If the CT secondary circuit ground connection is removed without the
current transformer primary being de-energized, dangerous voltages
may result in the secondary CT circuits.
4.9 Checking VT circuits
M11724-2 v10
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 when applicable; this test is often omitted for CVTs
• VT circuit voltage measurement (primary injection test)
• Grounding 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.
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.
4.10 Using the RTXP test switch
GUID-F1E29C06-7FE8-44D8-AD5A-EE8990A2AA41 v5
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When pulled out, the test handle is mechanically stopped in half withdrawn position.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
1MRK 502 073-UUS A Section 4
Starting up
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062 55
Commissioning manual
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