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10 COMMISSIONING
10.3 GENERAL PRELIMINARY WORK
10.3.2 DIELECTRIC STRENGTH TESTING
The 745 is rated for 2000 V DC isolation between relay contacts, CT inputs, VT inputs and the safety ground
terminal G12. Some precautions are required to prevent 745 damage during these tests.
Filter networks and transient protection clamps are used between control power and the filter ground terminal
G11. This filtering is intended to filter out high voltage transients, radio frequency interference (RFI), and elec-
tromagnetic interference (EMI). The filter capacitors and transient suppressors could be damaged by applica-
tion continuous high voltage. Disconnect filter ground terminal G11 during testing of control power and trip coil
supervision. CT inputs, VT inputs, and output relays do not require any special precautions. Low voltage inputs
(< 30 V) such as RTDs, analog inputs, analog outputs, digital inputs, and RS485 communication ports are not
to be tested for dielectric strength under any circumstance.
g
GE Power Management
Figure 10–2: TESTING FOR DIELECTRIC STRENGTH
10
GE Power Management
745 Transformer Management Relay
10-5
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