11.1 Introduction

Because of the relatively high cost of electrical distribution by buried cable, power supplies to sparsely populated areas are invariably provided by overhead line conductors. The present-day overhead line distribution equipment is the product of innovation and evolution resulting from many years of application in the field of rural electrical distribution. Advances in technology, as they have become available, have been adopted to provide better security and continuity of the supply of power to remote centres of consumption, as well as providing the power supplier with information which was not readily available a few years ago.

11.2 Standards

The basic standard for autoreclosers is ANSI C37.60. This standard was modified when vacuum interrupters were introduced to recognise the longer contact life of the new technology. The standard requires many more fault operations with vacuum than with oil, recognising the inherent longer life of vacuum interrupters.

The only other known standard for autoreclosers is the UK EATS41-26, which accepts the ANSI standard but adds to it the IEC values for transient recovery voltage as well as introducing a three second short time current fault rating and internal arc fault requirements.

11.3 Historical background

Electrical power supplies to remote consumers are invariably provided by radial overhead line feeders with pole mounted transformers at the consumer's end to provide a low-voltagesupply. The voltage of the over headline from the source to the consumer's transformer can be anything from, typically, 3.3 to 38 kV.

The earliest systems consisted of a source transformer...