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Section 4
Starting up
4.8
Checking VT circuits
Check that the wiring is in strict accordance with the supplied connection diagram.
Test the circuitry.
•
Polarity check when applicable; this test is often omitted for CVTs
•
VT circuit voltage measurement (primary injection test)
•
Earthing check
•
Phase relationship
•
Insulation resistance check
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.
4.9
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When pulled out, the test handle is mechanically stopped in half withdrawn position.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 and the
IED is in test mode. Before removing the test handle, check the measured values in the IED.
Not until the test handle is completely removed, the trip and alarm circuits are restored for operation.
Current circuit
1.
Verify that the contacts are of current circuit type.
2.
Verify that the short circuit jumpers are located in the correct slots.
Voltage circuit
1.
Verify that the contacts are of voltage circuit type.
2.
Check that no short circuit jumpers are located in the slots dedicated for voltage.
Trip and alarm circuits
1.
Check that the correct types of contacts are used.
52
Correct possible errors before continuing to test the circuitry.
While testing VT secondary circuit and associated secondary equipment, care shall
be exercised to isolate the VT from the circuit being tested to avoid backcharging the
VT from the secondary side.
Verify that the contact sockets have been crimped correctly and that they are fully
inserted by tugging on the wires. Never do this with current circuits in service.
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1MRK 504 165-UEN Rev. K
M11724-2 v10
GUID-F1E29C06-7FE8-44D8-AD5A-EE8990A2AA41 v6
Transformer protection RET670
Commissioning manual
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