Sensitive Earth Fault Protection; Definite Time Sensitive Earth Fault Protection - NR Electric PCS-9611 Instruction Manual

3 Operation Theory
34 A.50/51G4.OutMap
35 A.50/51G4.Opt_Curve
36 A.50/51G4.TMS
37 A.50/51G4.tmin
38 A.50/51G4.K
39 A.50/51G4.C
40 A.50/51G4.Alpha

3.6 Sensitive Earth Fault Protection

3.6.1 Definite Time Sensitive Earth Fault Protection

This relay provides a four-stage sensitive earth fault protection with independent definite time
delay characteristics. Each stage can be enabled or disabled independently by the corresponding
logic setting respectively, and can be controlled by the directional element respectively. The stage
4 SEF also can be set with inverse definite minimum time (IDMT) characteristic. Each stage can
be used for tripping or alarming through the PCS-Explorer and the default is for tripping.
When this relay is used in non-effective grounding (such as the delta side of a transformer) or
small current grounding system, the grounding zero sequence current during earth fault is
basically small capacitive current. Correct selection of faulty phase in zero sequence protection
can not be ensured by detection of such a current. One current transformer input is dedicated to
the sensitive earth fault (SEF) protection. The input CT is designed specially to operate at very low
current magnitudes.
The following figure shows the stage 1 sensitive earth fault protection logic diagram, other stage
has the same logic diagram.
I > [50/51SEF1.3I0_Set]
0S
50/51SEF1.Dir
[50/51SEF1.En]
[50/51SEF1.En1]
[50/51SEF1.Blk]
Figure 3.6-1 Logic diagram for the stage 1 sensitive earth fault protection
Where:
[50/51SEF1.3I0_Set] is the current setting of the stage 1 sensitive earth fault protection;
3-28
The output matrix setting of the No.2 stage 4 zero
sequence overcurrent protection
The setting is for selecting the inverse time
characteristic curve for the No.2 ROC4 protection
The time multiplier setting of the No.2 stage 4
zero sequence IDMT overcurrent protection
The minimum operation time setting of the No.2
stage 4 zero sequence IDMT o vercurrent
protection
Constant "k" for the No.2 stage 4 zero sequence
IDMT o vercurrent protection, see Section 3.5.2
Constant "C" for the No.2 stage 4 zero sequence
IDMT o vercurrent protection, see Section 3.5.2
Constant "α" for the No.2 stage 4 zero sequence
IDMT o vercurrent protection, see Section 3.5.2
&
Date: 2014-04-08
[50/51SEF1.St]
t 0
SEF1
[50/51SEF1.Op]
0x00000 ~
1
0xFFFFF
0~13 1
0.05~100.0 0.001
0~100s 0.001s
0.001~120.0 0.0001
0.00~1.00 0.0001
0.01~3.00 0.0001
PCS-9611 Feeder Relay