ABB RELION REX640 Technical Manual page 886

Protection and control

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Protection functions

Improper analog channel configuration causes a validation error if the analog

channels are not completely configured or they do not match with certain settings.

For troubleshooting, check the contents of this chapter and also the preprocessing

blocks in this document. The configuration can be written to the protection relay

once the mismatch is corrected.

Operation principle

The function can be enabled and disabled with the

corresponding parameter values are "On" and "Off".

The operation of OEPVPH can be described using a module diagram. All the

modules in the diagram are explained in the next sections.

Figure 495: Functional module diagram

U/f calculation

This module calculates the U/f ratio, that is, the excitation level from the internal

induced voltage (E) and frequency. The actual measured voltage (U

from the internal induced voltage (E), a value the equipment has to withstand. This

voltage compensation is based on the load current (I

) of the equipment. The leakage reactance of the transformer or generator is set

The internal induced voltage (E) is calculated from the measured voltage. The

currents are to be used. If the

or "phase-to-phase", the

phases or phase-to-phase voltages ("A or AB", "B or BC" and "C or CA") and currents

are to be used for the calculation of the induced voltage.

Leakage React setting in percentage of the Z base.

Voltage selection and Phase supervision determine which voltages and

Phase supervision setting is used for determining which

Phase selection "1", "2" or "3") if Voltage

selection is set to "phase-to-phase".

The function requires that all three voltage

channels are connected if

set to "pos sequence".

Operation setting. The

Voltage selection setting is set to "phase-to-earth"

1MRS759142 F

Voltage selection is

) and the leakage reactance (X

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