Siemens 7SC80 Manual page 255

tion voltage 3 · V
Parameter 213 VT Connect. 3ph in Section
the calculation of the summation voltage 3 · V
voltage inputs must therefore be connected to the voltage transformers in a grounded-wye configuration.
When setting Vab, Vbc, VGnd, the three phase-to-ground voltages of both connected phase-to-phase
voltages and the connected displacement voltage are calculated. If the device is only provided with phase-to-
phase voltages, it is not possible to calculate a displacement voltage from them. In this case, the direction
cannot be determined.
If the displacement voltage is calculated, then:
3 · V = V + V
0 A B
If the displacement voltage is directly applied to the device, then V
not affected by parameter Vph/Vdelta (address 206).
Pickup performed by the displacement voltage can be delayed (64-1 DELAY) for tripping.
It is important to note that the total trip-command time then consists of the displacement voltage measure-
ment time (about 50 ms) plus the pickup delay time 64-1 DELAY.
After the voltage element picks up due to detection of a displacement voltage, the grounded phase is identi-
fied, if possible. For this purpose, the individual phase-to-ground voltages are measured or calculated, irre-
spective of the connection type of the voltage transformers. If the voltage magnitude for any given phase falls
below the set threshold VPH MIN, that phase is detected as the grounded phase as long as the remaining
phase-to-ground voltages exceed the set threshold VPH MAX.
[7sj6x_erdschlussbehaftete_phase-150502-kn, 1, en_US]
Figure 2-87
Current Elements
There are two current elements available. Both elements operate directionally, whereby the tripping zones can
be set individually for each element (see margin heading "Tripping Range").
Both elements are provided with a definite time characteristic. Two current/time elements are used for ground
fault protection. Analog to the time overcurrent protection function, the overcurrent element is named
50Ns-1 PICKUP and 50Ns-1 DELAY and the high-set element 50Ns-2 PICKUP and 50Ns-2 DELAY.
The pickup of the definite time overcurrent protection can be stabilized by the configured dropout delay time
(address 3121 50Ns T DROP-OUT).
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017
can be calculated according to the connection type of the voltage transformer (see also
0
+ V
C
Determination of Ground-faulted Phase
2.13 Ground Fault Protection 64, 67N(s), 50N(s), 51N(s)
2.1.3 Power System Data 1). When setting Van, Vbn, Vcn,
is based on the three phase-to–ground voltages. The three
0
is the voltage at the device terminals. It is
0
Functions
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