Page 340 - Practical Power System and Protective Relays Commissioning

Protective Relays Testing and Commissioning Chapter | 20 335

TABLE 20.3.1 Relay Test Sheet 1
Angle (degrees) R E Y E B E R Y Y B B R

Z Z Z Z Z Z
40
80
120
160
200
240
280
320
360

distance protection schemes as a permission overreach blocking scheme
to detect reverse faults and this zone is not used to trip the line. Tripping
of the line is only in the forward direction.
Table 20.3.2 can then be completed, and the line angle in reverse
zone 5 80 1 180 5 260 degrees.

TABLE 20.3.2 Relay Test Sheet 2

Angle (Degrees) Z 3 R Z 3 Y Z 3 B Z 3 R-Y Z 3 Y-B Z 3 B-R
260

The new test set generates an automatic report for the test results and
can show every point in the test passed or not passed. The test is
correctly passed based on the criteria set by the test set user.
6. Power swing detection
At fault Condition the rate of change in Impedance dz is very high, but at
dt
power swing dz is very slow. We can simulate this by decreasing the imped-
dt
ance seen by the relay in slow dz between Z ps and Z 3 Then the relay should
dt
block operation of zones 1, 2, and 3, but if we change the rate of dz to be
dt
very fast then the relay will not block and will trip by Z 1 , Z 2 ,or Z 3 operation
according to the fault location.