Operation Principle - ABB RELION REX640 Technical Manual

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Protection functions

Analog signals

See the preprocessing function blocks in this document for the

possible signal sources.

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 Operation setting. The

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

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

modules in the diagram are explained in the next sections.

GUID-7BF39A6D-DAC5-43DF-8D35-26138AE01FBB V1 EN

Functional module diagram

Level detector 1

This module compares the phase currents (RMS value) to the set Start value high

setting. If all the phase current values are less than the set Start value high value, the

loss of load condition is detected and an enable signal is sent to the timer. This signal

is disabled after one or several phase currents have exceeded the set Start value high

value of the element.

Level detector 2

This is a low-current detection module, which monitors the de-energized condition of

the motor. It compares the phase currents (RMS value) to the set Start value low

setting. If any of the phase current values is less than the set Start value low, a signal

is sent to block the operation of the timer.

Three-phase currents

1MRS759142 C

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