HYDERABAD, June 18 The massive power breakdown that hit Karachi and lower Sindh on Wednesday has called into question reliability of transmission system of Wapda looked after by the National Transmission and Despatch Company (NTDC).

The outage occurred at 7pm after 500 KVA Jamshoro-Dadu and Jamshoro-Hubco circuit tripped, plunging lower Sindh and several parts of Karachi into darkness.

The tripping led to a shutdown of all the four units of Jamshoro Thermal Powerhouse whose two units - unit-I (Japanese) and unit-IV Chinese - had not yet been made operational while units-II and III had been synchronised at 8am, said sources in the powerhouse.

When people lost patience they took to the streets and held demonstrations in various localities of the city after Hesco's distribution network did not get electricity from 500 KV Jamshoro grid station off Indus Highway and other sources, the sources said.

Hesco officials blamed powerful windstorm for the tripping of 500 KVA transmission lines. Power shutdown had led to water shortage in Hyderabad and other parts of lower Sindh, which got water from Kotri barrage and public health schemes for water supply but they did not work in absence of electricity.

“After our units lost working we synchronised them at around 10.15 pm but again 500 KV line tripped and the second synchronisation process was completed at 2.35 am but it proved short-the lived as system kept showing variation in frequency.

“At last we made unit-II and unit-III functional by 8am but by then unit-I and IV were not made functional,” said a powerhouse source.

Unit-III and II were respectively generating 130 megawatts and 100 megawatts although their actual capacity is around 210 megawatts which it contributes to national grid through 500KV grid station.

Powerhouse itself needs eight to 10 megawatts for kick starting the generation process. Electricity crisis continued till Thursday morning with complaints of erratic power supply.

The 220KVA and 500 KVA transmission lines are looked after by NTDC management while the rest of the system i.e. 132 KVA and below are the sole responsibility of Hesco.

As a result of Wednesday's breakdown Hesco officials seemed to be at the receiving end as according to chief executive of Hesco Habibullah Khilji he was told by NTDC chief engineer Ameer Bachani about nature of fault in 500 KVA transmission line.

“NTDC chief told me personally about the fault. I don't know why he is making such statement because you know NTDC is solely responsible for upkeep of 220KV and 500 KV transmission lines and grid stations. It was a fault that occurred in transmission line and not at any powerhouse,” he said.

Mr Bachani, however, disputed his claim and said “it is in fact powerhouse issue at Hubco and Jamshoro powerhouses where actual crisis occurred. Our lines are absolutely okay and we don't have any problem,” he told Dawn over phone.

There is another report that another 220KVA transmission line that had developed fault around 10 days ago on T.M. Khan road has not been rectified.

Present power supply system is linked with a ring system that enables authorities to go for other transmission line. NTDC chief, however, dismissed the report that T.M. Khan transmission line had developed any fault.

Hesco chief claimed on Thursday that the system had been normalised fully and now only load-management was being implemented and that might be a cause of complaint by consumers otherwise everything stands cleared.

The actual fault did take place in Jamshoro-Dadu and Jamshoro-Hubco circuit that tripped and senior officials of the authorities concerned were required to revisit their “protection scheme” to ensure that so many power plants should not stop working at the same time.

“There is a theory of island operation through isolation process to ensure that in case one area gets overloaded it should not lead to collapse of all other connected power plants.

“It has become all the more necessary that other powerhouses must be saved so that they should withstand the load,” said a senior Wapda official working in a powerhouse.

He said that authorities must think in terms of rehabilitation of the system. “We need to protect transmission lines,” he said.

Hydro Electric Central Labour Union president Abdul Latif Nizamani call upon federal water and power ministry to order an inquiry into the breakdown.