ABB RELION 620 Series Technical Manual page 596

Section 6
Supervision functions
590
GUID-D083BF22-574C-4603-971F-5F4371632A28 V1 EN
Figure 300: CCM 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 trip
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 _ _
GUID-9CC931FA-0637-4FF8-85D4-6F461BD996A9 V2 EN
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.
−
_ I REF _
1MAC504801-IB E
(Equation 91)
620 series ANSI
Technical Manual