3.8 Checking VT circuits
Check that the wiring is in strict accordance with the supplied connection diagram.
Correct possible errors before continuing to test the circuitry.
Test the circuitry.
• Polarity check
• VT circuit voltage measurement (primary injection test)
• Grounding check
• Phase relationship
• Insulation resistance check
The polarity check verifies the integrity of circuits and the phase relationships. The check
must be performed as close to the IED as possible.
The primary injection test verifies the VT ratio and the wiring all the way from the primary
system to the IED. Injection must be performed for each phase-to-neutral circuit and each
phase-to-phase pair. In each case, voltages in all phases and neutral are measured.
3.9 Using the RTXP test switch
The RTXP test switch is designed to provide the means of safe testing of the IED. This is
achieved by the electromechanical design of the test switch and test plug handle. When the
test plug handle is inserted, it first blocks the trip and alarm circuits then it short circuits the
CT secondary circuit and opens the VT secondary circuits making the IED available for
secondary injection.
When pulled out, the test handle is mechanically stopped in half withdrawn position. In
this position, the current and voltage enter the protection, but the alarm and trip circuits are
still isolated. Before removing the test handle, check that no trip or alarms are present in
the IED.
Not until the test handle is completely removed, the trip and alarm circuits are restored for
operation.
1MRK 505 293-UUS A Section 3
Starting up
31
Commissioning manual
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