The Ultimate Guide: On the Maintenance of Electrical Power Transformers

Maintenance Inspection Tasks

Although there are many ways to test for power transformer condition, the majority of power transformer problems can be detected by visual inspection. Maintenance engineers are well aware of this. This best practice guide lists the inspections that can be performed on a power transformer in and out of service.

Infrared Thermography

Infrared thermography provides a visual representation of invisible infrared radiation emitted from objects by their thermal conditions. It is not possible to contact the object directly with the image. This can be used to identify a defect in transformer bushings, hot spot on surge arresters, blocked cooling system, and circulating currents that affect localized overheating of tank walls.

Infrared thermography is sometimes used to detect temperature rises in compartment types OLTCs.

These problems can be easily detected on OLTC designs, as the OLTC compartment is usually cooler than the main tank. Any IR scan showing the contrary should prompt an investigation.

Main Tank and Conservator

The transformer active element (core, coil assembly and insulating fluid) is contained in the tank. A compartment for the on-load tap changer can also be included in tank condition assessment. Its mechanical characteristics are the most important determinant of the tank's integrity. The tank should be able to hold pressure and not leak.

The condition of the following factors will determine the integrity of the tank:

* The gasket containing surfaces

* The tap changer door gaskets for the manhole, hand hole and manhole

* and tank integrity.

Oil leakage is a sign of a problem. Inability to seal a tank properly can make it unsuitable for current installations. Leakage prevention systems that use specialty sealants or unique hardware with gasket provisions may prove to be effective.

Deformation signs should be checked on the tank. Tank deformation can be caused by extreme pressure, electrical arc, poor foundation support, frequent removal of spare transformers, or from improper installation.

You can check the integrity of a bladder by inserting a swab stick fitted with a cotton cloth at the end through the bladder access port on the top of your conservator tank. Then, gently wipe the bladder's interior. If the cotton swab is saturated with oil, it indicates that the bladder has a leak and must be replaced.

These transducers can detect rupture:

* A capacitive transducer which detects oil contact

* To detect air, a gas collection relay is mounted at the top of the conservator.

Regularly check the oil level of the conservator system to ensure it is at the correct level. Also, make sure there isn't an oil leak in the transformer. The oil level gauge has a 25degC marking that can be used to adjust the correct oil level.

Conservator tanks weren't designed to withstand vacuum in the past. These conservator tanks were not designed to withstand full vacuum. The valve between the main and conservator tanks must be shut down when a vacuum is applied. Modern conservator tanks can be used for full vacuum, so the valve should not be closed. The transformer manual or manufacturer should always be consulted in all cases.

It is important to check the desiccant used in the bladder-type conservator system on a regular basis and replace it when it has reached its limit of moisture removal. A system like this with a non-functioning deiccant (especially in humid environments) can cause moisture to enter the tank or prematurely age the bladder.

These actions can be done on the main tank:

* Inspect for oil leakages and reseal if necessary

* Inspect for paint damage or corrosion and repair if necessary

* Inspect all compartments for oil levels

* Refill or replace the main conservator bladder and air dryer if necessary

* If an air freezer is installed, check it.

* Verify the grounding of neutral terminals and main tank

* Inspect the electrical insulation at the tank base if it is fitted

Before putting the valves back in service, make sure you check their status

If silica is used to dry silica gel, the silica color will change. This indicates that silica is saturated with water. The air that passes through the breather will stay humid. If silica gel has changed in color by more than 50%, it should be replaced.

The color change must be seen starting from the fresh-air input side (where the air enters the system on its way to the conservator). If silica gel color changes on the conservator side, or if silica gel color remains unchanged for several months, this is an indication that there is air leakage in connection piping, allowing air to bypass your breather.

Cooling System

Oil pumps

Regular visual inspections of transformer oil cooling circuit components must be done. Usually, this should not exceed every 12 months. To ensure proper operation, oil pumps should be manually energized. Any unusual noises, such as grinding, rubbing, scraping or oil flow cavitation, should be taken note and investigated. Flow gauges must indicate flow with no fluctuation. Oil leakage must be ruled out in all areas, including the piping and valves.

To ensure the integrity of bearings, pumps equipped with a bearing condition monitor need to have their readings taken every year. In-service failure is more common for pumps with ball bearings. It is recommended that pumps with ball bearings be replaced by pumps with sleeve-bearings.

Radiators and fans

To ensure proper operation, fans should be manually energized. Similar to oil pumps, any fan motor noises or fan imbalance shudders should be noticed, investigated, and rectified. For the safety of staff, fan blade guards should be maintained. Debris should be spotted and removed from the airflow.

To ensure heat transfer and oil flow, it is important to periodically take infrared images of radiators. Oil leakage must be prevented from all areas, including the piping and valves.

Pipe work flange joints and valve stems are common oil leakage points.

Air Coolers for Oil-Air Forced

Many generator step-uptransformers, mobile transformers, as well as some substation transformers use forced oil-air coolers. To provide the required cooling to dissipate transformer losses, these coolers require full airflow from the fans and full oil flow from the pumps.

These coolers will cease to function if the pumps and fans are not working. The environmental conditions in which the transformer is used can affect how the coolers age over time. These coolers may experience premature death if they are exposed to any one or more of these conditions.

Transformer Cabinets

This component needs special attention as most accessories are connected to the Transformer Cabinet. These inspection tasks should be performed:

* Verify power supply, backup feed, and signaling

* Verify the functionality of anti-condensation heaters

* Clean all contact points and tighten screws on current-carrying components

* If installed, check the service hour counter

Buchholz Relay Operation: Recommended Actions When It Operates

This section discusses the causes of Buchholz relay operation. It also recommends what to do after a Buchholz surge trip, or gas collection alarm is received. This section covers both operational situations as well as situations that may arise during commissioning new transformers.

Buchholz relays mounted on the transformer main tanks have two components, which are described below.

Gas Collection Element

This element captures gas that escapes from the transformer, and closes the contact when it reaches a set limit. If the limit is exceeded, any gas produced will be released from the relay and into the conservator. No further operations will be performed. It is important that the transformer was designed so that gas bubbles do not collect in its internal cavities.

When a certain amount of gas is collected, the gas collection element works. It does not give any indication of the gas production rate.

Know How the High-Performance Fans for Oil-Cooled Transformers Works

Oil-cooled transformers are a valuable asset in today's dynamic power market. Technology advances have made it difficult to supply and consume energy efficiently. This is why it is crucial to extend the operating life of these assets.

It is important to keep transformer assets in good condition. They convert incoming power to meet your plant's power consumption ratings.

All types of oil-cooled operational transformers around the globe are at various stages in their life expectancy, which can range from 1-30 years or older.

The following factors have been shown to reduce operational performance and life expectancy in oil-cooled transformers that have not reached or even come close to the 30-year mark.

Budget constraints for maintenance and spare parts

Reactive and unplanned maintenance of assets can lead to occurrences like the breakdown or rewinding because there are no critical spares.

It is a mistake to fail to implement planned and preventative maintenance programs, which is not ideal.

Recycled transformers can be purchased at higher prices because of high demand from power users. This makes it even more difficult to avoid a reactive or unplanned maintenance situation.

These situations can often cause the loss of power to your plantar machinery, which in turn results in loss of production. This in turn equates to the loss of revenue and a serious hit to the return of investment of your assets.

Transforming your return-on-investment

Oil-cooled transformer owners and users should first initiate and implement cost-effective planned and preventative maintenance systems. 

It is vital to implement a maintenance strategy. Anything less will not be accepted in today's competitive and fast-paced environment.

 There is a lot of information available on suppliers, systems and procedures for maintaining transformers. However, expert guidance is best.

This editorial will briefly summarize the most simple and reliable method for maintaining transformers based on ArmCoil’s extensive industry experience and knowledge - including the segment in which the company is successful -

A baseline, or record of the asset's history, is the best starting point in maintaining oil-cooled transformers or any other piece of equipment. This information can be used to accurately measure the asset's condition on a monthly or annual basis.

Instead, negotiate fixed rates with your supplier to ensure a three-year maintenance contract. This will ensure consistent quality and consistency that is tailored to your needs.

It is best to source from ISO-accredited companies who are well versed in the importance of traceability, quality and other high standards of work methods.

The ideal starting point is to determine the condition of assets as they are. For operational oil-cooled transformers, this is done by performing on-site oil sampling, testing, and visual inspections.

You should send these samples, images, testing, and visual inspections to us in a report format. This will include all results. You should also include any discrepancies and offer suggestions for rectifying them.

DGA testing (Dissolved Gas Analysis)

When there is a very slight flashing/ arcing between connections, gasses are emitted which can build up in the transformer tank.

Moisture content

This test measures the moisture content in the transformer.

Furanic testing (winding insulation tests)

This test is used to measure the insulation around electric conductors, mostly active coils/windings.

Corrosive sulphur tests

This test measures the corrosion of the material within the transformer as a result of corrosive reactions at ambient or high temperatures. This test measures the corrosion of all copper, steel, insulation, and other materials.

Test PCB

It is crucial to track the presence of polychlorinated biphenyls, or PCBs. These chemicals are banned from human and environmental use.

Thermal imagery

This test can be used to identify hot or cold spots around the transformer. It is also useful to check that cooling radiators have not become blocked by sludge. Thermal imagery can be conducted with a variety of equipment.

Testing of auxiliary equipment

This test is intended to verify the functionality of all auxiliary parts, including the Buccholz relay and winding temperature indicators. Pressure relieve valves. On- and offload tap changers. All types of breakers.

Visual inspection

This allows you to take photos of the unit under evaluation and note any visual faults such as loose cables, paint condition, leaking valves or plinth condition. This visual representation should be kept for historical purposes.

Last words

These eight inspections are just a guideline for what can be done to maintain your transformers. As the size of the transformer is different, the evaluations can vary from 11kV to 22kV to 33kV to 66kV to 88kV to 132kV.

It is therefore important that the owner/end-user clearly explains what is needed before an evaluation is performed. ArmCoil, a reputable contractor, is willing to help in the creation of specifications that can be approved by clients prior to any inspection.

How Power Transformers is play a major role in the global grid modernization

 In the digital era, the world is an increasing number of established on superior gadgets such as smart phones, laptops, and related technology, all of which rely on one critical component; electricity. Power transformers are among the impact elements of a grid.

From facilitating lighting fixtures in residential functions to making sure the characteristic of units and home equipment in industrial settings, a regular and tightly closed float of electrical energy is a must. In 2019, electrical energy consumption used to be about 3.9 trillion kWh (kilowatt-hours) in the United States alone, in accordance to the EIA.

Power transformers are massive power elements required to transmit strength from channelized sources to various distribution channels. These gadgets are regarded imperative factors of an electric powered provide distribution device and are used at distinct factors to facilitate an uninterrupted and tightly closed glide of strength from the grid to the end-users.

According to a learn about by way of Global Market Insights, Inc. the world strength transformers market dimension is set to attain past $24.5 billion in valuation via 2027.

Have you examined it?

Global clever grid improvement via 2024
Industrial and power sectors to force boom in the digital options market

In 2020 alone, some 6,000 strength transformers have been mounted globally.

Auto strength transformers to emerge as a desired answer for voltage regulation

In current years, auto electricity transformers have begun to emerge as a front runner in voltage legislation options and are gaining large traction. These gadgets are regarded one of the most essential components of the present day electricity grant chain and are used to tackle the fluctuation of voltages in strength traces intended for family electrical energy supply.

Auto electricity transformers are additionally used to convert voltages for use on special devices. Their capability to make units constructed for precise voltages feature even in case of fluctuations, alongside with their function as frequent linkage factors between voltages in family grids have made them an quintessential aspect in an electric powered grant distribution device throughout creating nations.

To that end, in November 2020, Indian state-owned engineering corporation BHEL set a new report by means of finishing the manufacture and checking out of the highest-rated Auto Transformer at the Bina, Madhya Pradesh-based NHPTL (National High Power Test Laboratory). The transformer, with a five hundred MVA 400/220/33 kV, was once designed and produced at the Bhopal plant of BHEL for the UP Power Transmission Corporation Ltd.

Auto transformers have contributed appreciably to the energy transformer enterprise in the region, given that they play a key function in bulk electricity transmission to large cities and load centres.

Retrofitting of current electrical energy grids will underpin energy transformer importance in utility applications

One of the most outstanding elements using strength transformer demand in the utility quarter is the burgeoning focal point on the retrofitting of current grid infrastructure.

Electric utilities are making investments with the aid of the hundreds of thousands every yr to exchange and refurbish getting old grid systems. For instance, in accordance to IEEFA (Institute of Energy Economics and Financial Analysis) estimates, in April 2019 India deliberate to make investments over $250 billion in the direction of grid modernization and expansion, to facilitate less difficult inexperienced power ability uptake.

There are numerous motives for this intensifying center of attention on grid restructuring, the most extraordinary being that many of these grids are nicely previous their provider life. In this case, energy transformers play a key function as fundamental property for T&D community improvement, through addressing the rising want for extra resilient and dependable strength transmissions structures and making sure bendy overall performance and excessive gadget reflectivity in complicated grid environments.

Another essential increase driver for the energy transformers market in the utility region is the rising focal point on the deployment of energy-efficiency grid equipment, and the fast development of renewable energy sources throughout developed and creating economies.

In February 2021, Hitachi ABB Power Grids Ltd. was once granted an order really worth $20 million from Turkey-based TSO (transmission machine operator) TEİAŞ, for the furnish of a number of 62.5-MVA and 100-MVA, 154-kV energy transformers for a grid enlargement assignment aimed at handing over less expensive strength provide to faraway areas nationwide. A key goal of the venture used to be to reduce dependence on polluting and unreliable electricity sources regionally available, such as diesel generators, and to make certain uninterrupted and great go with the flow of electricity.

Major gamer in the strength transformers enterprise are additionally setting greater center of attention on the integration of clever applied sciences and digital options in strength transformer technologies, to create extra energy-efficient solutions. As extra and extra agencies ink strategic technical collaborations to advance novel strength transformer solutions, product demand is anticipated to witness a significant expand in the years ahead.

The integration of the TXpert Ecosystem will additionally permit for digital web page administration and make contributions to greater grid reliability and carrier quality.