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 FRPFRQ can be described using a module diagram. All the modules

in the diagram are explained in the next sections.

GUID-67A36E21-2379-4164-9F8F-665BDB0033C5 V1 EN

Functional module diagram

Freq>/< detection

The frequency detection module includes an overfrequency or underfrequency

detection based on the Operation mode setting.

In the "Freq>" mode, the measured frequency is compared to the set Start value

Freq>. If the measured value exceeds the set value of the Start value Freq> setting,

the module reports the exceeding of the value to the operate logic module.

In the "Freq<" mode, the measured frequency is compared to the set Start value

Freq<. If the measured value is lower than the set value of the Start value Freq<

setting, the module reports the value to the operate logic module.

df/dt detection

The frequency gradient detection module includes a detection for a positive or

negative rate-of-change (gradient) of frequency based on the set Start value df/dt

value. The negative rate-of-change protection is selected when the set value is

negative. The positive rate-of-change protection is selected when the set value is

positive. When the frequency gradient protection is selected and the gradient exceeds

the set Start value df/dt value, the module reports the exceeding of the value to the

operate logic module.

Protection functions

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