Protection of the transportation and repartition networks : presentation

Electric power grids represent significant investments made by Transmission and Distribution System Operators (TSOs and DSOs) to supply their customers under the best possible conditions in terms of cost and service quality. In France, the TSO is RTE (Réseau de Transport d'Électricité). It primarily manages the extra-high-voltage (EHV) networks. The public high-voltage (HV) and low-voltage (LV) distribution networks, which historically operate under a concession regime, are managed by DSOs (Distribution System Operators as defined by Law 2000-108). In metropolitan France, ERDF (Électricité Réseau Distribution France) is the main DSO, as it manages approximately 95% of the public distribution networks. It should be noted, however, that 170 ELDs (Local Distribution Companies) also perform this function across territories of varying sizes, whose networks, for historical reasons, were not nationalized in 1946.

For obvious technical and economic reasons, it is not possible to build networks that are completely free of malfunctions; in particular, they are vulnerable to natural hazards such as lightning strikes. Networks are therefore subject to disruptions that can compromise the longevity of the equipment and the quality of service provided, and efforts must be made to minimize the consequences of these disruptions.

Any fault must therefore be identified immediately in order to isolate the section of the network where the fault is located from the rest of the network as quickly as possible. This is the purpose of network protection.

The International Electrotechnical Commission (IEC) defines protection as the set of measures designed to detect faults or other abnormal conditions in a power system, enable the elimination of faults, terminate abnormal conditions, and issue commands or signals.

The protection of various networks (transmission and interconnection, public distribution, and private industrial distribution) is the subject of specialized sections. As an introduction to these sections, this document outlines the key characteristics of these networks and provides information on the faults that can affect them. It also presents the criteria common to all networks that must be taken into account when designing their protection systems.

The following information pertains solely to protection against short circuits and insulation faults. Information on protection against incidents affecting the overall operation of the Generation-Transmission-Consumption system—such as overloads, loss of synchronism, voltage sags, and frequency drops—can be found in the "Transmission and Interconnection Networks: Control and Operation" document: [D 4 090]...