Abstract: This paper describes some of our experiences over the last 20 years related to damage from corona discharge in 5kv and 15kv indoor/outdoor Metal Clad Switchgear . Tracking it down and verifying our findings, using IR Imaging, UV Imaging, Ultrasonic Detection and visual inspection.
Corona is a serious issue in metal clad switchgear because of its highly destructive nature and is the cause of most flashovers in medium voltage metal clad electrical equipment. The fundamental cause of this symptom is an electrical breakdown of air brought on by electrical stress and poor air quality within the switchgear. If not rectified a flashover is imminent, possibly causing enormous damage and injury to personal. Tests have proven that when a flashover occurs the temperature is in excess of 20,000 degrees, with a bulk of the damage being caused by secondary explosions from a build up of compressed unburned gases within the enclosure. Dealing with corona discharge in the case of metal clad switchgear is very unpredictable and caution must be used at all times. With today’s instruments used for condition monitoring and predictive maintenance, we are able to help combat and verify this problem and do it successfully.