HIGH VOLTAGE CABLES
WATER INGRESS
Water ingress is well known for its damaging effect on electrical equipment, often resulting in partial discharge and switchgear failure. Gavin Cornall, Divisional Manager for Power & Process at Roxtec Ltd, explains the findings of a recent whitepaper about humidity to substation environments and outlines practical solutions to mitigate these conditions.
Water is vital to human life, but in the world of cable installation it often causes technological headaches.
PROBLEMS
Traditional seals of mastic or compounds are hard to install on HV single core cables in wet or running water conditions and don’t provide adequate cable retention. In the long term, these seals can’t cope with the expansion and contraction of cables in operation. Cables are also subject to further forces as the ground settles outside, plus their weight can cause retention issues.
An independent report found that partial discharge on high voltage switchgear was
occurring over time and interfering with the optimum operating conditions. This was due to cable ducts below ground allowing the ingress of water, dust, dirt, pollutants and gas. In particular, water ingress leads to high relative humidity, which in turn results in partial discharge and failure of switchgear.
These findings were backed up by a white paper report which Roxtec commissioned from EA Technology on the causes and effects of humidity within indoor substation environments and methods of mitigating these factors.
SOLUTIONS
Gavin has worked in the power transmission and distribution market for a number of years, he said the report showed why it is extremely important to control the substation environment and this can be achieved by minimising water ingress into substations and controlling the temperature and humidity within the building.
Roxtec developed specialist substation seals; the IP68 certified solution to the problem is Roxtec UG seals. These strong, mechanical seals can support the weight of cables. In addition, these seals can be used
on new build and retrofitted. In particular, the H3 200 UG product was specially designed for sealing trefoil formation cables against constant water pressure.
INNOVATIVE PRODUCT
This innovative product is made from malleable rubber so it is very flexible, it can also seal cable ducts that aren’t perfectly round.
It can be installed in running water conditions and provides a high degree of cable retention (tests have proven that this product provides a cable retention that withstands a pull force of up to 3300N which equates to 320kg of pull out force).
WET CONDITIONS
In the early days it became apparent that traditional systems were failing due to cable retention failure and wet conditions. That’s why the products fit so well to this application.
Owners are becoming much more aware of the impact of water coming into substations and the serious problems that can cause with switchgear.
Roxtec Ltd
www.windenergynetwork.co.uk
65
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