A year after India's biggest power blackout Why it happened and the lessons learnt
A year after India's biggest power blackout:
Why it happened & the lessons learnt
(This article is by Avinash Celestine, published in Economic Times)
One year after India's biggest power blackout, what have we learnt from a series of
technical failures which plunged large parts of the north, east and west into darkness?
Immediately after the incident, the blame fell on northern states such as Haryana and Uttar
Pradesh for drawing more than their quota of power from the national grid, thereby
weakening it, and ostensibly bringing about the failure.
Uttar Pradesh chief minister Akhilesh Yadav even proceeded to transfer the head of the UP
Power Corporation for the incident. A year later, the picture looks far more complex.
Northern states, being chronic offenders, can hardly avoid part of the blame for what
happened that evening.
Following the blackout, the Central Electricity Regulatory Commission (CERC) initiated a case
to look into the events of July 30 and 31, 2012 (quite apart from the official inquiry into the
incident). While the CERC's final ruling in the case is yet to come, it has become clear that
other states, including some in the western region that were drawing less power than they
had 'scheduled', also bear an important part of the blame.
"Messages were sent to these states to resolve the problem at that time, but for
commercial reasons they did not do so," says an official responsible for managing the
In the days and hours leading up to the blackout, engineers responsible for the overall
operation of the grid had repeatedly sent messages to offending states warning them about
potential problems, but these were ignored, according to records of CERC proceedings. "Our
biggest learning from the failure was the need for much tighter regulation, and the stronger
enforcement of those regulations," points out a senior official responsible for the safety of
Demand & Supply
In the initial days after the blackout, when officials looked at the data about the state of the
grid at the time, they noticed a seemingly odd fact: the 'frequency' of the grid, which in
India is supposed to be around 50 Hz (that's also the level at which all electrical devices from
television sets to washing machines operate), was only slightly below normal.
An indicator that should have been flashing red at the time, to flag any serious imbalance in
the system between the demand for power and the supply of it, was actually indicating that
conditions in the system were close to normal. The demand for power fluctuates sharply —
across months and even over the course of a single day. It typically shoots up early in the
morning as consumers wake up and switch on the lights or washing machines or geysers.
Demand drops over the course of the day but shoots up again in the evenings. In northern
states, the summer months are times of high demand due to the operation of air
conditioners and coolers. In winters, heaters suck up a large chunk of power from the grid as
well. Since power in the grid cannot be stored (at least not on any large scale), it has to be
generated as people demand it. Power stations tend to work overtime during peak demand.
But as demand drops, power stations too have to slow down.
If they don't, the frequency of the grid could move sharply away from 50 Hz, seriously
damaging both large-scale power equipment, as well as the appliances we use at home. And
if the system moves the other way, and more power is being 'demanded' from the system
than available, the same problem arises. On the evening of July 30 last year, despite the
allegedly large amounts of power being demanded by the northern states well beyond their
quota, a key health indicator of the system was actually saying that things were close to
Unlike in the West, the frequency of India's grid for long has fluctuated well beyond its
'ideal' limit of 50 Hertz. The incentives facing power stations and state power utilities has
meant that stations would often continue generating power well beyond the point at which
there was demand for it. For their part, utilities continued to draw large amounts of power
from the system more than it was prudent to do so. The result?
Sharp spikes and drops in frequency and a resulting damage to power equipment. To fix the
problem, grid operators evolved a mechanism of carrot and stick. Those drawing more
power than allotted, at a time when supplies of power were already tight (when the
frequency was below 50 Hz), had to pay more for the privilege. Conversely, power stations
willing to supply more power to the system at this time were rewarded with higher tariffs.
The opposite was true when the frequency was above 50 Hz indicating excess supply of
power. Power producers were penalised with lower tariffs, but those willing to buy more at
the time were rewarded. For a time this worked well and, over the years, the sharp spikes
and drops in frequency gradually evened out, though they never actually disappeared. Soon
the frequency of the system took on the role of key indicator of the health of the overall
Deviations from it would lead
to the grid operator, under
the control of the central
government, sending frantic
messages to state electricity
boards (SEBs) to draw less
power. SEBs, under political
pressure of their own from
their respective state
governments to maintain
supplies of power to
important constituencies such
as farmers, would often
ignore those messages.
At about 2.30 am on July 30,
2012, just a few minutes
before the entire northern
grid went down for the first
time, the net over-drawal by
northern states (the extent to
which they were drawing
more power from the system
than they officially committed
to) was around 500 MW.
A bulk of this power was
being drawn by northern
states from western India,
and flowing over just two key
transmission lines — the
Agra-Gwalior-Bina line and
the Zerda-Kankrauli line.
And what added to the
problem was that these were
weak links, partially shutdown
for upgradation and repairs.
So large amounts of power
were flowing across the grid
at a time when key parts of
the network were weak. In retrospect it was an accident waiting to happen.
The first inquiry report on the grid disturbance highlighted these points — the already weak
transmission lines, and the large excess power demand from northern states. But through
the CERC orders, it's also clear that western states such as Gujarat, Madhya Pradesh and
Maharashtra were also to blame for deviating from their planned power schedules — guilty
of drawing far less power than they had 'scheduled'.
Here's the clue as to why the frequency of the grid was just slightly below normal — while
states like Uttar Pradesh were drawing more power than 'scheduled', there was also a
greater supply of power in the system to match that demand, from the western states. The
grid frequency, which indicates the extent to which demand and supply are out of whack,
hence seemed close to normal.
But in the context of a weakened transmission system, a large amount of surplus power
available from the west for the north meant huge flows of power over key transmission
lines, far exceeding their capacity. In such a scenario, it was as essential for grid operators to
get western states to cut surplus power they were supplying to the grid, as it was to get the
northern states to curtail their demand.
At the time of the collapse, the 'surplus' power injected into the grid was 837 MW by
Gujarat, 437 MW by Madhya Pradesh and 537 MW by Maharashtra. It's clear that grid
operators at the time recognised this danger. But western states at least did not see
themselves as being part of the problem.
On July 29, the operator of the western grid asked Maharashtra to curtail its surplus power.
Maharashtra responded by pointing to the frequency of the grid which was slightly below 50
Hz, technically indicating that there was excess demand for power in the grid. In such a
scenario, according to the Maharashtra view, it was the job of the northern states to cut
their demand, rather than that of the western states to reduce power surpluses.
And this is where the money comes in as well. If Maharashtra and other western states are
supplying their surplus power to the grid at a time when there is excess demand, they are
earning extra-high tariffs for doing so. Therefore there is little incentive for them to reduce
generation and lose revenue. "The Commission observed that during crises, delay in
response or lack of response to the instructions of the [grid operators] is not acceptable,"
said the CERC.
Two hours before the grid collapse on July 30, the western region operator asked National
Thermal Power Corporation (NTPC) to 'back down' a unit of its power plant at Sipat. A series
of dialogues ensued and the end result was that NTPC did not reduce generation from its
Sipat unit. "The Commission ... observed that NTPC should have reduced the Sipat
generation...and if NTPC felt that the instructions were unreasonable, it was at liberty to
approach the Commission." "What is also of importance is the flow on the transmission
lines," says Puneet Chitkara, director at AF-Mercados EMI, a consultancy. "Many experts had
pointed out that the frequency of the grid should not be the only focus, but practically that
advice was ignored till now." A recent paper by the CERC proposes much tighter bands for
the frequency of the grid,and penalties against those who deviate from their power
Since the grid collapse, a series of changes have been put in place in the way the grid
operates. Drawing or supplying more power than 'scheduled' is now heavily frowned upon,
and is less widespread than it used to be. "Perhaps the biggest lesson has been in terms of
controls at each point, from the level of the individual power station onward, so as to be
able to respond to fluctuations in demand," points out Chitkara. With South India likely to
be integrated into the national grid by 2014, engineers and grid planners face a race against
time to upgrade infrastructure and enforce regulations. The costs of any failure will now be
much higher than they were last year. India's biggest blackout continues to make its
presence felt long after the lights came back on.