Indian Power Outage: Underdrawing and Overdrawing Involved

The Hindu Online has a piece by an independent consultant on what happened to the power grid on July 30 and 31.

“Demand-supply mismatch has been endemic, going by the reports of hearings being conducted by the regulator on the subject of grid indiscipline. Another uneventful night would have passed, had it not been for a trigger — which in this case was the reported tripping of a loaded line (400 kV Bina/Agra/Gwalior).

Further loss of load in a scenario where there already exists oversupply, overfrequency, (and presumably over-voltage) proved to be the proverbial last straw. Frequency went beyond trip settings, resulting in a series of generator and line shutdowns, known as a cascade tripping, because each tripping worsens the operating parameters for the surviving plant and has a snowballing effect.

So before we proceed to the events of July 31 (which were of a different type) we first need to identify the issues from the grid failure of July 30. These are broadly as follows:

Underdrawal vis-a-vis schedule by the constituents (States) at the time of the incident.

Excess generation vs schedule by the generators

Actions if any taken by the Northern Load Despatch Centre (NLDC)/Regional Load Despatch Centre (RLDC) to correct the imbalance.

Reason for tripping of the line/equipment which triggered the grid failure.

For a demand/supply mismatch which resulted in a grid frequency of 50.4 Hz it is certain that there was violation of grid discipline by some or all sections of the constituents, and/or failure of the NLDC/RLDCs to correct it in time.

The event of July 30 was a matter of ‘oversupply’ and not ‘overdrawal’ as widely reported in the media and by Power Ministry spokesmen, though the eventual outcome was the same — a grid collapse.

…AND THE SECOND

Having said this we can now turn to the events of July 31. It is difficult to piece together with any degree of exactitude the events leading up to this failure, but one thing is clear — there was excess drawal vis-a-vis schedule by certain constituents at a time when the grid was in a fragile condition, and a trigger event like a line/equipment tripping took place, thus exacerbating an existing demand- supply mismatch.

The lessons from both events are the same. Persistent underdrawal or overdrawal in disregard of LDC instructions amounts to grid indiscipline and needs to be firmly dealt with. Likewise, oversupply by generators, or failure to meet schedules also amounts to failure of grid discipline.

The action or otherwise of the NLDC/RLDCs is the next contributory factor, and all of these combine to produce catastrophic failure when a crucial line trips due possibly to poor maintenance, or some other random cause.

Therefore, State and generator discipline, and grid maintenance and operation all need more attention. All this is well within the competence of our power sector professionals and regulators, provided, of course, that they are not subjected to political interference.

The intent of the Electricity Act, 2003, is quite clearly to distance the Government from day-to-day operations of the power sector. A beginning can be made by further empowering the load despatch centres and making them independent of their respective State governments.

Respected professionals like those from Powergrid can be fully relied upon to take care of our grid and ensure reliable power supply, as they have done for the past 11 years.”

(The author is an independent consultant. blfeedback@thehindu.co.in)

Leave a Reply

Your email address will not be published.

Current day month ye@r *