Separation mechanisms in the Barbados Light and Power Company power system
University of New Brunswick
Reliability is a major concern for any electric utility and is made more complex in BLPC because it has no supporting interconnections. Additionally, the integration of a large amount of renewable energy in the system presents even more challenges. Historically reliability of the overall power system has been accomplished by better maintenance practices and the continual upgrading of the power system. Recently many papers have proposed that instead of a system wide failure, reliability would be improved by the retention of critical areas of the grid through selection and formation of partial grids or microgrids. The literature shows that significant work has been done on the automatic selection of the parts of the system to be retained in any microgrid. BLPC is interested in improving the reliability of their power system by avoiding island-wide blackouts through possible formation of electrical islands or isolated power system areas, also called microgrids. It has a natural separation point due to the fact the northern part of the island can be isolated by simply opening two transmission lines serving a major bus in the lower part of the northern section of the island. While historically all the rotational generation has been in the southern area, the northern section of the island now has rotational generation, a large solar farm, and a utility grade battery. The historical record of island-wide power failures appears to show that in many cases there has been some sort of cascading effect. The major questions then become what is the likely mechanism for causing separation, and what are the best measurement types and locations which would reliably allow a correct decision to be made to separate? This thesis examines different approaches for analysing the electrical mechanisms, which can be used to decide on separation into two microgrids. The classical instability mechanism of angular separation between the rotor angles of generators during the time of disturbance on the BLPC system is one possible mechanism. Voltage instability in the areas of low voltage deals with the necessity of a sufficient supply of reactive power supply to maintain the required voltage at each load bus. Based on available records, the analysis of blackout events due to cascading effects gives a clear picture of the issues faced in the past. Optimum measurements used to detect the state of the power system by installation of PMUs can assist with the decision of determining the system conditions and time to separate in order to avoid island wide blackouts. Finally, utilizing all the approaches mentioned above, the concept of stability indices has been developed to indicate the relative strength of each local load bus. Ultimately it will be necessary for BLPC to use all the elements of the thesis to develop logical statements allowing them to arrive at a decision to separate the BLPC system into northern and southern microgrids therefore avoiding island wide blackouts.