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 296: 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 out-
puts by resetting
timers
Table 297: 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
Table continues on the next page
1MRS758755 C Protection functions
REC615 & RER615
Technical Manual
275
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