8
4. Disconnect the MV switchgear from the grid and all possible power supplies (external, auxiliary, and inverters as well as any parallel
connection stations), secure by locking and tagging.
a. Stop the string inverters outside the MVCS. Open the DC disconnecting switches in each inverter unit and add warning notices. If appli-
cable, open the AC disconnecting switches in each inverter unit, lock and add warning notices.
b. Open all auxiliary breakers, switches and fuses in the auxiliary service board, lock and add warning notices.
c. Open main low voltage circuit breaker (if present), and all fuse base switches of the inverter inputs (AC Cabinet), lock and add warning
notices.
d. Turn the vacuum circuit breaker of the MV switchgear (V/L module) to open position. Lock and add warning notice.
e. Turn the disconnecting switch of the MV switchgear (V/P module) to open position. Lock and add warning notice.
f. Turn the earthing switch of the MV switchgear (V/P module) to earthed position. Lock and add a warning notice.
g. Turn the disconnecting switch of the MV switchgear (C/L modules) to open position. Lock and add a warning notice.
h. Turn the earthing switch of the MV switchgear (C/L modules) to earthed position. Lock and add a warning notice.
i. With above operation the MV Switchgear, and so the MVCS, should be disconnected. See “Switchgear”, “MVCS Interconnection Cables
and Electrical Layout” and the general scheme of the PV plant to assure that no external supply is connected to the MV Switchgear.
5. Check that all shrouds/screens are in place.
6. Check that you are not near to any live parts while working. All live circuits must be protected with shrouds/screens.
7. Make sure that the MV switchgear is dead.
–Check the status of voltage indicators in all MV switchgear bays. Also note that all phase LEDs which were switched on AC cabinet
before step 3 are now switched off).
8. Check that the MV transformer is dead (high voltage terminals, low voltage terminals, any auxiliary power, and instrumentation). Use an
appropriate high voltage tester only for the high voltage side, and a voltage detector with suitable testing heads for the low voltage side.
Safety instructions for the auxiliary services board
1. If there is no main low voltage circuit breaker installed in the power section, then follow Safety instructions for MV switchgear and MV
transformer area
a. Check that there is no voltage presence, with a voltage tester, neither in the power section nor in the auxiliary services board.
2. If main low voltage circuit breaker is installed, then follow:
a. Obtain a work permit.
b. Open the main circuit breaker or main switch upstream auxiliary service transformer, secure by locking and tagging.
c. Open the circuit breaker downstream auxiliary service transformer, secure by locking and tagging.
d. Open all switches, breakers, and connectors of the auxiliary service board, and secure by locking and tagging.
e. Make sure you are not near to any live parts while working. Disconnect the live circuits or protect them with shrouds/creens.
f. Check the status of the voltage indicators in the auxiliary service board.
g. Check that the auxiliary service board is dead.
1 - Introduction to this manual
