ABB RELION 620 Series Technical Manual page 885

1MRS757644 F
620 series
Technical Manual
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Figure 459: CCSPVC operating characteristics
When the differential current I_DIFF is in the operating region, the FAIL output is
activated.
The function is internally blocked if any phase current is higher than the set Max
operate current. When the internal blocking activates, the FAIL output is deactivated
immediately. The internal blocking is used for avoiding false operation during a fault
situation when the current transformers are saturated due to high fault currents.
The value of the differential current is available in the monitored data view on the
LHMI or through other communication tools. The value is calculated with the
equation.
I DIFF _ I A I B I C _ _
= + +
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The Start value setting is given in units of ×In of the phase current transformer. The
possible difference in the phase and reference current transformer ratios is internally
compensated by scaling I_REF with the value derived from the Primary current
setting values. These setting parameters can be found in the Basic functions section.
The activation of the BLOCK input deactivates the FAIL output immediately.
Timer
The timer is activated with the FAIL signal. The ALARM output is activated after a
fixed 200 ms delay. FAIL needs to be active during the delay.
_ I REF _
−
Section 6
Supervision functions
(Equation 173)
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