Table 3: Primary Cause of Transformer Failures. This category pertains to those cases where actual Overloading could be established as the cause of the failure. It includes only those transformers that experienced a sustained load that exceeded the nameplate capacity. Often, the overloading occurs when the plant or the utility slowly increases the load in small increments over time.
The capacity of the transformer is eventually exceeded, resulting in excessive temperatures that prematurely ages the insulation. Then, forces from an outside fault may cause a deterioration of the insulation, leading to failure.
One part water in 10, parts oil has been known to decrease the dielectric strength 50 percent. Oil samples from each tank, except of course small distribution transformers, should be given a break-down test at least once each year … so that moisture may be promptly detected and removed by filtering. All recommendations are general guidelines and are not intended to be exhaustive or complete, nor are they designed to replace information or instructions from the manufacturer of your equipment.
Contact your equipment service representative or manufacturer with specific questions. Privacy Statement Legal Notice. Bartley, P. Cause of Failure Hartford Steam Boiler has collected information about transformer failures for decades. A transformer maintenance program should include the following recommendations: Installation and Operation Install transformers and keep electrical loading within the design range. Protect units from surges and other external hazards.
Test the Oil Gas-in-oil analysis should be performed annually to measure the dissolved gases in the oil that are created by developing faults in the transformer. Additional Maintenance Keep the porcelain bushings and insulators clean. On liquid-cooled units, check the radiators for leaks, rust, accumulation of dirt, and any mechanical damage that would restrict the oil flow. Keep electrical connections tight. Inspect tap changes on a regular basis.
The transformer windings, bushings, and arresters should have a Power Factor test on a three-year basis. Check the ground connection on the surge arrester annually. About the Author William Bartley received a bachelor of science degree in electrical engineering from the University of Missouri at Rolla. Swering, chief engineer of the Electrical Division, wrote: "There are a number of factors which affect the life expectancy of insulation and these should receive the careful consideration of persons responsible for the operation of electrical equipment.
Table 3: Primary Cause of Transformer Failures Lightning Lightning surges are considerably less than previous studies, because of our changes in categorizing the cause. Today, unless we have confirmation of a lightning strike, a surge type failure is categorized as "Line Surge. Line Surges According to our database, the Line Surge or Line Disturbance is the number one cause for all types of transformers failures.
If the necessary oil level is not maintained, the windings will begin to overheat, eventually leading to transformer failure. Preventative maintenance of this issue should involve regular oil filtration. Aging transformers may display signs of electrical or mechanical failure. Mechanical failures involve physical displacement or damage of parts, and happen for a number of reasons, including but not limited to seismic activity and through faults.
Preventative and early onset maintenance of mechanical failure typically involve frequent Sweet Frequency Response Testing and induced voltage testing. Partial discharge present during voltage testing often indicates some sort of mechanical failure.
Electrical failure typically involves line surges, which is a very common cause of transformer failure. Voltage spikes, switching surges and line faults are a few common culprits of electrical failure. The primary method of preventing this is high quality surge protection and regular maintenance of the existing surge protection system. The regular checks and balances of surge protection should involve annually checking the ground connection of the surge arrester.
Connection should be tight. Preventative maintenance of this issue should include making sure the electrical load settings are appropriate for the specific type of transformer being used. Also, both mechanical and electrical damage may be prevented or detected early through use of the built-in devices that most transformers come with.
These include the Buchholz and pressure rise relays and pressure relief device for mechanical purposes, and the differential, overcurrent and ground current relays for electrical. Failed transformers can create a variety of hazards, so it is very important that you do not approach it. Alert authorities by calling Please provide any additional information you think may be of value such as gate combinations or pole tag numbers to BEC dispatch.
A distribution transformer can take one hour to a few hours to replace; but widespread damage can take much longer to repair. What is a transformer?
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