What are the common transformer maintenance procedures?

Visual inspections can be a low cost, early predictor of potential trouble. The asset file will build an easily interpreted history. Photographs of key points can be reinforced by thermographic. images. Comparing base line (initial) images allow for comparative troubleshooting. What’s different? Color, fan speeds, temperatures - tracking this type of information can be very helpful.

Visual inspection of transformer maintenance involves, -External Inspection - Check for oil leaks around the transformer. - Inspect bushings, connections, and cooling systems for any abnormalities. - Examine the general cleanliness of the transformer and its surroundings. -Internal Inspection - Review the condition of insulation materials. - Inspect the core and windings for any visible damage. - Check for loose or damaged connections inside the transformer. -Corrosion Check - Examine the transformer for any signs of corrosion, particularly in areas prone to moisture. Regular visual inspections help in early detection of problems, ensuring the transformer operates efficiently and extends its lifespan.

During a visual inspection of a transformer, key steps are taken to assess its condition. This includes checking for leaks, corrosion, and damage on the external tank, inspecting cooling systems for obstructions, and ensuring secure grounding connections. The oil level and clarity are examined, and components like bushings and tap changers are visually inspected for any faults or signs of wear. Connections, insulators, and labels are checked for proper condition and legibility. Any findings are documented for maintenance records. These visual checks, typically performed quarterly or semi-annually, help ensure the transformer's reliability and longevity

For Transformer test we can do Physical inspection, Insulation resistance test, Tan delta test, Vector group test, CT ratio, Ct polarity l, Ct burden etc. Turn ratio, Winding resistance, Sweep frequency response analysis test, Oil test like Breakdown voltage, Parts per million test etc.

Oil Leaks: Check for oil leaks and reseal if necessary. Paint and Corrosion: Inspect for paint damage and corrosion, repairing as needed. Air Drier and Conservator Bladder: Check air drier and main conservator bladder; refill or replace if necessary. Air Freezer (if installed): Verify its functionality.

Une procédure courante d'entretien des transformateurs est l'analyse du diélectrique lorsque applicable. Elle permet d'anticiper la plupart des problèmes qui peuvent subvenir sur un transformateur. Le mode operatoire de prelevement doit etre rigoureusement respecté et les mesures de securité prises lors du prelevement. Elle est plus co?teuse et plus longue que les autres procedures mais les résultats sur les caractéristiques physico-chimiques et les propriétés du dielectrique du transformateur, l'état des gaz dissous, la teneur en eau ... par rapport aux valeurs limites recommandées (NF ISO2049, NF EN60156...) sont très fiables. Pensez à vous adresser à un laboratoire accrédité pour ces analyses. A renouveller périodiquement.

Another critical aspect of oil testing for transformer maintenance is measuring the levels of dissolved gases in the oil. Transformers are designed to release small amounts of gases during normal operation. However, an increase in the levels of gases such as hydrogen, methane, ethylene, and acetylene could indicate potential problems such as overheating, arcing, or insulation breakdown within the transformer. Regular monitoring of these dissolved gas levels through oil testing allows for early detection of developing faults, enabling timely corrective action to be taken to prevent more significant damage and downtime.

Transformers are often filled with insulating oil to dissipate heat and provide insulation. Periodic oil analysis tests the quality of the oil, detecting contaminants, moisture, and degradation products. This helps in assessing the transformer's health and identifying potential issues early.

Polarization Index (PI) can be easily done with a modern, battery or 110v AC powered Meg-ohm-meter (megger) can perform this simple test. Safety and voltage class need to be considered. Record and track the PI values. Virtually every maintenance crew can accomplish this task.

Winding resistance measurement is conducted to assess the condition of the windings. After ensuring the transformer is de-energized and isolated, a low-resistance ohmmeter is used to measure the resistance of each phase, typically following the sequence of A-B, B-C, C-A. For three-phase transformers, measurements may also include phases to the neutral. Results are recorded and corrected to a standard temperature for accurate comparison. Deviations from baseline values can indicate winding degradation, loose connections, or hot spots, prompting further analysis or corrective action. This data, recorded alongside dates and ambient temperatures, provides valuable insight into the transformer's health and informs future maintenance decisions.

Oil temperature and winding temperature are the most common daily testing, Visual inspection ,sound ,vibration mechanical fitment radiator cooling system protection system and other peripheral safety equipment testing is also required for an ICT transformer.

Insulation resistance testing evaluates the integrity of insulation materials within the transformer. By measuring resistance to electrical current flow, it helps identify any deterioration or moisture ingress, which can lead to breakdowns or failures. Moreover Bushings Inspection is also important must be free from dust before conducting test, bushings provide electrical insulation and support for conductors entering or leaving the transformer. Regular inspection ensures their integrity, detecting signs of degradation, cracks, or leaks that could compromise performance or safety.

DGA involves analyzing gases dissolved in the transformer oil. Abnormal gas levels can indicate internal faults, such as overheating or arcing, allowing maintenance teams to take preventive action before serious damage occurs.

After visual inspection this would be a test I would want to have results for on an annual basis. By testing this annually you can see trends of the gas generation that is occurring in your unit. This will give you a good idea of the overall health of the unit.

Operator round and basic care : check any sign of seep or leak, check gauges within normal operating limit (temperature, pressure, level) associated with transformer load, check any alarm shown from the transformer, check cooling system working normally, check any sign of water ingress or condensation from terminal box or control box, visual check bushing/LA/insulator surface, check for abnormal sound or humming, check any sign of coorossion, check any loose connection on ground or bonding connection, thermal visual check heat distribution on radiator or terminal

Tapchanger maintenance is a fundamental of Transformer maintenance. Inspection of fixed/moving contacts, corona shielding on through tank connections is an absolute must. As well as the usual gaps, measurements, resistor values between transition/resistor contacts from A-B, spring tensions and locking nut tightness. Also worth noting HV/LV bushing checks for potential hot joints & gassing within the bushings. A Tan Delta test can ensure PF capacitance loss angles are within the bushings rated value. SFRA tests also with a measuruable characteristic waveform that can be using as diagnostic for performance of your Tx.

One thing that I have found helpful in my time spent around voltage transformers below substation levels is when doing monthly inspections spend a minute listening to the hum. Usually they will sound the same, but a slight change in sound can also be a predictor of failure, and for smaller non-oil filled transformers that do not have scheduled down times this can be very helpful.

Cooling System: Transformers rely on cooling systems to dissipate heat generated during operation. Regular inspection and maintenance of cooling fans, radiators, and cooling oil ensure efficient heat dissipation, preventing overheating and thermal damage.

Maintenance Procedure for Transformator _ PM Monthly Inspection _ PM 6 Monthly Inspection _1Year PM Inspection Test Oil Transformer Breakdown