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
addresses 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.
IEC/ANSI characteristics
For an inverse time element 51Ns, a characteristic according to IEC or ANSI standards may be used. These
characteristics can be employed for the measurement method cos φ / sin φ.
The type of IEC characteristic can be selected under address 3144 51Ns IEC CURVE. Setting options that can
ve selected are Normal Inverse, Very Inverse, Extremely Inv. and Long Inverse.
The type of ANSI characteristic can be selected under address 3145 51Ns ANSI CURVE. Setting options that
can be selected are Very Inverse, Inverse, Short Inverse, Long Inverse, Moderately Inv.,
Extremely Inv. and Definite Inv..
As dropout time, set under address 3146 51Ns Drop-out Instantaneous or Disk Emulation.
Logarithmic Inverse Time characteristic (Inverse Time)
The logarithmic inverse time characteristic is only used for the standard measurement method cos φ / sin
φ (address 130 S.Gnd.F.Dir.Ch).
The characteristic (see Figure 2-94) is set with the parameters 3119 51Ns PICKUP, 3141 51Ns Tmax, 3140
51Ns Tmin, 3142 51Ns TIME DIAL and 3143 51Ns Startpoint. 51Ns Tmin and 51Ns Tmax deter-
mine the tripping time range. The slope of the curve is defined in 3142 51Ns TIME DIAL. 51Ns PICKUP is
the reference value for all current values with 51Ns Startpoint representing the beginning of the curve,
i.e. the lower operating range on the current axis (related to 51Ns PICKUP). This factor is preset to the value
1.1, analogously to the other inverse time curves. This factor can also be set to 1.0 since in logarithmic inverse
curves the tripping time on a current value, which is identical to the specified pickup threshold, does not
approach infinity, but has a finite time value.
Functions
2.13 Ground Fault Protection 64, 67N(s), 50N(s), 51N(s)
SIPROTEC 4, 7SJ62/64, Manual 213
C53000-G1140-C207-8, Edition 08.2016
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