Distribution transformers are vital in power distribution systems, stepping down high-voltage electricity to a usable level for end users. However, they are susceptible to various issues that can disrupt service, reduce efficiency, and lead to costly repairs. Here are some common issues with distribution transformers and troubleshooting methods for each:
Overheating
Issue: Overheating can result from overloading, high ambient temperatures, poor ventilation, or cooling system failure. Prolonged overheating can deteriorate insulation, cause winding damage, and reduce transformer lifespan.
Troubleshooting:
Check Load Levels: Monitor the transformer’s load and ensure it does not exceed its rated capacity. If overloading is a recurrent issue, consider load balancing or upgrading the transformer.
Inspect Cooling Systems: Check fans, oil pumps, and radiators for blockages or failures. Ensure that the cooling system is clean and operating effectively. Improve Ventilation: Ensure the area around the transformer is clear of obstructions to allow proper air circulation.
Insulation Breakdown
Issue: Insulation degradation is generally a result of heat buildup, material degradation or decomposition, and or physical or chemical pollution by moisture or particles. This can cause partial discharges, arcing, and transformer failure.
Troubleshooting:
Perform Insulation Testing: The insulation condition should be determined through dielectric tests including insulation resistance and polarisation index tests. Regular Oil Analysis: For oil filled transformers, conduct dielectric strength, dissolved gases and moisture density tests on the oil. That is to say, the moisture content or existence of gases in the insulation regions shows degradation of the insulation material.
Visual Inspection: Any physical signs of insulation wear, say, in the form of cracks or discoloration must be looked for.
Moisture Seepage
Issue: When moisture gets into a transformer, it will reduce the dielectric strength of the insulation materials, leading to arcing and corrosion among others. This is even worse with oil-filled transformers.
Troubleshooting:
Check Seals and Gaskets: Oil leaks can be checked readily by examining all seals, gaskets, and the transformer’s conservator tank. In case of signs of seal degradation, restore it to ensure no moisture is allowed to infiltrate its surface.
Dehydrating Breathers: To minimise the moisture entering the dew point use silica gel breathers. Ensure to check on it always and replace it when you feel it is no longer absorbing the moisture as required.
Perform Oil Drying: Dehydration methods or change in the oil may also work on the transformer where moisture concentration has been recorded to reduce the dielectric strength.
Voltage Instability And Load Shedding
Issue: Causes of voltage fluctuations include load unbalance across the phases, wrong tap settings or supply voltage. This can subject transformer windings to tension and cause a raise in energy loss and expenses.
Troubleshooting:
Monitor Load Balancing: It must also be ensured that all phases of winding receive equal load so that no particular winding is stressed out.
Check Tap Changer Settings: Ensure that tap changers are in their correct position to ensure proper voltage regulation for the area served by the transformer.
Inspect for Loose Connections: Abnormal voltages on the primary or secondary windings may be due to loose connections, so tighten or replace any that are loose
Noise And Vibrations
Issue: Transformers will give off some levels of noise during operation, but extra noise or vibrational levels may imply problems with the core, winding or some sort of structural problem.
Troubleshooting:
Examine Core and Windings: If there is humming noise, check if the laminations have come off or if the windings are loose. High levels of noise can indicate such critical defects in the core or displacement of windings.
Check Mounting and Bolts: Vibrations are most likely to be increased where the mounting bolts are loose. Tighten any bolt that may be loose to reduce noise. Perform Acoustic Analysis: If the noise level is abnormal, then use acoustic instruments to trace the origin of noise to solve the problem.
Oil Leaks
Issue: They include worn out gaskets, cracks in oil tanks, and general poor sealing which may cause reduced oil level, overheating.
Troubleshooting:
Inspect Gaskets and Seals: Inspect and replace old worn-out gaskets and seal for better performance of equipment.
Monitor Oil Levels: Check oil levels frequently. If it is considerably lower, then you need to look for a leak which will allow you to address the problem with cooling and insulation in a timely manner.
Perform Pressure Testing: In the case where the leakages are hard to detect, pressure the tank so as to expose areas that need repairs because of leakage.
Short Circuits And Ground Faults
Issue: Internal or external short circuits are very harmful to the transformer windings and cause failure. If not detected, ground faults can cause various degrees of winding degradation.
Troubleshooting:
Perform Winding Resistance and Ratio Tests: Measure winding resistance and check transformer turns ratio frequently to determine whether you have a shorted turn or a damaged winding respectively.
Check Grounding: Check and confirm that the grounding connections are properly attached and that they are operating as they should.
Use Protective Relays: Check on protective relays, in case of an occurrence of a fault; these relays isolate the transformer in order to avoid damage while keeping the device safe.
