Application; Signals - ABB RELION REX640 Technical Manual

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1MRS759142 C

Technical Manual

Once activated, the timer activates the START output and the phase-specific ST_X

output. The time characteristic is according to DT. When the operation timer has

reached the value set by Operate delay time, the OPERATE output and the phase-

specific OPR_X output are activated. If the fault disappears before the module

operates, the reset timer is activated. If the reset timer reaches the value set by Reset

delay time, the operate timer resets and the START output is deactivated.

The timer calculates the start duration value START_DUR, which indicates the

percentage ratio of the start situation and the set operating time. The value is available

through the monitored data view.

The BLOCK signal blocks the operation of the function and resets the timer.

Application

In some cases, smaller distribution power transformers are used where the high-side

protection involves only power fuses. When one of the high-side fuses blows in a

single-phase condition, knowledge of it on the secondary side is lacking. The resulting

negative-sequence current leads to a premature failure due to excessive heating and

breakdown of the transformer insulation. Knowledge of this condition when it occurs

allows for a quick fuse replacement and saves the asset.

The Start value low setting can be set to zero to not block PHPTUC with a low three-

phase current. However, this results in an unnecessary event sending when the

transformer or protected object is disconnected.

Phase-specific start and operate can give a better picture about the evolving faults

when one phase has started first and another follows.

PHPTUC is meant to be a general protection function, so that it could be used in other

In case of undercurrent-based motor protection, see the Loss of load protection.

PHPTUC Input signals

Protection functions

Three-phase currents

Block all binary outputs by resetting timers

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