ABB RELION REX640 Technical Manual page 966

Protection and control

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Protection functions

Considering the load in case of a single line-to-earth fault, conventional distance

protection might overreach at the exporting end and underreach at the importing

end. DSTPDIS has a load compensation functionality which increases the security in

such applications. Load compensation is enabled with the setting

x (x = 1...5) = "True".

Figure 538: Operation principle of load compensation functionality

When three-phase feeders are placed close to each other, a mutual inductive zero-

sequence coupling of the current path exists. This has an impact during earth faults.

If no measures are taken, this leads to errors in the impedance calculation. The

residual current of the parallel line induces a voltage in the protection line and

changes the measured voltage at the relay location. The influence depends on the

system configuration, that is, the magnitude and polarity of the residual current in a

parallel line.

The phase-to-earth impedance measuring elements in DSTPDIS take the zero-

sequence mutual coupling into account in impedance calculation. The compensation

is enabled and set with settings

x and Mutual X0 zone x (x = 1...5). The residual current of the parallel line must

be available and connected to the I3P_PAR input. The earth-current balance logic

is implemented to prevent malfunctioning of the protection relay on the healthy

parallel line. This means that the parallel compensation functionality is internally

Earth return path resistance = (R0 - R1)/3 from measuring point to fault location

Earth return path reactance = (X0 - X1)/3 from measuring point to fault location

Zero-sequence resistance from measuring point to fault location

Zero-sequence reactance from measuring point to fault location

Physical fault resistance between phase and earth (includes arc and earthing resis-

Load compensation is used only with single phase-to-earth faults. Load

compensation is not used if multiple phases are included in the fault

(more than one single earth fault release).

Load import (No load compensation)

Load compensation in use

Load export (No load compensation)

Par line Comp zone x (="True"), Mutual R0 zone

1MRS759142 F

Load Comp zone

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