Cost-efficient Fire Detection to Secure Maximum Availability – Fulfilling Today’s and Future Requirements for Fire Detection in Wind Power Plants
a report by Marcus Wallin Application Manager, CN System AB
Abstract
Highly valuable, unmanned, often located in remote areas and subjected to extreme weather conditions like lightning strikes – there is no doubt that wind power plants require state-of-the-art fire detection systems that immediately detect signs of fire. However, one of the most important features besides reliable fire detection is to minimise the number of unwanted alarms, as these cause unnecessary production losses and may eventually lead to the system being turned off. To make sure that the system is operational and effective at all times, the following requirements should be fulfilled:
• •
a high level of integration; apt design taking into account vibrations, humidity, air turbulences;
• easy maintenance; • built-in redundancy; • •
the voting or ‘double knock’ function; and the possibility to store historical events.
As the level of control required varies depending on the technical solutions, it may also be a good idea to invest in a customised system.
Wind power plants, along with their numerous components, represent a huge investment and having to restore a wind power plant may therefore be a financial disaster for the owners, operators and insurance companies alike. Wind power plants represent extremely harsh environments, as they are subjected to many different types of disturbances like lightning, vibrations, electrical environments, etc. To avoid production losses and having to make financial investments, a sound fire detection system is of immense importance. A wind power plant presents the following risk factors:
•
concentration of ignition sources within the nacelle increases the risk for lightning strikes;
• unmanned operation; •
• •
no possibility for firefighters to stop the fire as the construction is too high;
remote locations, which sometimes make it very difficult to reach, for example, offshore installations; and
unwanted alarms, which may cause substantial production losses.
Today, components such as switch gears, inverters, control cabinets, transformers, etc., are all placed in the nacelle, which significantly increases the risk of fire. Also, the fire can spread rapidly in the nacelle due to the high density of technical and combustible equipment. If the nacelle is completely destroyed, the restoration costs may well reach the original value of the total investment of the wind power plant.
When designing a system to detect the presence of real smoke/heat and flame there are a number of aspects to consider. For example, the
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fire detection system must be designed to meet different requirements regarding vibrations, humidity and air turbulences so that the number of unwanted alarms is minimised. One has to balance the need for a solution that detects the fire as early as possible with the request to minimise the risk for unwanted alarms. In general, the rule is that the earlier a fire can be detected, the higher the chance of minimising risks and costs. However, one must remember that early fire detection solutions can, if not designed and installed in the right way, trigger unwanted alarms, which, besides reducing the reliability of the total safety solution, may lead to loss of revenue and unnecessary damage of the wind power plant. Moreover, too many unwanted alarms may lead to the detection systems being turned off, which can cause a complete disaster if a fire occurs.
Therefore, a reliable fire detection system that is able to determine if there is a real fire or not is of vital importance to the wind power plant.
Fire Detection System
As mentioned earlier, there are several aspects to consider when designing and installing a fire detection system in a wind power plant. Besides choosing a reliable fire detection system, which gives a minimum of unwanted alarms, it is important to use a system that not only meets standard requirements but also integrates them to a high degree. A slim design can be of great advantage as it may be installed in narrow spaces, like low voltage cabinets. The system must also be easy to maintain, even for untrained personnel, to minimise the time that the wind power plant is out of availability. If one chooses to install a modularised fire detection system (see Figure 1), one also gets the benefit of customising the system to one’s specific needs.
By installing an addressable fire detection system, the fulfilment, according to EN 45545 standard, is attained. The EN 45545 standards specify that the location of the fire must be possible to identify and indicate.
To ensure reliable operations even when the detection system is exposed to fire, the system must have built-in redundancy. Built-in redundancy in a fire detection system is a design where the system still works with full function even if one source has stopped functioning.
The control functions needed in the wind power plant vary depending on the technical solutions, for example, extinguishing, remote alarms, power control and their integration with other safety functions, etc.
All of these control functions can be delivered separately by different manufacturers, but in order to reach the optimal level of safety in the most cost-efficient way it is advantageous if the fire detection system
© TOUCH BRIEFINGS 2011
Wind – HSE
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