Bushings are generally well tempered and well behaved, but occasionally their behavior deteriorates and the consequences can be unpleasant. A bushing is a device that allows a conductor to pass through a barrier which is usually grounded; the bushing has an insulating medium, which must be sustained to prevent the passage of excess current to ground. Bushings are like the tires on your car: they enable the car to do what it is supposed to do, but are not the reason why you buy the car - they are enablers, and when they fail the results can be catastrophic. Generally, bushings have a low failure rate, less than 1% a year while in service. Some individual designs may be more prone to failure; some less. Managing the population through a combination of off-line testing and targeted on-line condition monitoring can reduce both failure rates and risk.
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