Author | Rialdo Suwandi
Founder at Aldora Electric | Expert in Renewable Electrical Engineering & Cable Systems | Problem Solver | FIEAust CPEng NER
HV Bushings & Connectors
As medium voltage (MV) power systems grow in scale and capacity, manufacturers have introduced electrical equipment, such as transformers and switchgear, capable of handling up to 1250A at 52kV and 2500A at 36kV.
To ensure interoperability across manufacturers, these Interfaces are standardised under EN 50180 and EN 50181 as Interface F Bushings.
Furthermore, EN 50673 standardises 630A and 1250A bushings at 72.5kV.
What Are Interface F Bushings Used For?
Interface F bushings are typically used to connect gas-insulated switchgear (GIS) and transformers to cable circuits using separable connectors distributing electrical power at 11kV, 33kV and up to 66kV – manufactured by Nexans Euromold the connectors are suitable for cable termination of polymeric (XLPE EPR) insulated cables with copper wire or copper tape screen, wire armoured (SWA/AWA), wire braided or unarmoured cables into MV-HV Electrical Equipment with Interface F bushings.
Advantages of Electrical Equipment BushingsÂ
As defined in EN 50180 and EN 50181:
F1 Bushings: Um ≤ 36 kV; Ir = 2500 A
F2 Bushings: Um ≤ 52 kV; Ir = 630 A
F3 Bushings: Um ≤ 52 kV; Ir = 1250 A
For 72.5kV high voltage power systems, EN 50673 defines the following:
F4 Bushings: Um = 72.5 kV; Ir = 630 A
F5 Bushings: Um = 72.5 kV; Ir = 1250 A
Note: F5 interfaces are commonly used in offshore wind applications but can adopted for large onshore installations as well.
Pictured | Nexans Q900AR-1Q900AR-2 Interface F Equipment Bushing 52kV MV HV
To ensure proper fit and reliable performance the following information must be established:
Interface type? e.g. F1
Maximum system voltage? e.g. Um = 36kV
Cable insulation type? e.g. XLPE
Conductor material and cross-section? e.g. copper, 800sqmm
Insulation over-diameter? e.g. 52.8mm
Number of circuits per phase? e.g. 2 circuits
Are surge arresters required? Confirm via an insulation coordination study
Interface F bushings enable safe, standardised, and high-capacity MV cable connections to GIS, and transformers, both for on-shore and off-shore applications.
Selecting the correct separable connector Interface F Connector —matched to interface type, voltage, current, cable type, and system design—ensures long-term reliability, safety, and maintainability.
Definitions of International Electrical Standards
EN 50180 | This European Standard is applicable to ceramic and resin insulated bushings having highest voltages above 1kV up to 52kV, rated currents from 250A up to 3150 A and frequencies from 15 Hz up to 60 Hz for insulating liquid filled transformers. This European Standard establishes essential dimensions, to ensure interchangeability of bushings and to ensure adequate mounting and interchangeability of mating plug-in separable connectors of equivalent ratings.
EN 50181 | This European Standard is applicable to insulated bushings for maximum voltages above 1kV up to 52kV, rated currents from 250A up to 2 500A and frequencies from 15 Hz up to 60 Hz for equipment other than liquid filled transformers. This European Standard establishes essential dimensions, to ensure adequate mounting and interchangeability of mating plug-in separable connectors of equivalent ratings.
EN 50673 | Extend the scope of the EN50180-1/2/3 and EN50181 for plug-in type bushings up to 72.5 kV
Thorne & Derrick distribute the most extensive range of MV HV Medium & High Voltage Cable Joints, Terminations & Connectors from manufacturers including 3M, Prysmian, Nexans Euromold, Elastimold, Pfisterer CONNEX & SEANEX and Shrink Polymer Systems.
Cable Jointing Solutions
Network resilience requires advanced technology solutions manufactured from highest performance materials; if high harmonics, Sine wave distortion, AD8 protection, abnormal thermal cycling, high-water table, ALE of legacy PILC or general cable failure prevention to critical 11/33kV circuits matters to you, then talk to us.
Where cables undergo dynamic cyclical load in high harmonic and non-linear load applications the Lovink range of cable joints demonstrate years of fault-free field performance in high temperature installations – additionally, the cable joints are “flame-free” and therefore safe for installation in potentially explosive atmospheres as no heating source or naked flame is required for the installation.
Resin encapsulation provides the highest levels of mechanical impact protection and electrical insulation eliminating voids, discharges and ionisation within the cable joint – the seawater resistant resin and “wet area” (2 bar at 20m water head) performance counters premature electrical cable joint failures in the renewable sector where damp soil conditions, flooded duct and water immersion can induce premature service failure to jointing solutions utilising other technologies.
The compact design permits reduced size joint holes reducing excavation and associated civil engineering preparation costs – ideal for confined space applications where volume displacement is a factor and close quarter working necessitates a compact profile solution.
Thank you to Stephen Davies (Lovink Enertech Account Manager) for todays emphatic Presentation and roundtable with our incredible Team.
Lovink Cable Joints
For straight, transition and branch connections of MV Power Cables – this includes 11kV and 33kV paper-insulated (PILC/PICAS) and polymeric (XLPE/EPR) cables up to 1000sqmm.
Lovink Cable Joints
From CSD Sealing Systems
The recent fire at the electrical substation next to Heathrow Airport, which led to its temporary closure and disrupted thousands of flights reminds the industry of the importance of critical fire protection measures in substation environments.
Thorne & Derrick are Approved Main UK Distributors for CSD Sealing Systems, specialising in advanced cable duct sealing solutions designed to enhance the safety and resilience of electrical substations.
The CSD Sealing Systems range of products, including the NOFIRNO range are engineered to prevent the spread of fire, smoke, and water, thereby safeguarding essential infrastructure and minimising the risk of catastrophic failures.​
By integrating CSD’s pipe and duct sealing technologies, substation operators can significantly reduce the potential for fire-related disruptions, ensuring continuous operation and protecting both assets and the public.​
Critical Fire Protection of Substations
A dry cable basement achieved by cable duct sealing is a cornerstone of reliable GIS (Gas Insulated Switchgear) substation operation – substations provide electricity distribution for both medium (MV) and high voltage (HV) power systems in the UK typically distributing electrical power at 11kV, 33kV, 66kV and 132kV voltages.
Water intrusion, even in limited volumes, can have severe and catastrophic consequences to the provision of uninterrupted LV MV HV power supply:
Corrosion: Water ingress and flooding accelerates cable corrosion including metal components compromising the structural integrity of the substation
Electrical Faults: Water can bridge insulation, leading to short circuits, arcing, and potential substation fires
Reduced Equipment Lifespan: Moisture can degrade insulation materials and accelerate equipment aging
Operational Disruptions: Water ingress through unsealed cable ducts can necessitate unplanned maintenance and outages, impacting power delivery
To safeguard GIS substations, implement these preventive measures:
Robust Drainage Systems: Ensure effective drainage to divert water away from the substation basement.
Waterproof Cable Duct Sealing: Regularly inspect and maintain ducting seals on cable entries plus doors, and other openings.
Regular Inspections: Conduct routine inspections to identify and address potential water ingress points.
Emergency Response Plans: Develop and implement contingency plans for water intrusion events.
By prioritizing a dry cable basement, you can enhance the reliability, safety, and longevity of your GIS substation, MV HV cables and electrical infrastructure – view our complete range of duct seals.
The NOFIRNO Duct Seal System is the proven choice for watertight and gas-tight protection for cable ducts, manhole entries, duct bank entries, and similar applications to prevent flood damage to GIS substations on the UK DNO and private network.
Duct Seals | Stocked & Supplied by Thorne & Derrick
uploaded by Chris Dodds – Sales & Marketing Manager at Thorne & Derrick
NE ENGLAND UK : A POWERBASE PARTNERSHIP | Yesterday with Carl Cox (Thorne & Derrick – Sales Engineer), I was very privileged to be invited to the Grand Opening of the RelyOn UK Electrical Training Facility by Jess Churchman and Ryan Muscroft following introductions by Paul Livingstone from NOF – located within Redcar & Cleveland College the facility will assist the provision of a skilled workforce in HV via a collegiate and multi-faceted approach up to 33kV.
The official launch of the new electrical training Facility located at Redcar & Cleveland College has been a huge success and will assist the development of an electrically skilled workforce capable of rising to the challenges of energy transition.
The highly-engaged audience benefitted from the exciting vision for the Facility in driving Energy Transition across local Wind Energy, Hydrogen & CCUS projects provided by RelyOn UK’s Speakers Jason Faulkner (Deputy Chief Executive) and Colin Leyden (Regional Managing Director) – “essential skills for critical infrastructure.”
The Facility will provide both standard and tailored courses for clients including Amazon Web Services (AWS), Vestas and Siemens Energy.
Via Video Link the Mayor of the Tees Valley, Mr Ben Houchen, nut-shelled it perfectly: “TEES VALLEY, ANYTHING IS POSSIBLE – thousands and thousands of local jobs for local people.”
Thorne & Derrick look forward to continuing to realise the possible as an integral supplier to the global renewable industry.
Switchroom wired by Slaters Electricals | Gear by Lucy Electric, Schneider Electric, ABB and Alstom Power.
Pictured | Ryan Muscroft (Head of Electrical Services – RelyOn Nutec UK) with Chris Dodds and Carl Cox from Thorne & Derrick, a Specialist Distributor of High Voltage Cable Accessories, Electrical Safety Equipment & Products to the renewable industries.
RelyOn UK | High Voltage Electrical Engineering Training Courses
Safety Training & Digital Learning Specialists | Renewables and Offshore Energies Sectors
The new electrical facility, located within Redcar and Cleveland College, and officially supported by Tees Valley Mayor, Ben Houchen, is part of the RelyOn Group’s wider growth strategy which includes building a robust global electrical training and consulting service, with an emphasis on HV and LV electrical systems.
The Welcome Speech & Introduction to RelyOn Open Day
Selection of Photographs of High Voltage Electrical Switchgear & Transformers – the HV Training Centre is equipped with leading brand and cutting-edge technology equipment to enable the upskilling of High Voltage AP’s, SAP’s and Electrical Engineers to install 11kV/33kV Cable Accessories including Joints & Terminations.
Thorne & Derrick are Specialist Distributors to international Utilities, UK DNO’s, ICP’s and HV Jointing Contractors of an extensive range of LV HV Cable Jointing, Substation, Tooling & Installation Equipment from 600V to 66kV –  we service wind energy, solar power, battery storage, rail, utility, datacentre and the explosive atmosphere industries.
Based in the UK, we are highly customer responsive and absolutely committed to providing a world-class service.
Since 1985, we have provided expert technical support and express delivery from extensive UK stocks to world-wide destinations.
Key Product Categories: Connectors, Joints & Terminations MV HV | Cable Preparation & Jointing Tools | Duct Seals | Cable Transits | Cable Cleats | Cable Glands | Electrical Safety | Arc Flash Clothing & Protection | Cable Pulling | Earthing & Lightning Protection | Feeder Pillars
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