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.
4.1.4.5 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 Current block value 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
cases too.
In case of undercurrent-based motor protection, see the Loss of load protection.
4.1.4.6 Signals
Table 277: PHPTUC Input signals
Name
Type Default Description
I_A SIGNAL 0 Phase A current
I_B SIGNAL 0 Phase B current
I_C SIGNAL 0 Phase C current
BLOCK BOOLEAN 0=False Block all binary outputs by resetting timers
Table 278: PHPTUC Output signals
Name
Type Description
OPERATE BOOLEAN Operate
OPR_A BOOLEAN Operate phase A
OPR_B BOOLEAN Operate phase B
OPR_C BOOLEAN Operate phase C
START BOOLEAN Start
ST_A BOOLEAN Start phase A
ST_B BOOLEAN Start phase B
ST_C BOOLEAN Start phase C
1MRS758755 A Section 4
Protection functions
REC615 and RER615 261
Technical Manual
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