On the 2nd and 3rd of July, we will be holding an open day in Corsham. Find out more by clicking here



On the 2nd and 3rd of July, we will be holding an open day in Corsham. Find out more by clicking here


We are PENTA, a multinational industrial leader, pioneer, and expert manufacturer of electrical safety solutions, committed to ensuring your safety at every intervention.

The PBwel was established in 1937 to manufacture electrical instruments.

In the mid-1940s, the company identified a requirement for gas and oil operated (Buchholz) relays to protect oil filled transformers and the first production units were installed at that time. A continual development programme, in conjunction with the Central Electricity Generating Board, led to the production of the Mk10 Buchholz relay.


For use in situations subjects to seismic disturbances and mining activities such as blasting.

Shock and vibration acting along the tube of a conventional Mercury switch can cause the Mercury within it to move and momentarily bridge the switch electrodes, even though the switch is tilted in the open position.

This is considered to be a mal-operation of the relay, in that it is caused by external influences and not by a fault within the transformer. Consequently, where relays are to be used in situations as described above a more suitable alternative to the usual Mercury switch is required. Magnet operated reed switches were selected specifically for this purpose and this choice is supported by the following type tests which successfully withstood.


Single element type relays are available for 1? bore size designed 1 SE, which operate indiscriminately for Gas or Oil collection and are suitable for small oil filled transformer, capacitor and potential transformer protection.

A special range of single element relays are also available for Tap-Changer type transformers which operate for a surge conditioner or loss of oil only and allow gas, normally produced during tap changing operation to pass freely. The single element relay has only one operating element and operates in a similar manner to that described for the double element types.

Contact us for the full technical details using the button below.


  • Portable Earthing Equipment for EHV sub station and overhead line applications.
  • Gas and oil operated ?Buchholz? transformer protection relays
  • Electrical instruments and Test Equipment


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