90
95.2
95.1
95.3
7.3.2.5.2 Cleaning and checking of the voltage transformers and anti-ferroresonance circuit
a) Fixed version voltage transformers
• Make the plant you want to work on safe (follow the plant safety regulations);
• Make sure that the circuit-breaker is in the open position;
• Rack the circuit-breaker out from the service position to the test/isolated position;
• Remove the circuit-breaker from the panel;
• Manually close the earthing switch;
• Open the cable compartment door;
• Remove the circuit-breaker plate 27 to get larger access;
• Visually check the voltage transformer connections.;
• Using a dynamometric spanner check tightness of all the screws. Refer to the table on page 87 for
the tightening values;
• Carry out a visual inspection of the transformers and check for any presence of dirt;
• Remove any deposits of dust using a dry cloth that does not leave any deposits on the treated
surfaces (do not use woollen cloths).
b) Voltage transformers in removable version
• Make the plant you want to work on safe (follow the plant safety regulations);
• Make sure that the circuit-breaker is in the open position;
• Rack the circuit-breaker out from the service position to the test/isolated position;
• Manually close the earthing switch;
• Open the cable compartment door;
• Manually withdraw the VT truck (figure 17).
• Carry out a visual inspection of the transformers and check for any presence of dirt.
• Remove any deposits of dust using a dry cloth that does not leave any deposits on the treated
surfaces (do not use woollen cloths).
c) Voltage transformers in withdrawable version
• Make the plant you want to work on safe (follow the plant safety regulations);
• Make sure that the circuit-breaker is in the open position;
• Rack the circuit-breaker out from the service position to the test/isolated position;
• Open the cable compartment door;
• Manually withdraw the VT truck (figure 141);
• Carry out a visual inspection of the transformers and check for any presence of dirt;
• Remove any deposits of dust using a dry cloth that does not leave any deposits on the treated
surfaces (do not use woollen cloths).
Figure 141 Withdrawable part with measurement unit
95.1 Voltage transformer
95.2 Resin tube (with fuse)
95.3 Fuse
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