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Many power industry players suffer from humidity in their substations, caused by water ingress from badly sealed cable entries. Roxtec recently solved the problem for a wind power operator using innovative Roxtec seals, backed-up by arguments in a white paper written by experts from EA Technology. One of the main conclusions of the white paper is that there is an obvious connection between flooded cable trenches and excessive humidity, and that cable trenches need to be properly sealed.
The EA white paper on “Humidity effects in substations” states that high relative air humidity increases the risk of partial discharge. This is electrical discharges occurring inside or on the surface of insulation materials caused by high-voltage electrical stressing of the system when equipment is energized. Over time this can leave switch gear vulnerable to circuit failures and power outages. The shutdown of equipment may stop manufacturing processes and a failure for a large generator corresponds to a huge loss of income, potentially leaving thousands of homes and businesses without power. All failures must also be followed by costly and time-consuming investigations, replacements and functionality tests.
“Keeping water out of a substation is vital,” says Gavin Cornall of Roxtec. Rain, flood water, high relative humidity or even dust must be prevented from reaching control equipment via roofs, walls, cable trenches or leaking basements. To avoid condensation caused by high humidity inside the substation, it is important to maintain a stable indoor climate through adequate insulation. Otherwise, the substation must be equipped with heaters, dehumidifiers or air-conditioning.
Gavin Cornall summarizes what the optimum substation cable sealing solution should be able to handle:
•High water ingress protection
•High dust ingress protection
•Ability to seal a range of cables, including trefoil cables
•Oil egress protection
•Install in wet or high relative humidity conditions
•New-build and retrofit