ABB RELION 670 Series Applications Manual page 283

Transformer protection

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1MRK 504 152-UEN B

In some applications, for instance cable lines, the angle of the loop might be less than 60°. In

these applications, the settings of fault resistance coverage in forward and reverse direction,

RFFwPE and RFRvPE for phase-to-earth faults and RFFwPP and RFRvPP for phase-to-phase

faults have to be increased to avoid that FDPSPDIS characteristic shall cut off some part of the

zone characteristic. The necessary increased setting of the fault resistance coverage can be

derived from trigonometric evaluation of the basic characteristic for respectively fault type.

Phase-to-earth fault in forward direction

With reference to figure 157, the following equations for the setting calculations can be

Application manual

Index PHS in images and equations reference settings for Phase selection with

load encroachment function FDPSPDIS and index Zm reference settings for

Distance protection function (ZMQPDIS).

Impedance protection