D-Tec CCTV-based Video Smoke Detection deployed in seven Irish power stations

(08/07/2009)

CCTV-based Video Smoke Detection (VSD) from D-Tec is being relied upon in seven power stations operated by the Irish Republic’s main generating company ESB - to keep a watchful eye on all important turbine halls.

Video Smoke Detection, because of its careful analysis of CCTV images, is ideally suited to this sort of voluminous, potentially, dusty environment. By contrast conventional smoke detection systems struggle in this type of situation, delivering a relatively slow speed of detection. Crucially, VSD using CCTV cameras as the means of detection is able to recognise genuine smoke patterns - something previously confused in power stations with dust and steam - and distinguish them from other vapours.

So how does VSD actually work? In practice, this approach to fire detection utilises standard CCTV images in real-time that can then be analysed by specialised image processing software. This seeks out the particular pattern that smoke produces by applying extensive detection and known false alarm algorithms.

By programming the software to look for anticipated motion patterns of smoke over a specified area, typically the turbines in a power station, within a camera image and looking for pixel changes, CCTV-based VSD has the potential to deliver an exceptionally fast response – typically in seconds. Crucially, once smoke has been detected the system can alert the operator as well as delivering a visual representation of the smoke on the system’s monitor.

This ability to effectively detect smoke at source, unlike more traditional methods, means that VSD does not have to rely on the proximity of smoke to a detector and is therefore unaffected by distance. Whether the camera is situated 10 metres or 100 metres from a risk area, VSD has the capacity to detect smoke in the same amount of time, providing an early warning that would be impossible with conventional detection as it is not waiting for the smoke to reach the camera.

When it comes to the experience of an actual end user of Video Smoke Detection, the Republic of Ireland’s Electricity Supply Board (ESB) is a logical place to start to appreciate the real impact which VSD is having on the ground.

The power generator – which is 95% government owned – has been close to this technology for nearly a decade now and boasts what is reckoned to be, the largest installed base of power stations covered by Video Smoke Detection anywhere in the world.

Currently there are seven ESB stations monitored by Video Smoke Detection. These include: Aghada (gas), Ardnacrusha (hydro), Marina (gas), Moneypoint (coal), Northwall (oil/gas), Poolbeg (oil/gas) and Dublin Bay (part ESB owned). Over the years two additional stations have featured VSD, namely Great Island - which saw the very first deployment of the technology by ESB back in 2000 – now used by another Power Utility - and Tarbert which also changed hands recently.

Kevin Grace from Safety Services at ESB Power Generation takes up the story of how the power generator has now come to depend on the protection afforded by VSD: “With regards to Video Smoke Detection, the first power station to actually have the system installed was Great Island in Wexford back in 2000. Originally VSD, from D-Tec, was specified because of a requirement to protect the very large space of the turbine hall. The reality was then, and still is today, that conventional detectors simply don’t have the speed of detection in this type of voluminous environment should there be an incident. With beam detectors near the roof, for example, we could be talking several minutes before anything actually happens – far from ideal.”

Before turning to Video Smoke Detection, according to Kevin, Safety Services at ESB looked carefully at a number of other options: “Prior to 2000 Safety Services tried out, what was then one of the latest techniques, specifically, high sensitivity smoke detectors which were being promoted at the time as being able to cope with dirty environments typical of power stations. However in the case of ESB they simply did not work. This was due in part to the high propensity for smoke to diffuse in what are extensive, high roofed, turbine halls.”

Having been unable to achieve the necessary performance, the next step for the Safety Services team was to consider more radical solutions such as CCTV-based Video Smoke Detection (VSD). This was seen as being at the forefront of technology at the time but also being very new, something of an unknown quantity. The upshot of this was extensive testing as proof of concept, before ESB would commit to any firm decision.

Said Kevin Grace: “At the request of Safety Services, in conjunction with D-Tec, an intensive test project was established at Wexford’s Great Island power station. This necessitated smoke pellets being set off in the turbine area of the station to carefully simulate the effects of a fire. After the VSD system had settled in and been configured, and reconfigured, it was possible to achieve a detection rate in line with the time parameters Safety Services were looking for i.e. within a minute. The test was considered a great success and led ultimately to the roll-out of VSD across our thermal stations from 2000 onwards.”

Typically, in ESB power stations, the VSD system is used in conjunction with standard B&W CCTV cameras all of which have hoods in place to help keep them clean of the dirt and grime which can build up.

Commented Kevin: “Normally when it comes to the optimum layout of the CCTV cameras they are positioned quite high up, with D-Tec’s engineers ensuring that they are at the right angle as part of the commissioning process. As our power stations have anywhere from one to three turbines the number of cameras required will vary from site to site. The rule of thumb is two cameras per turbine, with each being used to focus on a specific half of the turbine concerned.”

The initial phase of ESB’s deployment of Video Smoke Detection was confined to thermal stations, specifically oil, gas, and coal, with a hydro plant only coming on stream much later in the process.

Said Kevin: “The real challenge for any fire prevention or detection measure is the environment into which it is placed. In our case a key defining factor is the type of station, as, from experience we feel that the risks are much greater for thermal powered stations, compared to hydro plants, where seal oil or control oil leaking onto very hot pipes – which can be above the auto ignition temperature of the oil – may heat-up, smoulder and ultimately start a fire. It was natural for oil, gas and coal station to be the focus at the inception of the programme and critical that the VSD solution would be able to pick-up early signs of smoke before the stage of potential ignition. By contrast hydro stations do not contain the hot surfaces of thermal plant required to ignite oil. A risk of fire still exists however and we did put VSD into one of our hydro stations – Ardnacrusha – and are currently investigating the possibility of expanding this to the remaining hydro stations.”

For ESB the whole commissioning process has been critical to optimise the performance of the system in each station.

Commented Kevin: “Basically the system has to learn by building up a background reference image over time. Station-by-station, D-Tec worked with us over a few months, testing and refining the system parameters to increase sensitivity and avoid false alarms. They also come back periodically for fine tuning – typically every six months. Overall we have been very pleased with the performance of D-Tec’s Video Smoke Detection."

Related topics:  CCTV system and accessories   Fire detection and alarm 

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