Major parts of Punjab and Khyber Pakhtunkhawa on Friday suffered a power breakdown as Tarbela and Mangla power houses tripped on Friday morning because a 500 kV line broke down near Muzaffargarh. Consumers in Rawalpindi/ Islamabad Lahore, Gujranwala, Sheikhupura, Sialkot, Faisalabad, Gujrat, Muzaffargarh, Peshawar. Haripur, Nowshera, etc, remained without electricity for at least seven hours.
According to official spokesperson, at 9.21am, the 500 kV transmission line between Muzaffargarh and Multan tripped due to excess generation which put the entire NTDC system under a serious stress.
"When transmission lines trip, generation exceeds demand, supply comes backward, as a result the entire system trips and generators operate on an island mode," explained an official.
Since the NTDC system protection had been upgraded in the aftermath of last year''s blackout, the zoning mechanism was activated and the south and north regions operated in separate islands.
The four Discos in south remained by and large unaffected. However, the generation units tripped in north zone due to higher loads than the available generation. The Secretary Water and Power and the NPCC officials gathered in the control room and the generation units were restarted gradually. The supplies to bigger cities were restored within 2-3 hours.
The circuit system of 220 kV and 500 kV was completely restored by 12.45 am. The supply load gradually increased and all DISCO supplies normalised by 4.45pm.
The system protection measures taken in 2015 have positively contributed towards better handling of such emergencies this time, when the system was restored in a shorter time as compared to the previous occasions when it took more than 24 hours to restore supplies.
An official told Business Recorder that Mangla dam, Tarbela dam and Ghazi Barotha dam operated in island modes.
He further stated that the generator continuously functions in island mode but its synchronisation takes time, frequency of hydel system and thermal system are entirely different.
An official told this scribe that Secretary Water and Power, Younus Dagha has constituted a committee to hold an inquiry into the blackout incident and submit a report to the Ministry which will subsequently be presented to the Prime Minister.