Automatic disconnector: Influence on the performance of medium voltage arresters and a new design proposal

• We have evaluated the performance of conventional disconnectors.
• The reasons for the high rate of failures in disconnectors are discussed.
• We have analyzed the effects of disconnectors misoperation on the performance of arresters.
• Reliability and economical operation of protection medium voltage lines is compromised by disconnectors.
• A new design of disconnector is proposed.

This paper discusses the modes of actuation and misoperation of the automatic disconnector of distribution surge arresters. Taking into account the laboratory test results and field data search campaigns, the main problems concerning the operation of these devices and how it affects the reliability of the surge protection of transformers are discussed. In general, the misoperation of the disconnector is a design problem, concerning materials and production quality control. Considering this, a new design is also proposed, trying to avoid the main operation problems, resulting in a more simple and reliable device.