Signals - ABB RELION REX640 Technical Manual

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1MRS759142 C

Technical Manual

In a power factor correction application, the ALARM and START outputs can be used

as controls to switch in capacitive loads when the Alarm value and Start value settings,

respectively, are exceeded. The ALARM output is set for a higher value to add the first

corrective load and the START output set for a second stage of corrective load, if

needed. The Start reset value and Alarm reset value settings allow their respective

outputs to remain activated to maintain the correction after power factor rises as a

result, but to drop out after it reaches a level where corrective capacitive loading is no

longer needed.

There are two general applications which can best utilize under power factor

protection; power-factor control and loss of excitation.

When applying the function for power-factor control, both the start value and the start

reset value should be the same sign (positive/negative) as well as the same direction

(leading/lagging). Additionally, the absolute value of the start reset value should be

greater than or equal to the absolute value of the start value. This allows the function

to properly control any power factor controls within the system.

When applying the function for loss of excitation, both the start value and the start

reset value should be the same sign (positive/negative), but the directions should be

different (leading/lagging). This application is well-suited to protect against back-

spinning. In this case the start reset value will only come into play once the system

provides power in the opposite quadrant of the start value, for example, lagging PF

turns to leading PF.

Signals

MPUPF Input signals

MPUPF Output signals

Protection functions

Three-phase currents

Three-phase voltages

Block signal for activating the blocking mode

Signal to block the function during machine startup

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