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Cable Fault Location Equipment | Power Cable Testing Post Installation

• By Damon Mount | Head of Business Development at Megger

Power Cable Testing

Cable Fault Location Equipment

An essential stage in the commissioning of any power cable is testing prior to energisation.

Properly performed, this test will provide the information needed to ensure that any problems that have occurred during the manufacture or installation can be corrected before they lead to costly and disruptive faults.

But what is the best way to approach post-installation cable testing?

Without any shadow of doubt, the first step is to get the cable preparation right and, if you are using a contractor to carry out the work, this means choosing one that can unequivocally demonstrate that they know what they are doing.

This may seem obvious but there are good reasons to be wary and, although this sounds paradoxical, one of the main underlying reasons is that modern cable test sets, such as those in the Megger range, are very easy to use.

This is undoubtedly a good thing overall, but a possibly unexpected side effect is that contractors with little or no cable test experience may believe that if they hire one of these test sets and quickly peruse the manual, they’re ready to offer cable testing services. They are not. There is much more to cable testing than simply knowing how to operate the test set, especially if the work is to be carried out safely and to deliver accurate results.

An experienced contractor will first formulate a safe method of work, and will manage the test area effectively and efficiently. It is important to keep anyone who is not involved with the testing away from the area, remembering particularly that there’s no visual difference between an energised cable and a de-energised cable.

This doesn’t just mean keeping members of the public away as colleagues acting as onlookers can be even more hazardous – they are the ones who are most likely to poke at the test set in an attempt to be helpful, and to offer distracting comments and suggestions.

The next step is to prepare the cable for test and, in particular, to prepare the cable ends so that, when carrying out a cable sheath test, there will be no flashover between the metallic sheath or screen and the semiconducting oversheath. Checking that the semiconducting material has been properly removed by carrying out a quick and simple test using an ordinary handheld insulation tester is always worthwhile.

TDR1000/3P Handheld TDR by Megger

It is now necessary to remove any cross-bonding links that are used in the cable system and it is essential to allow sufficient time for this. It is by no means unusual for a single link box to contain 30 or even 45 links. Removing these prior to testing and refitting them after testing will involve hours of work, something that those setting deadlines for testing often fail to realise.

Cable Fault Location Equipment

With preparations complete, testing can commence, but there is another essential factor that needs to be considered – the right test equipment must be available on site.

This doesn’t just mean the test set that will be used for carrying out basic sheath testing, but also the additional equipment that will be needed to diagnose and locate the cable fault, if one should be found.

Few cable operators will be happy about the delays involved in returning to base to fetch more test equipment – it needs to be on site already, so that cable faults can be dealt with quickly and effectively.

This is another area where experienced cable testing contractors score. Since they carry out cable testing regularly, it is worth their while investing in a full range of test equipment and, just as important, in training their staff to use it safely and effectively. Companies that carry out cable testing relatively infrequently are unlikely to be able to match this level of investment and commitment.

The test voltage should, of course, be applied in line with the appropriate standards and specifications, and a good suggestion is that the test results should be written down on paper, even if they are stored in the instrument. The paper records may hardly ever be needed, but  they are a simple and inexpensive precaution against stored results being accidentally erased or overwritten.

If all has gone well, it only remains to discharge the cable, issue the test certificate and, in the case of a contractor, send the client an invoice. Never rely on the test set alone, however, to discharge the cable! Even if the test set is indicating zero volts it takes only a few seconds to make sure the cable really is discharged by using a discharge stick. Failing to do so could, in the worst case, lead to a fatality.

What about those cases where a fault is found? The first thing to do is to STOP and assess the situation. Turn off the test equipment, discharge the cable and check that all connections at the local and distant ends of the cable have been made correctly. Re-test and, if the fault persists, decide on a testing strategy that will allow the fault to be diagnosed and located with the minimum risk of causing further damage to the cable.

This will typically involve the use of TDR to pre-locate the fault, and then a pin-pointer to find its exact location. Once again, it’s important to keep the crowds away, especially when using an acoustic pin-pointer, as footsteps in the vicinity can make it much more difficult to determine the precise fault location.

Pictured: Megger TDR1000/3P Cable Fault Location Equipment showing an LV underground mains cable fault. Fault location from substation at 104 metres. The images show an open circuit and then an issue 13 metres from point of electricity supply – this cable fault was caused by incorrect cable laying.

Accurate, dependable results are essential because, for the fault to be remedied, the cable will need to be excavated. This is a costly and time consuming task, so the risk of digging in the wrong place must be eliminated as far as possible.

It is always worth bearing in mind that post-installation sheath tests are relatively inexpensive to carry out and they are an excellent way of guarding against potentially costly future problems. A vital point, however, is to resist the temptation of opting for cheap solutions.

If you carry out the work yourself, make sure that you have the right equipment, that it’s calibrated and in full working order and that your staff are properly trained. Allow plenty of time for the work to be carried out – rushing work significantly increases the risk of making mistakes and, in cable testing mistakes can be fatal.

Megger TDR1000/3P Handheld TDR For Power Application

If you subcontract the work, choose your contractor with care – opting for the lowest price may well turn out to be false economy. Ensure that your chosen contractor has a proven track record in cable test and, bearing in mind the points discussed in this article, check that they will be able to cope efficiently and safely, even if the work turns out not to be straightforward.

Post-installation cable testing, properly carried out, is an excellent and very affordable form of insurance. But as with any other form of insurance it pays to check the details carefully and to avoid automatically opting for the cheapest option, unless you’re really sure that it meets your needs.

Electrical Test Equipment LV MV HV

JOINTING, EARTHING, SUBSTATION ELECTRICAL & SAFETY EQUIPMENT DISTRIBUTORS

Thorne & Derrick International are specialist distributors of LV, MV & HV Cable Installation, Jointing, Duct Sealing, Substation & Electrical Equipment – servicing UK and global businesses involved in cable installations, cable jointing, substation, overhead line and electrical construction at LV, 11kV, 33kV and EHV.

THORNE & DERRICK 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 

Distributors for 3M Cold Shrink & Scotchcast | Nexans Euromold | Pfisterer Connex

Working Loads & Break Strength | The Key is Your Factor of Safety

Line Pulling Swivels By Slingco

Line Pulling Swivels By Slingco

Working Loads & Break Strength

Safety is critical when dealing with utility, construction or maintenance projects.

One of the main ways to ensure safety is by working within the load limits of crucial equipment. Slingco promote the safety critical role of cable support grips and the need for independent break load testing to safeguard project, people and reputations.

Swivels designed for use in stringing high tension wires for electrical transmission and distribution. Line Pulling Swivels are important in pulling when the lines develop torsion during the installation. This torsion must be released.

Use of a swivel will release torque and prevent it from reaching dangerous levels, which can cause damage to the cable or cable socks.

Slingco also offers a ‘bull nose’ style swivel designed for underground and overhead applications. All swivels are stringently quality tested and inspected to ensure optimum performance and reliability with working Loads from 10 to 134 kN.

What is Factor of Safety?

This is the factor used to ensure sufficient break load to handle working load spikes. It is critically important that all devices and tools used for pulling conductor are rated for the working loads expected on each job.

Factor of Safety (FOS) is often notated as X to 1 or X:1. It is the ‘extra’ coverage of the breaking load over the working load expected. When pulling conductor or cable, many factors impact how much load your equipment must handle.

Sometimes the conductor can get hung up on something which will cause the load tension to spike. The factor of safety helps accommodate a normal spike without dropping wire or experiencing equipment failure.

How do you determine Break Load?

Break Load must equal or exceed the Working Load x Factor Of Safety.

To help explain this, imagine the tension for a pull is calculated to be 1,800kg – this is Working Load of the pull. If the equipment used is only rated to a Break Load of 1,800kg, any variation in the load tension over the standard can cause failure. So, project designers assign a factor of safety (FOS).

• A FOS of 3 to 1 is commonly accepted in the UK for overhead line pulls. Different countries may have a different standard.

This means that the Break Load of any tool used must be 3 times the expected load tension. In this example:

Working Load of 1,800kg x FOS of 3 = Break Load of 5,400kg.
Grips and swivels would need to be selected with a break load of 5,400kg or more.

When selecting equipment for a pull, be sure you know whether items are rated at BREAK LOAD or WORKING LOAD. If rated at working load, you must know the Factor of Safety this working load is based upon to ensure it matches your project’s working load. If rated at break load be sure it meets your project’s break load including the Factor of Safety.

Here are a few common rules of thumb for the Utility industry:

Pulling & Support Grips – usually rated at approximate BREAK load. This means a factor of safety for your project must be applied. To determine the working load, divide the break strength by your project’s Factor of Safety. For example, a grip with an approximate break load of 5,400kg to be used on a project with a FOS of 3:1 has a safe working load of 1,800kgs.

Swivels – This is where it gets tricky (or trickier). Most (but not all) manufacturers will label swivels at a 3:1 FOS working load. Slingco (along with two other prominent manufacturers of swivels) go ahead and CONVERT THE BREAK LOAD INTO THE WORKING LOAD. Our 2,240kg swivel is rated for a 6,720kg Break Load – we have already built in the Factor of Safety of 3:1.

Connectors – (90 degree, Rope to Rope, Rope to Swivel): Similar to swivels these are typically listed at their rated 3:1 WORKING LOAD. Connectors are used to connect grips when pulling though a tensioner or around an angle greater than 50 degrees. Swivels should not be pulled around a tensioner. Swivels are not designed to handle the side loads experienced when going around a tensioner wheel. This can cause damage to the bearing structure within a swivel.

These are only a few of the tools used. Remember to make sure you understand how each tool is rated (Working Load at what FOS or Break Strength). The key to ensuring a safe project is making sure all tools meet or exceed your project’s Working Load.

➡ Contact Thorne & Derrick for technical support on your cable pulling, laying and installation projects.

Cable socks and support grips are available to enable the installation of 33kV 66kV array cables prior to MV HV Jointing & Terminating in windfarm towers, turbines and offshore substations.

Further Reading

• Slingco Take A Firm Grip on The Future With Cable Socks
• How To Lace Up Cable Socks By Slingco
• Cable Grips | Supporting Inter-array, Export, Umbilical & Subsea Cable Installations
• How Do Cable Socks React To Salt Water?
• Cable Laying, Installation & Support Products | Offshore Oil & Gas Cables
• MV HV Cable Laying, Installation & Support Products | Offshore Windfarms

Supplying Cable Termination, Jointing, Pull-in & Electrical Equipment up to 66kV

Specialist Distributors to the UK and international Offshore Wind & Renewable industry to provide safe and reliable LV HV Electrical Cable & Power Distribution Systems up to 66kV – we are highly customer responsive and absolutely committed to providing a world-class service. Contact our UK Power Team for competitive quotations, fast delivery from stock and technical support or training on all LV-HV products.

Cable Hangers for the Support & Management of Cables

Ellis Patents | Cable Hangers & Cleats Supplied in the UK by Thorne & Derrick

Cable Hangers & Support

Pegasus is a modular cable hanger system that is stronger, lighter and, because it is has been designed to be made to order, incredibly flexible in comparison to traditional J-type galvanised steel cable hanger systems.

Pegasus from Ellis Patents comprises a non-corrosive marine grade, extruded aluminium spine that supports any number and combination of plastic cable hangers that are manufactured from a high strength nylon especially formulated to meet the requirements of the London Underground 1-085 specification.

Pegasus Benefits for Hanging Cables 

– Corrosion free nature as a result of there being no bimetallic contact and the aluminium spine being fully enclosed to protect the hanger system against the corrosive effects of brake dust.
– Curved saddle shape on all cable hangers that prevents cable damage caused by sharp edge contact with the outer sheath or jacket of the supported cables.
– Modular design that allows assembly with any number of hangers in any combination, giving designers the ability to produce the cable layout they want.

Manufactured by Ellis Patents, the global market-leader in the manufacture of cable cleats for the management and support of LV MV HV cables.

Thorne & Derrick in consultation with the Asset Manager at Transport for London and their appointed Telecoms & Power contractor secured formal Authorisation & Approval for the Pegasus range of non-metallic cable support hangers.

The product will provide safe cable management of the cable route within the Bridges & Structures category – over 1000 hangers with proven lifecycle performance and utilising the standard J-type design for support of multiple cable runs including single, 3-way and 5-way configurations are now scheduled for delivery.

Associated Articles

• Cable Hangers for Railway Tunnels | Ellis Pegasus Cable Hangers
• Ellis Patents Pegasus Cable Hangers For Rail Cable Support
• Cable Cleats Help Tackle Copper Cable Theft on Railways

Rail Cable Accessories, Electrification

& Installation Equipment

Thorne & Derrick supply an extensive range of 400V-33kV Rail Cable Accessories & Power Distribution Sytems including feeder pillars to contractors undertaking Low Voltage Power Distribution, HV Electrification & Substations, DC Traction & Networks, OLE and Track Feeder Cable Renewals – a complete range of Network Rail PADS approved track terminations, cable joints, cable repair and connection products up to 25kV AC.

Full range of Cable Pulling Equipment & Products to ensure safe and efficient of rail cables in to cable ducts and containment infrastructure including cable troughs.

CONNEX & SEANEX | Jointer Courses from PFISTERER with Thorne Derrick

PFISTERER Cable Jointer Training Courses

CONNEX & SEANEX

Medium & High Voltage Jointer Courses from PFISTERER | 33kV & 66kV

PFISTERER are working in co-operation with their UK Distributor Thorne & Derrick to promote and deliver Medium Voltage CONNEX & SEANEX Training Courses from PFISTERER’s purpose built training facility in the UK.

When expertly installed by Competent & Certified Jointers the PFISTERER range of Cable Accessories operate reliably and are absolutely maintenance-free over decades.

Safety and reliability are essential factors in MV & HV Power System applications placing particular demands on cable preparation, accessory assembly and installation skills of the cable jointer.

The Training Courses are aimed at professional installers as well as technicians, engineers and other project managers with several years‘ experience and appropriate skills in the installation of medium or high voltage cables.

You can contact Thorne & Derrick to arrange your PFISTERER training course today, call 0191 4104292. 

CONNEX & SEANEX Jointing Courses

PFISTERER also has a worldwide trainer network: so training courses can be held close to you anywhere in the world.

The training courses provide the MV- HV Jointer with the required product know-how demonstrated in many practical examples. All training courses include:

• Product Training
• General & Individual Installation Requirements
• Installation & Cable Preparation
• Performance of Installation with Practical Work and Exercises

After successful completion of the training course, every participant will receive a time-limited certificate for the trained PFISTERER product.

Different training courses are available throughout the year – contact us to discuss your requirements.

➡ Please Note – Only specialists certified by the manufacturer are allowed to perform the installation of High Voltage Cable Accessories. This is required to secure your warranty claims.

Medium Voltage Jointer Training

• CONNEX Size 0 – 3 XL: £895 + VAT

High Voltage Jointer Training

• CONNEX Size 4: £1100 + VAT
• SEANEX: £1100 + VAT
• CONNEX size 6: £1800 + VAT

(all prices are per person)

PFISTERER offer a wide range of other training courses that can be tailored to suit your needs please contact Thorne & Derrick for further information.

 ➡ SEANEX | Jointers currently certified as Competent by PFISTERER to install the CONNEX range of 33kV inner cone separable connectors must arrange for additional certification to install the SEANEX range of products at 66kV.

SEANEX – High Voltage Connector for Offshore Inter-Array Cabling. SEANEX is a dry pluggable inner cone connection and contact system especially for renewable energy and offshore high voltage power systems up to 72.5kV

ON SITE JOINTER TRAINING

Contact us to discuss your specific medium/high voltage jointing training requirements.

Thorne & Derrick stock and recommend the use of Alroc tools for the preparation of medium/high voltage cables to effectively remove the cable sheath, semi-con screen and insulation.

General Terms & Conditions

Extensive, in-depth experience in working with and installing medium and high voltage cables is a prerequisite for participation in the PFISTERER training courses. Training courses are held in English. Participants must be able to understand and speak the respective language or the customer must provide a qualified interpreter.

The PFISTERER certificate will only be awarded to the participant on successful completion of the training course.

Cancellation Costs: Up to 14 days before the training course. Cancellation costs for bookings/reservations (hotel, flight, etc.). Less than 14 days before the training course: 50% of the cost of the booked installation training course and cancellation costs for bookings and reservations.

Dates: All training courses are held throughout the year.

Dates on request contact Thorne & Derrick.

Prices: Valid until June 2022 (pricing terms and conditions are subject to change).

PFISTERER Training CONNEX MV & HV

Stocked & Supplied by Thorne & Derrick

THORNE & DERRICK are national distributors of LV, MV & HV Cable Installation, Jointing, Duct Sealing, Substation & Electrical Equipment – we service UK and global businesses involved in cable installations, cable jointing, substation, overhead line and electrical construction at LV, 11kV, 33kV and EHV.

Thorne & Derrick stock and distribute PFISTERER CONNEX Connectors for medium / high voltage cable connection and termination to electrical systems up to 33kV – we provide competitive prices for PFISTERER CONNEX connectors used to terminate and connect polymeric insulated MV-HV cables into gas insulated switchgear and electrical equipment from extensive UK stocks.

Testimonial From Paul Morrow At Klauke UK Ltd

Paul Morrow

Klauke uk LTD

Country Manager UK & Ireland

“Since 2018 when Klauke were acquired by Emerson along with the Greenlee and Ridgid brands, Thorne & Derrick have helped our Group supply contractor requirements with tools for cable crimping, cutting and punching electrical panels.

Today our partnership is going from strength to strength.

Thorne & Derrick’s Sales Engineers receive ongoing training at their offices to promote technical competence and build commercial confidence in our tooling products – they are supported by Klauke’s national field sales team to provide onsite or online product demonstrations to end users when and wherever required.

Since 1985, Thorne & Derrick have gained a solid reputation for contributing to improvements in Workplace Electrical Safety throughout the industry – this includes assisting the launch of product innovations into the market, such as the Greenlee LS50 & Klauke VDE Orange and being a “go-to” supplier of electrical safety equipment to power industry contractors working with underground cables or overhead lines.

Increasing sales of our Strut Channel Cutter are an excellent example of a success story – the RIDGID STRUTSLAYR is recognised as the strongest and safest strut channel cutter on the market and is available from Thorne & Derrick stocks.

The sales and marketing staff at Thorne & Derrick worked hard and smart on introducing the STRUTSLAYR product to their clients and marketplace during COVID and are now seeing the impressive sales results.

Together during 2022 we welcome the opportunity to jointly promote more Workplace Electrical Safety improvements to be delivered through product innovations including the first remote-controlled cable cutters –  for example, the Klauke ESG105RMCCFM and ESG65RMCCFM battery-powered, hydraulic cutting tools which will allow the user to maintain a safe distance whilst cutting cables,” comments Paul.

Featured Product

RIDGID together with Thorne & Derrick introduce an innovative Strut Channel Cutter that improves workplace electrical safety called STRUTSLAYR™  which offers reduced risk of sparking when compared to grinders and chop saws and still manages to produce a clean, consistent cut.

The RIDGID® STRUTSLAYR™ delivers shop quality, burr-free strut channel cuts on the jobsite in 5 seconds or less. Compatible with RIDGID 32kN press tools, the STRUTSLAYR strut cutter offers a clean, consistent cut with a simple pull of a trigger.

STRUTSLAYR | Stocked by Thorne & Derrick

Klauke – DISTRIBUTORS & SUPPLIERS

Thorne & Derrick provide competitive prices and fast delivery for the range of Klauke cutting and crimping tools. Cable cutting and crimping tools manufactured by Klauke are renowned for high-quality, electrical connection tools for crimping, cutting and punching – special cable tooling solutions for applications in a range of different sectors.

LV MV HV Power, Cables, Jointing, Substation & Electrical Discussion Group

Specialist Electrical Distributor

Thorne & Derrick distribute the most extensive range of Low & High Voltage Cable Installation & Electrical Distribution Equipment to the Power Transmission & Distribution industry in the onshore and offshore wind, solar, rail, oil/gas, data centre, battery storage and utility sectors – this includes Joints, Terminations & Connectors to enable the installation of low, medium and high voltage power cables into underground trench or duct.

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

Main UK Stockists for:  3M Electrical, PFISTERER Connex, Nexans Power Cable Accessories (Euromold), Alroc, Ellis Patents, ABB, Roxtec, Cembre & CATU Electrical.