ISLAMABAD: A massive power breakdown on Thursday morning left nearly half the country — inclu­ding the most populous provinces of Sindh and Punjab — without elec­tricity throughout the day, exposing the weaknesses of the country’s fragile transmission network.

Attributed to an “accidental fault” by Power Minister Khurram Dastgir Khan, this is the third such event since Sept 1 last year.

The fault is said to have occurred near Karachi around 9:15am, and led to full to partial closure of power to the Hyderabad, Sukkur, Multan and Faisalabad and Lahore electric supply companies as well as K-Electric, when power plants supplying more than 8,500MW shut down within minutes of each other in a cascade effect.

Mr Dastgir said human error could be behind the fault, but he could not comment on this until the inquiry committee filed its report in four days. “We have to find the actual cause, whether it was an accident or there was another reason,” he added.

Disruption in two 500kV lines near Karachi ‘cascades’ to other areas; power division estimates full recovery by Friday

By 9pm, the power division said that transmission network had been fully restored after the disruption in two 500kV lines south of Karachi was cleared and power supply from alternative plants was gradually enhanced.

It was hoped that full recovery would be achieved by Friday morning, but the ministry later stated at around 10pm that about half of the 1,000MW supply to KE from the national grid had been revived, to be followed by normal supply over the next few hours.

The National Transmission & Despatch Company (NTDC) — responsible for the national grid — constituted a four-member committee of its own officers to probe the reasons behind the causes of the partial blackout within four days.

NTDC experts Dawn spoke to, however, suggested that the breakdown originated due to overloading of the 27-year-old existing lines near two major 2,200MW nuclear power plants because of a delay in completion of new lines, which should have been ready before these two plants.

Officials suggested that the power generated by K2 and K3 was being evacuated through two 500kv transmission lines of NK1 Jamshoro and Hub-Jamshoro, which were already overloaded and obsolete as they were commissioned in 1995.

It is believed that the NK1-Jamshoro line fell down, shifting the entire 2200mw load to Hub-Jamshoro line, which could not sustain it.

In a spur of the moment decision, the system operator tried to shift partial load to Port Qasim-Matiari line, which also could not be immediately energised as the Port Qasim plant was already closed. This resulted in the automatic closure of a number of other power plants of about 1,800MW, resulting in a cascading effect that affected 500kv and 200kv lines upto to Gati-Faisalabad.

This also closed power supply to Hesco, Sepco, Mepco and Fesco, and to some extent Lahore through the Matiari-Lahore 600kv High Voltage Direct Current transmission line. With exit of Lahore-Matiari, around 8,500 to 9,000MW went out of the system, an NTDC officer said, although the power minister put the shortfall from closure of plants at 8,000MW.

Another senior power sector expert said the occurrence should not be seen in isolation, given that a series of similar events over the past 6 to 7 years. In this time, NTDC has only been able to put in place a system that allowed them to save distribution companies in cities like Gujranwala, Islamabad, Peshawar, Quetta and the erstwhile tribal areas from being affected.

The expert said that Pakistan’s national grid is quite different from others in the world; the hydropower stations are mostly located in the north, which provide VAR (Voltage Ampere Reactive) support to stabilise the main power generation capacity, which is installed either in the mid-country or mostly in the south. On the other hand, renewable sources like wind and solar are located mostly in the south, which cause instability of the national grid but can be balanced either through Static VAR Compensation (SVCs) or battery banks, which are both missing at this stage.

As a result, the transmission network is inherently not that stable and any imbalance can lead to a major breakdown. The only success achieved over the last five years has been that north and south turn into island modes and do not cause countrywide blackout as this time.

Published in Dawn, October 14th, 2022