Poor maintenance of transmission circuitry caused the nationwide blackout on Saturday, the National Transmission and Dispatch Company said Tuesday.
It blamed human error for the fault that plunged the country
into darkness. The circuit breaker that tripped had been maintained without
supervision of the National Power Control Center, the NTDC said in its report.
Pakistan was without electricity on the intervening night of
January 9 and 10. It took the government over 24 hours to restore power supply.
suggested the frequency within the electrical grid had dropped to critically
low levels. It caused grid stations around the country to shut down
In a simple circuit, such as a battery powering a torch,
electricity flows in a single direction around the circuit. However, in
sophisticated circuits such as national power grids, electricity switches
directions back and forth several times a second. The frequency is the number
of times the current switches directions per second.
Seven employees of the Central Power Generation Company Ltd in
Guddu were suspended
in connection with the breakdown Sunday.
The NTDC report to the Ministry of Energy said a breaker in
the CPGC switchyard was grounded for maintenance but the day shift didn’t turn it
off at the end of duty hours. The night shift, unaware of any error, switched
off the breaker without undoing the earthing. As a result, the power plant and
its transmission lines tripped. As the low frequency spread around the
nationwide grid, other stations tripped too and the country plunged into darkness.
The circuit breaker in the switchyard was switched off
directly from the control room, which was against procedures, according to NTDC.
The National Power Control Center said that no approvals were sought or given
for the maintenance of the breaker, it added.