ABB RELION REX640 Technical Manual page 356

Protection and control

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Protection functions

Figure 213: Two-phase short circuit, short circuit is between phases B and C

Negative sequence voltage as polarizing quantity

When the negative voltage is used as the polarizing quantity, the angle difference

between the operating and polarizing quantity is calculated with the same formula

for all fault types:

This means that the actuating polarizing quantity is - U

The equations are valid when network rotating direction is counter-

clockwise, that is, ABC. If the network rotating direction is reversed,

180 degrees is added to the calculated angle difference. This is done

automatically with a system parameter

Phase rotation .

1MRS759142 F

(Equation 21)

Technical Manual