ALL POWER SYSTEMS suffer from disturbances from time to time. However, an electricity service must be able to maintain its integrity and remain practically intact after suffering these disturbances.
Repeated outages which have become a feature of Barbadian life suggest that more can be done to improve service quality by making our power system more robust and reliable.
There are several sources of instability that put the system under stress. Being an island grid and not part of a larger interconnected system makes the task of regaining equilibrium that much harder. Yes, the task may be harder but not impossible.
And this is why, in the absence of any satisfactory official explanation, the recent prolonged nationwide outage points to a failure of systems operation that could have been mitigated, if not avoided.
The actions taken in the first few minutes after a major disturbance are critical in preventing the power system from cascading out of control and triggering a total shutdown.
To regain a state of equilibrium requires that the systems supervisory control move swiftly to dampen the large frequency and rotor angle excursions to nominal values.
Maintaining control over these variables in an unstable grid environment is a difficult task. But the task is made less difficult when criteria and algorithms required for stability are established ex ante through modelling of various fault conditions such as short circuits and line outages. Advanced distribution design schemes that include automation and the use of sensors for condition monitoring are also very important.
Performance standards are also helpful in managing system reliability and delivering service quality. BL has agreed to performance metrics that set quantifiable reliability targets intended to reduce the frequency and duration of outages.
However, some of the guaranteed performance standards are set so low that it is almost impossible not to return 100 per cent compliance. This means that customers are sometimes not compensated for meaningful but preventable losses.
One such example applies to the guaranteed performance standards GES1 and GES2, whereby a business customer, even in the absence of a hurricane, must suffer a loss of service for 12 hours before being eligible for compensation.
During the 12-month period ending March 31, 2016, BL reliability indices show that on the average customers only suffer interruptions of 34 minutes total duration. While this is a remarkable statistic, it shows that information using averages can be misleading and can lead to erroneous conclusions and decisions.
Nearly 70 per cent of customers are residential but they are responsible for only 15 per cent of the electricity demand. Therefore, indices with more proportional weighting of large and medium size customers based on KVA load interrupted tell a different story and are needed to gauge the true economic impact of these outages.
Another area of reliability that is not part of data capture is that of momentary interruptions. These events, while frequent, are of short duration and do not have a great impact on the reliability statistics. However, they can create significant damage to sensitive loads, many of which go unreported.
Already businesses are calling for a power protection plan to save themselves millions of dollars from crippling power outages that occur outside of natural disasters and other force majeure events. They are searching for suggestions to prepare themselves for more serious and lasting outages. One suggestion is that they look no further than to BL and the Fair Trading Commission for more robust, reliable and lasting solutions.
– TONY E. GIBBS
