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UK Power Networks (previously part of EDF Energy) own and operate over 130,000 substations and more than 100,000 miles of underground cables and overhead lines.
Paul Blake - a senior project manager in the EHV cables division - kindly wrote the following piece about how the PHD-4 helium detector is used to leak check their underground cables to help ensure reliable service to more than 8 million customers in the south east of England.
"Our old method was to use SF6 as the tracer gas, but there were numerous problems with this: the detector had a radioactive source, SF6 seemed to linger in the ground, extensive rock drilling was required, and SF6 is of course a greenhouse gas."
"So we had been looking for an alternative method to locate leaks on our gas cables for some time. The gas used in pressurised cables is oxygen-free nitrogen running at about 200psi, and the circuit is generally live when we're carrying out this work, so any tracer gas we use needs to be inert."
"We obviously don't want the gas to dissipate too quickly as we need to locate the leak, but it equally can't linger in the ground as it then makes it difficult to locate a second leak in the same vicinity. Helium seems to permeate the ground without too much rock drilling, thereby saving us time and money. The PHD-4 is also proving to be an accurate tool for finding the helium, again saving money in excavations."
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