Problems encountered with connecting decentralized generating plants to the distribution networks

Since the early 1990s there has been a surge in the number of decentralized generating facilities connected to the distribution network. The problems encountered are not new in themselves-what is new is the large number of applications the distributor now finds itself confronted with. Small installations are usually barely economically viable so given the modest size of decentralized generation the cost of the disconnection protection should not be prohibitive. While this is a demanding technique the engine-network interface must be sufficiently simple to make the project worthwhile. What is more, the large number of installations means that it is impossible to opt for any solution which would require constant surveillance. This technique concerns decentralized generation of up to 15 MVA operating in parallel on the distribution networks. We examine the steps that need to be taken to ensure a suitable connection with the distributor´s low and medium voltage networks which are assumed to be fully earthed. The target is the network protection and operating personnel safety. A distinction is drawn between in-plant generation and independent generation because a different system may need to be set up depending on circumstances. The aim of independent generation is to supply the network, while the primary aim of in-plant generation is to supply the generator´s own equipment and can supply the excess power to the network if required.