Decentralised Electrical Distribution Network in Power Plants

摘要

A centralized network is the most common network solution in today's powerplants. In this study a centralized and a decentralized network were designed in order to compare them economically and technically. The network of the Kirkniemi (Lohja, Finland) power plant was used as a model case. The emphasis of this study was on economical aspects, but also the most important technical aspects were considered. The decentralized network requires less space cabling since there is no switchgear building and distribution transformers are placed closer to the consumption. Medium voltage motors and distribution transformers build up to a ring. Less cabling and an absent switchgear building cause considerable savings. Component costs of both the networks were estimated by using data from completed power plant projects. Component of the decentralized network wer smaller than those of the centralized network. An essential question of the network is the relay protection and associated fault location. Simulation for the decentralized network were done in order to find a way to carry out earth fault protection and location. It was found out that in high resistance earthed system the fault distance can be estimated by a relatively simple method.