ABB RELION REX640 Technical Manual page 408

Protection and control

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Protection functions

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.

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.

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 cases too.

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

Table 468: PHPTUC Input signals

Table 469: PHPTUC Output signals

Current block value setting can be set to zero to not block PHPTUC with a low

1MRS759142 F

Three-phase currents

Block all binary outputs by resetting

Operate phase A

Operate phase B

Operate phase C

Start phase A

Start phase B

Start phase C

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