Manual 37138C
ESDR 4T - Current Differential Protection Relay
Page 34/46
© Woodward
Differential Current Testing Using Single-Sided Three-Phase Supply
The operating limit can be approached by slowly increasing the test current. The tests can be carried out consecu-
tively on the high and low-voltage sides.
Threshold value:
the threshold value in A is generated from the following ratio
B
N
ESDR
d
prim
W
W
a
d
k
I
I
I
I
I
⋅
⋅
=
%
100
)
(
)
(
(sec)
)
(
I
d(ESDR)
Differential current setting value [%]
I
w(prim)
Primary transformer rated current [A]
I
w (sec)
Secondary transformer rated current [A]
I
d(a)
Differential current threshold value
I
N
Rated current of the protection object (reference value)
k
B
Reference
factor
Reference factor k
B
:
the reference factor is used for standardization on the reference side.
Low-voltage side:
1
=
B
k
High-voltage side:
)
(
)
(
LV
Tr
HV
Tr
B
V
V
k
=
V
TR(LV)
Transformer rated voltage (low-voltage side)
V
TR(HV)
Transformer rated voltage (high-voltage side)
Example:
I
d(ESDR)
20 % = 0.2
I
w(prim, HV)
100
A
I
w (sek, HV)
5
A
I
w(prim, LV)
400
A
I
w (sek, LV)
5
A
U
Tr(HV)
20.0
kV
U
Tr(LV)
6.3
kV
I
N
350
A
175
,
3
3
.
6
0
.
20
=
=
kV
kV
k
B
Low-voltage side:
A
A
A
A
I
LV
a
d
875
.
0
1
350
%
100
%
20
400
5
)
,
(
=
⋅
⋅
=
High-voltage side:
A
A
A
A
I
HV
a
d
10
.
1
175
.
3
350
%
100
%
20
100
5
)
,
(
=
⋅
⋅
=
Commissioning Using Primary Values
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
Prior to commissioning a unit, the following must be verified:
•
All test equipment must be removed from the system
•
There are no open circuits on any current transformer
During commissioning, the system should be configured to permit for the finest current adjustment. This can be
accomplished by:
•
Utilizing suitable jumpers (observe current carrying capacity) for unit connections on the high-voltage
side of the transformer
•
Disabling the automatic voltage regulator and manually adjusting the excitation current
