How trapped key interlocking protects workers at HV substations

Interlocking switchgear within HV substations ensures that personnel operate equipment safely, according to the correct procedures. Using a well-designed trapped key interlocking scheme will prevent personnel accessing potentially dangerous areas before the switchgear system has been put into a safe condition.

A good interlocking scheme will also ensure that the system functions correctly, so that there is no chance of, for example, switching two incoming feeds onto a common bus bar. This protects the equipment from damage and greatly reduces the risk of fire or arc flash.

A well-designed trapped key interlocking scheme will prevent personnel accessing potentially dangerous areas before the HV switchgear system has been put into a safe condition

There are four ways trapped key interlocks (TKIs) protect HV substations and their operators:

  1. Many HV substations are located in remote, unmanned sites which can attract attempted unauthorised access. TKIs help to safeguard this kind of vulnerable equipment.
  2. TKIs intended for HV substations have a proven design life of 45 years, allowing the safety devices to perform through decades of operation.
  3. Trapped key interlocking enforces the correct operation of equipment and therefore protects the continuity of supply.
  4. TKIs ensure that part of a system is isolated and correctly earthed before maintenance can be carried out on that section.

By: Adam Felton, Technical Marketing, Castell Safety International Ltd.

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