The P634 calculates the negative-sequence current from the three phase current
values according to this equation. This is based on the setting at MAIN: Phase
sequence.
Phase sequence A-B-C:
I
neg
=
1
3
⋅
| (
I
A
+ a
2
I
B
+ aI
C
) |
Phase sequence A-C-B:
I
neg
=
1
3
⋅
| (
I
A
+ aI
B
+ a
2
I
C
) |
a = e
j120°
a
2
= e
j240°
The negative-sequence current is monitored by the P634 with three-stage
functions to detect when it exceeds the set thresholds. One of two different
threshold types can be active. The “dynamic” thresholds are active for the set
hold time for the “dynamic parameters” (see Section 3.12.8, (p. 3-88)) and the
“normal” thresholds are active when no hold time is running. If the current
exceeds the set thresholds in one phase, timer stages are started. Once the time
delays have elapsed, a trip signal is issued. The timer stages can be blocked by
appropriately configured binary signal inputs.
The first stage of the negative-sequence current protection function can
optionally be blocked by the inrush stabilization function of differential
protection.
3.23.4 Residual Current Stages
The residual current is monitored by the P634 with three-stage functions to
detect when it exceeds the set thresholds. One of two different threshold types
can be active. The “dynamic” thresholds are active for the set hold time for the
“dynamic parameters” (see Section 3.12.8, (p. 3-88)) and the “normal”
thresholds are active when no hold time is running.
If the residual current exceeds the set thresholds, timer stages are started. Once
the time delays have elapsed, a signal is issued. If the operating mode of the
general starting decision is set to With start. IN/Ineg, a trip signal is issued as
well.
There is also a separate setting for each residual current stage whether the
starting decision shall be based on the fundamental or on the r.m.s. value.
The timer stages can be blocked by appropriately configured binary signal
inputs. In addition these timer stages can also be automatically blocked by
single-pole or multipole starting (depending on the setting).
3 Operation
P634
P634/EN M/R-42-A // P634‑311‑653 3-157
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