Transformer rating for solar PV plants based on overloading capability as per guidelines

Step up transformer is used to connect renewable PV power to grid. Such transformer is critical and plays a vital role in both commercial and technical aspects. Being an intermittent resource, sizing methodology of transformer shall vary towards the conventional method of transformer sizing for a permanent source. It's a known fact that the transformers were manufactured for certain overload capability subject to some limitations. Here, those criteria and capability shall be taken into account for sizing a transformer by serving efficiently to an intermittent solar resource. In the present paper a design methodology is proposed with a sizing tool to determine the optimal size of a transformer based on IEEE guidelines and Indian standards considering overloading factor and its duration, winding hot spot temperature, loss of life. Proposed Sizing tool caters the need to peak generation by fixed PV array and also the tracker based PV plants but without standby resource such as battery backup. A Case study is also analyzed to key in the actual values to determine the optimum rating of a transformer subject to guidelines and standards referred.