Woodward ESDR 4T, Руководство пользователя

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Manual 37138C ESDR 4T - Current Differential Protection Relay
© Woodward Page 35/46
Testing for Correct Connection
The excitation should be set so that the generator is loaded to approx. 20% rated current. If the connections are
correct, the displayed differential current should be approximately zero. The displayed restraint current should be
checked using an external measuring device. Record all measured values.
Restraint current
% 100
(sec)
(sec)
) (
) (
⋅ ⋅ ⋅ =
m
N
B
W
prim W
a s
I
I
k
I
I
I
I
m(sec)
Measured value
I
s(a)
Restraint current display value on ESDR4T
I
w(prim)
Primary transformer rated current [A]
I
w (sec)
Secondary transformer rated current [A]
I
N
Rated current of the protection object (reference value)
k
B
Reference factor
The value calculated using this ratio must be the same for both the high and low-voltage sides. If the currents
displayed are not of approximately the same magnitude, or if high differential currents are already displayed, the
equipment should be shut down and the transformer assignment checked.
Testing with Cyclical Swapping
With the system off, the secondary connections of the CTs should be rotated between phases. Turn the system on
and increase the excitation to gradually increase the load current. .
The resulting displayed values must be in accordance with the following:
) ( ) (
3 2
a S a d
I I
⋅ ⋅ =
%) 100 (
2
1
(sec)
(sec)
) (
) (
⋅ ⋅ ⋅ ⋅ =
m
N
B
W
prim W
a s
I
I
k
I
I
I
I I
s(a)
Restraint current display value
I
d(a)
Differential current indicated value
I
w(prim)
Primary transformer rated current [A]
I
w (sec)
Secondary transformer rated current [A]
I
N
Rated current of the protection object (reference value)
k
B
Reference factor
I
m(sec)
Measured value
During this test it is possible that the threshold value may be exceeded causing the relay to trip.
Attention
In the event of an extreme tripping, it must be ensured that the trip does not open the short-circuit
bridge (in this case a tripping of the breaker would lead to large overvoltages).
If these current relationships are correct, the equipment can be shut down and the original condition restored..