A POWER transmission fault in 500kV grid station of National Transmission and Despatch Company (NTDC) off Indus Highway led to a major electricity breakdown on June 30 once again. An inquiry is underway but it perhaps calls for an evaluation of NTDC’s grid stations’ and distribution companies’ working across Sindh. Sindh’s power distribution network, except for the provincial metropolis of Karachi, is managed by Hyderabad Electric Supply Company (Hesco) and Sukkur Electric Supply Company (Sepco) separately.
NTDC manages 500kV and 220kV grid stations that supply power to distribution companies of the Water and Power Development Authority (Wadpa). The distribution companies manage their 132kV grid stations which are fed by NTDC’s above-mentioned two systems. A huge electricity spark in NTDC’s grid station — located at a small distance from the Jamshoro Thermal Power House — on June 30 disrupted the electric supply to 13 districts of lower Sindh, falling in the jurisdiction of Hyderabad Electric Supply Company (Hesco).
This grid station — considered one of the major NTDC installations in Sindh — feeds around 600 megawatts of electricity to K-Electric through Northern-Karachi Interconnections (NKI) station and 800 megawatts to Hesco. Apart from such supplies, it is a part of the national grid system connected through Dadu, Shikarpur and Guddu under a ‘ring’ like system.
The electric supply system within a 500kV grid station works at different levels before a normal power supply reaches end-users through transformers. The system involves electricity that is generated in different power plants and reaches 500kV and 200kV grid stations. Hesco’s transmission lines or conductors are hooked to these installations through company’s 132kV transmission lines to receive the electric supply.
“It is just like the water distribution system through River Indus to the agriculture, industrial, commercial and domestic sectors where the mighty Indus doesn’t supply water to consumers directly. While the river remains the main source of freshwater, the dams, barrages, off-taking canals, distributaries and water lagoons of civic bodies serve as the water distribution network across Pakistan”, explains an NTDC official.
Multiple stages are involved in a power supply system before electricity reaches consumers. Electricity from powerhouses is received by a 500kV grid station/system first. It then reaches the 220kV grid station located on the same premises through a ‘step down system’. Eventually, it enters a 132kV system through an identical ‘step down’ process to be finally supplied to consumers through distribution companies’ 11kV lines, emanating from their several separate 132kV grid stations in the region.
Sensitive equipment worth millions of rupees is installed in grid stations. Sometimes, even a minor fault leads to a major disruption in the electric supply system, causing damage that requires days to fix. Wind, dust storms and heavy rainfall in coastal areas and hilly terrain can uproot pylons. Such a situation takes weeks to rebuild the structure and to energise the system.
Following the June 30 incident, major damages were not reported in the system but a final word has to come after the conclusion of the ongoing inquiry. Electric supply to most parts of lower Sindh was normalised by Hesco. Complaints from several areas about the frequent tripping in the power utility’s system, however, kept pouring in till July 3.
NTDC sources claim fault on June 30 occurred first in Hesco’s Qasimabad’s 132kV system which is called the Jamshoro-Qasimabad grid station and then the isolator of the Jamshoro-Rajputana 132kV station got burnt. The fault led to a fire in the yard of NTDC’s grid station which was extinguished by the staff of the grid station to avert major damages. Isolators and conductors were burnt.
“The Jamshoro-Rajputana fault produced a huge electricity spark in the 500kV grid station which was witnessed by people miles away in Hyderabad and Latifabad at 1:45 am”, says an official. He points out that in the three-phase system, the grid station receives from three different poles and on that day two of the poles were functional in Hesco’s Qasimabad 132kV grid whereas NTDC’s three-pole system worked normally in Jamshoro.
One NTDC official with somewhat sound knowledge of the system claims that the safety system, called the “over current relay” and the “distance relay”, which senses the ‘fault in offing’ didn’t respond, resulting in the incident. But luckily, the 450MVA transformer remains safe, he says and adds that the inquiry team must find whether the concerned executive engineers and sub-divisional officers did their job of examining the protection system.
Another official — posted at one of NTDC’s grids — observes that Hesco is unable to ensure proper upkeep of its 132kV grid stations where the equipment is many years old. And the June 30 problem occurred at their end in the Qasimabad 132KV grid station which then affected the 500kV grid station and caused a fire in the yard.
Hesco’s official position, however, has been that fire occurred in the yard of the 500kV grid station and disrupted the power supply to 66 grid stations which get electricity from two NTDC’s 220kV Tando Mohammad Khan road and Hala Naka gird stations besides the 500kV Jamshoro grid station. Its spokesman Sadiq Kubar says due to NTDC’s system, Hesco’s whole network was affected. “There is no issue in our 132 kV grid stations”, he says.
Notwithstanding Hesco’s claim, its 11kV distribution lines/network is, by and large, fragile. It cannot cope with mild storms or moderate-intensity rain, making devastating monsoonal rains seen last summer a nightmare for Hesco’s power consumers in 13 districts.
It doesn’t cope well with mild storms or even with moderate intensity rains what talk of devastating monsoonal rains. What was seen in last summer rains was just a nightmare for power consumers of Hesco in its 13 districts. Prolonged and frequent power outages primarily affected civic agencies’ pumping stations thus leading to urban flooding. The power utility’s system fails to respond to emergencies, multiplying people’s miseries.
The veteran Wapda leader Abdul Nizamani is concerned about the lack of regular upkeep of the system, be it NTDC or Hesco, which not only damages system but claims the lives of lower-scale employees in fatal incidents. “After the June 30 incident, we bought expensive electricity from private producers which is a national loss. We need investment in the system and we should examine options of erecting heavy transmission lines carrying pylons in areas which are easily accessible for maintenance purpose”, he asserts.
NTDC is a federal body which was once part of Wapda but now works as an independent organisation. NTDC manages 61 heavy grids, 16 of 500kV and 45 of 220kV, stretching over 5,970km and 11,322km respectively across Pakistan. Considering past experiences, NTDC avoids sharing details of damages and causes that led to faults. NTDC’s team headed by chief engineer Bashir Memon has started its inquiry for the June 30 incident and one should wait for its outcome. But given repeated such incidents NTDC and Hesco, indeed, have much to answer for.
Published in Dawn, The Business and Finance Weekly, July 6th, 2020