Operation Principle - ABB RELION REX640 Technical Manual

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1MRS759142 C

Technical Manual

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 Operation setting. The

corresponding parameter values are "on" and "off".

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

in the diagram are explained in the next sections.

GUID-26CB5DA8-8360-4A14-BFE7-89A7FD0C6FA2 V1 EN

Functional module diagram

Under voltage detection

Under voltage detection compares the fundamental frequency component of all three

phase-to-phase voltages with the set Voltage start value. When all three phase-to-

phase voltages are lower than the set Voltage start value, the Under voltage detection

module sends an enable signal to the Timer indicating an undervoltage condition at the

grid connection point.

Reactive power monitoring

This module calculates and monitors the reactive power based on positive sequence

current and voltage. The use of a positive sequence component makes the

determination of power insensitive to a possible asymmetry in current and voltages.

When the reactive power exceeds Min reactive power and flows in the operating area,

the module sends an enable signal to the Timer indicating that the reactive power is

being consumed at the grid connection point. A slight tilt in the curve can be obtained

by the setting Pwr sector reduction.

To avoid false tripping, reactive power calculation is blocked if the magnitude of the

positive-sequence current is less than the set Min Ps Seq current.

The magnitude of calculated reactive power Q is available in the Monitored data view.

Protection functions

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