ABB Relion 670 Series Technical Reference Manual page 580

Line differential protection ansi

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Multipurpose protection

Operate region

ANSI05000253 V1 EN

CVGAPC, IcosPhi&V directional operating principle

RCADir is -75°

ROADir is 50°

Note that it is possible to decide by a parameter setting how the directional feature

shall behave when the magnitude of the measured voltage phasor falls below the pre-

set value. User can select one of the following three options:

Non-directional (operation allowed for low magnitude of the reference voltage)

Block (operation prevented for low magnitude of the reference voltage)

Memory (memory voltage shall be used to determine direction of the current)

It shall also be noted that the memory duration is limited in the algorithm to 100 ms.

After that time the current direction will be locked to the one determined during

memory time and it will re-set only if the current fails below set pickup level or voltage

goes above set voltage memory limit.

Voltage restraint/control feature

The overcurrent protection step operation can be can be made dependent of a measured

voltage quantity (see table 298). Practically then the pickup level of the overcurrent

step is not constant but instead decreases with the decrease in the magnitude of the

measured voltage quantity. Two different types of dependencies are available:

Voltage restraint overcurrent (when setting parameter VDepMode_OC1=Slope)

en05000253_ansi.vsd

1MRK505222-UUS C

Technical reference manual

Relion red670