[RohitAK96]

Since afternoon the power has gone about three times with the last outage lasting for more than an hour. When we called and enquired with KSEB, they said they were "preparing" the grid for the 9 pm event.



It has to be mentioned that after the lockdown was initiated to this date, we have not faced any power outages. Only today all this is happening and god only knows what more is gonna come.

[Jeroen]

Guys relax. When everybody switches on their telly to watch the cricket match, that is a considerable higher load increase than what is likely to happen here with some house hold lights.

[msdivy]

Last 10 minutes have been uneventful event in terms of power supply.

Originally Posted by msdivy

Though there will be drop in usage, there isn't much to be concerned.

[saket77]

Short summary of what exactly happened during the event:

Before 9 PM





At 09:05 PM




At 09:17 PM- I could see around my locality that many lights were not turned back on even after 09:09 PM.

[nagr22]

While everyone was busy turning off the lights and bursting crackers (I don't know why! ) me and my wife were busy recording the line voltage and this is what we found!
Voltage at 8.55 PM was 232Vrms. I didn't take any picture of this as I hadn't thought about it. Then we saw the voltage surging till 242Vrms.

The picture shows 241 Vrms as the voltage was fluctuating and this is what was recorded at the instance of capturing.

Again at 9.10 PM we could see the voltage dropping slowly and currently it is settled at 233 Vrms.


I know I am crazy to be doing this while everyone was busy doing their lights off thingy but having a partner who is also an electrical engineering nerd has its perks

Hats off to the electrical engineers working at the grid who managed this event successfully!

Edit:
Just got this below snapshot from a friend working in one of the distribution companies and the power drop is ~26GW which is more than a 20% drop in load. The corresponding change in voltage has been managed within 5% (13Vrms) as seen from the previous two posts which is a commendable job!

[diyguy]

We are facing voltage values of about 215V, 40+ mins into the hour.

[poloman]

Not sure the increase in voltage was due to the reduction in the load or purposefully boosted for the oncoming surge when people switch on the lights.

Just got this below snapshot from a friend working in one of the distribution companies and the power drop is ~26GW which is more than a 20% drop in load

This looks too high for lighting load. People/societies must have switched off the entire power in most cases.

[ampere]

A power grid like I said earlier is to be seen like a set of sources (read power stations) feeding to a network and sink-points tapping source power out of it as loads.

Some types of power station, cannot go down this way simply because the nature of the fuel for prime mover. And hence they also are planned on how to run at no load. Though islands can be created for such stations, by and large its difficult insulate in the event of an instability.

Originally Posted by nagr22

While everyone was busy turning off the lights and bursting crackers (I don't know why! ) me and my wife were busy recording the line voltage and this is what we found!

Originally Posted by saket77

Short summary of what exactly happened during the event:

I am not sure, if the reading would be any indication of the load change. The Vrms has a lot of dependence on the reactive load as well.

[Safety is Param]

Originally Posted by Safety is Param

On the power fluctuation and load variation front, enclosing couple of docs received from my engg. batch friends who are currently placed at various power stations across India (20+ yrs. experience)

Received update from the same group. Sharing FYI -

[ampere]

Mod Note: Please let us keep this thread technical.

Reason on how this topic came up for discussion may be be un-related to the topic itself. Power Systems, Transmission and Stability are deep technical subjects taught in core Electrical Engineering Courses. So it would be good to discuss basics here and in that process clear some myths if there be any.

[nagr22]

POSOCO which is a GoI enterprise for managing national level electrical load as released a preliminary report about yesterday's lights off event. (See Attachment)

Highlights from the report:

1. The calculated reduction in load was 12-14GW. (This is in the ballpark of the entire installed capacity of Singapore! source)

2. The actual reduction in load peaked at 31 GW!

3. Hydro and gas generation was ramped up across the country and thermal stations were tuned down 15 minutes prior to the event.

4. All the clocks across all power stations in India were synchronised prior to the event.

5. Health of all protective devices like Under frequency relays, df/dt relays and Automatic demand management systems were checked and ensured to be operational.

6. Frequency of the grid was tuned towards the lower end (49.9 Hz) starting from 20.30 in anticipation of the frequency rise due to load removal. Similarly it was kept on the higher side (50.15 Hz) at 21.09 to control the reduction due to load surge.

7. All reactors were put in service to control voltage fluctuations

8. Telephone numbers of all control centres, generating stations and substations etc were kept handy

9. Staff count at control centres were strengthened and kept on high alert. Evening shift timings were extended such that it overlaps with overnight shift thereby increasing staff count during the event.

10. All senior staff were made to be available from 18.00 till 22.0p


Finally, the event was managed without a glitch! 31GW of power is more than the total installed capacity of many of our neighbouring countries! Kudos to the team for working hard and making this a success!

[saket77]

Really admire the efforts of people working behind the scenes but there’s one query which is troubling my mind which domain experts might be able to clear up. I’ve posted it somewhere else on the forum but I think it’ll be more relevant to post it here.

When the lock down (24th March) was announced almost suddenly, all factories, industries and commercial establishments went off the grid by the next morning, which is almost immediately; that too off routine and without any notice to the grids to prepare unlike for this event. That was far far more load decrement than turning off home LED lights. If the grids were able to tackle that, then why this hoopla over turning off 9W LED lights?

[srini1785]

Guys, I don't understand the whole fear of what would be the effect on the power grid / generation due to switching off lights for 9mins. Even if all 1.3 billion of us jump and manage to land at precisely same time, it would not result in an earthquake. Forget it. True, there would be load imbalances but the distribution system are designed to take the impact. Further there are switching yards which would trip if the load exceeds a certain value or if peak voltage / frequency exceeds a certain value. Please note that power generation is usually at a lower voltage and very high current ( not sure of values ). It is then stepped up to around 31KV ( or higher) while its transmitted and finally stepped down when reaching our homes at 230V AC.

The primary element which would take the load imbalance is the road corner transformer and not the power grid. If you have observed carefully there is a Horn gap fuse which connects the secondary to the load ( our homes ). Even in case of surge of current , its this fuse which breaks and protects the transformer. Continuing back there are SF6 circuit breakers at switching yards which trip at over loads and we are not even at the grid level. So why worry about a 9 min blackout?. The only real concern is when a power plant trips. This would mean a few KW of power suddenly going off the grid and would result in a cascading effect. Its really difficult to start a power plant and synchronize it to the grid. By synchronizing it means that the power plant should have three parameters exactly the same as the grid i.e terminal voltage, frequency and the phase sequence. Its takes months to synchronize a station to a grid and once this marriage has happened its difficult to break down ( typical hard indian arranged marriages ! ). So next time don't worry about switching off your lights for few mins.

P.S : what i really don't understand is the logic of 9 o clock , 9 mins and diyas. What next 10 o clock ring the bell 10 times?, 11 o clock ring the bell 11 times?. Its plain BS. Mods can delete this post script if not relevant to topic.

[anb]

Originally Posted by nagr22

3. Hydro and gas generation was ramped up across the country and thermal stations were tuned down 15 minutes prior to the event.

The hydro generation was reduced from 25.59 GW to 8.016 GW between 08:45 and 09:10 pm and the gas generation by 1.95 GW as per the report

[nagr22]

Originally Posted by anb

The hydro generation was reduced from 25.59 GW to 8.016 GW between 08:45 and 09:10 pm and the gas generation by 1.95 GW as per the report

Before 08.45 PM, the hydro generation was ramped up so that they can respond to the sudden drop that occurred between 08.45 to 09.10 PM. Attaching this screenshot from the report regarding the same.

Originally Posted by srini1785

Guys, I don't understand the whole fear of what would be the effect on the power grid / generation due to switching off lights for 9mins. Even if all 1.3 billion of us jump and manage to land at precisely same time, it would not result in an earthquake. Forget it. True, there would be load imbalances but the distribution system are designed to take the impact.

Imagine you are driving a car in highway on 6th gear and redlining the engine. Now imagine somehow the car is lifted off the ground which removes all load from the engine but you are sill flooring the pedal. What would be the consequences? Eventhough the ECU is programmed to cut off fuel after certain rpm, in this scenario you can definitely expect few broken piston and worse. Had the ECU knew that you are going to do this stunt, it would have kept the brakes on standby thereby arresting the excess rpm. Power systems are definitely designed to absorb such abnormalities but it is always better to be proactive rather than reactive. Another unique challenge was, imagine that you somehow arrested the engine rpm while you were lifted up. Now at 9.10 pm you will be once again dropped on the road and expected to run at the same speed as before, instantly! Doesn't this require some planning?

Originally Posted by saket77

When the lock down (24th March) was announced almost suddenly, all factories, industries and commercial establishments went off the grid by the next morning, which is almost immediately; that too off routine and without any notice to the grids to prepare unlike for this event. That was far far more load decrement than turning off home LED lights. If the grids were able to tackle that, then why this hoopla over turning off 9W LED lights?

This is a good question. Very large industries generally have their dedicated substations and power purchase agreements with the electricity board where in they have to share their load curve and any deviation from that curve beyond some tolerance will attract large penalities. Also, whenever they go from no load to full load or drop the load abruptly, they will have to give notice to the power department which will be mandated by contract.
I couldn't immediately find any references in public domain about such contracts and I shall provide the same as soon as I get it.