Protection of transportation and distribution networks against short-circuits and insulation defects

This dossier deals with the protection of extra-high voltage (EHV) and high-voltage (HV) networks against short-circuits and insulation faults; protection against abnormal operation of the generation-transmission-distribution system (loss of synchronism, drop in frequency, voltage drops) was the subject of a dossier entitled "Electrical power transmission and interconnection networks. Fonctionnement et réglage" [D 4 090] and will not be repeated here.

Network faults cause disruptions that affect network operation and the quality of supply to customers (see [D 4 800v2] "Network protection. Overview"). For example, a poorly eliminated fault on the EHV transmission and interconnection network can lead to a large-scale incident depriving a large part of the country of power, while faults on HV distribution networks cause voltage dips, short interruptions or even long outages at customer sites.

While the number of faults depends on the characteristics of the structures, notably their level of insulation, and their environment, in particular their exposure to atmospheric disturbances, the quality of their elimination is a direct function of the performance of protection systems and equipment.

The performance and constraints imposed on protection systems by different types of network are specified.

After a presentation of the internationally accepted classification of protection devices, and a reminder of the influence of transient regimes on the behavior of protection devices, the basic relay measurement functions are described in detail.

In this document, in line with common usage, we will retain the notations THT (225 and 400 kV) and HT (63 and 90 kV), although the current designation (UTE C 18-510) is HTB for all voltages above 50 kV.

This dossier is part of a series on the protection of transmission and distribution networks:

• " Presentation " [D 4 800v2] ;

• "Short-circuit and insulation fault protection" [D 4 801] ;

• "Line and cable protection" [D 4 802] ;

• ...