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Limiting solar power during Avurudu was purely due to technical reasons, CEB says
View(s):By Niranjala Ariyawansha
The Ceylon Electricity Board (CEB) has stressed that the decision to limit the use of rooftop solar power from April 11 to 13 to maintain the stability of the national grid was purely due to technical reasons.
The CEB points out that in order to maintain the stability of the national grid while addressing those technical issues, it was necessary to turn off some of them between 11 am and 3 pm, as the very high rooftop solar power generation of about 100,000 was a serious obstacle.
They emphasised if that decision had not been made, the national grid could have collapsed and the entire island would have been in darkness, similar to what happened on February 9.
“We have taken such a measure to ensure that this does not happen and to provide uninterrupted electricity supply to the country’s 7 million electricity consumers during the festival season” said CEB media spokesman Engineer Dhammika Wimalaratne to the Sunday Times. He said that to main the stability of the national grid, its frequency must be kept within a specific range. In order to maintain that specific range, it is essential to have inertia. Inertia is provided by spinning turbines in large power plants. Solar or wind power plants do not have inertia.
“On holidays, the demand for electricity is lower, so large power plants are taken offline, which decreases system stability. This reduces inertia in the system. On sunny Sundays or holidays, electricity demand is lower, but solar power plants are not concerned about sudden power demand changes. They automatically generate electricity when the sun is shining. However, we do not have the technical ability to monitor the electricity production of solar power and mini hydro power plants. This is a significant problem. The absence of large power plants also makes it hard to maintain proper frequency levels, risking system stability due to the loss of inertia” he said.
Though general daytime demand is 2200 MW, by April 12 that daytime demand had dropped to 1300-1400 MW.
“Also, power generation and demand should always be a match. Even if the demand is low on sunny Sundays or holidays, if a customer suddenly turns on an AC, that increased demand needs to be supplied immediately. During such a sudden demand, a large power plant with inertia can supply a part of its power to that increased demand. Then the speed of that power plant will decrease, but it will be able to increase the speed again in a short time. However, solar or wind power plants do not have inertia, so they are not able to respond to a sudden demand changes,” he added.
He noted that without enough inertia, even a small mistake could lead to a frequency drop and cause a system collapse, like the total blackout on February 9 this year. He further said that consumers were informed to disconnect their rooftop solar connections from the national grid from April 11 to 13 to prevent such a sudden total failure.
Accordingly, as a long holiday commenced, CEB took steps to turn off about 500 rooftop solar power generators of more than 100KW on April 10.
“We have informed about 100,000 rooftop solar producers to disconnect from the system between 11 am and 3 pm when the sun is at its peak. Also we took steps to disconnect mini hydro power plants located across the country from the national grid. These decisions were taken keeping in mind the 7 million electricity consumers in the country,” he emphasized.
According to him, due to low demand, as another step, they stopped one phase of the Norochcholai coal power plant, while the other two are running at low capacity. That was necessary to match nighttime demand and keep system stability with inertia.
“Some question why not stop the remaining two Norochcholai power plants. You have to understand that if a coal power plant is stopped today, it will take several days to restart it” he added. He said that CEB can absorb any amount of solar power if it comes with local storage that can supply electricity during peak hours and if there is continued growth in electricity demand.
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