Operation Principle - ABB RELION 620 Series Technical Manual

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Protection functions

Operation principle

The function can be enabled and disabled with the Operation setting. The corresponding

parameter values are "Enable" and "Disable". Additionally, each zone can be "On" or

"Off" individually with the help of the Operation Znx setting. When selected "On", the

particular zone is enabled, and respectively "Off" means a particular zone is disabled.

The operation of the phase step distance protection function can be described with a

module diagram. All the modules in the diagram are explained in the next sections.

GUID-9D582A33-E46E-4C1E-A848-E04C325AB17B V1 EN

Functional module diagram

General Fault Criteria

The proper operation of 21P requires all three-phase currents and phase-to-phase or

phase-to-ground voltages to be available for measurement.

Reliable identification of fault and faulty phase(s) is done in a module called General Fault

Criteria or GFC. This function is compulsory to release the correct impedance-measuring

elements of the protection zones and to guarantee a selective operation of the phase

distance protection.

In GFC, the overcurrent method is used for identifying the faulty phase(s). The magnitude

of each phase current is compared to the Ph Str A Ph Sel GFC setting. If the phase current

magnitude exceeds the set limit, the respective phase is identified as faulty.

1MAC504801-IB E

620 series ANSI

Technical Manual

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