An area where critical processes can suddenly be interrupted (by loss of electrical power) is in the cabinets containing the switching gear. Switch contacts can, in time, develop roughness and corroded surfaces from arcing, aggravated by any ingression of corrosive gasses. With the passage of time, the elevated contact temperatures accelerate the degradation of the contacts, initially volt-drop problems occur, followed by a runaway resistive heating process, where complete contact failure results. This is when a sudden and unpredicted loss of power to a critical process can occur, causing great damage with severe cost implications.
The problem can be detected quite early by monitoring the heat given off by the offending contacts. Traditionally one would open the enclosure and take 'snap-shots' of the equipment within, using a thermal imaging camera. To be sure of finding problems before they became serious, this would have to be done regularly, using stored images to compare results, and then try to see if there are any significant tendencies towards excessive heating at any point in the switchgear. This would be a tedious and expensive task - often futile, as it is possible for switchgear to run for extended periods with few or no problems at all. Often some critical parts would be hidden behind other parts, or behind partitioning within the cabinet. Standard thermal imaging could not be used accurately assess the condition of the switchgear under such circumstances.
Cost-effective solution
The solution offered by Finger is elegant and simple, operates continuously and costs far less. Finger's solution, the Exertherm, is a system that makes use of infrared thermocouples. These detectors are small, require no power, exhibit a fast response (0,1 s) and are intrinsically safe.
They are mounted inside the switchgear cabinet; one sensor for each spot that is required to be monitored. A choice of different optic options caters for different distance/spot-size ratios. Each sensor monitors its own target, automatically referenced to the ambient temperature. They produce an output that indicates the temperature rise above the ambient temperature. Since the sensors are small, standard cabinet arrangements may be used, with efficient use of available space.
This industry-proven system allows the sensors to be directly connected to the 8-channel data acquisition input cards and simple daisy chaining of cards makes for an easy to implement arrangement. Connection is made to a PC via remote RS232. The easy to use software permits data to be logged and viewed in MS Excel, for a visual trend analysis. Two alarm points per channel provide adequate warning of potential problems, permitting maintenance to be carried out only when necessary, and when it would be convenient.
This product is recommended for the continuous monitoring of switchgear that is switching power to a critical process. Organisations to benefit can be diverse, ranging from financial services, telecommunications, IT, medical, petrochemical to defence, etc.
| Tel: | +27 31 701 4861/2 |
| Email: | telco@telcosa.co.za |
| www: | www.gailnortoninstrumentation.co.za |
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