Table of Contents
1. General
2. Insulation Resistance Tests
3. High Potential Tests
4. Protective Relays
5. Short Circuit Rating
6. Potential and Current Transformers
7. Circuit Breakers
8. Busbar
9. Earthing
10. Wiring and Cabling
11. Cable Boxes and Stuffing Glands
12. Battery and Charger
13. Miscellaneous
14. Insulators
15. Shutters
16. Current Carrying Capacity of Rectangular Copper Conductors Temperature Rise 30°C - Air Temperature 35°C
17. Distance of Busbars and Other Life Parts
18. Meters
19. Accessories
20. Painting
1. General
Before the high voltage switchgear is ready for shipment, the manufacturer shall make suitable tests to establish to the satisfaction of the owner’s engineer that all equipment, devices, protection relays and wiring have been correctly installed, are in satisfactory working conditions and will operate as intended.
All tests shall be made in accordance with nationally recognized standards and this inspection procedure. Prior to testing, the switchgear shall be dust-free and thoroughly cleaned of all waste material. The vendor of the switchboard(s) will take care that all the test equipment necessary to do all the tests will be available at the factory and at site.
2. Insulation Resistance Tests
2.1 The insulation resistance of each high voltage bus shall be measured from phase to phase and from phase to ground with the transformers or capacitors disconnected. Measurements shall be done with circuit breakers in the “off” position, but in full “draw in” position. Insulation resistance test shall be done with a 2500 Volt Megger. Minimum insulation value of the whole switchboard will be 40 M Ohm. 2.2 Each circuit breaker shall be drawn out of its cubicle, closed manually and the insulation resistance measured of the primary part from phase-to-phase and from phase-to-ground. Test shall be done with a 2500 Volt Megger. Minimum insulation value will be 50 M Ohm. 2.3 The insulation resistance of all secondary wiring shall be measured from phase-to-ground. Insulation resistance measuring shall be done with a 500 Volts Megger. Megger test to be carried-out after the high voltage test of 3.2. Minimum insulation value will be 2 M Ohm. 2.4 Using of insulation material to get the required air distance is not acceptable, only exceptions are circuit breakers, but only when it is standard construction of circuit breaker.3. High Potential Tests
3.1 High potential tests shall be made in accordance with IEC publications 56-4, 1959 for the primary side of the switchgear. Test time 60 seconds.The test voltages shall be as given in the following table.
| Switchgear rated insulation level higher rate voltage (rms) V |
One minute power frequency withstand voltage in V (rms) |
| 3,000 - 3,600 3,601 - 7,200 7,201 - 12,000 12,001 - 17, 500 17,501 - 24,000 24,001 - 27,500 27,501 - 36,000 | 16,000 22,000 28,000 38,000 50,000 60,000 70,000 |
Tests will be done with potential transformers disconnected or high tension fuses removed from the holders.
3.2 High voltage test for the secondary wiring shall be 2000 Volts for one minute. For motors of switching mechanism test voltage shall be (2U + 500) Volts.4. Protective Relays
4.1 Circuit breaker protective devices shall be secondary relays. 4.2 Each adjustable protective relay shall be set, calibrated and tested by using a load box, ammeter, voltmeter, variable transformer and any other equipment if required. Settings, calibration points and test points shall be in accordance with values given in the approved relay setting curve. 4.3 Each protective relay shall have operating indicators. 4.4 Secondary current type relays, if withdrawable, shall have provisions for automatically keeping the secondary side of the current transformers closed when the relay is drawn out. 4.5 Check rotation of directional relays.5. Short Circuit Rating
Check the indicated short circuit/time rating of the board, breakers, current transformers, fuses, etc. against the design data.6. Potential and Current Transformers
6.1 Test all current transformer secondary circuits by applying current to current transformer’s primary side and verify that relays and/or meters operate properly. 6.2 Test all potential transformer secondary circuits by applying voltage with the voltage transformers disconnected and verify that relays and/or meters operate properly. 6.3 Check all potential and current transformer’s type, ratio’s, class and output. 6.4 Check that all current transformers are located in the stationary part of the switchgear. 6.5 Check that potential transformers and their fuses are mounted in a separate compartment arranged in draw-out construction or equivalent so that the primary connection will be disconnected before access can be obtained to either the transformer or its primary fuses. 6.6 Check the automatic transfer of service transformers, with the service transformer disconnected. 6.7 Check if capacity of each service transformer is sufficient to wind the springs of all breakers simultaneously. To avoid sequential winding of springs set all UV relays in auxiliary motor circuits identically or bypass their contacts.7. Circuit Breakers
The following tests shall be performed on all circuit breakers: 7.1 In case of low oil circuit breakers the oil level shall be checked prior to testing the breaker; all breakers shall be carefully checked for oil leakage. 7.2 Trip each circuit breaker by its mechanical trip devices. 7.3 Trip breaker manually by switch and by applying current and/or voltage to each of its associated protective relay. 7.4 Inspect the closing mechanism, auxiliary contacts, tripping mechanisms, etc. 7.5 Check that all circuit breakers or load-break switches of the same ratings are fully interchangeable also with regard to auxiliary contacts and sequence of auxiliary contacts. 7.6 Check the mechanical interlock. It shall not be possible to insert or withdraw the breakers when the breaker is in the closed position. 7.7 Check rapid sequence operation of breakers, starting from closed position of breakers, open-closed-open. (Stored energy). 7.8 Check “the anti pump” device by initiating the closing mechanism with the trip coil energized. 7.9 Close and trip circuit breaker from its control switch, push-button or operating handle. 7.10 Ensure satisfactory tripping (electrical and mechanical) of the breakers with the closing coil energized (“free to trip”). 7.11 Moving of the breakers shall not depend on situation of substation floor. 7.12 Contact alignment of each breaker shall be checked and adjusted where necessary. 7.13 It must be impossible to close the breaker mechanically or electrically when the breaker is between the test position and plugged in position. 7.14 Take out the circuit breaker and check if the springs are automatically unloaded if the breaker moves from the test into the completely draw out position, or, a mechanical interlock to prevent moving of the breaker when springs are loaded. 7.15 Each mechanical closing button shall have a removable locking device in such a way that it will be impossible to close the breaker at the switchgear. 7.16 The mechanism of breakers must be suitable for tripping and closing by continuous remote contacts. 7.17 By-passing of the “breaker closed” lamp may not cause tripping of breaker. Otherwise resistor shall be adjusted. 7.18 It must be impossible to close the circuit breaker, when the grounding switch is in the closed position. 7.19 Close a circuit breaker outside the switchboard and bring the breaker in the test position or fully draw in position. 7.20 Measure the resistance between the fixed contacts of the switchgear and the removable contacts of the breaker. 7.21 All moving mechanism parts shall be life time lubricated with an adhesive lubricant. 7.22 All breakers shall have mechanical driven contact position indicator. 7.23 Cubicles shall be provided with padlocking devices for test and disconnected positions of breakers.8. Busbar
8.1 Inspect the busbar connections and supports, control busbar and connections. 8.2 Check the busbar size with busbar rating with an ambient temperature of 35°C and a temperature rise of 30°C. See table, section 16. Busbars shall be manufactured from copper. 8.3 Check the busbar colors. 8.4 The main earthbar size shall not be less than 25 x 5 mm. Earth bar shall extend throughout the length of the switchgear assembly. 8.5 Check the possibility for later extension which shall be connected at site. 8.6 Reducing of current capacity of main horizontal busbars is not acceptable. Section of horizontal copper over switchgear will be of the same size. 8.7 Check sizes of holes in the busbar system. Reducing of copper section over center line of bolts may not be more than 40% of original copper section. 8.8 Perform a powerpath continuity test determining the through going resistance of each current carrying circuit and phase. Testing is done by applying a constant current and measuring the voltage at the current wiring connection points.9. Earthing
9.1 Inspect earthing bars and connections inside the board. Inspect the earthing bolts and connections for equipment earthing. 9.2 Inspect the earth sliding contacts between switchgear structure and breaker. Breaker shall be grounded by sliding contact all the time that the shutters are not completely closed. 9.3 If a ring current transformer is used for each fault protection, check that earth connections do not short circuit the primary current transformer winding. 9.4 Inspect earthing connections to secondary side of current and potential transformers. Earthing will be direct to current and potential transformers from the earthbar. 9.5 All housing of current and voltage transformers shall be earthed direct to primary earthing system of the switchgear. 9.6 All doors shall be earthed by means of a flexible connection. 9.7 Inspect earthing bolts inside the cable boxes.10. Wiring and Cabling
10.1 Each wire shall be numbered at both ends shall be terminated in a separate terminal. 10.2 Control wiring shall be at least 1.5 sq.mm. current transformer circuits shall be at least 4 sq.mm. Stranded wiring is required. 10.3 All cable lugs shall be of the compression type. 10.4 All current transformer circuit terminals shall be provided with short circuit devices. 10.5 Cable trays or other clamps shall be provided to support all incoming and outgoing cables. 10.6 Check separation between terminals carrying different voltages. 10.7 Check identification markers on relays, fuses, switches, terminals etc. which shall be in accordance with certified drawings. 10.8 Check terminals for outgoing or incoming auxiliary circuits. For example, cables from DC battery to switchgear, cables from LV switchgear to battery charger etc. 10.9 Wiring of primary circuits between busbars and fuses and wiring of secondary circuits between potential transformers and the first fuse shall be as short as possible and shall not touch any metal parts, live parts or other wiring.11. Cable Boxes and Stuffing Glands
11.1 The HV cable boxes for 3 core cable shall be suitable for the cable as specified and shall be provided with armor clamps. 11.2 Inspect the quantity, type and size of the stuffing glands and potheads in accordance with the drawings. 11.3 Inspect the flexible connections between current transformer or busbars to potheads. 11.4 Cable boxes shall be of the split type. 11.5 Auxiliary cables shall not run through compartments with high tension live parts. Only exception is breaker compartment when cables are mounted on cable tray.12. Battery and Charger
12.1 Check battery voltage under normal operating conditions with the trickle charger on and with the quick charger on. Check also battery voltage with the selector switch on “hand”. 12.2 Check battery voltage under normal working conditions after disconnecting battery supply for four (4) hours followed by checking of the battery capacity. 12.3 After restoring battery feeder supply, check the time required to recover to the maximum charging current. 12.4 Check alarms of battery and battery charger. 12.5 Check ratings of all switches. 12.6 Check the selectivity between fuses and battery capacity.13. Miscellaneous
13.1 It shall be impossible to touch live parts with a piece of straight metal wire through holes, gaps etc. 13.2 Inspect the separation of the compartment for secondary wiring and terminals. 13.3 Check framework for mounting of potheads. 13.4 If link cubicles are concerned check their mechanical lockings. 13.5 Check whether the switchgear has been provided with splits for shipping sections as per the approved vendor print. 13.6 Inspect separation of compartments for potheads, breakers, and busbars. 13.7 Check the main dimensions of the switchgear. Dimensions will be in accordance with the certified drawings (special floor plan drawings). 13.8 Check nameplates (on front and back of cubicles). Nameplate will be mounted on the fixed part of the switchgear. 13.9 Check doorlocks and keys.14. Insulators
14.1 All insulators must be free of paint and dust.15. Shutters
15.1 Shutters shall be completely closed either when the breaker is in the test position or in fully draw out position. 15.2 Shutters will be made of metal and grounded with a copper connection direct to the main ground rail. 15.3 Shutters and shutter mechanism shall be mounted in the breaker compartment and not in the busbar compartment. 15.4 Shutters shall be painted red for busbars and yellow for circuit or clearly marked “busbar”, “circuit”.16. Current Carrying Capacity of Rectangular Copper Conductors Temperature Rise 30°C - Air Temperature 35°C.
MAXIMUM CONTINUOUS LOAD IN AMPS AC 40 to 60 HzTake care!! Sometimes special formed bars exist, ask for temperature rise tests. Use table below as guideline or apply DIN standard!| NUMBER OF PARALLEL BUSBARS | ||||||||||
| W x D | q | WEIGHT | PAINTED | BARE | ||||||
| (mm) | (mm2) | (kg/m) | 1 | 2 | 3 | 4 | 1 | 2 | 3 | 4 |
| 12 x 2 15 x 2 15 x 3 |
23.5 29.5 44.5 |
0.209 0.262 0.396 |
125 155 185 |
225 270 330 |
110 140 170 |
200 240 300 |
||||
| 20 x 2 20 x 3 20 x 5 |
39.5 59.5 99.1 |
0.351 0.529 0.882 |
205 245 325 |
350 425 560 |
185 220 295 |
315 380 500 |
||||
| 25 x 3 25 x 5 |
74.5 12.4 |
0.663 1.11 |
300 395 |
520 670 |
270 350 |
460 600 |
||||
| 30 x 3 30 x 5 |
89.5 149 |
0.796 1.33 |
355 450 |
610 780 |
315 400 |
540 700 |
||||
| 40 x 3 40 x 5 40 x 10 |
119 199 399 |
1.06 1.77 3.55 |
460 600 850 |
790 1000 1500 |
2060 | 2800 | 420 520 760 |
710 900 1350 |
1850 | 2500 |
| 50 x 5 50 x 10 |
249 499 |
2.22 4.44 |
720 1030 |
1220 1800 |
1750 2450 |
2300 3330 |
630 920 |
1100 1600 |
1650 2250 |
2100 3000 |
| 60 x 5 60 x 10 |
299 599 |
2.66 5.33 |
850 1200 |
1430 2100 |
1950 2800 |
2650 3700 |
760 1060 |
1250 1900 |
1760 2600 |
2400 3500 |
| 80 x 5 80 x 10 |
399 799 |
3.55 7.11 |
1070 1560 |
1900 2500 |
2500 3300 |
3200 4500 |
970 1380 |
1700 2300 |
2300 3100 |
3000 4200 |
| 100 x 5 100 x 10 |
499 999 |
4.44 8.89 |
1350 1880 |
2300 3100 |
3000 4000 |
3800 5400 |
1200 1700 |
2050 2800 |
2850 3650 |
3500 5000 |
| 120 x 10 160 x 10 200 x 10 |
1200 1600 2000 |
10.68 14.24 17.80 |
2200 2800 3350 |
3500 4400 5300 |
4500 5800 6900 |
6100 7800 9400 |
2000 2500 3000 |
3100 3900 4750 |
4100 5300 6350 |
5700 7300 8800 |
17. Distance of Busbars and Other Life Parts
Minimum distance in air from phase to phase and from phase to ground shall be:| Voltage (rms) V | Distance in cm |
| 3000 - 3600 3601 - 7200 7201 - 12000 12001 - 17500 17501 - 24000 24001 - 27500 27501 - 36000 | 6.0 7.5 10.0 14.0 18.0 21.0 26.0 |