Evaluating Earth Switch Bonding Configurations – What is Good and What is Bad?

Transmission & Distribution

The configuration and protection of power systems requires the operation of switches. By the definition of their purpose switches are required to clear faults, the most onerous conditions on a power system.

Because of this likelihood high power switches are usually remotely operated. Human-operated switches are nominally intended to be operated to reconfigure the network, under low or zero power, so that activities such as maintenance and reconfiguration can be performed. However, errors can be made, switches can fail, and these human-operated switches become subject to conditions beyond their intended purpose or rating.

The bonding arrangement of these physically operated switches, such as earth switches and air break switches, is the significant factor in controlling the hazard posed to the operator should the switch fail. Power utilities and other power system operators across the world utilise different bonding configurations to create equipotential zones around the operator, to protect the operator should a fault occur during switch operation.

For many years, the various bonding configurations of manually operated switches has been debated. This paper looks at relative efficacy of the various configurations and what general approaches are more effective.