Thermography in Sub-stations

Thermography is an extremely useful tool in the maintenance of substations. Thermography helps monitor the components in the substation. Using temperature-based imaging, it identifies hot spots which can indicate potential problems. Thermography is an integral part of predictive maintenance schedule. Thermography involves monitoring devices with a thermal imaging camera. Thermal imaging cameras operate on the infrared spectrum which is invisible to the human eye. The images formed by these devices show variations in temperature in the object. These variations in temperature can be interpreted as abnormalities and analyzed.

Thermal cameras work by measuring the wavelength of the radiation emitted by hot bodies. The wavelength of the radiation depends on the temperature of the equipment.

Most electrical problems such as loose connections, overloading, etc are accompanied by a rise in temperature. This rise in temperature can give timely warnings, which, if heeded can avoid major failures and breakdowns.

Thermography is usually carried out in the early mornings to enable clearer differentiations of the hot spots from the surrounding temperature. The components which are being inspected should be in the normally loaded condition.

Inspection should start from the top of the equipment and proceed downwards. This avoids omissions of any part of the equipment. It is ideal to establish inspection routes in the substation, through which the engineer moves across with the imaging camera. This ensures that all areas of the substation are covered.

Thermal images of all components should be recorded and temperatures noted. The temperatures of two similar components carrying similar loads should not differ by more than 17 degrees and the difference between any component and the surrounding air(ambient temperature) should not exceed 40 degrees.

If any anomaly is detected, the thermal image should be recorded along with a ordinary photograph. It is advisable to take the thermal images from different angles to obtain a good perspective.

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