Page 337 - Practical Power System and Protective Relays Commissioning

332 Practical Power System and Protective Relays Commissioning

Subchapter 20.3

Distance Protection Testing and
Commissioning

20.3.1 SECONDARY INJECTION TEST
In this test we will inject voltage and current (fixed current) as per the manu-
facturer’s test.
Recommendation 1 or 2 A. For the Current Transformer (CT) with rated
current of 1 A we decrease the voltage until we reach the zone reach for
pH-E and pH pH characteristic for each phase R, Y, B and R-Y, Y-B, B-R
phases as shown below:
1. Relay data
CT 5 2000/1 500 kV Transmission Line (TL)
Phase-E characteristic Mho relay, pH pH characteristic, quadrilateral
characteristic.
Z 1 , Z 2 , Z 3 are given by relay setting engineer for pH-E and pH pH
where:
K 0 5 residual earth compensation factor.
ðZ 0 2 Z L Þ
K 0 5 0:6 5
3Z L
Z 1 5 positive-sequence impedance of TL
Z 0 5 zero-sequence impedance of TL
500; 000 100
VT ratio 5 =
O3 O3

CT ratio 2000
Z s 5 Z p 5 Z p
VT ratio 5000
(Z s 5 Z p 0.4) and Z 3 reverse 5 0.25Z 1 5 5.25+ 260 degrees
Z 1 5 21 Ω+80 degrees t 1 5 0
Z 2 5 26 Ω+80 degrees t 2 5 500 ms
Z 3 5 33 Ω +80 degrees t 3 5 1000 ms
Z power swing 5 Z ps 5 1.3Z 3 5 42.9 +80 degrees blocking action after
t 5 5 seconds.
Fig 20.3.1 Relay characteristic for pH-E and pH pH.
2. Pretest procedures:
1. The current circuit of the CT secondary should be short-circuited if
the relay is to be tested in load condition.