GPL says…
GUYANA Power and Light (GPL) issued an advisory yesterday, informing consumers in the Demerara Interconnected System of new developments taking place in the company. The utility company revealed that last Friday, a network fault in the Sophia area caused a complete system shutdown at 08:05hrs.
According to the advisory, it was discovered that the DC supply at the company’s Sophia Complex had failed. The failure resulted in the failure also of the back-up lube oil supply for the two frequency converters. Consequently, both units suffered bearings damage.
Also resulting from the shutdown, the 50Hz Wartsila plant at Kingston encountered electrical problems, which prevented the machines from being returned to service.
The problem, the company said, was corrected at 15:06hrs the same day, and three machines were placed into service shortly afterwards, thereby restoring the supply to 50Hz consumers in Georgetown.
It stressed that in the absence of any frequency converter, the 50 and 60 Hz systems are being operated independently. This means that excess 50Hz generation capacity cannot be converted to 60 Hz, and 50 Hz consumers are completely dependent on the Wartsila 50 Hz plant.
The company’s No.3 machine at the Wartsila plant, located at Garden-of-Eden, on the upper East Bank, also suffered a major mechanical failure at 14:30h. The problem was a damaged engine block.
GPL said that an initial inspection suggests that a replacement block is required. This machine, it said, was given a major overhaul during the last quarter of 2010, and was not due for major service until 2012. Both the power company and Wartsila are awaiting the arrival of the experts who will make a final pronouncement.
All these developments, the company says, are taking place at a time when the No.1 unit at the Wartsila 50 Hz plant at Kingston is undergoing a major overhaul, therefore 11MW of Wartsila capacity is unavailable, and the available capacity in Demerara is reduced to 70.3MW.
The Wartsila 50Hz unit, which is undergoing a major overhaul, is expected to be back in service by Thursday. GPL expects that by then, it should be able to return the second frequency converter to service.
To remedy the problem, GPL stated that the company has been working to restore the converters to service and expects that the first unit should be restored by tomorrow. As the utility explained, the frequency converters are used not only to convert power but also to support voltage, hence their absence necessitates power interruptions to ensure an acceptable distribution voltage.
The company is making an urgent appeal to all its 60Hz consumers in Demerara and particularly those in Georgetown and on the East Coast to ensure that every effort is made to reduce power consumption. Scheduled load-shedding would be necessary in any case, but reduced demand will alleviate the problem, GPL explained. 
GPL will continue to advise consumers of developments, but is asking for the patience and understanding of the public. Consumers will be advised on the load-shedding schedule via NCN television station.