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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Castell supplies safety interlocks to Tianwan Nuclear Power Plant

FS interlocks and key exchange boxes provided for Phase II project

Castell is to supply interlocking systems to the Tianwan Nuclear Power Plant Phase II project under construction in Lianyungang, Jiangsu province, China. Tianwan is the nuclear power plant with the highest unit capacity in China. To date, it is the largest joint technical and economic project undertaken by China and Russia.

Tianwan Nuclear Power Plant Phase II project in Lianyungang, China, uses Castell safety interlocking products to ensure the safety of maintenance staff

Castell will provide multiple sets of mini FS industrial safety interlocks and key exchange boxes for the China National Nuclear Corporation construction project. These devices prevent the busbar earthing switch from connecting during maintenance on high-voltage switchgear, thereby guaranteeing the safety of maintenance staff.

Since 2010, Castell has provided customised safety interlocking devices for six successive nuclear power projects in China. Project supporter ABB China recommended Castell to the China National Nuclear Corporation as part of this latest Power Plant Phase II project.

Christy Zhang, Castell senior sales manager for the China region, said: “Once again, Castell has retained the trust of its Chinese nuclear power industry clients. The company continues to establish its products’ leading edge within the high-end field of nuclear power.”

The unit capacity for the Tianwan Nuclear Power Plant’s Units 3 and 4, which are currently under Phase II construction, will be one million kilowatts. Units 3 and 4 are expected to be put into commercial operation in February and December 2018 respectively.

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