation to be self-extinguishing and it shall not emit toxic fumes in case of a fire.
2.4.9 The busbar joints and connections shall be made by plated high tensile strength steel bolts, nuts and washers and be secured against loosening. All related fixing torques shall be indicated in the maintenance manual.
2.4.10 The busbars, the incoming and the outgoing high voltage circuits shall be marked with a painted color code, if stated in the requisition, or else be coded L1, L2, L3.
2.4.11 Insulators for busbar supports shall be made of high quality non-hygroscopic insulating material, suitable to withstand the occurring dynamic forces.
2.4.12 Specially designed cast insulation parts shall have good tracking properties, have a smooth finish and shall be free of cracks and internal stresses as caused by the casting process.
2.4.13 Earthbar
A one piece copper earth bar of at least 25 x 5 mm shall be extended throughout the total length of the switchboard for equipment earthing purposes, color coded as stated in the requisition. This copper bar shall have branches to all circuit breakers, starter units or and other main electrical equipment such as but not limited to: current and potential transformers and earthing switches and the switchboard structure and enclosure it self.
2.4.13.1 The earthbus shall not be insulated or be interrupted and it shall be mounted directly onto the steel frame of the switchboard in each cubicle.
2.4.13.2 Circuit Breaker Earthing
The trucks of the circuit breakers, shall have a direct copper connection with the earthbus, both in the test position and the fully engaged position, as well as during traveling to and from these positions.
2.4.13.3 MV Fused Starters
If a test link for the control wiring is to be used with a starter unit, it is acceptable that the unit is only connected directly to the earthbus in fully engaged position, whereas in the test position the copper earth connection is made via the test link itself. The construction of the test link to be such that the starter unit can not be inserted in the compartment when the test link is connected.
The fixed earthing part shall be silver-plated to prevent corrosion.
2.4.13.4 Earthing Switches
The earthing switch frame shall have a direct copper connection to the main earthbar.
2.4.14 Cable Earthing
2.4.14.1 Safety Earthing
Each cubicle with MV incoming or outgoing cables shall have an earthing switch. All circuit breaker panels shall be arranged so as to permit visible earthing of the circuit side of the equipment, in addition to the earthing switch.
2.4.14.2 Fixing facilities for the earthing gear shall be provided inside the compartment, a special earthing point shall be provided. Insertion of the switching device is to be impossible with the visual earthing still connected.
2.4.14.3 On piece of the visual earthing gear per busbar side shall be part of the scope of delivery.
2.4.14.4 Manual Earthing
2.4.14.1 If only manual earthing is required, the earthing point shall be located on the outside of the switchboard enclosure. This earthing point shall be directly copper connected to the earthbus.
2.4.14.2 The earthing gear shall be part of the scope of delivery, including all the required testing facilities and poles, the safety insulation plates and gloves. Any parts subject to alteration shall be suitably protected.
2.4.14.3 Adjacent to each the earth connection point a warning plate shall be provided, in the job language, referring to safe operation and discharging of the cable. The instruction manual shall clearly demonstrate how to test and to operate.
2.4.14.4 If manual earthing only is required, capacitive voltage dividers for each MV cable shall be provided.
2.4.14.5 Cable Armor and Lead Sheath Earthing
The switchboard shall be provided with one separated earthing screw for each cable, attention shall be paid to core balance protection and the system of cable earthing.
2.4.14.6 Busduct Earthing
The structure of the busduct shall be connected through a flexible braiding, having the same cross section as the main earthbar, to a copper branch of the main earthbar, having the same dimension as the main earthbar.
The connection point shall be at the connecting flange. The flexible braiding is part of the switchboard supply.
2.4.14.7 External Connections to the Earthbus
At both ends of the earthbar, on the outside the enclosure, a connection for a cable lug with a hole suitable for M 10 shall be provided.
2.4.15 Auxiliary Busbars
Small, rigid copper busbars shall be used to distribute the AC, DC, (and the undervoltage) control supply to the panels. These busbars shall be fully insulated and they shall run protected inside a separate metal enclosure.
2.14.15.1 In some cases the auxiliary power supply is done with wiring from compartment to compartment being Vendors standard design.
Vendor shall ensure that the connections are reliable and are not depending on a lot of individual connectors.
If panel to panel connections have to be made, this shall be done with multiple pin plugs and sockets having a locking facility in the engaged position.
Vendor shall describe, in his technical description attached to the quotation, his auxiliary power distribution system.
A wired kind of auxiliary distribution system is always subject to approval before ordering.
2.5 External Cable Connections
2.5.1 All cables shall enter the switchboard from below, unless stated differently in the requisition. A steel cable support system shall be provided to fix and support the weight of all incoming and outgoing cables within and on the outside of the switchboard.
2.5.2 Provisions shall be made to connect each core of a power, control, or signal cable to a separate screwed or bolted cable terminal installed in the switchboard. The copper connections between a cable termination box and the connections points of the switchboard from part of scope of supply.
2.5.3 LV terminals shall not be located in MV compartments.
2.5.4 It shall be possible to connect or disconnect secondary wiring or cables, while the switchboard is in service, without any danger arising from MV parts during the entire operation.
2.5.5 All the required cable glands, cable terminations and or MV connectors, including all accessories, such as but not limited to compression type cable lugs, necessary to install or terminate and or connect all cables entering into the switchboard are part of Vendor’s scope of supply.
2.5.5.1 Cable Lugs
All cable lugs shall be of the full tube, compression type, shall be make Burndy or equal. Cable lugs shall be provided for conductors over 2,5 mm2, unless the terminal is designed to be suitable to accommodate the conductor directly.
The conductors of MV cables shall be provided with cable lugs in any case.
If not indicated differently in the requisition, the materials as described below shall be supplied as specified.
2.5.5.2 Cable Glands
The brass cable glands shall clamp the armor of the cable, they shall be make Hawke type 153 or a fully equal design. Attention shall be paid to the insulation and earthing of the gland and the gland plate, if core balance earthfault protection is required. If single core cable or steel tape armor is applied, the cable gland shall be: Hawke type 121 or fully equal design. Compression rings in cable glands for single core cable shall be made of non-magnetic material
2.5.5.3 Cable Terminations
A complete kit shall be provided in a sealed box, one for each termination to be made. The kit shall include all the termination and filling materials, such as the cable oil or the compound. A clear multi-lingual and pictorial installation instruction shall be included in the package.
2.5.5.3.1 All dry type MV cable terminations shall be make Raychem or fully equal, they shall be suitable for the cable type and size as specified.
2.5.5.3.2 If an oil or compound filled cable termination is specified, depending on the type of construction of the termination, the following is applicable:
Indoor wiping types:
The wiping types shall have adequate, provision to clamp both the cable and the sealing pot to prevent stresses on the wiping connection. Copper foil shall be provided to enable the Jubilea clamps to have the same potential as the cable lug.
Outdoor types:
The cable termination box shall be of the split type. An earthing terminal inside the cable termination shall be provided to earth the lead sheath or the earthing wire(s) of the cable.
2.5.5.3.3 The earth connection required for a cable termination, either of the ‘’dry’’ or the ‘’filled’’ type, shall directly be connected the earth bus. For the box type through its external earth stud.
2.5.5.3.4 All cable termination shall be installed above the station floor.
2.5.5.3.5 Adequate supporting shall be provided to carry the extra weight of the cable termination by the switchboard.
2.5.5.3.6 Vendor shall verify that the cable termination, made according to the installation instructions of its manufacturer, ample fits into the available cable termination space of the switchboard.
2.5.6 MV Connectors
If MV connectors are specified or required by Vendors standard design, they shall be make Elastimold.
The connectors shall be of the elbow type, and be provided with capacitive cable voltage indicators.
If specified, through going short circuit indicators shall be provided, being clipped on the finished cable conductor.
2.5.7 If single core cables are to be installed, a non-magnetic gland plate shall be provided, attention shall be paid to prevent a current flow in the supporting steel frame of and in the gland plate itself.
2.5.8 Insulation in Relation with Core Balance EF Protection
Attention shall be paid to the insulation and earthing of the cable gland, the gland plate, or the outdoor cable termination, if a core balance earthfault protection is required. They shall be electrically insulated from the switchboard structure, but be earthed through a separate conductor passing through the core balance transformer.
2.5.8.1 Part of the scope of supply of the switchboard are the green/yellow insulated flexible copper conductors required to earth the cable and all its entry parts.
This flexible conductor shall have at least a cross-section of 70 mm2.
2.6 Draw-out Circuit Breakers
2.6.1 The following of types of circuitbreakers may be applied:
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SF6,
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Vacuum,
- Others such as the ‘’Minimum oil’’ or the ‘’Air(blast)’’ design can only be quoted for if specifically required by the requisition.
If the requisition does not specify a specific design, vendor may quote for either SF6 or Vacuum circuitbreakers, in this sequence or if an alternative is not present, Vendors standard design shall be quoted for.
2.6.1.1 The application of surge suppressors may be considered for SF6 and or Vacuum circuit breakers, if small current applications could introduce virtual chopping.
2.6.2 SF6,
2.6.2.1 If SF6 as the arc quenching medium is selected, Vendor shall guarantee, in his quotation, that processing/recycling of the contaminated SF6 gas is possible through his organization. The circuit breaker shall be serviceable, by Vendors organization at site.
2.6.2.2 Each circuit breaker enclosure(s) containing SF6 gas shall be provided with a lockable check valve for filling and purging purposes.
2.6.2.3 Each enclosure containing SF6 shall be provided with:
2.6.2.3.1 A pressure indicator having a green and red indicating field.
2.6.2.3.2 A minimum pressure switch, this switch shall be wired into the circuit breakers control system, it shall prevent closing and tripping under adverse conditions.
This minimum pressure switch shall operate directly a lockout relay with a flag indicator, preventing operation of the circuit breaker and activating the external alarm indication.
2.6.3 Vacuum
2.6.3.1 Vacuum circuit breakers shall not be applied for applications where short cable lengths are involved.
The manufacturer of the Vacuum circuitbreaker shall state the minimum cable length required to provide sufficient damping to prevent over-stressing of the connected equipment windings.
2.6.3.2 If vacuum circuit breakers are specified in the requisition, switchboard Vendor shall in any case state the minimum cable length required to prevent damage to the connected equipment and or if surge suppressors shall be supplied.
2.6.4 General
2.6.4.1 All circuit breakers shall be electrically operated with stored energy operating mechanisms.
2.6.4.2 The springs of the circuit breaker mechanism have to be automatically unloaded before the circuit breaker is moved from the test to fully drawn-out position.
2.6.4.3 A mechanical interlock shall be provided to prevent moving of the circuit breaker when the springs are still loaded.
2.6.4.4 All circuit breakers and/or load switches shall be of the 3 pole type, all poles shall operate simultaneously.
2.6.4.5 All circuit breakers shall be fully in accordance with the IEC recommendations, in particular with IEC 56, 267, 427.
2.6.4.6 The short circuit capacity and momentary peak value of the short circuit current shall be given on the single line diagram.
2.6.4.7 Under the specified conditions, starting from the closed position, the circuit breaker shall be capable to perform a switching cycle ‘’Open, 2 seconds delay, Close, Open’’ without any damage and without any time delay necessary to rewind the springs of the operating mechanism.
2.6.4.8 The circuit breaker shall have anti-pump control, preventing undesired operation, when an trip command is present and (repeated) close commands are given. The anti-pump feature shall be maintained despite the loss of the busbar voltage during a fault. The circuit breaker shall not close even when operated mechanically.
The control schematic shall prevent closing in any case if a trip command is present.
2.6.4.9 The circuit breaker shall be ‘’Free to trip’’, whether manually or electrically, even when the operating pushbutton or handle or control switch is kept in the ‘’Close’’ position.
2.6.4.10 Outgoing feeder circuit breakers shall trip preferably instantaneously and without any time delay when closed on a short circuit.
If the circuit breaker cannot be equipped with a series trip coil, the trip activating device may be the I>> section of the protection relay, provided this relay operates without time delay.
2.6.4.11 All circuit breakers shall be of the fully draw-out design.
2.6.4.12 All electrical control connections between the stationary and with drawable part have to be made by means of contacts blocks or a socket and plug, such that the circuit breaker can be withdrawn without disconnecting any wiring or using tools. If a flexible conduit is containing the control wiring between the circuitbreaker and the connection plug is applied, this flexible conduit shall be protected by the circuitbreaker body itself against flash overs.
A mechanical interlock with the circuit breaker assembly and the control cable plug shall be provided such that the plug only can be removed in the test position of the circuit breaker and moving of the circuit breaker to the engaged position is impossible without the plug locked in.
2.6.4.13 The main power contacts shall be self-aligning, ensuring a sure and good contact and optimum contact pressure.
2.6.4.14 The main contacts of the fixed part shall all be aligned against the same dummy switching device. The main contacts of all circuit breakers shall be aligned to the mating part of the dummy switching device.
2.6.4.15 The main power contact arms of the circuitbreaker shall be fully insulated.
2.6.4.16 The surface of the main power contact material, both on the fixed and the movable part shall be silver-plated.
2.6.4.17 A circuit breaker or switching device test position is required in which only the control wiring to the circuit breaker remains connected.
Mechanical interlocking shall be provided on all circuit breakers (or switching device) to prevent:
-
The movement of the circuit breaker to or from the engaged position when it is closed.
-
The closing of the circuit breaker, neither electrically or mechanically, between the test position and the fully engaged position.
- Reference is made to the functioning of the shutters and of the earthing switches, if any.
2.6.4.18 The circuit breaker assembly or truck is to be supported and to be guided by the switchboard structure until the fully drawn out position, ready for lifting or moving the assembly or truck from the stationary part.
If a loadbreak switch is used in combination with fuses, the fuses shall be mounted on the withdrawable part.
2.6.4.19 The circuit breaker guiding mechanism shall be provided with a padlock facility, to prevent that the circuit breaker is to be inserted accidentally.
2.6.4.20 The circuit breaker mechanisms shall allow for emergency manual mechanical closing and tripping. The closing mechanism shall include the disconnection or the blocking of the electrical closing operations.
In case that a circuit breaker has to be used for a motor starter, the mechanical closing possibility shall not be blocked such that operation is impossible.
However, in order to maintain full interchangeability with the circuit breakers for the incomers, sectionalizer or (transformer) feeders to this blocking shall be panel related and not be performed in the circuit breaker mechanism itself. Locking shall be done for instance by installing a screwed cap over the closing button, adequately sealed to prevent misuse.
2.6.4.21 The circuit breaker shall operate with AC closing supply and a DC battery backed up tripping power supply source.
In case the requisition does not specify differently the closing voltage shall be 220 V AC, derived from a downstream LV power source, the tripping voltage shall be 110 V DC.
2.6.4.22 Switching operation counters shall be provided on each circuit breaker.
2.6.4.23 Circuit breakers shall have a mechanical ‘’Open’’ and ‘’Closed’’ position indication, in the color coding and indications as per IEC shall be provided.
In addition mechanical indication of the loaded or unloaded position indication of the energy storing springs shall be provided.
These indications shall be visible when standing in front of the circuit breaker.
2.6.4.24 All circuit breakers of the same rating shall be fully interchangeable, also with regard to the auxiliary contacts, the sequence of terminal connects, the number of auxiliary contacts and the control circuit diagram and components.
2.6.4.25 All circuit breakers shall have at least two single pole change over contacts, direct circuit breaker shaft driven spare contacts for future interlocking.
These contacts shall be wired on to terminals in the LV compartment of the relevant circuitbreaker.
2.6.4.26 All circuit breakers shall be grounded by means of a copper brush or sliding contact, which shall be mounted on the switchboard structure and connected to the earth bar.
The fixed part of the sliding contact shall be silver plated to prevent corrosion.
Other earthing methods are only acceptable, if Vendor can prove this method, before the order, with a test certificate, that his construction successfully conducted the full through going short-circuit current against earth without substantial damage to the equipment.
2.6.4.27 The control circuitry of a circuit breaker shall be designed such that a momentary operation of a remote switch shall directly close or trip the circuit breaker.
However if a permanent contact is applied, for closing or tripping this shall not damage or block the closing or tripping system.
2.6.4.28 The draw-out assembly shall permit handling by one man without excessive effort.
Heavy circuit breakers shall not be directly manually moved, but they shall be driven via a hand operated gear.
Motor driven truck operation shall only be provided if specified in the requisition.
A guiding system shall be provided in order to prevent misalignment.
2.6.4.29 For all limit switches which are actuated by the switching device/or circuit circuit breaker assembly, care shall be taken that the switching action is independent of the circuit breaker assembly movement, but only is related to its position.
2.6.4.30 Position Switches ‘’Circuit Breaker Removed’’
Auxiliary contacts of circuit breakers, serving functions necessary to be maintained when the circuit breaker is removed from the stationary part, shall be provided. These position limit switches shall take over the auxiliary contact function of the circuit breaker in the disconnected position.
Examples of such circuits are: Spaceheater, pressure alarm, if applicable and the ‘’Off’’ position. A contact for remote indication circuit breaker ‘’Out of service’’ shall be provided.
2.6.5 Circuit Breaker Transport Devices
2.6.5.1 Circuit Breaker Truck
For circuit breakers having their wheels at floor level, the finished surface of the station floor is to be considered adequate for the truck movement. However facilities shall be provided by Vendor ensuring that the circuit breaker truck can slide in and out of the panel, without only having to rely on the quality of the finished floor surface (sliding plate).
2.6.5.2 Circuit Breaker Cassette
For circuit breakers having their wheels at an elevated level, transport trolleys shall be provided. This trolley shall have facilities to level the circuit breaker wheels at the different panel positions.
The trolley shall have a means to align it in a fixed position, against the structure of the switchboard to ensure proper matching of the switching element cassette and the guiding mechanism of the stationary part.
The trolley shall have a feature to block the wheels once in the correct position in front of the panel.
2.6.5.3 A manual operated hoist shall be provided to lift a circuit breaker off a trolley. The hoist shall be fixed to one of the roof beams of the station by purchaser.
2.7 MV Contactors
Note:
This section is only applicable for contactors fitted on the same size of truck or cassette as the circuit breaker.
For different designed equipment, the Specification for Medium Voltage Draw-Out Motor Control Center is applicable additionally.
This last specification is valid for starters for motors and transformers or capacitors, if specified, controlled by a fused contactor.
The below given description for MV contactors does not relief any of the other requirement of this specification.
2.7.1 Vacuum Type
2.7.1.1 The contactors shall have the minimum duty class as specified in the requisition.
2.7.1.2 The contactors must additionally be capable of interrupting at least the motor starting current (minimum 6 x In) at power factor of 0.15.
In case EEx-e motors are to be powered, the contactor shall be able to switch the occurring starting current at the actual powerfactor. The contactor shall also be capable of withstanding the switching on a shortcircuit and withstanding a through-going fault until the short circuit current is interrupted by the MV fuse(s).
2.7.1.3 The contactor shall be so designed that the effect of current chopping is eliminated, nor shall there be a restrike when the contactor is being opened.
2.7.1.4 Switching performance shall be such that contact bouncing will not occur.
2.7.1.5 Direct-driven auxiliary contacts shall be provided. All contacts shall be self-cleaning even when applied in very low current circuits such as electronics, therefore special attention to be paid to the contact material to be applied.
2.7.1.6 In case of vacuum loss in one of the switching tubes, its shall be impossible to close the contactor.
2.7.1.7 If the switching action of the contactor can not be completed when activated by a pulse contact of 200 ms, Vendor shall provide a time delayed action to ensure that the started action is completed.
2.7.1.8 Each contactor shall have a mechanical position indication.
2.7.1.9 Each contactor shall have a mechanical switching operations counter.
2.7.1.10 Latch contactors shall have a mechanical trip button, this button shall be shielded against accidental tripping.
2.7.1.11 If the contactors are magnetically held and are DC operated, they shall have an economy resistor.
2.7.1.12 If the contactor closing coil requires an auxiliary contact duplication, Vendor shall install his standard type of relay.
2.7.2 SF6 Contactors
2.7.2.1 All the requirements as stated above except 2.7.1.6. are applicable for this type of design.
2.7.2.2 Additional requirements for SF6 filled contactors:
2.7.2.2.1 The SF6 contents shall be limited as far as possible.
2.7.2.2.2 The contactor shall be provided with a pressure indicator.
2.7.2.2.3 A low pressure switch shall block any switching actions.
2.7.2.2.4 Filling and bleeding facilities for the SF6 gas shall be provided, these facilities shall each be provided with a sealing cap. If these facilities are not available, Vendor shall state in writing how and where the contactors can be serviced.
In any case Vendors service organization shall be capable of overhauling the contactor unit without any danger for the environment and recycling of the SF6 gas.
2.8 Fuses
2.8.1 All MV fuses shall be of the high rupturing capacity type adequately rated for the occurring short circuit level.
2.8.2 The MV fuses installed in the main power line shall be provided with a device to trip the contactor if a fuse has operated. The striker pin of the fuse shall be capable of activating the operating switching mechanism.
2.8.3 MV Fuse Sizing
Fuses for Motors:
The sizing shall be done such that the number of starts per hour as specified, using the starting current, shall be taken into account. For the current value the maximum value of the start current shall be used: The design value as specified with on top the tolerance.
Fuses for Transformers:
The inrush current of the transformer and its rated current shall be taken into account.
If motor starters and transformer feeders are installed in the same panel, the same fuse design shall be applied.
Fuses for Capacitors:
If a capacitor is switched, either as a single unit or in parallel with an inductance, attention shall be paid to the occurring inrush surges, in particular when other capacitors are connected to the same busbar.
The (high frequency) inrush current shall be calculated individually taking into account the impedances in the switched circuit.
2.8.4 Control Circuit Protection
LV auxiliary power protection shall be done with Miniature Circuit Breakers, (MCB) or if fuses are specified they shall be of the HOLEC ISODIN type with the matching HOLEC fuse holder.
Vendor shall check the selectivity and the occurring shortcircuit currents in the control circuits to ensure proper tripping under all circumstances.
2.8.5 MV/LV Transformer Secondary Protection
2.8.5.1 The secondary side of a PT shall be protected by MCB’s having a characteristic providing the optimum protection against secondary overloads and shortcircuits, taking into account the very limited shortcircuit level behind the voltage transformer. (ABB STOTZ Z range or fully identical.)
2.8.5.2 The secondary side of a Service Transformer shall also be protected by MCB’s having the Z characteristic providing the optimum protection against secondary overloads and shortcircuits, taking into account the limited shortcircuit level behind the transformer and the normal occurring peak loads on the transformer.
2.9 MV Link
The application of an MV link, intended for use as a busbar manual separation possibility, is only acceptable if specified in the job documents. The link shall be mounted on the same removable assembly as a circuitbreaker. Special, all different mechanical locks (Kirk key type) on each switching device connected to the relevant busbarsides shall be provided. The key shall only be removable when the switching device is in the open position, closing of the switching device shall not be possible without the relevant key.
All keys shall be required to remove the MV link from its engaged position after which the keys can be removed blocking the insertion of the link.
2.10 Earthing Switches
Earthing switches shall be provided according to the One Line Diagram.
2.10.1 An earthing switch shall be capable of making the full shortcircuit current, the operating mechanism shall be charged spring operated in both directions.
2.10.2 The knives of the earthing switch shall be directly connected through a copper connection with main earthing bar, the flexible braided conductor shall jump the shaft mechanism.
2.10.3 The earthing switch shall be interlocked mechanically with its upstream circuit breaker such that mutual inadvertent closing is impossible.
2.10.4 If a feedback can be expected, interlocking coils (energized to close the earthing switch) shall be provided.
2.10.5 For remote interlocking, direct shaft driven auxiliary contacts shall be provided to prevent operation of the downstream circuit breaker.
2.10.6 For busbar earthing switches a special designed electrical interlock system shall be prepared excluding any maloperation.
2.10.7 The operating mechanism of the earthing switch shall be accessible from the front only, with all doors or covers closed. Preferably access to operating shafts shall be prevented when the circuit breaker is closed, this to avoid damage to the interlocking mechanism.
2.10.8 The earthing switch operating mechanism shall be padlockable both in the ‘’Open’’ and the ‘’Closed’’ position.
2.10.9 The knives of each earthing switch shall be visible from the front, without opening doors or covers, if the view is limited an additional direct shaft driven position indicator shall be provided.
2.11 Distances between Live Parts & Earth and Related Test Voltages
Depending on the design of the switchboard the following is applicable for the different types of design:
2.11.1 Air Insulated Types:
2.11.1.1 The straight distance between live parts mutually and live parts and parts having earth potential shall be as given in the requisition.
2.11.1.2 The application of insulation material to achieve the specified air distance is not acceptable.
2.11.1.3 The value of the nominal power frequency withstand voltage test shall be as per IEC 71-1 or as stated in the requisition.
The nominal lightning impulse voltage shall be as per IEC 71-1 List 2.
2.11.2 Insulated Types
2.11.2.1 The above described requirements as under the air insulated type are applicable, or:
2.11.2.2 The switchboard has successfully passed the nominal lightning impulse voltage testing as per IEC 71-1 with the levels as described in List 2 and the nominal power frequency withstand voltage test as per IEC 71-1 or as stated in the requisition.
For tailor made designs the straight air distances as specified remain fully applicable.
2.11.3 SF6 Insulated Types:
2.11.3.1 The switchboard has successfully passed the nominal lightning impulse voltage testing as per IEC 71-1 with the levels as described in List 2 and the nominal power frequency withstand voltage test as per IEC 71-1.
2.11.3.2 The SF6 pressure indication and minimum SF6 pressure switches shall be provided identical as described above for SF6 circuit breakers.
The control of the switching devices shall be as per control schematics attached to the requisition. This setup shall ensure proper protection tripping and safe interlocking of the operation of the switching device. Adaptations to the given schematics may be required due to particular material requirements, such as the time required for activating of the closing and or tripping mechanisms.
3.1 Protection Relays
The protection relays shall be of the make, range and type as specified in the job documents. It is quite well possible that relays types, produced by other suppliers than the switchboard Vendor’s ones, are specified this might have been done for several reasons:
Interchangeability or standardization,
Physical properties of the relay type: wide selection of the curves and settings of subject relays.
In most cases, the selection of the time delay and the curve characteristics is to be done far later than the ordering time of the switchboard.
Therefore the selection of a multi-functional relay, preventing extra costs, delivery time problems etc. is made.
3.1.1 The types and makes as specified shall be quoted for in any case.
3.1.2 Vendor may quote for his own relays alternatively, provided that the relays are 100% identical to the ones as specified.
3.1.3 A deviation from the specified type, is only acceptable when this is agreed upon in writing, by Company before the order.
3.1.4 The protection relays shall be located in a modularized rack unit.
3.1.5 The protection relays shall have been tested to withstand electromagnetical phenomena occurring.
Special attention shall be paid to harmonic currents in those MV installations where variable speed drives, filters and or capacitorbanks are involved.
3.1.6 To increase the stability of the auxiliary power supply for the protection relaying, a DC/DC convertor shall be provided, at least one unit per switching device to be protected.
3.1.7 As a general rule, protection relays, complete with its fault indicators shall be mounted on the front of the cubicles.
3.1.8 All relays shall have adjustable actual value and time setting possibilities, the settings shall be adjusted during the final inspection in Vendors shop.
3.1.9 It is not allowed to have to change the setting of a relay by means of rearranging the secondary connections of a current or voltage transformer or by changing of the internal or external relay connections.
3.1.10 Switch operated relay setting shall be provided.
If the relay setting has to be done with a potentiometer, this potentiometer shall have locking facilities in the required position.
Locking can be done with a screw or with proper varnish.
3.1.11 Internal relay tap setting selection shall be done by means of single pin plugs.
3.1.12 The relay casing shall be lockable after setting with a wire and a lead seal, resetting of the relays shall be possible without opening of the relay casing.
3.1.13 If withdrawable type relays are used, provisions shall be made for automatically short-circuiting of the CT-circuits. Removing of a relay from its casing may never cause a trip.
3.1.14 Test Socket and Plug
If specified, a relay test socket and plug shall be provided per 3 phase power circuit to test the protection relaying during operation. The test plug shall connect the relays to the current or voltage injection device and the timing device. During the engaging of the plug in the socket, the outgoing relay trip circuit(s) shall be interrupted before any other connection is made or broken.
3.1.15 For electric motors special electronic protection relays can be used, these relays may require to operate in combination with a speed switch mounted on the motor.
3.1.16 100% Motor Load Indication
Only if specified in the requisition, or indicated in the schematics for motor feeders the current transformers shall be selected such, that the ‘’100% running load’’ indication of the relay equals the full load current of motor. In order to achieve this adaptation CT’s might be required.
3.1.17 Core balance earthfault protection shall be provided as indicated. The earthfault detection circuit shall be time delayed, or the measuring circuit may be provided with a suitable swamping resistor to prevent nuisance trips caused by energizing of the circuit.
3.1.18 If flag indication is required for a function where this facility is not incorporated in the activating device itself, a separate, manual reset, relay shall be provided. The flag indicator to be used shall be make Mauell, it shall be of a type, where the activating function can be changed from an energizing into a de-energizing system, whilst during the alarm and the acknowledge stage the outgoing alarm contact shall remain in the same position (for instance type MR 11: control schematic 10-2a).
The relay shall be engraved indicating the device initiating the alarm.
3.1.19 A relaying control panel, away from the MV switchboard, shall be provided only, if the requisition specifically calls for this type of design. The panel shall be suitable for wall mounting, having bottom cable access, be amply sized and be arranged such, that all relaying for a switching device is grouped together, to maintain the overview of the control systems, therefore a clear physical separation shall be provided. All requirements as described in this specification are also applicable for this panel, in particular the IP 20 requirement.
If a design with a separate control panel complete with control switches, relaying and protection devices, etc., is required, all cabling between the switchboard and the control panel, inclusive the supply of the necessary ready to connect cabling is part of Vendor’s supply.
3.2 Control Switches
A three position stay put type selector switch shall be provided for the master control of a circuit breaker or the switching device. This switch shall located on the front door of the LV control cubicle.
The three positions shall be marked:
-
For electric motors
For all other panels
Pos.1. Off
Pos.1. Off
Pos.2. Trip
Pos.2. Trip
Pos.3. Remote Control
Pos.3. Ready for closing
3.3 Pilot Lights
The switch position of each circuit breaker, load switch or contactor shall be indicated by a long life multiple LED lamp.
Therefore the application of filament or neon lamps as pilot light is not permitted.
Red: Indicating that the circuit breaker or contactor is ‘’Closed’’; it shall also indicate that the trip circuit is healthy.
Green: Indicating the circuit breaker is: ‘’Tripped’’.
3.3.1 LED lamps connected to an AC circuit shall not use a stepdown transformer, but apply a suitable capacitor to act as a voltage divider in series with the rectifier, the capacitor shall be capable of withstand switching transient voltages as occurring.
3.3.2 For DC application an internal resistor in the LED lamp fitting or inside the LED lamp shall be used.
3.3.3 The LED’s shall have a bajonet type socket.
3.3.4 Healthy Trip Circuit Indication
The Red ‘’ON’’ LED shall be wired in series with a blocking diode and an suitable sized, adjustable, wire resistor.
The resistor shall be adjustment such that in case of a short circuit in the LED, this shall not cause tripping of the circuit breaker or damaging of the blocking diode.
3.3.5 Replacement of LED’s shall be done by removing the front cover of the LED indicator. Removal on the inside of the switchboard or panel board is not permitted. A lamp retraction device shall be provided if the LED cannot be easily removed by hand.
3.3.6 Neon indicators may only be applied for capacitive voltage indication.
3.4 Wiring and Terminals
3.4.1 All LV wiring shall be of the stranded copper type, having a minimum cross section of at least 1,5 mm2.
3.4.2 The wiring for CT circuits shall be:
4 mm2 for 5A secondary circuits,
2,5 mm2 for 1A secondary circuits.
3.4.3 The color of all wiring shall be black, except for the earthing wiring this shall be green/yellow.
Trip circuit wiring may be colored differently for instance red, but only if specified in the requisition.
3.4.4 Each wire, except the green yellow ones, shall be numbered at both ends with wire markers.
The only alternative may be if Vendor’s standard wiring system uses a durable embossed or a thermal ‘’printed’’ wire coding system.
3.4.5 All wire ends shall be finished with a compression type cable lugs or compression type wire pins.
3.4.6 Each wire shall be terminated in a separate terminal.
It is not allowed to clamp more than one wire pin or cable lug under one screw or nut. If a circuit has to continue, this shall be done with two wires in the same wire pin or lug preventing interruptions of the circuit during fault finding etc.
3.4.7 In any case shall wires not be joined in between terminals.
3.4.8 LV control wiring in MV compartments shall be protected by totally enclosed grounded metal housings or conduits. The wiring itself shall run completely inside a plastic flexible conduit or sleeve or a wiring channel inside the metal enclosure or conduit. The individual wires shall not be pulled through the metal protecting enclosure or conduit.
3.4.9 All the internal LV wiring shall run in plastic wire ways or flexible conduits.
All wiring shall be mounted nearly, be bundled together, even when Vendors standard is a wiring method using a mounting plate/wire board, where the components are located on one side of the plate and the wiring is on the other of the plate passing through openings in the plate.
Where wiring is passing through openings in the plate, grommets or the like shall be provided to prevent damage to the insulation of the wire.
3.4.10 If wiring is located below or behind hinged mounting plates or doors, the wiring shall be nearly bundled or be running in a flexible conduit leaving ample movement of the plate or door.
3.4.11 For rail mounted control terminals, in order to reduce the number of control wiring failures, pre-spring loaded types shall be applied. Vendor shall use either Klippon RSF 3 or Entrelec LTVV. These terminals are of the DIN rail mounted type.
Although it is appreciated that this requirement might cause some inconvience in Vendors parts ordering system, this type of terminal is improving the long time reliability of the switchboard such that a deviation is not acceptable.
3.4.12 Terminals shall, with regard the different voltages levels and sources be grouped together. Either a minimum distance of 5 cm between terminal groups shall be observed or a divider plate system shall be used, between any two blocks or groups of different voltages.
3.4.13 All terminals of CT secondary circuits shall be provided with short circuit devices. The short circuit devices shall be mounted such that in the non-short-circuited position, the link is pointing downwards or that the link is resting against a separation plate, this to prevent that the CT circuit is shortcircuited by a loose link.
3.4.14 Measurement Transformer Secondary Earthing
Current and potential and or service transformers secondary circuits shall have earth potential, unless specifically excluded in the control diagrams. Both secondary wires of the transformer shall be brought out on terminals adjacent to each other.
The earthing shall be done on a third terminal connected with a link to the transformer wiring terminals. The link shall normally be fixed with two bolts. If the schematics ask for a fuse holder type link according BS practice this shall be indicated in the schematics as required.
The connection to earth shall be done with green/yellow wire. Any switching arrangement shall be made on the terminal strip.
Using an earthwire as a conductor in a control circuit is not permitted.
3.4.15 Power Company Circuit Terminals
If the switchboard contains any wiring for the circuits of the power company, the terminals of those circuits shall be grouped together and they shall be covered with a Sealable transparent cover.
The terminal identification references of the power company’s documents shall be strictly adhered to.
3.5 Identification of Equipment
3.5.1 All components such as but not limited to: relays, fuses, switches, terminals etc., shall be marked in accordance with the certified drawings.
3.5.2 Marking shall eighter be engraved or be photographically processed.
3.5.3 Typed or printed marking on self-adhesive stickers is not acceptable.
3.5.4 The switchboard shall be provided with an identification an a rating plate.
4. Measurement Transformers, Indicators and Measurement Devices
Voltage Transformers
Voltage circuits for measurement and protection purposes may be derived from the same transformer, provided that the indicating circuits are protected with their own MCB, such that protection circuits remain live in case of an indicating circuit failure.
Secondary MCB’s shall only be omitted if specifically indicated in the control diagrams, such as for the AVR circuit of a generator.
The secondary wiring between the potential or service transformer and the protecting MCB shall be as short as possible. Each wire of this part of the secondary side shall be double insulated. The wiring itself shall run completely inside a plastic flexible conduit or sleeve or a wiring channel inside the metal enclosure or the metal conduit. The plastic conduit shall be laid in, not pulled through, the metal protecting enclosure. The plastic conduit shall not contain any other wiring. It shall be protected completely directly up to the terminals of the MCB by the metal enclosure.
4.1 Potential Transformers
4.1.1 These transformers shall be Class 1, used for non-tariff purposes. For tariff purposes Class 0,5 is applicable, if not other wise specified. The rated output shall be selected to match the rated burden.
4.1.2 The transformers shall be protected by primary fuses suitable for the short circuit capacity as given on the one line diagram. These fuses shall be specially design for this purpose, whilst the thermal overloading and secondary short circuits shall be switched off secondary by a MCB having a Z type characteristic. Only if specifically required in the documents the primary fuses shall be not be installed.
4.1.3 The transformers with their fuses shall have provisions for disconnecting the primary circuit, before any access can be obtained to either the transformer or its primary fuses. The disconnecting facility shall be either by moving a PT truck or be equipped with an isolator.
4.2 Service Transformers
Service transformers providing power for closing and winding the energy storing springs of the circuit breakers shall preferably not be used, the AC supply required for these duties shall be normally taken from an external LV source. A black start is possible because of the manual winding facilities of the circuit breaker. A service transformer shall only be installed if the requisition requires so.
4.2.1 If the service transformer is not withdrawable because for instance by its weight, the connection to the busbar shall be made with a three phase fault make-load break switch, excess to fuse and transformer compartment(s) shall only be possible with load-break switch in the open position.
Live parts shall not be accessible from within these compartment(s) nor shall it be possible when these compartment(s) are open that the load break switch can be closed.
4.2.2 The rating of service transformers shall be sufficient to wind all the circuit breakers simultaneously of the busbar-side to which they are connected, without dropping the secondary voltage below the value as specified by the winder motor manufacturer. The service transformer shall be capable to wind the closing springs of all circuit breakers to be installed initially plus for future ones at the same time.
4.2.3 Sequential energizing of the closing mechanisms is not acceptable. If a busbar-side related service transformer is connected to a control power transfer system, the transformer shall not be sized for the winding of all circuit breaker mechanisms simultaneously, the side where the standby duty is required shall be switched timed delayed on, after a after the first winding cycle of the own busbar is completed and so on.
4.2.4 The other requirements as above for the Potential transformers remain fully valid.
4.3 Current Transformers
Current circuits for measurement and protection purposes shall always be galvanically separated, unless specifically indicated on the drawings.
The transformers shall maintain sufficient accuracy under all overload and shortcircuit conditions, ensuring proper protection relay operation, maintaining the discrimination as required.
4.3.1 The rated output of the current transformer shall be selected to match to the actual burden, taking into account all possible impedances, including the external cabling.
4.3.2 The current transformers shall be selected according the following table:
Measuring cores (according to IEC and VDE):
- Class 0,5 Tariff, only if specified. Power company use
- Class 1 Metering,
- Class 3 Over-current relays.
Protection cores (according to IEC and VDE):
- 5P (10P is only acceptable in special cases.)
Attention to the overcurrents as occurring during inrushes and the matching settings of the relays.
In principle the I>> for outgoing circuits will always be set over the inrush current of the device to prevent nuisance tripping.
For a transformer the inrushcurrent is taken as 1:Uk x In, any reduction factors are neglected.
4.3.3 For measuring cores the rated overcurrent factor shall be as small as possible for instance M5 or M10, to protect the connected measuring instruments from excessive overcurrents.
Where necessary an additional burden shall be installed to ensure proper matching.
4.3.4 The transformers shall be capable of withstanding the rated and peak momentary current as specified for the switchboard.
If the thermal current is specified as:
1 second:
The current transformers of all circuits shall be rated for 1 second, except if specified differently.
This can be the case for instance, for incoming or busbar protection transformers, to prevent damage to the transformers in case the back-up protection is switching off the fault. A 3 seconds rating therefore might be necessary.
Outgoing circuit current transformers in general shall have a 1 second rating.
3 second:
This time is rare for industrial installations, occurs mainly if the switchboard is used as the main MV distribution with downstream MV switchboards.
4.3.5 The current transformers shall be mounted in the stationary part of the switchgear only.
4.3.5.1 In the case of withdrawable contactor units, it is acceptable that the current transformers are mounted with all other equipment on the cassette or truck, provided that the current circuits do not go outside the withdrawable part, this to prevent an open current transformer circuit.
If the current transformers are located on the withdrawable part, the current transformer for the remote ammeter shall be located in the fixed part.
An other method of data transfer may be applied, provided that interference with the current path does not occur, using a current transducer where a secondary open voltage circuit is not a problem. (0-1 A / 0-10V).
4.3.6 The rated secondary current of current transformers shall be normally be 1 A .5 A is possible, but only if specified in the job documents.
4.3.7 Remote Current Measuring:
If the phase angle of the current is not relevant for the remote indication, a current transducer (0-1A/0-10V), or (0-5A/0-10V) shall be installed.
In any case shall the main current circuits not leave the switchboard. If specified intermediate current transformers shall be provided (1/1A or 5/1 A).
4.3.8 Multi-turn Transformers
4.3.8.1 Primary winding, multi-turn, current transformers where the primary winding exists of MV wiring, are only acceptable when the primary circuit is upstream protected by an MV fuse.
4.3.8.2 Current transformers having more than one transformation ratio, achieved by selection of secondary winding taps, are only acceptable, if a single secondary winding design does not fit in the available space.
4.3.8.3 Vendor shall indicate the application of any of the multi-turn designs as described above, in the technical description of his quotation.
4.4 Core Balance Current Transformers
The core balance transformers shall be constructed such that they fit ample around the entire cable, including the outer sheath.
To ensure proper functioning of the protection system, the cable earth wire (earthing the cable armor, the cable termination and if applicable the (lead) sheath) shall pass through the core balance transformer, to eliminate the earthfault flowing in the cable armor and or sheath.
The device detecting the earthfault shall match to the core balance transformers to obtain optimum protection.
Core balance Transformers of the split type are not preferred.
4.5 Metering Transformers for Power Company Use
The metering transformers shall be constructed according to the requirements of the power company, according to the IEC recommendations.
Each transformer shall be provided with a manufactures test certificate. If special witnessed testing is required, for instance by an independent third part, this shall be indicated in the requisition.
4.6 Adaptation Transformers to Correct Phase Angles or Data
Part of the scope of supply are the transformers to:
4.6.1 Correct the phase angles for instance the differential protection over a transformer.
4.6.2 To match the actual data with the 100% indication of the instrument.
4.7 Indicating Instruments
4.7.1 The indicating instruments shall be flush mounted in the front of the switchboard and they shall have a minimum size of 96 mm2. The only exception is a possible ammeter for a space heater of the device to be switched, this device can be 48 mm2.
4.7.2 The Voltmeter scale shall be selected such that the system voltage of the switchboard is 100% scale.
4.7.3 The Ammeter scale shall be selected in such a way that the full load equipment current equals approximately 75 percent of the full scale reading.
4.7.4 The kW indicators shall have their 100% indication at approximately 80% full scale.
4.7.5 Protection relays having a current indication do not replace an Ammeter as indicated in the schematics.
4.8 Capacitive Voltage Indicators
When live indication of the outgoing or the incoming circuits is required, this shall be done by means of capacitive voltage dividers imbedded in the current transformers or in special designed insulators. The design shall be such that phasing out is possible. Permanent indication is strongly preferred.
4.9 Transducers
Transducers shall be used to transmit Volts, Amps, kW, kVar and cos phi to other locations. The output signal shall always be 0-10 V unless otherwise specified in the job documents.
Where the direct relation volts and current is involved, including the occurring phase angle such as for a Generator capability indicating instrument, these data shall be transmitted in volts and current at the corresponding phase angle. Vendor shall ensure that despite the intermediate transformers the correct relation is presented on the outgoing terminals.
4.10 kWh and kVar Counting Instruments, Summation Counting etc.
The description covers only metering for internal accounting purposes. Any Power Company equipment is excluded.
The purpose of the instruments is to obtain comparable data, they shall not be used for external accounting purposes as the related transformers are Class 1 or less.
4.10.1 The kWh counters for symmetrical loaded equipments such as distribution transformers and motors shall be of the single current design, using the same circuit as the ammeter.
4.10.2 If a summation kWh counting is required, the individual kWh counters shall have an impulse contact with a given relation to the counted kWh consumed. The pulse contacts shall be combined in a combination of counters and the final summation counter.
4.10.3 To enable a better economical control of a plant which can operate with switchable electrical loads, maximum demand metering can be used to switch off load during peak periods.
Maximum demand metering and remote indication shall be ordered from one supplier only to ensure proper matching.
4.11 Current Transformers to Be Used in Differential Protection Systems
The transformers applied shall have suitable and identical characteristics, in some cases coordination and data exchange with other suppliers is required to ensure proper matching.
Company shall receive copies of the related correspondence, and shall where necessary coordinate the contacts between the two suppliers. In some cases it is required that one supplier shall provide transformers to the other supplier for installation in his materials, close cooperation is required.
5.1 Tools etc.
5.1.1 If Vendor’s design requires a special truck or trolley to lift or to remove the circuit breaker, or starter unit, or service transformer or other withdrawable equipment from the switchboard, it shall form part of this specification.
5.1.2 The truck shall allow for certain tolerances in the floor level. Each substation in which the MV equipment is to be located shall have two trucks and or trolleys of each type that is required for the withdrawable equipment to be handled.
5.1.3 Vendor shall supply a complete set of special tools if required for the protection relays.
5.1.4 Vendor shall supply a set of standard tools required for the switchboard, those tools not being the ones normally available in the simple tool kit of an electrician.
5.1.5 A completely furnished standard electricians tool kit shall be supplied additionally if specified in the job documents.
5.1.6 The portable flexible cables for grounding purposes of the switchboard and or outgoing circuits are part of Vendors scope of supply even when a grounding switch is specified.
The sets shall be complete with a relevant testing gear.
See above under ‘’Safety Earthing’’.
5.1.7 Test Box
A test box for the circuit breaker shall form part of this specification if required by the requisition. The cabinet shall allow proof operation and inspection of the with drawable units, completely separated from the main switchboard.
For contactor units it is acceptable that the contactor has a test position created by plugging a fixed test box in between the withdrawable part and contactor cassette unit.
5.2 DC Unit with Battery Back-up
As a rule the DC unit shall be supplied with the switchboard. A deviation is possible when enough capacity is available on the stations DC supply system. The job documents shall indicate if the DC will be supplied from the existing source.
A DC unit to be supplied shall comply fully with the Standard Specification for DC Units.
Tests and Inspection in Vendors Shop
All the equipment shall be subject to purchaser’s functional tests and inspection in Vendor’s shop, all as listed in the inspection procedure attached to this specification.
Six copies of the reports of these tests shall be furnished by Vendor and shall be countersigned by purchaser.
7.1 The switchboard may be split into separate sections for shipment. In that case it shall be stated and identified in Vendor’s proposal, how the sections will be split for transport.
Panels or units separate from the switchboard such as the DC unit etc. shall be shipped combined.
Shipping and packing instructions as attached to the purchase order shall be strictly adhered to. In particular if prolonged storage and or areas where severe climatic destinations occur.
7.2 If necessary additional bracing shall be provided to ensure that the alignments of and in the assembly remain correct.
Circuit breakers or the like are to be shipped separately, however if Vendor’s standard procedure is to ship the circuit breakers and or the contactor units inside the assembly, they shall be locked in position to prevent damage.
Each circuit breaker or contactor unit, separately shipped, shall be packed and tagged, before crating, with additionally the panel reference.
7.3 Each part of the shipment shall be, crated if required, tagged with a machine type soft metal tag, securely fixed and showing the switchboard order number and details of the address.
7.4 The equipment shall be provided with removable lifting eyes to permit easy transport and lifting.
Following items shall form part of this specification:
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One piece of each type of insulator or bushing used in the switchboard
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Three pieces of each type of MV fuse used in the switchboard
- A set of brushes for the closing mechanism.
The manufacturer shall supply the information regarding the maintenance procedures to be observed under normal service condition and what do after a fault has been switched off.
It is required that the manufacturer indicates the number of operations (or the time) after which different parts of the circuit breaker and contactor shall be maintained. The manufacturer shall give information regarding the overhaul caused by:
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After shortcircuits switch-off,
- Operations in normal service.
The maintenance manual shall be in the language as specified.
If site erection is part of Vendor’s supply the following items are in the scope of others.
10.1 All cables and the connection of these cables to Vendor’s equipment.
This applies only for those cables to locations outside of the switchboard and its direct control environment.
10.1.1 Vendor shall provide, install, connect, and test all switchboard interconnection cables, necessary for control and the auxiliary power interconnections in between all units of the switchboard(s).
If a separate protection/control board is supplied, all cabling between the switchboard and this control board(s) and or connections between the panels mutually are part of the switchboard order.
10.2 The Civil Provisions Outside Vendor’s Equipment
However, this applies only, in case the necessary information has been transmitted by Vendor to Company within 2 weeks after placing of the order.
Provisions or changes required for Vendor’s equipment received at a later date shall be fully for Vendor’s account.
10.3 Transport and Off-Loading Facilities on Site
10.3.1 In general, cranes are available on site, which Vendor may use for his own account and under his own responsability. Availability of cranes and/or other necessary equipment has to be checked with the Construction Superintendent or his representative on site at least 1 week before arrival of equipment.
10.3.2 Transport from car, train, or boat to the relevant building shall be done by the Vendor.
In all cases, transport, provision of temporary protection of equipment (in case unloading on the same day would be impossible or because of weather conditions) and/or carrying out of other handling procedures shall be done under Vendor’s full responsibility and for Vendor’s account.
The transport of the materials ends inside the station in which the materials shall be installed.
In no way its is possible to deviate from this requirement, even when temporary storage in the site store is required.
11.1 Quantities of Drawings
Vendor shall furnish all drawings and other technical data according to the ‘’Vendor Furnished Documents’’ sheet, which is part of the requisition, in the quantities and at times specified.
The language on the drawings, instructions, or nameplates shall be as stated in job documents.
11.2 Drawings and Data to Be Furnished with the Quotation
11.2.1 A One Line Diagram showing all relays, meters, transformers and control devices. The drawing shall indicate relay ranges, makes and type.
11.2.2 The schematic diagrams for each type of unit.
11.2.3 All data indicating, the capability of the circuit breakers, the contactors and the fuses as well as the current capacity of busbars.
11.2.4 A list of subvendors for all materials bought from others.
11.2.5 Manufacturer’s leaflets, giving complete descriptions, data and curves of switchboard material, circuit breakers, contactors, relays, special meters, fuses etc.
11.2.6 Outline drawing showing overall dimensions, required aisle space and clearances and location of major equipment. This drawing shall also show position of cable terminations.
11.2.7 Front-view drawing showing meters, control switches, relays, mimic diagram etc.
11.2.8 Sketch of the busduct (if applicable).
11.2.9 Foundation plan for all pieces of equipment or assemblies.
11.3 Drawings and Data to Be Submitted in for Approval after Ordering
11.3.1 Within 2 weeks after receiving the order, Vendor has to send all drawings as above however, brought in line with Company’s certified requisition and comments received during the quotation stage.
11.3.2 Within 4 weeks after placing the order Vendor has to send following drawings:
11.3.2.1 Drawings showing all the civil provisions that have to be made by others including cable holes etc. Drawings shall show to weight of equipment(s).
11.3.2.2 Drawings showing the construction of busduct with detailed outline dimensions and details of flange to transformer and air barrier, the flexible copper connections, if a busduct is to be supplied.
11.3.3 The schematic control diagrams, but now complete with terminal and wire numbers.
11.3.4 Explosion frames to be built in into the substation wall(s).
11.3.5 All the documents shall show Company’s purchase order number. The documents will be provided by Company with a Vendor print coding. If required Company shall impose a document numbering system.
11.3.6 In case that static relays are installed. Full detailed schematics and wiring diagrams of these parts shall be supplied.
11.4 Drawings and Data to Be Sent in for Construction
Within two weeks after the drawings and data as above, have been returned to Vendor, Vendor shall submit the same drawings but now corrected to Company.
11.5 Instructions
Eight weeks before the delivery date indicated in the purchase order, Vendor shall supply the installation, operating and maintenance instructions in the language as stated in the requisition.
12.1 Within 8 weeks after placement of the purchase order, Vendor shall submit a spare part recommendation based on two years continuous operation.
12.2 Next to the spare parts for two-year operation, like MCB’or LV fuses and LED’s , as supplied with the switchboard, Vendor shall supply the quantity of the above mentioned materials for start-up purposes. This quantity shall be as indicated in the requisition.
12.3 Installation Instructions
Vendor shall ship together with the switchboard one set of installation, maintenance and operating instructions.
13.1 Vendor shall, provide all certificates confirming that the entire switchboard complies with all standards and regulations as per this specification.
These certificates shall be issued either by the Authorities of the country of or by recognized institutes acting on behalf of these Authorities. Certificates of internal arcing tests have to be provided with the quotation.
13.2 Any costs related with such certificates shall be for Vendor’s account.
13.3 Any test(s) if required for obtaining of the certificates shall not cause any extension of the delivery time.