When protection system fell like pack of cards, dark night rose

No, overdrawing from states did not cause grid failures. It was a red herring to divert attention from the real issue


Prasanna Mohanty | August 17, 2012

Was it really overdrawing of power by Uttar Pradesh that caused the massive grid failure for two consecutive days – Northern Grid on July 30 and Northern, Eastern and North-eastern Grids on July 31 – as the then power minister Sushilkumar Shinde told the country? Or were there other factors which his successor M Veerappa Moily merely hinted at on August 1 but refused to elaborate by taking the cover of an independent committee set up to look into the issue? Facts that emerge now seem to support Moily more than Shinde.

For one, technical analysis carried out by private sector power utilities shows that power frequency of the Northern Grid was stable moments before the tripping – standing at a very healthy 50 Hz one second before the July 30 tripping and 49.8 Hz one second before the July 31 tripping.

Power frequency of the grid reflects a balance between power supply and withdrawal at any given time and according to the present grid code (devised for efficient and safe operation of the grid) it has to be maintained within a range of 49.75 Hz - 50.20 Hz at all time. Deviation on either side creates disturbances and endangers the grid. In case of overdrawing of power, the frequency dips and vice versa. But as the private power utilities found, “there was no disturbance at the time, neither by of overdrawing nor of underdrawing”.

RN Nayak, chairman of Power Grid Corporation, which runs all the power grids in the country, confirmed to Governance Now that on both occasions power frequency stood “at 49.8 Hz or more” just before tripping. He, however, kept mum when told that this clearly negated Shinde’s assertion.

Knowledgeable sources point out that a fault developed on the Bina-Gwalior-Agra line that led to an overflow of power in the line, which can happen for various reasons, including overdrawing and poor maintenance. This is not an unusual phenomenon and happens all the time. What happened next was the real problem.

There are a series of protection mechanisms in the electric lines and at power substations, known as circuit-breakers and isolators that automatically disconnect the line or the substation from rest of the network in case of a fault. These protection mechanisms failed to operate and isolate the faulty section. The failure caused a cascading effect that travelled through the entire Northern Grid and tripped it. This was an alarming situation.

As if that was not enough, on July 31, a similar fault led to the tripping of two other grids too (Eastern and North-eastern Grids) the very next day.

Obviously, the protection mechanism of all three grids, which are all interconnected, failed. Interestingly, the Western Grid which is connected to the rest isolated itself. (Southern Grid is not connected with any.) And so did Kolkata, which is connected but could isolate itself like the Western Grid. Delhi suffered because it doesn’t have islanding system.

All the protection mechanism works automatically, without human intervention. Since the tripping happens at a lightning speed, it provides no chance for human intervention.

Even if, for the argument’s sake, we accept that overdrawing of power was the culprit, it won’t explain tripping of the entire Northern Grid or all the three grids. The protection mechanism would have restricted tripping to a section of the Bina-Gwalior-Agra line or to the nearest power substation it is connected to.

A tacit acceptance of this came only on August 6 when Moily held a meeting with chief ministers and power ministers of the states and a union territory that were affected by the breakdown and adopted a 12-point resolution to prevent a recurrence. The first point said: “Adequate defence plans and protection system shall be put in place to ensure integrated operation of the National/Regional Grids in adherence with the Indian Electricity Grid Code (IEGC). All the states shall ascertain preparedness of power system defence plans and cooperate at the regional level for coordinating their protection systems.”

The rest of the resolution talked about preparing “islanding schemes”, independent third party audit of the “protection system”, strengthening and upgrading state load dispatch centres that monitor the grids, “training of system operators”, good operating and maintenance practices and so on. Moily has already promised to provide adequate funding to the states. What is needed is a protection system that works and isolates the grids at various levels and prevents a cascading effect that was witnessed on the fateful days. Talks of inadequate power generation, constraints of fuel supply, lack of reforms, poor financial health of state utilities etc are valid but unconnected with the issue at hand.



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