This thesis was made for Suomen Energia-Urakointi Oy. The purpose of the thesis was to create a description of the service center operating principles, and help to create low-voltage electricity distribution network in real-time to maintain the connection status. The service center was established because the Helen Electricity Networks Ltd wanted to start following the low-voltage electricity distribution network interruption times.

In this thesis the client´s and the service provider’s practical experience, and standards is-sued by the customer concerning low-voltage network realtime connection status maintenance, were utilized. The result is a description of the service center operations and practical instructions for maintaining the low-voltage network realtime connection status.

In this thesis the structure of the low-voltage network and low-voltage components used in the network, such as cables and distribution cabinets, are explained. The study examines mainly the underground urban electricity network. Overhead networks are discussed briefly.

Fault calls that are related to the Helsinki electricity network, come to the service center, so the management of fault conditions is a significant part of the service center activity. This work discusses the occurrence of the fault and the fault locating in electricity network, and goes through the theory of calculating symmetrical and unsymmetrical fault current, together with fault causes in the low-voltage network. In addition, how fault situations are handled in service center is clarified.

Maintaining a real-time connection status is one of the main priorities of the service center. Maintaining a real-time connection status has not been previously carried out in low-voltage network. As a result, this thesis presents how maintaining the low-voltage network’s realtime connection status is carried out in the service center and what kind programs service center is using.