Cable Joints & Terminations HV

Cable Joints & Cable Terminations

Offshore Substation High Voltage Cable Re-alignment

March 26th, 2021

HV Cable Re-alignment

High Voltage Cable Re-alignment

Offshore Substations

Special thanks to Geoff Briggs MIET from MGL Cable Services for the kind permission to republish this short case study in Wind Energy Network

When substation high voltage cable routing design and installation specifications do not align, MGL Cable Services bring expertise and professionalism to maintain cable integrity during the re-alignment process.

One of MGL Cable services teams recently stepped up to this challenge by demonstrating those qualities, they successfully delivered a project to re-align previously installed cables on offshore windfarm substations.

Process Preparation

As the cables were required to be removed from the high voltage switchgear this required the removal of the terminations from the switchgear, the terminations were then cleaned and protected from exposure to the harsh offshore elements.

Following the termination protection, the cables protective cable transit blocks and cable cleats were removed, this enabled the team to expertly manoeuvre the cables from the switchgear and safely suspend the cables away from the existing cable containment structure, paying careful attention to keep the cable within the manufacturer bend radius limit and protecting the cable from any sheath damage when manoeuvring to maintain cable integrity.

High Voltage Cable Re-alignment

Once the cable was safely suspended, the cables and containment structure were then modified to re-align the cable routing design and installation specifications.

The process involved manipulating the cable into the realigned cable containment structure whilst maintaining cable integrity and ensuring all terminations aligned with their respective switch gear bushings.

Once the team had effectively accomplished the re-alignment, the terminations were re-greased and re-attached to the switchgear and all fastening torque tightened to required specification. The cables were cleated into final position.

Each cable was the sheath tested to verify the cables integrity had been maintained throughout the process. The team delivered progress reports on a daily basis and sheath testing reports to ensure the client was confident MGL were delivering the high standard and workmanship required to execute the re-alignment process.

Client Feedback

Feedback from client’s representative commented on ‘genuine experts, real professionals and they were impressed with how the team handled the extreme pressures effortlessly. The team earned my highest recommendations.’

ABOUT MGL Cable Services

MGL Cable Services is a cabling focused electrical engineering company based in the North East of England. Part of the MGL Group of Companies, we have the expertise to fulfil the full scope of a large project or deliver a single service as part of a smaller scope within a large project. Our processes and procedures enable us to deliver consistent outcomes and we share our knowledge and lessons learned with clients and delivery partners.

MGL Cable Services work to high quality standards embodied within our SHEQ management systems, endorsing our Zero Harm policy to provide every client with complete peace of mind. We ensure that customer service and satisfaction are our priority and as a service provider, we work closely with the client to ensure the smooth delivery of services and projects, to specification, on time, and on budget.

Specific expertise includes High Voltage Cable Jointing up to 400kV, High Voltage Cable Testing, Fibre Optic Cable Splicing, Fibre Optic Cable Testing, Offshore Termination & Testing, Project Management, Project Support, Technical Documentation Drafting, Client Witnessing, Civil Construction and Plant, High Voltage Cable Fitters and Specialist Engineering Consultancy.

Thorne & Derrick are 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.

See how T&D support, supply and service the Renewable Energy industry.

MV HV Cables 11kV 33kV 66kV | Cable Joints, Terminations & Connections

Oil Leak Repair – Taking Leaks Seriously

March 24th, 2021

Oil Leak Repair

The following Technical Article about oil leak repair has been republished, with kind permission, from Transmission & Distribution World

Authors: Jon Allen and Anthony J. Picagli

Transmission & Distribution World’s mission is to provide utility executives, managers, engineers, supervisors, operators and linemen with must-read information on:

Medium Voltage Cable Replacement

Design
Engineering
Construction
Operation
Maintenance of the Electric Power-Delivery Systems

This includes an in-depth understanding of transmission, distribution, substations, automation and power flow control.

Oil Leak Repair

Taking Leaks Seriously

If oil is leaking out, air and moisture can and often do get inside transformers.

Moisture can migrate into transformers through several methods. One of the most common is through aged, leaking gaskets. Even though a transformer is at positive pressure, capillary action can draw moisture and air into a transformer, even when it is leaking oil.

Rapid pressure changes attributed to cold weather operation and sudden removal from service (a transformer switched out or de-energized) can increase the rate at which water is introduced into the transformer. Wherever oil is seen leaking from a transformer, the leaks should be repaired so moisture and oxygen cannot infiltrate the unit through those areas.

United Illuminating Addresses Oil Leak Repair with a Proactive & Ongoing Maintenance Program

The United Illuminating Co. (UI) regards the repair of oil and SF₆ leaks as a critical component in its apparatus maintenance program. When a new leak is identified and immediate regasketing or replacement is not feasible, a temporary solution is scheduled to stop the leak. More than 10 years ago, UI began using outside specialists to seal oil leaks in its transformers and circuit breakers.

Previously, a special epoxy mixture was used to seal leaks at seams, pin holes, cracks and pipe connections. This option was easy to perform and inexpensive.

However, the results were inconsistent. With proper preparation, the epoxy repairs were effective about 50% of the time. In addition, removal of the epoxy for regasketing or replacement was extremely labour intensive. The utility’s fleet was aging, and UI engineers were interested in a better solution.

The utility had an initial experience with an outside contractor to repair a leaking circuit breaker that was going to be removed from service soon. As a test case, UI tested a leak repair technique as a temporary fix. The intent was to get by until the unit was changed out. The contractor used a flexible sealant material that had advantages over epoxy and was more effective in sealing the leak. The results were good, and UI has used the outside contractor approach elsewhere. The time and total cost savings were substantial.

Leaks Are Serious

Oil leaks need to be taken seriously and addressed with a proactive and ongoing maintenance program. The major issues addressed with leak repair are as follows:

Environmental issues – Some of UI’s substations are located adjacent to the Long Island Sound, streams or wetlands; therefore, environmental impact absolutely must be avoided and clean-up costs kept to a minimum.
Public perception – In reality, leaks may be contained and not be an environmental concern. But, if they are visible to the public, perception becomes an issue.
Equipment outages – The extended outages required for conventional repairs are often difficult to obtain. Leak repairs can be done in areas with limited access and require shorter outage durations. In many instances, repairs can be made with the equipment energized.
Resource availability – Resources are limited, whether people, time or money, and UI needs to maximize these resources. Additionally, staffing levels are influenced by the state of Connecticut’s Public Utilities Regulatory Authority.
Replacement parts – As with any aging infrastructure, original equipment parts are often scarce, difficult to locate, expensive or simply no longer available.
Delivery times – Along with the availability issue, parts that are available or need to be custom manufactured often have long lead times.

Cost Considerations

Oil leak sealing is not thought of as a permanent repair; it is a temporary patch until permanent repairs can be scheduled. Poor performers are known, whether by manufacturer, vintage or design, and are regularly inspected for problems. It really comes down to the financial analysis. In some cases, it can cost US$20,000 to filter the oil and another $20,000 to regasket properly. The leak repair alternative costs from $3,000 to $10,000. The interim fix must be considered.

Leak Seal Process

For more than seven years, UI has worked closely with The Colt Group in a proactive leak repair program. It began as an intensive series of repairs at multiple sites. It has matured into a more limited but ongoing inspection and maintenance routine. Some of The Colt Group’s repairs have become long-term solutions unintentionally, while other repairs were short-term fixes until UI could properly schedule and complete permanent repairs. Although the repairs are guaranteed for two years, many are still in place and working effectively several years later.

Repair Sealant for High Voltage Transformers HV

Sealant has been injected through an injection valve to fill a void inside this custom nylon enclosure installed on a UI bushing. The injection valves will be removed after the sealant cures and the enclosure will remain in place.

Over the years, UI has called on The Colt Group to make a variety of leak repairs to both transformers and circuit breakers. Two different methodologies are used, either a drill and tap using injection valves, or custom-fabricated clamps or enclosures. The drill-and-tap technique is used for oil leaks, while clamps or enclosures are used for certain oil leak applications, or for SF₆ or nitrogen leaks.

The sealant used in these methods is not an epoxy. Flexible and easily removed, the sealant is specially formulated for use with high-voltage electrical apparatus. It maintains a memory that allows for expansion and contraction as needed, as a result of temperature changes and vibration. The substance has excellent dielectric properties as documented by test results from an independent laboratory.

Drill & Tap

In the drill-and-tap method, an experienced technician drills and taps a ¹/16-inch (1.6-mm) blind hole in between the bolt holes to intersect the groove or gasket. (A blind hole does not completely penetrate, stopping short of the opposite side of the work space.) Next, an injector valve is installed into the tapped hole. This injector valve allows the technician to control any oil flow that may occur during the next step. Using a ¹/8-inch (3.2-mm) drill bit, the technician will then drill a hole through the injector valve to penetrate the seal area.

Transformers | Leak Repair Tool Specialty leak repair tool and equipment includes a manually controlled injection gun used for injecting sealant for both the drill-and tap method and installation of the custom clamps and enclosures.

The injector valve is then turned to the closed position. This process is repeated with additional injection sites and valves; the objective with the multiple ports is to carefully control the amount of sealant injected.

This is highly specialized work performed by technicians with years of experience. They have the expertise to know exactly where to drill, how deep to go and how much sealant to inject. Think of it as injecting a gasket from the outside in. With this non-invasive process, the oil does not need to be drained. Depending on the location of the leak, some of these repairs can be made with the unit energized. An example of a common in-service leak repair might be the bottom of a tap-changer flange or lower radiator flanges.

A two-part compound, the sealant has the consistency of peanut butter when first mixed. It is injected into the positioned valves one by one, using a manually controlled gun with pressure gauge. It takes approximately 1 hour for the sealant to cure. Once the sealant has cured, the injection valves are removed and Teflon-coated pipe plugs are inserted in the threaded holes.

On repairs that have a grooved or recessed area where the O-ring or gasket is located, that is a perfect spot to penetrate using the drill-and-tap technique. By intersecting this grooved area, there is a channel where the sealant can travel around and create a seal. This process can be used on tap-changer handles, tap-changer flanges, cover plates, belly bands, bushing mounting flanges and other locations.

Clamp Or Enclosure

The second leak repair methodology is a custom-fabricated clamp or enclosure. This creates a barrier around the leaking component by injecting the cavity of that piece of hardware to obtain a seal. This special hardware allows the sealant to be injected under pressure to successfully seal the leaks.

For enclosure repairs, two brief outages may be required. On the morning of day one, a 1-hour outage may be required for the leak seal technician to take precise measurements for the enclosure. The device can be fabricated that same day and delivered overnight. If required, a second outage of 4 hours to 6 hours is taken to install the enclosure. Sealant is injected into a channel inside the clamp to seal the leak. The clamp remains in place and can be removed easily when needed.

Many leak repair jobs are unique. In addition to the drill-and-tap method and the custom clamp or enclosure method, sometimes a weir can be fabricated and filled with sealant to seal leaks at the base of radiator fins or cooling rods. This somewhat decreases the cooling capacity but can be an effective short-term solution until a replacement is possible.

Repairing Leaking Transformers | High Voltage

A leak repair technician injects sealant into a custom enclosure at UI. The injection valve will be removed after the sealant has cured.

Substantial Savings

This is a proven process. UI and The Colt Group work closely together to seal any new leaks that develop while monitoring past repairs. Some leak repairs considered temporary fixes years ago are still holding well. The overall situation is greatly improved and under tight control. UI estimates significant savings in annual maintenance costs by using leak repair as an integral part of its overall maintenance strategy and reducing the need for regasketing and replacement.

Companies mentioned

The Colt Group

Public Utilities Regulatory Authority

Risk Management Int’l

Thorne & Derrick stock and supply the DrainEezy range of transformer bund filters for use with LV MV HV Oil-Filled Transformers providing passive, self-regulating environmental protection and preventing bunds from overflowing during rainfall events; the DrainEezy Bund Filter System is field-ready to fit and retrofittable allowing clean water to drain freely while automatically blocking and retaining insulating oil in the event of a leak or catastrophic transformer failure.

600/1000V | 11kV | 33kV | 66kV Transformer Bund Filters

Further Reading

THORNE & DERRICK

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 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

11kV Transformers | Bushing Oil Leak on High Voltage Distribution Transformers

March 17th, 2021

Low (LV) to Extra High Voltage (EHV) Power Services to Distribution Networks

Guest Post by Simon Brown

Business Development Manager/33kV Senior Authorised Person at Ipsum Utilities (Private Networks) at Ipsum. Specialising in the installation, maintenance, testing, commissioning and switching of High Voltage networks up to and including 33kV.

If you require any of these services please contact Simon on 07889706194 or [email protected] to discuss your needs.

Transformer Oil Leak

Video | This is an 11kV bushing oil leak on a 500kVA distribution transformer.

Most likely caused by the end gaskets of the bushings having been penetrated and then the rubber flexible boot has held the oil until I released it as seen in the video. We will be isolating the 11kV transformer to drop the oil level below the bushing, remove it and replace its gaskets before putting it all back together – the cork gaskets on either end of the bushing have been penetrated by the transformer oil and it has travelled from the main tank to the 11kV cable box through the bushing. The rubber flexible bushing boot insulating the 11kV cable connection integral to the heat shrink cable termination was holding it back until I released the pressure.

This video demonstrates the critical value of cyclical inspection and maintenance of substation equipment as required by law associated with the installation and on-going maintenance of high and low voltage equipment.

About Ipsum

At Ipsum, we provide specialist infrastructure services across the UK’s regulated water and energy companies and private sector businesses. We work with our customers to maintain, optimise and develop their above and below ground assets to ensure security and resilience, and with our smart systems and ways of working, we ensure we deliver on time, on budget and safely. At Ipsum, we develop long-term working relationships with our customers by providing essential utility services on both public and private networks.

We have many long-term contracts and framework arrangements in place which are built upon great customer service, safe working practices and the ability to flex and deploy specialist skill sets at short notice. The growth of Ipsum has been built upon our people and our ability to meet the demanding and ever-changing needs of our customers.

The UK utility sector is evolving and expanding to meet increasing customer demand, regulatory driven outcomes and to exploit new innovative technologies, at Ipsum we will continue to grow in this sector by being a reliable, flexible and agile service partner that helps customers meet these new challenges.

As we know, utility service provision is not a 9 to 5 business, our customers don’t switch off their networks or assets at night, or at the weekends, or on holidays, or when things are quiet. They need them to work round the clock – and we at Ipsum are right beside them 24/7 to make sure they do. We pride ourselves in providing specialist scheduled maintenance services, being able to respond to an individual call-out or mobilise onto a major upgrade project and that our customers can rely on Ipsum 24/7/365.

11kV 33kV Joints Terminations Connectors - 3M Pfisterer Nexans Elastimold

Stockists | 11kV 33kV 66kV Joints Terminations Connectors – 3M Pfisterer Nexans

THORNE & DERRICK

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

Using Astute HV Monitoring To Target Maintenance

March 16th, 2021

EA Technology

HV Montioring Of Cables & Switchgear

Astute® HV Service

Failure of your high-voltage switchgear and cabling could cost millions in repairs, replacements and fines. But most cable failures don’t happen in a flash – they can be predicted from warning signs, most notably partial discharge (PD).

By watching your cables and switchgear, EA Technology’s Astute® HV service can alert you to suspicious spikes and pinpoint which parts of your HV system should be investigated.

The below case study shows how a major UK utility company decided to keep a cautious eye on their HV assets by using the EA Technology Astute® HV monitoring service through continuously partial discharge monitoring.

Background

Our client is a major UK utility company that owns and operates electrical networks supplying 1.4 million customers. As such, they are responsible for maintaining electrical assets and repairing faults in a safe and prompt manner. Failure to do so can cause supply interruptions, which is costly to our client and frustrating for their customers.

Most electrical asset failures are not instantaneous but develop slowly over time. These failures can be predicted by searching for distinct signatures, most prominently, partial discharge (PD).

PD is commonly caused by the breakdown of asset insulation, which leads to electrical currents propagating through the insulation, which further deteriorates insulation; this is a cyclic process which inevitably leads to faults. With the right equipment installed, PD can be detected, and failures can be avoided before they cause unplanned outages.

HV Monitoring

EA Technology specialises in producing and managing hardware that monitors PD in high voltage networks. The Astute HV Monitoring® system is a comprehensive monitoring package that includes:

Astute HV Monitoring® hardware
A software platform to manage asset monitoring
Remote monitoring by EA Technology
Expert interpretation of results
Automatic email and text alerts
Advice from experts in the field

One large HV substation owned by our client had a history of PD activity and asked EA Technology to investigate.

Astute HV Monitoring

Our Approach

The substation in question was home to a very large, and ageing switchboard (with 50 panels/circuits). To investigate the suspected PD, an Astute HV Monitoring® system was installed to monitor every panel of the switchboard. In total, over 150 sensors were installed to pinpoint the exact location of the faulty equipment.

The data collected by the sensors triggered automatic alarms and were subsequently analysed by our expert data team remotely. Our team identified four panels that showed clear signs of PD and were in instant need of intervention. The PD signals for these panels are shown in the graph overleaf. This information was passed on to our client in a timely fashion, who took action to investigate this further.

Entering HV substations known to house defects poses many risks. Therefore, before investigating the faults, the Astute HV Monitoring® dashboard was used to view recent data as part of the risk assessment on entering the substation.

Astute HV Monitoring Dashboard

The panels identified by the monitoring system were targeted to be investigated individually. It was immediately evident that the old insulation had broken down; this is shown in the figure above. The centre of the wooded insulator displays scorched burning marks, which is indicative of PD activity.

Degraded insulation, leading to partial discharge

The faulty insulators were promptly replaced with modern, high-density polyethylene insulation, as shown in the figure below. With the monitoring devices still in place, data was continuously collected and analysed to evaluate if the PD issue was solved. The results showed healthy ultrasonic readings with no signs of PD.

Client Benefits

The Astute HV Monitoring® system was successfully deployed to identify 4 specific panels (out of a total of 50) at risk of future faults. This allowed our client to prioritise the maintenance of their assets, ultimately saving time and money, and ensuring a reliable electricity supply for the thousands of customers connected to this substation.

Average ultrasonic readings activity of the four suspect panels

Now that the monitoring system is in place, our client can rest assured that any future PD-related issues will automatically be detected and raised before assets fail. The exact cost savings for such catastrophic asset failures is difficult to estimate, but regulatory financial penalties for supply interruptions can reach hundreds of thousands of pounds for a single occurrence.

Astute HV Diagram

About EA Technology

EA Technology’s mission is to promote the development of resilient, accessible, low cost energy networks globally, accelerating the transition to energy decarbonisation.

EA Technology is a specialist in asset management solutions for owners and operators of electrical assets. Headquartered in the UK, our operations and customers are global with four regional offices around the world. We originated in 1966 as a groundbreaking research and development organisation serving the electricity industry.

We are committed to providing our customers with innovative products and services, consultancy and training which deliver tangible benefits for their businesses enabling them to create safer, stronger and smarter networks for today and the future.

We work with many clients on a long-term basis to safeguard their power networks. We can advise on strategy and implementation solutions using a range of products, providing an ongoing service to ensure the reliability of equipment, together with highly trained customers’ staff in specialist areas. Our software helps our customers to manage their assets to achieve maximum life and reduce costs.

Thorne & Derrick

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

Thorne & Derrick International

High Voltage Enabling Works at Bryn Pica Eco Park Development

March 11th, 2021

High Voltage Enabling Works at Bryn Pica Eco Park Development

High Voltage Enabling Works

Special Thanks To Tristian Jones For His Kind Permission To Republish

C&P’s high voltage company, C&P High Voltage Services have been busy this week completing the 1st phase of construction of a high voltage ring for the future development of a multi-million-pound Eco Park development for Rhondda Cynon Taf Council – the facility will be the first of its kind in the UK.

Once completed the electrical infrastructure will be extended into phase 2 to supply further factory buildings for future recycled materials production.

C&P High Voltage services division will provide enabling works which includes design, supply, install, test and commissioning for a 2MVA package substation, Ring Main Unit (RMU), HV cable system for a 2MVA package substation, Low Voltage (LV) cable system for Mattress recycling, visitor centre fence distribution board, feeder pillar to replace perimeter fence distribution board and Low Voltage (LV) cable transfers.

This week a smart feeder pillar was installed, along with a 2MVA transformer and RN2D close coupled RMU with VIP protection on the circuit breaker. This will allow for remote monitoring and operation through a BMS or website control platform.

Eco Park Development – which would be the first of its kind in the UK

Over the past 18-months C&P has been rapidly expanding its high voltage services and maintenance activities, securing a number of critical projects and contracts across the UK.

David Demock, C&P’s High Voltage Engineering Director commented: “We are extremely pleased to partner with Rhondda Cynon Taf County Borough Council to deliver such an important phase for this prestigious project. We have been adding to our power engineering capabilities over the past few years which has assisted us to grow and offer clients such as Rhondda Cynon Taf Council even more value through our unique approach.

Using our own people, plant and highly experienced engineering solutions we are pleased that we can play a vital role in the development of the park. This will ultimately help to recycle more, protect the environment and create commercial opportunities and job creation in the Cynon Valley”.

About C&P High Voltage Services

C&P High Voltage Services provide a full range of high voltage electrical contracting services across a diverse range of customers. Their full turnkey high voltage engineering services cover design, installation, testing, commissioning, energisation, operation and maintenance for both new high voltage electrical installation and refurbishments for private networks up to and including 132kV.

High Voltage Services include:

• Design & Installation
• SAP Services
• Operation & Maintenance
• Jointing & Cable Installation
• Commissioning
• Fault Analysis & Management
• Voltages – 11kV, 33kV, 66kV, 132kV
• HV Testing up to 68kV – Substation, Transformer, Switchgear, Cables
• Consultancy & HV Safety
• Contestable New Electricity Connections

Thorne & Derrick

LV, MV & HV Jointing, Earthing, Substation & Electrical Eqpt

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.

Cable Joints & Terminations HV

Offshore Substation High Voltage Cable Re-alignment

High Voltage Cable Re-alignment

High Voltage Cable Re-alignment

ABOUT MGL Cable Services

Oil Leak Repair – Taking Leaks Seriously

Oil Leak Repair

Taking Leaks Seriously

Leaks Are Serious

Cost Considerations

Leak Seal Process

Drill & Tap

Clamp Or Enclosure

Substantial Savings

THORNE & DERRICK

11kV Transformers | Bushing Oil Leak on High Voltage Distribution Transformers

Transformer Oil Leak

THORNE & DERRICK

Using Astute HV Monitoring To Target Maintenance

HV Montioring Of Cables & Switchgear

About EA Technology

Thorne & Derrick

High Voltage Enabling Works at Bryn Pica Eco Park Development

High Voltage Enabling Works

About C&P High Voltage Services

Thorne & Derrick

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