Prototype arrester set-up now being evaluated on 63kV and 90kV lines in France.

Electricité de France (EDF) is currently in the midst of a research program designed to assess operating experience with a new design of line arrester for use on the utility’s 63 kV and 90 kV transmission networks. The program, which is being conducted in collaboration with a French-based manufacturer who has supplied the prototypes, has already seen the installation of some 500 of these units since 1998.

According to Project Manager Frédéric Maciela, an engineer specializing in dielectric behaviour of equipment and working with EDF’s R & D Division at Les Renardières, the main purpose of these trial installations has been safety in what are referred to as sensitive areas. These include parking lots, outdoor swimming pools and even rural locations such as near farmhouses. “Basically”, says Maciela, “we want to prevent any rise in potential around towers due to overvoltages to ground and which can represent a threat to people and livestock. Also, we want to avoid any possibility of danger due to follow currents when towers are located near certain industrial facilities.”

	Maciela. Secondary application of arresters will be to improve quality of service.

The prototype arrester being used in this evaluation program has been manufactured according to the specifications and requirements supplied by EDF. Weighing a total of 12 kilograms with its attached arcing horn, the arrester is of zinc oxide type with an EPDM housing and utilizing an air gap design. Observes Maciela, “although we recognize that there is some pressure in the industry toward gapless arresters, in France we still prefer the gap type which we feel offers certain advantages.”

“For example,” he explains, “this design permits a lower voltage rating for the active part of the arrester. It also allows a smaller-sized unit which can more easily be installed on the four-disc insulator string used at 63 kV. Without the air gap, the arrester would have to be longer and could not be installed in parallel with such a string. Finally,” he notes, “these types of arresters have a lower cost and there is less ageing of both the blocks and the housing.”