Principle Of Operation; Full Scheme Measurement; Impedance Characteristic - ABB Relion 670 Series Technical Reference Manual

Line differential protection ansi

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1MRK505222-UUS C

IEC09000143 V2 EN

Mho, offset mho characteristic and the source impedance influence on the mho characteristic

Technical reference manual

Principle of operation

The execution of the different fault loops within the IED are of full scheme type, which

means that each fault loop for phase-to-ground faults and phase-to-phase faults are

executed in parallel.

The use of full scheme technique gives faster operation time compared to switched

schemes which mostly uses a phase selector element to select correct voltages and

current depending on fault type. So each distance protection zone performs like one

independent distance protection function with six measuring elements.

The distance function consists of five instances. Each instance can be selected to be

either forward or reverse with positive sequence polarized mho characteristic

alternatively self polarized offset mho characteristics with reverse offset. The operating

characteristic is in accordance to figure

Offset mho, zone5

Impedance protection

where zone 5 is selected offset mho.

IEC09000143_2_en.vsd

Relion red670