Dear Editor,
In Stabroek News of July 25 it was stated that “The Guyana Power and Light (GPL) suffered a shutdown last night after one of its units was taken out of service because of an oil leak which was deemed as high risk for a fire starting… GPL said that an initial analysis suggests that the rapid offloading of the 8.7-megawatt unit led to a “significant frequency decline” and despite the intervention of other generators and the under-frequency load-shedding scheme, the system collapsed”.
GPL has always claimed that system shutdowns are due to lack of spinning reserves. However, now that GPL has adequate spinning reserves, they are now blaming system frequency decline for a system shutdown. The fact of the matter is that GPL only has three (3) units at Vreed-en-Hoop operating in isochronous load sharing mode and when one of them tripped, none of the other units online could respond quickly enough to prevent the system from tripping. Even if the under- frequency load-shedding scheme was operational, the system would have tripped because there was not enough system inertia to prevent a shutdown.
“Isochronous Load sharing allows multiple generators to operate in isochronous control on a common bus. This is advantageous because the bus load can vary from 0 to the total generating capacity of all the units in Isochronous mode on the bus without deviations in bus frequency or units tripping offline. The generators will pick up and reject load quickly to maintain frequency while the Load sharing controller trims them back to equal loads”.
GPL would only be able to prevent the frequent shutdowns of the existing system by adding more
Isochronous load sharing units to the system. This can be done by connecting the Kingston 2 power plant controllers to the Vreed-en-Hoop power plant controllers by the fibre optic line on the submarine cable and running both power plants in Isochronous load sharing mode. It is a travesty that GPL purchased the new power plants at Kingston and Vreed-en-Hoop with the Isochronous load sharing modules and never configured them to provide the system inertia required to prevent a
total shutdown of the Demerara- Berbice interconnected system.
Yours truly,
Tara Singh
