ABB RELION 620 Series Technical Manual page 497

1MAC504801-IB E
620 series ANSI
Technical Manual
The activation of the PICKUP_GFC output indicates a two-phase or three-phase short
circuit. The identification of the faulty phases is indicated in output PICKUPS_GFC.
Depending on the faulty phases, the corresponding impedance-measuring elements in
zones are released and indicated in the RELEASE_PP output.
Table 362: Pickup of the overcurrent elements and the respective outputs
Pickup of over-current PICKUP_GFC
element
IA> & IB> TRUE
IB> & IC> TRUE
IC> & IA> TRUE
IA> & IB> & IC> TRUE
To prevent undesired tripping due to large loads, an optional load discrimination logic can
be enabled by the Load Dsr mode GFC setting. When selected "On", the load
discrimination is enabled and respectively "Off" means the load discrimination is
disabled. When load discrimination logic is enabled, the load impedance is estimated
continuously with three phase-to-phase impedance measuring elements:
Z ( V V ) / ( I I
= − −
AB A B A
GUID-05622598-A59C-4BD1-AFE8-B24420A373C8 V1 EN
Z ( V V ) / ( I I
= − −
BC B
B C
GUID-2C63A640-5B5B-4D3D-B7B6-8B4D35DC4D23 V1 EN
Z ( V V ) / ( I I
= − −
CA C A C
GUID-0850934A-5B7E-4407-8D6E-80717CDFFC45 V1 EN
The load discrimination logic reserves an area for load impedance in the impedance plane
(RX-plane) defined by the Ris reach load GFC and Angle load area GFC settings.
PICKUPS_GFC
AB Fault
BC Fault
CA Fault
ABC Fault
)
B
)
C
)
A
Section 4
Protection functions
RELEASE_PP
AB
BC
CA
ABC
(Equation 77)
(Equation 78)
(Equation 79)
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