October 30, 2015 / Markets & Industries, Products applications

Helagaine: the anti-stress programme for torsion cables in wind turbines

Helagaine: the anti-stress programme for torsion cables in wind turbines

Alongside photovoltaic and hydroelectric power sources, wind farms have rapidly become one of the chief suppliers of renewable energy in Germany. Today’s onshore wind turbines provide between 1.5 and 4 megawatts (MW) of power; offshore installations up to 8 MW. But as the importance of wind power increases, so too do the demands on the performance and reliability of wind turbines. HellermannTyton offers solutions that help operators meet this challenge.

Cabling in wind turbines undergoes enormous strain because the rotor blades must constantly face into the wind to efficiently generate power. Protecting and maintaining the critical cables connecting the generator outlet in the rotating nacelle with the grid inlet below is paramount.

The cables in the so-called loop – the connection running from the generator in into the tower – are constantly exposed to twisting forces. The cable grips commonly used to suspend the loop can fray, which in turn can rub and damage the cable insulation. (What is a cable grip? See some pictures here.)

Helagaine braided sleeving helps ensure that the insulation of adjacent power cables in the loop is not damaged. Proven in long-term tests, this highly abrasion-resistant polyester material protects cables and increases their service life significantly when fitted prior to cable installation.

Optimum protection for cables in the loop

Loop Cables
Strain relief on loop cables in a Nordex N90 wind turbine (Photo: Georg Schreiber)

Wind turbines are designed for an operating life of 20 years. For the copper cable this means up to 15,000 torsion cycles at rotations of up to 900 degrees in both directions.

The cable sheathing is subjected to considerable movement as the cables twist around each other in the loop. In worst case scenarios they can break.

See the pictures of a test rig in this German-language article on all.electronics.de for an impression of how the cables get twisted.

Damage to the cable not only reduces the output of the facility, but costly repairs may also be required. Replacement of a single loop cable can cost two man-days. However, cable wear and tear caused by friction or heat can be counteracted with the application of cable protection sleeves.

Braided tubing, made of highly durable polyamide yarn, is pre-assembled during manufacture of the cable sections. Later, when the loop cables are ultimately installed in the tower, the sleeving is pulled over the suspended cable grip to provide abrasion protection. Helagaine is easily pulled over irregular shapes and offers excellent surface coverage. Helagaine can be simply pulled down for inspection purposes.

Helagaine Twist-In: ideal for retroactive fitting

Wind power facilities with power cables that have not been protected from the outset with Helagaine do not have to dispense with the high degree of abrasion protection. HellermannTyton’s Helagaine Twist-In product combines the robust protection of Helagaine with a high degree of application flexibility. The result is an open, but self-closing protective polyester tube that is simple to apply and unfurl at any time. Loop cables are accessible at all times for maintenance, repairs and inspection. Maintenance costs can be noticeably reduced and unnecessary disruption and downtime can be curbed.

Turbine Installation Nortorf Germany
Installation of a 3.2M114-Turbine in Nortorf, Germany (Picture source: Senvion GmbH 2014)

But that isn’t the only option in HellermannTyton’s broad portfolio of products.

HelaHook: perfect protection for bundled cables

HelaHook protective cable sleeving is particularly elastic and flexible and can be closed with a Velcro fastening. Like the Helagaine Twist-In braided sleeve, it can be easily attached and removed time and again. The HelaHook sleeve protects bundled cables from the effects of torsion and also delivers good fire protection properties. It is particularly suitable for cables that have already been installed. Overall, it is a pragmatic alternative to braided sleeving. Read here about Key Features, Applications and Benefits of HelaHook.

HSG0 hot cutter: the tool for shortening polyester sleeving

When braided sleeving needs to be shortened, it cannot be simply cut off with a knife or scissors as the ends will then fray and the degree of protection diminishes. Therefore, it is a good idea to cut off braided sleeving using the specially designed HSG0 hot cutter. The device charges quickly at the press of a button, melts the individual threads and welds them together in one action to combat fraying.

HelaTape: rapid damage limitation

Even with the best protection in place, localised areas of loop cable damage can still occur on account of the torsion or shearing forces at play. HellermannTyton provides two professional tapes for such eventualities: HelaTape Power 500 and HelaTape Flex 2000+.

HelaTape Power 500 is an ethylene-propylene rubber tape with excellent electrical, chemical, mechanical and thermal properties. The fast-welding high-voltage tape forms an airtight and watertight insulation layer that is suitable for protecting high-voltage cable splices.

HelaTape 2000+ is an all-weather insulation tape ideal for the primary insulation of cable joints up to 1kV. It can be worked with superbly over a wide temperature range and is suitable for indoor and outdoor application.

In short, specialised HellermannTyton cable protection products give engineers and operators just the support they need to help ensure the reliability of wind turbines can be maintained in the face of rising performance demands.

With HelaTape, HellermannTyton offers engineers, designers and electricians a wide range of PVC- and rubber-based electrical tapes that are ideal for insulating, attaching, bundling, sealing and marking cables.

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