Sef - Toshiba GRE110 Instruction Manual

SE3 0.001 – 0.250 A
TSE3 0.00 – 300.00 s (*1)
SE4 0.001 – 0.250 A
TSE4 0.00 – 300.00 s (*1)
[SE1EN] Off / On
[MSE1] DT / IEC / IEEE / US / C
[MSE1C]
MSE1C-IEC NI / VI / EI / LTI
MSE1C-IEEE MI / VI / EI
MSE1C-US CO2 / CO8
[SE1R] DEF / DEP
[SE1S2] Off / On
[SE2EN] Off / On
[MSE2] DT / IEC / IEEE / US / C
[MSE2C]
MSE2C-IEC NI / VI / EI / LTI
MSE2C-IEEE MI / VI / EI
MSE2C-US CO2 / CO8
[SE2R] DEF / DEP
[SE3EN] Off / On
[SE4EN] Off / On
(*1) Time setting of TSE1 – TSE4 should be set in consideration of the SEF drop-off time
80-100ms.

SEF

SEF is set smaller than the available earth fault current and larger than the erroneous zero-phase
current. The erroneous zero-phase current exists under normal conditions due to the unbalanced
feeder configuration. The zero-phase current is normally fed from a core balance CT on the feeder,
but if it is derived from three phase CTs, the erroneous current may be caused also by the CT error
in phase faults.
The erroneous steady state zero-phase current can be acquired on the metering screen of the relay
front panel.
High impedance REF protection
CT saturation under through fault conditions results in voltage appearing across the relay circuit.
The voltage setting of the relay circuit must be arranged such that it is greater than the maximum
voltage that can occur under through fault conditions. The worst case is considered whereby one
CT of the balancing group becomes completely saturated, while the others maintain linear
operation. The excitation impedance of the saturated CT is considered to approximate a
short-circuit.
0.001 A 0.100 A SEF3 threshold setting
0.01 s 0.00 s SEF3 definite time setting.
0.001 A 0.250 A SEF4 threshold setting
0.01 s 0.00 s SEF4 definite time setting.
On SEF1 Enable
D SEF1 characteristic
SEF1 inverse curve type.
NI Required if [MSE1] = IEC.
MI Required if [MSE1] = IEEE.
CO2 Required if [MSE1] = US.
DEF SEF1 reset characteristic. Required if
[MSE1] = IEEE or US.
Off SEF1 stage 2 timer enable
Off SEF2 Enable
D SEF2 characteristic
SEF2 inverse curve type.
NI Required if [MSE2] = IEC.
MI Required if [MSE2] = IEEE.
CO2 Required if [MSE2] = US.
DEF SEF2 reset characteristic. Required if
[MSE2] = IEEE or US.
Off SEF3 Enable
Off SEF4 Enable
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6 F 2 T 0 1 7 2