Cold Shrink Joints & Terminations for Renewable Energy and Wind Farms

Cold Shrink Joints & Terminations for Renewable Energy and Wind Farms

3M Cold Shrink : High Voltage Cable Joints & Cable Terminations



Cabling is the ‘bloodstream’ of most power networks, responsible for taking energy from the very point of generation, through to transmission and distribution - and this is as true of wind farms as more traditional forms of power.

Indeed, the pivotal role of the cabling network is why this largely unseen part of the infrastructure is becoming such a focus for contractors involved in wind farm projects.

Simply, unless some of the new hurdles faced by wind projects are overcome, they could become more complex, time-consuming and costly.

Fortunately, there are a raft of technologies and techniques – some new, some existing and some adapted for onshore and offshore wind farms – that can help address these challenges, ensuring that cabling is not a barrier to wind energy deployment.

One of the biggest issues is that wind farms are typically remotely located yet still need to be connected via cables to the main power grid.

Frank Carey is contract director for Murphy Limited Cable Contractors and Civil Engineers, a major contractor to electricity companies, cable manufacturers, petrochemical companies, rail and industrial clients.

He says: “Connecting wind farms to the grid can be a challenge due to the environments being worked in - like working across peat bogs, for example.”

Traditionally, ‘heatshrink’ was the method used for connecting power cables, but this has its limitations, as explained by Brendan McNally, managing director for Connect Power Ltd, one of the UK’s premier installers of power joints and terminations, with considerable experience in the emerging wind farm market.

“Getting heat sources to the site isn’t easy. For instance, you don’t want to be carrying gas bottles across a field or up the side of a mountain.

Also, with heatshrink, you have to finish the job an hour earlier working under a hot works permit, so you can go back and check there is no post-work ignition.

We want to do the job as quickly as possible and avoid contamination getting into the joint, so the sooner we can complete the job, the better.”

Perhaps it is therefore not surprising that an increasing number of contractors are specifying that their cabling installation sub-contractors use cold-applied jointing techniques.

Pioneered several decades ago by companies like 3M, cold-applied jointing is already widely used in traditional electrical networks, where the joint bodies have an integral faraday cage which is then literally shrunk to a watertight fit around the joint that connects the two cables.

Additional heat sources and hot works permits are not required, while the amount of equipment that needs to be carried to the site is also reduced, making it highly suited for challenging wind farm environments.

Frank says: “Cold shrink gives jointers flexibility. It is quick and easy to work with.”

Brendan adds: “Cold shrink also means that you do not need to break your back bending over to make sure that the joint has been shrunk or recovered properly underneath.”

Arguably just as important, cold-applied techniques leave less room for user error and joints can be completed more quickly.

Although the details of each installation will vary, a joint might take less than a couple of hours to complete, as opposed to half or even a whole day.

“With cold jointing techniques, less skill is needed. The instructions are pretty simple. You can install joints a lot quicker once the cable is stripped,” says Brendan.

This is no small matter, considering the UK’s nationwide shortage of power engineers, particularly for wind farm projects.

Established power engineers are transferring their skills from more traditional power environments to renewable energy projects and the National Grid has also launched initiatives to reach out to students to encourage them to consider engineering jobs.

But still, any equipment that brings installation of cabling within the reach of a wider range of potential workers has to be beneficial.

Of course, the joint that connects the wind farm to the grid is just one place where cabling is present in the network.

Even offshore wind turbines contain cabling and certainly present one of the most challenging installation environments of all.

Imagine the scenario: a large (sub-) sea cable comes into the bottom of the tower’s sub-structure platform and contains three power cores plus the fibre optic communications core to remotely operate the turbine itself.

All four cores need to be connected to different points within the tower and therefore, the cable needs to be stripped back by a number of metres to ensure flexibility.

However, this presents another problem: once the connections have been made, the cable needs to be re-protected, both for performance and safety reasons.

In the past, re-protecting a large diameter cable would typically have involved use of heatshrink, but of course, this would mean carrying gas bottles into the turbine - and operating these is far from ideal when working in a confined space, especially when time is limited.

The wind turbine engineer often has only a small window of time during which to complete a task, due to weather and sea conditions.

That is one reason why cold-applied jointing techniques are increasingly being used for this particular application, because not only is additional equipment minimised, large expanses of cable can be re-insulated relatively quickly and consistently.

Onshore to Offshore

Once generated, there is the issue of transmitting offshore wind to the onshore grid.

Most offshore wind turbines are located along remote shorelines, so the nearest - and most obvious – point to connect them to the onshore grid tends to be remote ‘end of the line’ substations.

In many cases built a number of years ago, these remote outposts in the network simply are not designed
for the volume of power that our offshore wind farms are predicted to produce.

The situation could be compared expecting country ‘B’ roads to carry the same volume of vehicles as the M1 motorway.

Replacing these remote substations is not a simple answer, not least because of land rights, environmental objections and of course, the additional cost and time involved. A breakthrough in high capacity conductor technology could prove to be the solution.

By pushing the properties of aluminium to new levels, power transmission capacity gains can be two or threefold and achieved with a conductor that weighs significantly less than traditional steel conductors, and without the ‘sag’ that would normally be associated with transmitting greater volumes of power.

The key benefit for wind farm power transmission is that this new technology can be deployed as a ‘drop in’ replacement to existing conductors, so there is no need to replace existing sub stations, build new towers or increase clearance heights.

This is just one example of the challenges that wind farms present and which unless solved, would be bottlenecks to deployment.

While cabling is just one element of a wind farm project, it clearly has potential ‘make or break’ impact, so whether adapting existing approaches to new applications or making the most of innovative breakthroughs, cabling technology is an important link in the chain in meeting the government’s renewal energy targets.

Adobe 3M Cold Shrink Cable Joints, Cable Terminations HV - 6.6kV, 11kV, 33kV