Main keywords for this article are MV and LV Switchgear Checking List Before Energization, SEL relay testing, ductor test, Transformer CT stability test.
MV and LV Switchgear Checking List Before Energization
Step -1:
4160 & 480 volts switch gear physical checks , to be inspected by commissioning and maintenance teams.
All out going cables tightness and torque mark checking.
1) All breakers contact engagement checking.
2) Outgoing cables shield wire through CBCT to be confirmed for all feeders (applicable to 4160 switch gear).
3) Breakers front and back side internal inspection, removal of material inspection tags if any in the cubicles, housekeeping of switch gear etc.
4) Main ground cables tightness and torque marking checking on the ground bar.
5) Inspection of Front and back door interlock with breaker service position.(applicable to 4160 Switchgear)
6) DC circuits point to point check from DCDB to each feeder.
7) Bus PT and Line PT ground connection checking.(applicable to 4160 swgr)
8) Check CT and PT loose connections.
9) Check all the breakers close /open operation manually and electrically.
10) Check the breakers closed breaker spring discharge when removing male plug and physical alignment during rack in and rack out condition.(applicable to 4160 Switchgear)
11) Verifying of equipment labeling.
12) Inspect the excess gaps / cable gland holes on the panel top which are to be plugged.
13) Physical inspection of transformers HRG disconnect switch and HRG resistor links (T1,T2 ,T3 and T4)
Step-2 :
Functional checks by commissioning team
1) Perform ductor test randomly on the main bus joints
2) Check the annunciation indications for alarms (transformers and relays) and remote indications , check target LED indication on the SEL relay.
3) Partial differential function check (applicable to 480 volts swgr).
4) Tie breaker lock out functional check at less than 80 % bus voltage.
5) Transformer CT stability test (applicable to 34.5 /4.16 kv TR).
6) Check the breaker open operation when main and tie breaker closed manually and bus voltage is dead.
7) Check the breaker tripping on relay protection functions.
8) Check ATS and sync operation
9) Transformer function checks (OTI, WTI, PRV, rapid pressure, LLG, fan operation by activating the electromechanical devices.
10) Earth pit resistance check for main swgr body.
11) Battery charger and battery bank commissioning and load test by vendor
12) Meggering of bus bar.
Step-3
Functional checks by commissioning and maintenance team before Energization
1) Breakers ATS and parallel operation checks.
2) Verifying the Relay settings and breaker tripping via relay
3) Down load the final relay settings and maintain the record.
4) Annunciation signals and alarms functions.( SEL 2523 and 2505 I/O modules)
5) Tickle test of the incoming cables from transformer secondary to swgr).
6) Meggering of bus bar.
Testing and functional checks by PMT Before Energization
1) HI-pot of the incoming cables , cable phasing continuity .
2) Interlock checking ( upstream to downstream) via SEL 2505 I/O module.
3) EPMS functional checks.
After Energization
4) ATS Automatic transfer witch and parallel operation of the bus.
5) Transformer differential CT stability check
6) Lock out relay function check
7) Phase sequence of bus A and bus B and noting of incoming voltages
8) Inter lock check between upstream to downstream breakers
9) Adjusting of the tap setting of transformers to higher tap for voltage boost up.
Detailed knowledge of MV and LV Switchgear are here.