20
ANSI MEDIUM VOLTAGE METAL-CLAD DIGITAL SWITCHGEAR
DANGER
WARNING
CAUTION
NOTICE
SAFETY
INSTRUCTIONS
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Table 3: Zero-clamping limits
Function
Zero-clamping limit
Three-phase current
measurement (CMMXU)
1% of nominal (In)
Residual current
measurement (RESCMMXU)
1% of nominal (In)
Phase sequence current
meas. (CSMSQI)
1% of nominal (In)
Main bus and breakers installed in the
switchgear frame
This testing procedure includes the influence of
applications such as the circuit breaker or
contactor. Installed busbars are used to make the
electrical circuit between two neighboring
frames.
Danger:
If high voltage cables are terminated to
switchgear frame, ensure the installation is dead.
Protect against any other live parts.
• Step 1/5
Verify sensor parameters set in the protection
relay with sensor rating plates found on the
sensors. These may be found on the circuit
breaker compartment door or in the low voltage
wiring compartment.
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28
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28 Example of a
current sensor label
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29 Current sensor
parameters
On protection relay LHMI go to
-> Main Menu/
Configuration/Analog inputs/Current (3I, CT)
• Primary current = Application nominal current
• Amplitude Corr A = sensor rating plate, phase A
• Amplitude Corr B = sensor rating plate, phase B
• Amplitude Corr C = sensor rating plate, phase C
• Nominal current = Primary current
• Rated secondary Val = Rated secondary value in
mV/Hz
• Angle Corr A = sensor rating plate, phase A
• Angle Corr B = sensor rating plate, phase B
• Angle Corr C = sensor rating plate, phase C
• Step 2/5
Move two neighboring circuit breakers into the
connected position and close them.
Notice:
Default values of
overcurrent, earth fault and
unbalance protection functions
can operate the circuit breaker
during primary injection. Disable
all related protection functions in
the protection relay or disconnect
the tripping coil (MO) from the
negative potential of power supply
in the low voltage compartment
before primary injection to avoid
unwanted tripping of the circuit
breaker.
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29
NOTICE
