Shearbolt Connectors for LV/MV Underground Power Cables: Reliability & Failure Modes
Published 05 Nov 2020
The technology of shear bolt connectors for current transmission has developed quickly. The principle was first introduced in the early 1980s when manufacturers sold the first types of low voltage bolted connectors. The next step was adopting shear bolt technology for use in low voltage cable applications, where required torque moment was a pre-set parameter machined into the bolt. Based on positive field experience, shear bolt connector technology was adapted for use in medium voltage applications as well. But cable accessories up to 42kV require concentric connector bodies and smooth outer surface, without sheared off bolts standing proud and no sharp edges at the connector and bolts.
In the 1990s, connector manufacturers introduced different types of multiple shear bolts, allowing a requested torque moment to a particular cable cross-section while ensuring that bolts shear off flat with the outer circumference of the connector body. At the same time, IEC 601238-1 was established to replace former local standards and set higher requirements in terms of contact ageing. The most important advantage of bolted contacts is that one connector type applies for different cross-sections and conductor materials. This created a user-friendly and reliable connector, simplifying allocation of conductor cross-section to connector. Those same principles and connector body design have been adapted and optimized to cover cross-sections of up to 3000sqmm and even for HV/EHV applications.
By Fak Hardt | Head of Product Portfolio & Cable Accessory Development, Pfisterer Holding, Germany
Mr. Hardt is an Electrical Engineering professional. He has had more than 24 years of experience in manufacturing as R&D-Manager for connectors and fittings with Pfisterer as well as in development of underground power cables and accessories. He has in-depth knowledge of related production processes, quality and environmental management and holds patents for bolted technology and ring connector technology. Pfisterer is a leading independent manufacturer of cable, connectors, insulators and overhead line accessories for sensitive interfaces in energy networks. The Group is headquartered in Winterbach, near Stuttgart in southern Germany.
Thorne & Derrick are national distributors of LV, MV & HV Cable Installation, Jointing, Substation & Electrical Equipment – servicing businesses involved in cabling, jointing, substation, earthing, overhead line and electrical construction at LV, 11kV, 33kV, 66kV and EHV. Supplying a complete range of power cable accessories to support the installation and maintenance of low/medium and high voltage voltage power systems:
- Slip-on Cable Terminations
- Cold-shrink Cable Terminations
- Heat-shrink Cable Terminations
- Cable Joints – Heat & Cold-shrink
- Separable Connectors (Euromold)
- Surge Arresters & Switchgear/Transformer Bushings
Key Product Categories: Duct Seals | Cable Cleats | Cable Glands | Electrical Safety | Arc Flash Protection | Cable Jointing Tools | Cable Pulling | Earthing | Feeder Pillars | Cable Joints LV | Joints & Terminations MV HV