Functions
2.12 Ground Fault Protection 64, 67N(s), 50N(s), 51N(s)
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
232
2.12.4 Setting Notes
General Settings
During configuration of the protection function (Section 2.1.1), under address 131 Sens. Gnd Fault it was
determined with which parameters the ground fault detection is functioning. If address Sens. Gnd Fault =
Definite Time is selected, then the definite-time parameters are available. If Sens. Gnd Fault = Log.
inverse A is set, a logarithmic inverse characteristic is available. If Sens. Gnd Fault = Log. Inverse
B is set, a logarithmic inverse characteristic with knee point is active. If Sens. Gnd Fault = User Defined
PU is selected, a user-specified characteristic can be used for the overcurrent elements 50Ns-1 or 51Ns. The
superimposed high-set element 50Ns-2 is available in all these cases. If this function is not required, then
Disabled is set. The logarithmic inverse characteristics and user characteristics are only available if under
address 130 the standard measuring method cos ϕ / sin ϕ is set.
The characteristic for determining the direction is set at address 130 S.Gnd.F.Dir.Ch. It is optional to select
either the standard measurement method cos ϕ / sin ϕ or the V0/I0 ϕ mea. with one sector charac-
teristic.
At address 3101 Sens. Gnd Fault, the function ON or OFF can be set to either ON with GF log or Alarm
Only. If settings ON and ON with GF log are applied, tripping is also possible, otherwise a fault log is created.
A ground fault log is created for ON with GF log and Alarm Only. Setting ON with GF log is only
available if characteristic V0/I0 ϕ mea. has been selected at address 130 S.Gnd.F.Dir.Ch.
The parameters 3111 T-DEL
AY Pickup and 3130 PU CRITERIA are only visible if the standard measure-
ment method cos ϕ / sin ϕ has been selected when setting the direction characteristic. The ground fault
is detected and reported when the displacement voltage was sustained a certain time T-DELAY Pickup).
Address 3130 PU CRITERIA specifies whether ground fault detection is enabled only for pickups of V
N
and
I
NS
(Vgnd AND INs) or as soon as one of the two has picked up (Vgnd OR INs).
The pickup can be stabilized for ground fault protection with definite time curve by a settable dropout time delay
(address 3121 50Ns T DROP-OUT). This facility is used in power systems with intermittent faults. Used to-
gether with electro-mechanical relays, it allows different dropout responses to be adjusted and time grading of
digital and electro-magnetic relays to be implemented. The setting depends on the dropout time delay of the
electro-magnetic relay. If no coordination is required, the preset value (zero = no dropout time delay) remains.
Note
Address 213 VT Connect. 3ph specifies how the voltage transformers are connected (phase-to-ground or
phase-to-phase). Furthermore, adjustment factor Vph / Vdelta for displacement voltage is properly set in
address 206, primary and secondary nominal transformer current in the ground path are properly set in ad-
dresses 217 and 218.
Overcurrent Elements Definite Time/Inverse Time
A two-element current/time characteristic can be set at addresses 3113 to 3120. These elements operate with
the amounts of the ground current. They are therefore only useful where the magnitude of the ground current
and maybe its direction can be used to specify the ground fault. This may be the case for grounded
systems
(solid or low-resistant) or on electrical machines
connected to the busbar of an ungrounded power system,
when in case of a network ground fault the machine supplies only a negligible ground fault current across the
measurement location, which must be situated between the machine terminals and the network, whereas in
case of a machine ground fault the total ground fault current produced by the total network is available.
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