By AVA TURNQUEST
Tribune Chief Reporter
THE “catastrophic” island-wide outages that plagued New Providence late last year stemmed from widespread equipment failures at the Clifton Pier Power Station, according to Bahamas Power and Light.
The company reported on the findings of its investigation into two island-wide outages, and another major outage that occurred between November 29 and December 4 last year, in an internal memo sent to the government and obtained by The Tribune.
The memo includes assurances that the overhaul and maintenance of generators at both Clifton and Blue Hills power stations will be completed ahead of the summer peak season.
At the Clifton station, three generators broke down during the scheduled maintenance of one of the station’s largest generators.
The report stated that the reduced output from the Clifton Pier Power Station placed extreme pressure on transmission cables out of Blue Hills Power Station to the Big Pond Substation, which led to a major cable fault and the resulting outages.
The memo read: “On November 29, with three of the five largest units at Clifton Pier out of service, the system’s load was forced to flow primarily from Blue Hills Power Station through the four main transmission cables connecting the Blue Hills and Big Pond substations.
“These cables, though sufficiently sized for normal operations, were not able to withstand the significantly increased load, resulting in two faults, one on the Big Pond-Blue Hills #2 transmission cable, and a second on the Big Pond-Blue Hills #4 transmission cable.
“Once the grid recognised the existence of the faults, automatic protective systems began operating to isolate the faults and prevent them from adversely impacting the entire network,” the memo noted.
“The combination of critical faults on two of the four transmission cables, the proximity of the faults to the Blue Hills Power Station, and the reduced output at Clifton Pier resulted in a total shutdown of the entire transmission and generation networks. While this shutdown prevented critical damage to BPL’s network, resulted in an island-wide outage.”
More than half of customers on New Providence suffered through another major outage on December 1 due to the uneven load distribution, which forced a shutdown at Clifton even though Blue Hills remained operational.
On December 4, with Clifton’s largest generators offline, one of two remaining units faulted, exposing transmission cables between Big Pond and Blue Hills to added load pressure. In a bid to prevent another island-wide blackout, the memo read, BPL took preemptive action to disconnect the cables from the grid.
“The result, however,” the memo states, “led to voltage and frequency challenges on the network, causing generation to trip offline as part of its safeguard mechanisms, and leading to an island-wide outage. The restoration time from this shutdown was extended due to the additional failure of an overhead transmission circuit during the outage.”
Unreliable electricity supply has been a lagging concern for residents; however, the issue became contentious last year after the capital suffered two island-wide outages, and another major outage within one week.
At the time, Prime Minister Perry Christie told The Tribune that the outages were “too catastrophic, too unusual and [were] deserving of the highest investigation”. Mr Christie said he had been unofficially advised that the incident was the result of “human error”.
The memo, dated December 12, also outlines a “comprehensive strategy to mitigate future occurrences of a similar nature”.
These include the installation of supplemental transmission circuits between Big Pond and Blue Hills, which the company expects to complete within the first quarter of this year. In two cables, faults were repaired and returned to service - with one of those cables requiring the assistance of a fault location expert from American utility provider, Southern Company.
As for generation, BPL notes that all overhaul activities to generators at the Clifton station, inclusive of auxiliary systems, will be completed by April - ahead of the summer peak season. Winter period maintenance has also commenced at the Blue Hills Power Station, and is also expected to be completed before the summer peak season. Speaking to the overhaul of one of its largest units at Clifton, BPL said the major overhaul planned for January would “enhance its preparedness and/or performance for the 2017 peak load season”.
Computer issues impacting two of its largest units at Clifton have been identified, according to the memo, and a temporary solution was put in place until the company could begin upgrades to control systems in January.
PowerSecure signed a five-year management services agreement, reportedly worth as much as $25m, with the Bahamas Electricity Corporation in February 2016.
Despite repeated calls from the press and the opposition, the government has not released the power company’s business plan. The business plan cost taxpayers $900,000, and was expected to be completed within 60 days after PowerSecure signed a transitional agreement with the government in July 2015.
Since taking the helm last February, PowerSecure’s efforts at restructuring the cash-strapped utility provider have been marred by island-wide power outages in the capital, and on some Family Islands.
In January, one outage left some customers in western New Providence without power for more than 12 hours, and was reportedly caused by equipment failure at the Windsor Field substation. At the time, BPL said the outage was an “unforeseen” failure and advised that it was conducting a secondary review of all primary substations on the island to assess the functioning of key equipment post Hurricane Matthew.