Images: David Baldock (HV Cable Jointer)
by Chris Dodds T&D - estimated reading time 2 minutes
Prior to the installation of MV-HV cable accessories whether it be heat shrink, cold shrink or separable connectors, it is critical that careful and accurate semicon workmanship is achieved by the Jointer. The treatment and cut of the semicon screen by the 11kV jointer is essential to the stability and service of all joints, terminations and connectors on 11kV/33kV power systems.
The above cable preparation images clearly shows the straight and clean cut to the black semicon screen stepping down onto the 11kV cable insulation (XLPE) – here a constant force spring provides a straight edge for copper tape screen on the 11kV cable before installing the cable termination.
Semicon cutback has been enabled by the innovation and development of dedicated cable jointers tools which should provide precision engineered cable preparation.
However, jointers tools alone without the knowledge, expertise and skill of a Competent Jointer to use them are not worth diddly squat.
For instance the photograph below highlights the problem of unskilled labour, even if equipped with the correct cable jointing tools, inflicting catastrophic damage to MV-HV power systems through lack of training, experience and understanding of the criticality of semicon cutback.
Non-radial, rough and jagged semicon screens with protuding points at the cutback will cause cable termination or joint failure. Outage. Blackout.
David Baldock is an experienced LV-HV cable jointer up to and including 33kV specialising in electrical cable installation and repair to medium/high voltage power cables including XLPE, PILC, PILC/SWA, PICAS and EPR. Ranging in cable sizes from 25sqmm to 800sqmm and covering single cores to 3 cores with copper tape screen and wire screen.
Qualified and Competent to carry out all MV-HV cable terminations such as Tyco-Raychem, Nexans, Pfisterer, 3M, Euromold and ATEX Euromold cable terminations covering all heatshrink and cold shrink terminations.
➡ The Semicon Screen – A Most Critical Point In Any MV Cable Joint, Termination Or Connector – Read Blog
Thorne & Derrick are national distributors of Cable Installation, Jointing, Substation & Electrical Safety Equipment MV HV – we service UK and global businesses involved in cable installations, cable jointing, substation earthing, overhead line and electrical construction at LV, 11kV, 33kV and EHV.
Joint | Terminate | Connect Medium & High Voltage Cables MV HV
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ISS were contracted to carry out the Design, Build & Installation of 10 new low voltage switchboards and a 24 panel 11kV high voltage switchboard, cabling and terminations installation.
The high voltage cables were connected using 11kV cable terminations into Siemens NX air insulated switchgear – the armoured 3 core 11kV cables with polymeric insulation (XLPE) were glanded using top-hat type cable glands and terminated into the switchgear using 11kV indoor heat shrink cable terminations.
Careful selection of the correct cable lugs are required – 11kV lugs tested to relevant international standards should be used with extended barrels for excellent connection and circuit conductivity.
The 11kV cable containment design and erection shown in the image below was carried out by ISS – 11kV cable spacings and cable cleat ratings were calculated and correctly specified by ISS to protect and restrain the high voltage cable circuits in the event of a short circuit.
ISS design engineers created and installed a bespoke A frame arrangement located on the ground floor to support the bottom cable entry of 11kV cables into the switchgear units located on the first floor.
A total of 22 new 11kV/415V high voltage transformers manufactured by Wilson Power Solutions were installed by ISS and all associated new low voltage (LV) power supply cables.
The LV cables were BS5467 type single core XLPE insulated power cables with aluminium wire armour and stranded copper conductors, 300-500sqmm.
High Voltage Cable Chamber – showing 11kV high voltage switchgear, terminations, cable cleats and containment
Siemens NXAIR circuit-breaker switchgear is used in medium/high voltage transformer and switching substations up to 24kV for primary electricity distribution.
All HV switchgear from the Siemens NXAIR air-insulated range are approved with internal arc classification IAC A FLR, loss of service continuity category LSC 2B and partition class PM.
Some features of the high voltage switchgear include:
1 As an electrical insulating medium – air is always available
2 Type-tested HV switchgear according to IEC 62271-200 or VDE 0671-200
3 Use of standardised block-type current transformers
4 450,000+ air-insulated switchgear panels of Siemens in operation worldwide
5 Uses maintenance-free high voltage vacuum circuit-breakers or contactors
6 Testing of the vacuum circuit-breaker and make-proof earthing switch in switchgear panel
7 Pressure-resistant partitions
8 Flexibility regarding the low-voltage equipment (removable compartment, plug-in wires)
9 Quality assurance in accordance with DIN EN ISO 9001
11kV 24kV Air Insulated High Voltage Switchgear – Siemens NXAIR
ISS Ltd are a HV/LV Power Engineering company operating nationwide, undertaking Turnkey Electrical Distribution Projects and Site Service activities including installation, commissioning, pre-commissioning, final commissioning, HV/LV switching, maintenance, repairs, refurbishment of HV/LV AC & DC Switchgear, power transformers, SCADA systems, control panels, HV/LV cabling, cable terminations and associated ancillary equipment.
ISS Ltd manufacture low and high voltage switchgear, protection cubicles, LV generator changeover panels, marshalling cabinets and bespoke protection and control equipment.
“ISS have completed further 22kV high voltage protection upgrades, upgrading 5 circuits at this particular site, all communicating back to a new 22kV switchboard installed a few miles away on the cable network. ISS removed the existing MBCI Translay, MCRI Overcurrent, MRTP Pilot Wire Supervision, KCEG Directional Overcurrent/Earth Fault MVTW Destabilising Relays. These have been replaced with a new Line Differential ABB RED615 Relay and Modem and Agile P14D Back Up Protection Relays.”
“New multicore cables have been installed from the switchboard back to the Marshalling cubicle, with ISS successfully proving the SCADA signals back to the RTU and control room. ISS commissioned the circuit into service, carrying out On Load Line Diff stability checks. A great team effort, from the design and manufacture of the protection fascia’s from our Manchester HQ, to the installation and commissioning of the circuits for a London based rail network. Great collaborative interfacing and planning between everyone involved to upgrade 22kV cable circuits on an operational railway” – Peter McKenna (ISS Operations Manager).
22kV Rail Cable Installation
More ISS project information:
Commissioning 25kV AIS Switchgear On Containerised Rail Traction HV High Voltage Substations
The disaster recovery project involved the replacement of water damaged high voltage electrical equipment and cables – this included replacement of primary high voltage switchgear, cable terminations, associated power transformers and distribution cables.
Watch, listen and learn more about the project:
Should you require any further information about 11kV Cable Termination, Switchgear, Substation & High Voltage services provided by ISS please call 0161 344 1117.
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