Nearly every factory, shopping mall, airport, office complex and high-rise apartment has an electrical room providing power distribution throughout the facility. Most of these equipment rooms are in the basement or lower floors, out of sight and, in many cases, out of mind until there is a failure. The power distribution system usually includes high voltage metal-clad switchgear, cast resin transformers, low voltage switchgear and panel-boards. A fault or failure in any one of these components can result in power outages, loss of productivity, or even fire and explosions.
Infrared windows allows thermo-graphic snapshots
Routine checks of these components normally consist of current and voltage measurements and most recently thermo-graphic ‘snapshots’ of the temperature distribution in the switchgear. Safety procedures greatly restrict direct access to these components, hence the new practice of installing infrared windows to allow infrared cameras to take images without opening the doors. IRISS has approved windows and panels allowing thermal images may be taken through a special polymer material whilst not reducing the integrity of the panel.
Why is continuous temperature a better solution?
Overload, phase imbalance, power factor, corrosion and poor electrical connections all result in the generation of heat. Any generation of heat is an indication of loss of energy and wasted power. Heat also contributes to a shortening of the life of the equipment, conditions may develop slowly over time and can result in a catastrophic fault.
A ‘snapshot’ using a thermal imager only provides an analysis for less than one second out of a 24-hour operational period and sometimes only gets taken once per year. If the system is critical for total plant operation, often this may not be adequate. On plant service units like large air compressors, bearing temperatures and vibration are measured to try and predict failures. The same can be done with the busbar connections to ensure the correct temperature and limit outages due to connection burning. Continuous monitoring of the busbar within a switchgear cabinet can provide both instantaneous alarms for fault conditions and trend analysis for predictive maintenance.
A trend detected during continuous monitoring will allow for maintenance of the equipment to minimise downtime. The most effective solution to busbar temperature monitoring is the use of infrared point sensors that provide safe noncontact measurement of real-time temperatures.
The latest development from Raytek is the Mi3 series and is ideally suited for this monitoring function. The different optics between types of sensors allows the sensor to be safely mounted within the cabinet at a distance from the busbar to avoid flashover and electromagnetic interference.
The sensor head and mounting bracket do not require any special insulating material for mounting to the equipment structure. The sensor electronics are mounted remotely from the sensor head and outside the switchgear enclosure. The ability to have multiple heads and for the electronics to give analog outputs as well as communicate over Profibus or Modbus, makes this range ideally suited for this application.
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