Electrical Switchgear Interlock



The original Castell interlock concept dates from 1922 and was developed for the electrical switchgear industry. This remains today a very important part of the Castell product portfolio. Castell delivers solutions across the electrical network from power stations to transmission equipment and from sub stations to incomer rooms. The ability to work across HV, MV and LV means that a Castell system can be used as a single solution to provide personnel safety and ensure equipment is used in the correct mode.

Our range of products has been developed over 90 years to provide the industry with interlocks of high quality and integrity. Working closely with key switchgear manufacturers has enabled Castell to produce interlocks designed specifically for use on the leading manufacturers own breakers, isolators, disconnectors and earth mechanisms.


Castell products are available in a range of materials and finishes, to ensure the correct specification interlocks. High temperature locks for use on electrostatic precipitators, stainless steel and weatherproof locks for use in sub-stations, chrome plated locks for areas where aesthetics are important and brass as standard for locks in dry, clean, non-corrosive environments.


Castell products are used in the following areas:


  • Wind Turbine Isolation & Earthing

  • Rail Electrification Systems

  • Electrostatic Precipitators

  • UPS Systems

  • LV Distribution & Busbar Systems

  • HV Transmission & Distribution Sub Stations

  • Transformer Isolation & Earthing Systems


Through development and experience Castell has a number of methods to isolate switchgear or machinery. This can be done mechanically, through control circuitry or through power circuitry.

In complex operations a number of isolations may need to occur to ensure that switchgear or machinery is safe to work on.

The isolation keys are then used to either gain direct access, are transferred to a time delay unit or for multiple entry points access through an exchange box.



Castell has developed products to suit the following companies’ equipment:

ABB | Alstom | Terasaki | Schneider Electric | Siemens | Hawker Siddeley | George Ellison