WARNING
Before starting the test, open any triggering circuits for external devices so
that no inadvertent switching operations will take place.
10.2.5 Checking the Protection Function
Four parameter subsets are stored in the P634, one of which is activated. Before
checking the protective function, the user should determine which parameter
subset is activated. The active parameter subset is displayed at PSS: Actual
param. subset (Oper/Cycl/Log menu branch).
10.2.5.1 Checking Differential Protection
For single-side feed, the fault current characteristic crosses the first knee of the
tripping characteristic of the P634 so that the basic threshold value is always
checked.
The current I to which the P634 responds for single-side feed is calculated as
follows:
I =
I
diff >
⋅ I
nom,z
k
am,z
●
z: transformer end (a, b, c, d)
●
I
diff>
: set operate value
●
I
nom,z
: nominal current of the P634 for transformer end a, b, c, d
●
k
am,z
: amplitude-matching factor of transformer end a, b, c, d
For single-side one-phase or two-phase feed, a vector group-matching factor in
accordance with the set vector group ID needs to be taken into account in
addition to the amplitude-matching factor. The vector group-matching factors are
given in the tables below and the threshold current is calculated as follows:
I ≥
I
diff >
⋅ I
nom,z
k
am,z
⋅ k
s,y,z
●
z: transformer end (a, b, c, d)
●
I
diff>
: set operate value
●
I
nom,z
: nominal current of the P634 for transformer end a, b, c, d
●
k
am,z
: amplitude-matching factor of transformer end a, b, c, d
●
k
s,y,z
: vector group-matching factor (see tables below)
The differential and restraining currents formed by the P634 are displayed as
measured operating data. They aid in assessing whether the connection of the
P634 to the system current transformers and the setting of the vector group ID
are correct. The tables below give the factors ks which serve to calculate the
differential current for single-side feed. The display of differential and restraining
currents is prevented, however, if they fall below minimum thresholds that can
be set by the user.
I
d,y
= k
am,z
·k
s,y,z
·I
test,x
10 Commissioning
P634
P634/EN M/R-42-A // P634‑311‑653 10-7
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