DOC. MIE91093 Rev. 1.34
Page 103 of 145
3) Zone limits test
Given the fault impedances Z1, Z2, Z3, Z4 of the zone limits,
compute as follows the corresponding fault voltages V1, V2,
V3, V4:
Vf = Z*If
For instance: If = 10 A
Vf = 10 * Z
These voltages are the limits between following zones, as with
the other faults.
Once fault current and pre-fault voltage amplitudes have been
adjusted to VN, stop the test and start again. Adjust all fault
voltages at a value slightly less than V1, VT31: the trip time
should be the one of zone 1. Slightly increase the fault
voltages and start again with value VT32: trip time should
become T2. The procedure can be repeated at will, until the
first zone is checked with the desired accuracy: the result is
Z1 = (VT31+VT32)/(2*If)
Once a limit has been found, repeat the test for other zone
limits. During these tests, current and phase are no more
modified.
Example. Let us assume that the distance relay to be tested
has the following settings at line angle (75°).
ZONE LIMIT
ONE
TWO
THREE STARTER
IMPEDANCE
Ohm
0.2
0.4
1
2
TIMING
s
0.05
0.3
0.6
1.2
Let us assume: IV0 = 2.5 A; VN = 57.8 V (100 V). Maximum
test current is:
IMAX = 57.8/2 = 28.9 A.
