Roxtec Substation Cable Seals For Triplex Cables Prevent Water Ingress & Flood Damage

Cable Transits

Roxtec Substation Cable Seals For Triplex Cables Prevent Water Ingress & Flood Damage

Roxtec Cable Sealing


High Voltage Substation Cable Sealing For UK DNO's & Utilities

Roxtec Cable Transits Frames - Cable & Pipe Seals

Cable and pipe seal manufacturer Roxtec has won a new deal in the high voltage substation sector with UK electricity provider Western Power Distribution (WPD).

Roxtec cable seals have been specified to provide flood protection and water ingress protection to high voltage electricity substations operated by WPD in the South West of England. WPD is the electricity distribution operator to more than 7.7m customers living in the Midlands, South Wales and the South West of England.

Roxtec cable seals are being used to seal cable entry points into the substation to protect against flood risk. Roxtec’s triplex seals have been designed and tested for use with single core power cables, commonly used in the utility sector.


Pictured : Roxtec Cable Seals Protect MV HV Electricity Substations


Pictured : Roxtec Substation Cable Sealing

Roxtec cable and pipe seals provide certified protection against fire, gas, flooding water, dust and rodents. Substation applications include : sealing trefoil power cables on gas insulated switchgear, sealing cables entering core drilled holes, IP protection for 11kV 33kV power cables, sealing transformer cabinets, pad mounted shelters, transformer bund seals and sealing electrical enclosures. 

GIS Substation Transformer Cable Seals Substation Seals Roxtec R Transit Seal


Triplex cables provide high voltage (HV) mains power distribution for utility and industrial applications - 11kv triplex cable consists of three single core high voltage cables in triplex formation according to BS7870 - 4.10.

Triplex cable features circular solid aluminium (SAC) conductors, cross linked polyethylene (XLPE) insulation, copper wire screen and medium density polyethylene (MDPE) oversheath.

Roxtec H3 Trefoil Cable Seals have been installed to seal high voltage cables at the point they enter the substations. Roxtec cable seals are protecting 132kV and 33kV substations which are the primary and secondary connection points for the processing of electricity from the National Grid.

Roxtec mechanical cable seals are robust to support the weight of HV power cables and maintain an adequate and consistent seal around the cables. There will be natural flex and movement in the cables during operation which can create a leak path into the substation.

Pictured : Roxtec H3 Trefoil Cable Seals

Roxtec H3 Trefoil Cable Seals

With this project it is vital the substation is protected from flooding. Water ingress is hazardous for substations as even a small amount of water in a cable trench can increase the relative humidity in the air. This in turn increases the likelihood of partial discharge and ultimately a costly power outage.


  • Partial Discharge & Need For Advanced Cable Sealing

PD’s are electrical discharges occurring inside or on the surface of insulation materials – caused by HV electrical stressing of the insulation. PD leads to progressive deterioration and plays a significant part in failures. Partial discharge affects all types of HV assets critical to network operation including switchgear, cables and transformers. High humidity and particle contamination (typically dust ) cause and accelerate PD.

Large swings in humidity also have an adverse effect. Hard to detect until invasive maintenance is carried out or failure occurs. Most common cause of high humidity in electricity substations is water ingress through structure and below ground cable ducts. Most common dust ingress points include below ground cable ducts and cable entries in walls and roofs of electricity substations.

  • Effects of Partial Discharge

"Eventual catastrophic failure. Replacement of equipment, typically can’t be rectified through cleaning or minor refurbishment. Loss of supply." Read :  White Paper : Humidity Effects, Partial Discharge & Loss Of Power At Substations By EA

Roxtec cable seals are specified by the power transmission, distribution and renewables market supporting both new build and existing substations. Cable sealing systems can eliminate the risk of high voltage electrical equipment failure caused by partial discharge as a result of inadequate specification of cable transit or cable duct sealing systems.


  • Sealing Substation Cables

Roxtec cable seals are specified for electrical engineers working with HV cables, especially hard to seal trefoil formations where 3 single core cables are entering a cable duct. The Roxtec H3 trefoil seal effectively seals trefoil and Triplex cables.

This includes high voltage cable sealing applications with a tight bend radius from cable duct to termination under switchgear where traditional mastic or inflatable cable sealing products have difficulty achieving a good long term seal due to overall cable sizes and weight.

Retention Of Cables - Roxtec cable seals are specified in the masts of wind turbines offshore, the seal is not used as "traditional" seal it is used to retain the cable due to the constant movement when the turbine is in operation and in the worst storm conditions. Pull test data for cable retention is available on request. The cable seal gives a high degree of mechanical retention and performs well over long time periods providing a durable long term cable seal even where tight bend radiuses exist from cable duct to switchgear base.

Vermin Resistance - Roxtec have a fully verified and tested system. Roxtec have engaged with Huntingdon Life Sciences to perform tests on vermin resistance of cable seals - information available on request.

Flash Flooding - the Roxtec cable seal solution provides high levels of performance in relation to water ingress in both normal high water table situations and flood scenarios. Roxtec round seal performs up to 2.5bar pressure.

Pictured : Utility Switchgear, Transformer & Generator Sealing. Roxtec cable and pipe seals provide sealing protection against fire, gas, fluids, dust and EMI in the electricity generation and distribution market. Roxtec B type cable transit frame is shown here providing protection and sealing to underground power cables. 

Roxtec Frame

Roxtec cable sealing solution is simple to install requiring no special tooling.

Roxtec fixings vary depending on type but generally a socket set with a 10mm or 13mm socket is all that is required to complete the cable seal installation.


Video: Roxtec Substation Cable Seals - Triplex Cables Using H3 Cable Seal 

Video Playlist: Roxtec Cable Transits - Seal Cable Ducts & Pipe Entries


Video Tutorial : PD Partial Discharge - EA Tutorials, 13 Part YouTube Playlist