The country was held hostage by a faulty circuit breaker
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.
Initial reports suggested the frequency within the electrical grid had dropped to critically low levels. It caused grid stations around the country to shut down automatically.
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.