Parameter Setting Guidelines - ABB RELION RET670 Applications Manual

Relion 670 series transformer protection version 2.2 ansi

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1MRK 504 163-UUS A

Transformer protection RET670 2.2 ANSI

Application manual

phase-to-phase faults, this corresponds to the per-phase, or positive-sequence,

impedance. For a phase-to-ground fault, it corresponds to the per-loop impedance,

including the ground return impedance.

ANSI12000176 V1 EN-US

Load impedance limitation with load encroachment

During the initial current change for phase-to-phase and for phase-to-ground faults,

operation may be allowed also when the apparent impedance of the load encroachment

element is located in the load area. This improves the dependability for fault at the

remote end of the line during high load. Although it is not associated to any standard

event, there is one potentially hazardous situation that should be considered. Should

one phase of a parallel circuit open a single pole, even though there is no fault, and the

load current of that phase increase, there is actually no way of distinguish this from a

real fault with similar characteristics. Should this accidental event be given precaution,

the phase-to-ground reach (RFPG) of all instantaneous zones has to be set below the

emergency load for the pole-open situation. Again, this is only for the application

where there is a risk that one breaker pole would open without a preceding fault. If this

never happens, for example when there is no parallel circuit, there is no need to change

any phase-to-ground reach according to the pole-open scenario.

Parameter setting guidelines

IMinOpPGZx and IMinOpPPZx

The ability for a specific loop and zone to issue start or trip is inhibited if the

magnitude of the input current for this loop falls below the threshold value defined by

these settings. The output of a phase-to-ground loop n is blocked if In <

IMinOpPGZRV(Zx). In is the RMS value of the fundamental current in phase n.

Impedance protection

ANSI12000176-1-en.vsd

GUID-B28677F4-B909-42C1-B1B7-1C118B26E67D v4

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