Feature Cable Management Ingress protection is better than cure
The British summer has once again proved wetter than expected for many, with parts of the country experiencing torrential rain and flooding. With this in mind, Graham O’Hare, UK managing director of Roxtec, highlights the importance of properly protecting electrical cabling in cabinets and enclosures
Left: once the problem of flooding has been
eliminated, it is far safer to access the cable trenches to carry out
maintenance work
ecause electricity is so vital to individuals and institutions, so it is also key that electrical sub- stations, the beating heart of the electricity network, are properly pro- tected. Substations are an integral part of the generation, transmission and distribution process, and without a fully operational network, power out- ages can be hugely disruptive and expensive to repair.
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The flooding that has been seen in some parts of the country this summer has caused chaos. However, out of this chaos the electrical indus- try is seeking a means to safeguard sensitive electrical equipment from water ingress and damage.
The sharp shock of costly power outages and repairs faced by electricity suppliers has driven the industry to conclude that prevention is better than cure. If the threat can be sealed out before the onset of the problem, the industry has its solution. As a result of this Roxtec has seen an increase in demand for its cable sealing solutions as the industry tries to put a stop to power disruptions caused by flooding.
Problems in the substation Substations, particularly in the renew- able energy sector, are increasingly being constructed in remote areas with little drainage or on sub-prime land, such as a flood plain. This leads to an increased potential for flooding in the cable trenches. In terms of health, safety and operational reliability, access to a flooded
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cable trench will be restricted as it is unsafe to work with live cables around water. This may mean that essential maintenance work cannot be undertaken without a planned power outage. Even a small amount of water in a sub- station cable trench leads to increased relative humidity. Over time this will lead to the insulation on the cables being compromised and the occurrence of par- tial discharge. This in turn will lead to switchgear failure and ultimately a power outage in the substation. Traditionally, sealing compounds have been used to seal cable entries in substations. The problem with this type of seal is that it will not support the weight of the cables. During the installation, natural movement will occur because cables are not sup- ported. This makes it difficult to get an adequate, even seal around the cables. In operation, there will be a natural travel/flex in the cable. As a result of this, water leakage into the cable trench is a common problem. To combat the problem of increased relative humidity, sump pumps, fans, air conditioners and de-humidifiers are increasingly being utilised. These all control the effects of relative humidity but fail to deal with the initial cause of the problem of water being in the cable trench. These solutions also add an unnecessary operational cost.
Prevention at source However, the Roxtec solution prevents this problem at cause. The company’s
seals can be core drilled or cast into concrete and can be bolted or welded into place. The seal can also be fitted around existing duct work for simpli- fied installation. As the cables are clamped in place by the compressed seals, the problem of the cables moving and so allowing a leak path into the trench, has been removed. Typically Roxtec products can achieve a four bar water pressure rating. Another advantage of using the Roxtec sealing system is that a number of cables can be sealed in one transit. This reduces the number of entry points required and in-turn reduces the number of potential leak paths. In a substation, Roxtec seals are most commonly used to seal HV power cables, trefoil cables and earth tapes. As Roxtec seals protect against a range of hazards, including fire, explosions, flood, vibrations, dust, electro-magnetic disturbances and vermin, they can be used in numer- ous parts of substations. The solution can be used to prevent oil escaping from the transformer bund, in room to room penetrations to protect from fire and in below ground penetrations to prevent vermin and water ingress in the cable trenches.
Once the problem of flooding has been eliminated, it is far safer to access the cable trenches to carry out mainte- nance work. Also, with humidity levels at a constant, there is a drastically reduced risk of the switchgear failing because of compromised insulation.
Roxtec
www.roxtec.com T: 0161 761 5280
Enter 211
Right: of all of the infrastructures protected by Roxtec seals, electrical substations are some of the most important
SEPTEMBER 2012 Electrical Engineering
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