Safety system tackles growing threat of manhole explosions

One of the lesser-known dangers of the big city is manhole explosions.

While this might seem to be a freak occurrence that doesn’t need to concern the man in the street, in America’s biggest cities hundreds of manholes catch fire or explode each year. 

It’s a serious business: earlier this year manhole explosions in Massachusetts caused the loss of electricity supply in 1,400 households for several hours. In 2004, New York saw a fatality when a woman was electrocuted after coming into contact with an electrified metal plate. In this case, uninsulated wires carried the charge above ground because salt had been used to grit the roads.

“One of the biggest problems urban areas face today is maintaining and updating energy and electricity infrastructures,” says Dr Edward Klinger, CEO of CNIguard. When networks are under pressure, bad weather and flooding interact with ageing power infrastructure, with manhole explosions the result. 

Lives at risk

The problem isn’t just in the US: in London there have been more than 80 such incidents since 2010, “putting lives at risk, creating a pressing demand for UK power networks to provide a solution”. Increased urbanisation, grid complexity, legacy infrastructure, rising demand and the growth in distributed generation combine to make the scale of the problem “arguably ten-fold” higher than a decade ago.

Klinger says the solution comes in the form of monitoring to detect abnormalities owing to failing equipment, while safeguarding against human interference. And while this could be either asset vandalism or theft, it also includes resource-heavy call-outs and disruptive acts of nature. 

The key is operational predictability through the use of PAAS (‘platform as a service’) devices, such as methane gas sensors, monitoring systems for overhead electricity-carrying conductors and intrusion detectors. “By far the most complex system,” says Klinger, “is the Sentir array of environmental and operational sensors to monitor manhole infrastructures.” 

To get Sentir market ready, Klinger brought in the consultancy services of Plextek to provide system design as well as manufacture. Up until recently, he says, the approach taken by utility companies and power networks “would have been an entirely reactive process after an incident occurred. If you had 100 manholes or underground access points, each site would be scheduled for routine inspection and service.” When an incident was reported – usually on social media – “the site would garner more attention until a maintenance team was dispatched”. 

Klinger says that there was very little done in terms of preventing or predicting conditions that could cause an explosion or stray voltage event, “which is why for utility companies and energy providers operational predictability is a big issue”.

This shift in managerial thinking – from reaction to prediction – is the “justification for updating your network, to meet rising demands and usage. Part of which includes implementing new technologies that will help to protect it and increase longevity.” 

In the initial phase of Sentir’s development, Klinger realised there was time-to-market pressure coupled with a need to bring in external sensor expertise. “Signals from Sentir are transmitted securely from the embedded device to a dashboard on a smartphone or laptop. Over-the-air updates ensure that the firmware is current as well as enabling customisation,” he says. 

“False alarms are minimised by incorporating multiple sensors and technology-based sequential variation that removes or reduces human operating fallibility.”

Realtime readings

In collaborating with Plextek, CNIguard was able to “include 20 variations of the environmental sensor with cellular capability, powered by a reliable battery or harvested power from underground cables themselves”. 

This dual development strategy meant that CNIguard could work within the timescale and present prototypes to its client “capable of transmitting realtime manhole readings in situ. Having this gave us hard proof we could show our clients that the risks and dangers from stray/contact voltage and exploding covers could be mitigated,” he says.