Application of Directional Ground Overcurrent Relays to Transmission Lines

1
Application of Directional Ground Overcurrent
Relays to Transmission Lines

• John W. MillerGeorgia Power Company54th Annual
  Georgia Tech Protective Relay ConferenceMay 3-5,
  2000Atlanta, GA

2
Art versus Science
Art - There are a thousand different ways to do a
job.
Science - It only takes one way to make a mistake.
3
Comparison of Time Delayed Overcurrent Elements
4
B
N
1581 Amperes
1025 Amperes
o
o
u
r
l
c
e
r
v
o
a
s
r
s
67N
67N
d
All Lines In Study
32,627 Amperes
52,005 Amperes
on Local Bus
on Local Bus
5
All Lines In Review
6
Make Initial Default Settings
7
Find Maximum Line Out Fault
8
Increase IOC For Line Out Fault
Increase IOC
9
Review Reach of Instantaneous Unit
10
Mutual Coupling Effects
115 kV Current
3632 A coming in
1842 A going out
at Boulevard
B
N
115 kV Line Under Study
o
o
u
r
l
c
e
r
67N
67N
v
o
7672 Amperes
3787 Amperes
a
s
r
s
d
230 kV Mutual Line
Mutual Line Sliding Fault
67N
67N
33617 Amperes
54534 Amperes
on Local Bus
on Local Bus
11
Review of Induced Currents on Coupled Line
Out
In
12
Apply End Of Line Fault On Coupled Line
Induced Current
B
N
115 kV Line Under Study
o
o
u
r
l
c
e
r
67N
67N
v
o
a
s
End of Line Fault
r
s
d
230 kV Mutual Line
Remote Operates First
67N
67N
13
Plot Induced End Of Line Fault Current
14
Plot of Induced Current from End of Line Fault
15
Instantaneous Overreach from Mutual Effect
16
Additional Increase of Instantaneous Setting
Increase IOC
17
Plot of Revised Settings
18
Plot of Reduced Instantaneous Sensitivity
19
Remote End of Line Fault Review
20
Actual Transmission Corridor
2nd 115 kV Mutual Line
115 kV Current
3632 A coming in
1842 A going out
at Boulevard
B
N
115 kV Line Under Study
o
o
u
r
l
c
e
r
67N
67N
v
o
7672 Amperes
3787 Amperes
a
s
r
s
d
230 kV Mutual Line
67N
67N
2nd 230 kV Mutual Line
21
Actual Existing Settings for 115 kV Line
22
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