Operational Problem | Recurring 33kV Joint Failures Caused by Water Ingress to AXAL-F-TT Cables – a Medium Voltage Cable with XLPE Insulation 3 Core Construction.
Approved Technical Recommendation | Design, Specification & Supply of Customised Medium Voltage Polymeric Trifurcating Cable Joints (3 Core to 3 Single Core Cables).
Uploaded by Chris Dodds | Sales & Marketing Manager Thorne & Derrick
Thorne & Derrick have been working across several portfolios of renewable assets in the UK with Solar EPC’s to produce a reliable rectification to 33kV cable joint failures caused by water ingress. The Approved Polymeric Heat Shrink Trifurcating Joint with integral water-barrier features a “resin block” before the cable joint to prevent additional water from penetrating the seals of the joint shell.
Rather than use heat shrink shapes, such as a cable break-out, the client preference for the MV Joint was to include a combined Resin & Shell Water-Blocking Kit to overcome future water penetration compromising solar cable service, reliability and circuit integrity.
Cable reliability increases plant profitability and overall operational efficiency with reduced downtime caused by cable failures on PV power plants.
Water spread and the capillary effect under the cable sheath can cause excess stress on the seal leading to premature joint failure. The solution covered in the Jointing Instruction is to install the jointing encapsulation resin and shell 1000mm from the cable sheath and create a birdcage with the cores – note the core of the medium voltage cable must be separated to allow the resin to flow fully into all voids to eliminate air gaps and possible pathways for water ingress to travel into the Joint and minimise the risk of future failure.
With an expected shelf-life of 2-3 years the Joints have now been introduced to several solar farm sites as Strategic Spares – this provides the client with contingency planning, emergency response and immediate fault repair to any future 33kV cable failures.
The Joint features a “single-tube” shrink over the mechanical shearbolt connector overcoming the traditional multi-tube process with independent stress control and triple wall heat shrink tubes requiring additional working time. Repair and Jointing work should only ever be carried out by an Authorised & Competent Jointers.
The existing faulted 33kV 3 Core AXAL-F-TT specification cable was jointed onto new 33kV BS7870 Single Core BS7870 type cables in accordance with the manufacturers Jointing Instruction – here is an excerpt from the JI Document, ownership of Shrink Polymer Systems.
Thorne & Derrick are Specialist Distributors to Solar EPC’s & High Voltage Jointing Contractors working on the design, construction and maintenance of UK, European and international projects supplying an extensive range of LV HV Solar Cables, Jointing, Substation & Electrical Eqpt.
Based in the UK, we are highly customer responsive and absolutely committed to providing a world-class service.
We stock LV HV Solar Cables, Accessories & Electrical Equipment to enable the construction, maintenance and operation of utility-scale PV installations – our products connect 600V/1500V solar cables into combiner boxes, inverters, transformers and energise switchgear up to 33kV/132kV for high voltage grid connections.
Since 1985, we have provided expert technical support and express delivery from extensive UK stocks to world-wide destinations.
Uploaded by Chris Dodds | Sales & Marketing Manager at Thorne & Derrick
Here the Jointer, Steffan Evans, from HVSM is shown expertly removing the cable sheath and bonded aluminium screen using the Ripley US15 Cable Sheath Stripping Tool (10-50mm) – the Jointing tool when used by Trained & Competent Jointers effortlessly and safely removes both the outer sheath jacket with aluminium foil screen without incurring damage to the copper wire screens on a 33kV single core 800sqmm XLPE insulated cable.
Cable Preparation | Excerpt from Nexans Euromold Type C Interface Connectors (K), (M), (P) 800PB/G Up to 20.8/36 (42)kV | Note the instruction references the requirement to remove the outer cable sheath with Aluminium foil together.
Caution: in the case of conductive coated outer cable sheaths, the conductive coating must be removed during the installation of accessories in order to be able to carry out e.g. cable sheath testing. For this purpose, the conductive coating of the outer cable sheath must be removed with a suitable stripping tool for a length of approx. 400 mm below the end of the cable sheath.
Sheath Stripping with the Ripley US15
Stripping Bonded Screens 33kV
Here Steffan is shownly stripping bonded semi-conductor screen from medium voltage power cables (20/22kV) prior to terminating the cable into Siemens NXAIR type Vacuum Circuit Breaker – the Ripley US02-7000 comfortably caters for the precision stripping of the bonded screen from the 400sqmm cable for preparation of the Raychem (Tyco) heat shrink termination to be installed.
The US02 Tool manufactured by Ripley Tools features a revolving ergonomic handle and accessible adjustment knobs for comfort and ease-of-use, reducing effort and potential strain for cable jointers performing repetitive shaving functions in the field.
“Investing in innovation and introducing cable jointing tools to HVSM improves safety and reliability for our clients. The Ripley US02 is very Jointer-friendly with a spectacular finish to the XLPE insulation – the automatic cut-off and incremental blade adjustments ensure a professional perfection of cable preparation at medium voltages,” comments Steffan.
Stripping in the Switch| the US02 Tool is compact but robust allowing confined space working in Medium Voltage Electrical Equipment.
Cable Preparation Tools | Distributed From Stock | Approved Supplier
HVSM are one of Ireland’s most long-standing High Voltage Engineering companies, which has been operating since 1991. Headquartered in Ireland but present and operating globally, they provide best in class specialist service for High Voltage Power Industries such as Commercial, Utilities, Manufacturing, Life Science, Data Centres as well as the Renewable Energy Sector.
Thorne & Derrick are now Official Distributors for the Vicera range of Cable Jointing Stands – the introduction of this new product range is an excellent extension to our core ranges of Cable Jointing, Pulling Equipment & Preparation Tooling and we look forward to further supporting efficient, easier and more reliable power cable installations.
Thorne & Derrick distribute the most extensive range of MV HV Medium & High Voltage Cable Joints, Terminations & Connectorsfrom manufacturers including 3M, Prysmian, Nexans Euromold, Elastimold, Pfisterer CONNEX & SEANEX. Heat shrink, cold shrink, push-on and slip-over cable accessories enable the jointing, terminating and connection of 11kV-33kV and 66kV-132kV cables to oil, air or gas insulated switchgear, transformers, motors and overhead lines distributing electricity at medium/high voltages.
T&D hold large stocks of 11kV 33kV 66kV Joints & Terminations suitable for XLPE, PILC and EPR cables, in both heat shrink and Cold Shrink technologies, to service the medium/high voltage power cable accessory requirements of UK and international customers.
Unlocking The Power Of Solar | Electrical Balance of System in Solar Applications
Electrical Balance of System in Solar Applications
The hard parts are done. You have a solar farm site ready to build and an order placed for high performance PV modules, best-in-class inverters, and a tracking system to maximise energy production. Now you just need to figure out how to get it all connected.
Easy, right?
It’s not rocket science, but thoughtful selection of Electrical Balance of System (EBOS) components is essential for project success. In a recent audit from Solargrade, 62% of all utility-scale solar projects had critical safety issues, 91% of which related to direct current (DC) power distribution. Most issues were caused by field-made connectors and wire management, components of the EBOS.
To understand where to focus to create a reliable, high-performance EBOS, let us start with the PV module and work our way to the DC/AC inverters that connect to the grid.
➡ Thorne & Derrick partner with Panduit to bring the most innovative renewable energies solutions to the market.
Below discover how Panduit is at the forefront of accelerating solar projects, enhancing reliability, and increasing profitability with our expert insights on navigating Electrical Balance of System (EBOS).
Join us as we unlock the potential of solar energy for reliable, efficient projects.
Electrical Balance of System Components IN THE SOLAR iNDUSTRY
PV modules range in size and power output, but all have DC wires exiting from a junction box on the back. In a solar array, these wires are routed as a bundle or spliced together at prescribed intervals and fed into a combiner box. The combiner box, as its name suggests, combines the power from these strings of modules so that a pair of larger, high-voltage cables can carry their combined power in a “home run” to the inverter and then eventually on to the grid.
Commercial and utility scale solar projects necessarily have a large footprint to produce the amount of required power. Because each PV module only creates 400–600 W, you need 1,667–2,500 modules to produce just one megawatt (MW) of electricity, and utility projects can typically range anywhere from 20 to 500+ MW. With all that scale comes a huge amount of cable to manage. And because these projects are placed in areas with intense sun, all the components are exposed to the elements. To be reliable, solar cable management solutions must securely hold cables in high wind, protect from long-term abrasion, withstand harsh UV, potential chemical exposure, and extreme temperatures.
Several suitable options exist for routing smaller cables along the back of PV modules. The most common include dedicated solar clips that snap on the metal frame, specialised wire hangers that fit through holes in the frame, and heavy-duty cable ties. Arrays that move to track the sun create some additional challenges with abrasion, so flexible corrugated tubing is often used to surround cables and protect around potential pinch points.
At each combiner box, dozens of smaller cables enter and connect to a pair of busbar conductors, most commonly with power lugs. The lugs are crimped using tools or mechanically terminated to the ends of the wires and secured to the busbar with screws to ensure reliability and efficiency.
Power exits the combiner box through higher-voltage cables and is routed one of two ways: either below ground in a trench or suspended in bundles from steel cables strung in-between rows. These higher voltage “home run” cables carry power to an inverter connected to the grid, or directly to DC battery storage on site.
As with any electrical system, proper bonding and grounding are critical parts of a solar project. Grounding provides a super-low-resistance path for electricity to flow, so that power can safely complete a circuit should a fault occur.
In the EBOS, bonding components like lugs and straps connect each of the individual array components together and then to the grounding system. Without proper grounding, tray and racking surfaces can become energised in the event of a fault, creating a life-threatening situation for people working on the solar array.
Most solar safety and reliability issues emerge from mistakes in managing DC wiring and grounding. Selecting appropriate cable management, termination, and grounding solutions can prevent some challenges. Placing an emphasis on ease of installation, quality materials, and long-term reliability when specifying EBOS components will minimise problems once the project is built.
Maximising Return on Investment Through EBOS
Like any utility, the goal of solar farms is to produce the most usable energy at the lowest total cost over the life of the project. To optimise long-term return on investment, it’s important to consider ease of installation, durability, and safety when selecting BOS components.
Finding skilled labour continues to be a challenge in the construction industry, and the labour needed to connect 2,500 PV modules is significant, let alone 2.5 million. EBOS solutions that simplify installation and minimise re-work can noticeably reduce labour hours and total installation costs. Even components that save seconds per operation compound to significant time savings over the duration of the build.
Once a power plant is commissioned, any downtime directly impacts profitability. Because these projects necessarily involve hundreds of thousands of individual modules, any weaknesses in components will be exposed and magnified. Selecting products specifically designed to last years in harsh environments reduces unplanned maintenance costs and lowers the total cost of ownership over the life of the project.
Solar projects typically have a usable lifespan of 25+ years. To maintain the highest level of production, it’s necessary to perform regular maintenance, which includes everything from cleaning modules and controlling vegetation to replacing deteriorating components.
Effective labelling of all system components during installation is critical for future operations personnel to interact with equipment safely and efficiently. Exposure to UV and precipitation can lead to fading and make labels illegible, so high-quality, easy-to-read solutions designed for outdoor environments are a good investment to ensure efficient maintenance in the future.
Summary
Though EBOS components (excluding wire) represent less than 5% of total project costs, they can be an important way to control costs and optimise performance throughout the life of a solar installation. Quality components maximise labour efficiency during the initial build and result in fewer errors that require re-work. Using longer lasting environment-specific materials and easy-to-read labelling solutions simplifies future operations and reduces maintenance costs. And most importantly, getting EBOS right addresses the most common critical safety issues found in solar projects today.
Experienced Brand Marketer with a specialization in strategy, content marketing, product marketing, storytelling, public relations, event management, athlete and ambassador partnerships, advertising, and team leadership.
Andrew is a member of the Panduit Renewable Energy team as a Product Marketing Manager. He is passionate about building an electrified future and the technology powering energy transformation.
Panduit Electrical Group is a world wide leader in the manufacture of high-quality electrical products including cable ties, wiring accessories, terminals, and identification products such as computer printable labels and portable labelling systems, wiring duct, heat shrink tubing, wire abrasion protection, and accessories.
Thorne & Derrick are Specialist Distributors to Solar EPC’s & High Voltage Jointing Contractors working on the design, construction and maintenance of UK, European and international projects supplying an extensive range of LV HV Solar Cables, Jointing, Substation & Electrical Eqpt.Based in the UK, we are highly customer responsive and absolutely committed to providing a world-class service.
We stock LV HV Solar Cables, Accessories & Electrical Equipment to enable the construction, maintenance and operation of utility-scale PV installations – our products connect600V/1500V solar cablesinto combiner boxes, inverters, transformers and energise switchgear up to 33kV/132kV for high voltage grid connections.
Since 1985, we have provided expert technical support and express delivery from extensive UK stocks to world-wide destinations.
We look forward to working to with you on your next Solar project.
Joint | Terminate | Connect Medium & High Voltage Cables MV HV
MV HV High Voltage Cable Joints | Cable Terminations | Cable Connectors
Cable Sheath Bonding
Each HV cable sheath bonding method has its advantages and applications.
Solid bonding of high voltage cables is simple but leads to sheath losses, single-point bonding eliminates circulating currents but requires voltage control, and cross-bonding is the most efficient for long HV cables, minimizing losses.
The choice depends on High Voltage Power System requirements, cable length and operational efficiency.
Solid Bonding
In this method, the metallic sheath of the cable is bonded at both ends and connected to the earth. This results in continuous current flow in the sheath due to the induced voltage.
Solid Bonding Advantages: Simple to install. Disadvantages: High circulating currents in the sheath lead to power losses and increased heating. Best suited for: Short high voltage cable routes where sheath current losses are minimal.
Single Point Bonding
The sheath is bonded to the earth at only one end, with the other end left open and insulated. An earth continuity conductor is used to maintain equipotential grounding.
This method eliminates circulating currents but results in induced sheath voltages, which can be high. To control this, sheath voltage limiters (SVL) are used.
Single Point Bonding Advantages: Reduces power losses as no sheath currents circulate. Disadvantages: Requires careful management of sheath voltages. Best suited for: Medium-length high voltage cable systems.
Cross Bonding
The high voltage cable length is divided into three equal sections (minor sections) within a major section. At each section junction, the cable sheaths are cross-bonded using link boxes to balance out induced voltages. This technique cancels out circulating currents, reducing sheath losses significantly.
Cross Bonding Advantages: The most efficient method, significantly reducing losses. Disadvantages: Complex installation and maintenance. Best suited for: Long-distance high voltage cable routes.
T&D distribute the most extensive range of LV, MV & HV Cable Jointing, Terminating, Installation & Cable Pulling Equipment – we service UK and international clients working on underground cables, overhead lines, substations and electrical construction at LV, 11kV, 33kV and EHV transmission and distribution voltages.
Safety is a top priority in any industrial setting, fatal work injuries at work up 6% in 2022 shows OSHA some of these could have been avoided implementing dropped object prevention equipment. Building an enduring safety culture can be the most cost-effective and proven accident prevention process in any organisation. Creating, promoting and internalising this culture is the most successful way to minimise costly injuries and maintain a safer, more productive and engaged workforce.
OSHA recently announced that in December 2023 the numbers of fatal occupational injuries by event in the USA for the year 2022. The fatal occupational injuries have increased by almost 6%, which is a significant increase on the year before. The highest number of fatalities at work are found in the transport industry and are often related to controlling a vehicle. The second highest fatal injury for 2022 is slip, trips and falls.
Work-related fatalities due to falls, slips, and trips have increased 1.8% in 2022, resulting in 865 fatalities, up from 850 in 2021. Most fatalities 80.9% in this category were due to falls to lower levels, which had 700 fatalities in 2022.
This was a 2.9% increase from 680 fatalities in 2021.
Dropping objects highest risks for employees
Drilling down in the causes of these fatalities you find that: slips, trips and falls, also struck by falling object or equipment other than vehicle, is an high risk for employees and contractors. Both of these categories have fatalities resulting from dropping objects and falling from elevated work locations. The list further continues with the 3rd highest categories of fatalities in the industry with exposure to substance or environments.
A lot of these accidents can be prevented with decent housekeeping and well-designed work areas. Therefore special a focus should be on how to keep your workspace safe and clean. The walkways should be well prepared and suitable for work and designed with traffic segregation schemes. Safety standard ISO 14122 teaches that stairs, stepladders and guard-rails should be designed safely.
Adjustable Kick Plate installed to prevent objects from falling
The toe-board, or kickplates are designed as a solid lower part of a guard-rail. It is a upstand on a landing to prevent the fall of objects from a floor level. Toe boards is edge protection for the floor. It prevents that accidents happen when employees kick against a tool that slides off the edge to the work area.
The advantage for using toe board kick plates is that it prevents injuries and fatalities by reducing dropping objects.
Protecting work floors below with toe board kick plates
Guards, Gates & Netting
Guard-railings have openings, these openings in the guard-rail should be closed off and obstructed with safety gates to prevent persons from accidentally falling though an opening, or prevent persons from entering a hazardous area.
Self-closing safety gates are also called swing gates or just simply safety gates. A safety gate is part of the guard-rail is designed with a certified minimum strength and opens easily one-way, when you pass through the safety gate will automatically return to its closed position.
Vertical posts and stanchions should be well marked and protected with padding when located in the walkway areas. Height differences in the walking level should be marked and the work environment should have sufficient lighting.
Overhead hanging structures should be designed with steel dropped object prevention safety nets, as secondary retention methods to support the brackets and basic structure.
Walkways must be safe to walk over at all times. Keeping the walkways safe and clean with no clutter does make a difference for a safe and pleasant work environment. Locations for temporary maintenance or installation work should be visible, well-marked and obstructed.
How do I make my work environment safe?
Be critical to work environment, ask yourself the following questions; are your walkways safe and clean to work? Designed in the right place? Being used? Are they available for employees to use? What tasks are performed on this walkway? Is the walkway good visible, are hazards on the walkway visible?
Simple tools are available for walkway clearing and walkway design, according to ISO / OSHA the safety standards in combination with safety tools can reduce these risks and prevent future accidents.
Review and apply safeguards specifically designed to prevent slips, trips and falls. Examples of these safeguards are cable safety hooks or s-hooks and cable guards, they ensure a neat and tidy work environment by removing all tripping hazards from the temporary work spot.
Dropped object prevention equipment and slip, trip and fall safeguards have a positive influence on creating a safe work environment. The bottom line is; it prevents fatal injuries and lost time incidents. These tools help reduce the highest safety risks in your organisation as stated by the OSHA.
Extreme CableSafe Hooks from Stock | Call Thorne & Derrick with your Enquiry.
Dropped Object Prevention Equipment
Safety at work is of utmost important when working on elevated platforms especially if there are personnel or contractors working underneath. Dropped objects are still, unfortunately, a common contributor to severe accidents in industrial facilities across different sectors globally.
The accidental dropping of tools and equipment poses a very real risk to safety of workers operating at elevated heights. It is therefore important offshore development sites have systems in place to reduce the occurrence of such incidents.
Objects known to frequently cause accidents are hand tools or equipment left behind after a task. Also equipment mounted in an elevated location that has the potential to fall due to movement or environmental conditions.
CableSafe® offer a broad array of dropped item prevention tools to protect employees from potentially harmful injuries and accidents in a wide range of working environments within industrial facilities.
Additional information regarding protection of stairs, stepladders and guard-rails, step ladders or landings, platforms and walkways safety of machinery can be found in the International Standardization Organization ISO14122 – Permanent means of access to machinery: www.iso.org/obp/ui/en/#iso:std:iso:14122:-3:ed-2:v1:en:fig:10
For additional safeguards information against dropped objects visit: www.preventdrops.com
For additional safeguards information against slips, trip and falls visit: www.cablesafe.com
T&D are Specialist Distributors ofLV MV HV Cable Installation, Jointing, Substation & Electrical Equipment– we supply companies in the onshore and offshore wind, solar, rail, oil/gas, data centre, battery storage and utility sectors with products to enable the energisation, operation and maintenance of underground cables and overhead lines.
LV MV Cable Accessories | Joints Terminations Connectors 600V to 66kV Ex Stock
provide best in class specialist service for High Voltage Power Industries such as Commercial, Utilities, Manufacturing, Life Science, Data Centres as well as the Renewable Energy Sector.
