Transient overvoltage study of an Island wind farm

It has slowly becoming the norm for countries to include renewable energy as a percentage of their electricity generation mix. Wind is arguably the most mature technology of the available sources of renewable energy. Globally, the inclusion of wind farms in the generation of electricity is significant, both economically and environmentally. Countries that depend solely on fossil fuel to generate electric power have experienced economic stagnation simply because of the high cost of oil which has a direct bearing on the cost of electricity. Most disturbingly, the burning of fossil fuel is harmful to the environment; it produces greenhouse gases which negatively affects the ozone layer and increase global warming. Even though there are clear benefits to be gained from the integration of wind farms, there are also implications and challenges that should not be ignored. Some of these challenges are transient overvoltage, harmonic distortion and network dynamic stability. To measure the resultant benefits of this naturally replenishing energy source, it is imperative that these adverse effects are thoroughly researched and addressed. This paper explores the effects of lightning induced transient overvoltages on the integrated transmission grids. The methodology involves setting up transient models of the wind farms and transmission grid suitable for studying transient phenomena. Although the durations of transient phenomena are relatively short, it is during this time that the network is exposed to the greatest voltage stress and if proper controls including mitigation are not in place, it may results in severe damage to expensive equipment and lengthy power outage. The IEEE 14-bus system was used to represent the 69 kV transmission network in the Island of Jamaica with wind turbines connected to selected buses of the network. EMTP/ATP was used to simulate a lightning strike to one of the wind turbine blades. The resulting voltage surge through the network were recorded and presented. It was observed that the transient overvoltage exceeded the basic lightning impulse level (BIL) of the power system components.