Punjab Islanding Scheme - Northern Regional Power Committee

switching action is required.
ii)
The proposed island scheme shall required to be configured /reconfigured
for peak and off peak operating conditions. The preidentified
relays ( UFRs) at the sub stations shall be enabled during off
peak period to cover the extended load , to match the available
generation. These relays shall be disabled during peak period.
iii)
The proposed islanding scheme operations consists of three stages as
under;-
a) Stage I: When frequency dips to level of 47.9 Hz
b) Stage II: When frequency further dips to level of 47.7 Hz
c) Stage III: When frequency stays at 47.7 Hz*
* additional load shedding at an interval of 300
milli-seconds up to 2 seconds in steps
iv)
Disconnection of feeders will be triggered through UFRs proposed to
be installed at Sub stations. Two independent relays, for sensing the
frequency from each bus of sub station shall be provided at each of the
sub station falling under the islanding zone, classified as under:
Relay on Bus-1 = M1 and S1
Relay on Bus-2 = M2and S2
v) Up to 3 no 220 KV feeder will have dedicated set of relays (M1 and
M2) whereas in case of 66 KV feeders, one set of relay (S1 and S2)
will control up to four 66 KV feeders. S1 & S2 shall also control high
frequency swings in the island by operating at 50.5 Hz & 51.0 Hz for
auto reclosing the pre-identified feeders.
The setting of relays shall be as under:-
M1 M2 47.9 Hz
S1 S2 47.7 Hz
S1 S2 50.5 Hz (for Auto reclosing)
S1 S2 51.0 Hz (for Auto reclosing)
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