DTs on the threshold of transformation

Industry stalwarts envisage a bright future for distribution transformer (DT) on account of infusion of renewable energy as future energy while analysing reasons for failure of DTs as well as measures to curtail them. -Supriya A Oundhakar, Associate Editor

India has a total installed capacity of 380 GW that constitutes about 20 per cent of renewable energy. As per the International Energy Agency report, the demand for energy will triple in next 20 years. Further, the country has planned for 33.3 per cent renewable energy since 2022.

As a positive impact of the government’s thrust for providing quality power to each and every household through various schemes of electrification like the Deendayal Upadhyay Gram Jyoti Yojana (DDUGJY), Integrated Power Development Scheme (IPDS) and Sahaj Bijli Har Ghar Yojana (Saubhagya), the transformer sector has been witnessing a buoyancy. These government schemes have encouraged investments in the distribution sector.

Distribution transformers (DTs) play a very important and vital role in delivering electricity to the last mile. DTs set to get a boost on account of the Ministry of New and Renewable Energy under Green Energy Corridor (GEC) scheme’s planning for investment of Rs 43,000 crore for enhancing transmission network. Under this scheme, the projects of about Rs 11,500 crore have been awarded so far both through bidding and regulatory tariff-based route for the expected commissioning over the next two-year period. This paradigm shift towards alternative energy resources like nuclear and solar energy for power generation is expected to further boost the transformer deployments in the country in near future.

Current Status of DTs
The government’s electrification drive has led to multi-fold growth of distribution transformers. According to Manas Kundu, Director Energy Solutions, International Copper Association India (ICAI), the demand for transformers was 323,632 MVA in FY 18 which grew at 9 per cent year-on-year (y-o-y) i.e. 352,818 MVA in FY 19. Out of this DT share of market is 135,000 MVA having CAGR 14 per cent approximately over year 2017-2019. This is expected to have 8 per cent CAGR over 2019-2022. Rural share in DT segment have been steadily growing from 30 per cent in 2017 to 38 per cent in 2019.

DT is covered under IS 1180. On standards front, DT is currently under Quality Control Order of Government of India – Ministry of Heavy Industries and mandatory licensing process governed through BIS since July 2017.

On energy efficiency front, the DT is under mandatory star labelling scheme of BEE under the Ministry of Power.

“The DISCOMs are instructed to improve operational efficiency. The new standard IS 1180 standard for energy efficient DTs implemented last year, will improve efficiency and reliability of transformers. Since losses are fixed, tender evaluation will be easier,” hopes M Vijayakumaran, Senior Transformer Expert, Primemeiden.

Though both on reliability and efficiency front existing standards and regulatory framework in India provides an enabling environment, Kundu says, “However, compliance has been an issue like many other in India.”

Failure of DT
Transformer is a static machine with very high efficiency and rugged construction. Distribution transformers are more prone to failure in India. High failure rate of distribution transformers is a big concern for the transformer industry in India. The average operational life of a transformer is between 25 to 30 years; however, transformers in India are known to be recalled for repair in as early as two to three years.

Half a decade back the DT failure rate was alarming in India close to 25 per cent pan India with few states having failure rate upward 40 per cent. This in other words, the country was replacing a capital equipment every four years whereas a DT like capital equipment must serve the sector for nothing less than 25 years going by guidelines of CEA as far as technical life is concerned, informs Kundu. This has been serious concern to policy makers. He further adds, “So, Quality Control Order came. In last few years some semblance has creeped in DT sector though being heavily dominated by SME type of players, who has limited access to money or technology, the domain remains at the best limited with low skill-oriented manufacturing practices. Having said that the operating practices at field too have been far from wanting making DT high failure prone.

“Every year, nearly Rs 200 crore are spent by DISCOMs for repair and replacement of distribution transformers,” informs Atul Agrawal, Managing Director, Uttam (Bharat) Electricals.

While analysing the reasons behind failure of DTs, M Vijayakumaran, asserts, “The abolition of Licence Raj allowed many investors to set up new manufacturing facilities. The demand was very much less than manufacturing capacity. So, the price war broke out. Since any tender is decided based on lowest price, a manufacturer has reduced design safety factor, diluted manufacturing processes, used inferior quality materials, outsourced manufacturing activities to semi-skilled and cheap vendors.”

Manufacturers often point fingers to transformer users for running the transformers on overloading, single phasing, un-balance loading and no maintenance and protection while users put the onus on manufacturers for faulty design, poor workmanship and improper transportation etc.

While elaborating Pradeep Azad, Managing Director, UP Transformers (India) Ltd, informs, “Operating conditions like transformer overload, through faults, etc often result in transformer failure, highlighting a need for transformer protection functions, such as over excitation protection and temperature-based protection. Extended functioning of the transformer under abnormal conditions such as faults or overloads can compromise the life of a transformer.”

He adds, “Adequate protection should be provided for quicker isolation of the transformer under such conditions. The type of protection used should reduce the disconnection time for faults within the transformer and minimise the risk of catastrophic breakdown to simplify eventual repair.”

He further attributes major reasons to poor field conditions which are listed as follows:
• Improper installation without any proper fuse either on HV or LV side, and ground earthing.
Overloading: Transformer that experiences sustained loading that exceeds the name plate capacity often faces failure due to overloading and imbalance loading on each phase of a transformer.
• Loose HT/LT lines, resulting in short circuit conditions in a transformer.
Line Surge: Failure caused by switching surges, voltage spikes, line faults or flashovers, and other abnormalities suggest that more attention should be given to surge protection, or the adequacy of clamping and short circuit strength.
Loose Connections: Loose connections, improper mating of dissimilar metals, improper torqueing of bolted connections etc can also lead to failure of a transformer.
Oil Contamination: Oil contamination resulting in slugging, carbon tracking and humidity in the oil can often result in transformer failure.
Improper or inadequate Maintenance: Inadequate or improper maintenance and operation is a major cause of failures in transformers. It includes disconnected or improperly set controls, loss of coolant, accumulation of dirt and amp; oil, and corrosion.
• Zero maintenance.

Measures to Curtail Failure Rate
Failure of distribution transformers leads to considerable revenue loss and thus, entails heavy expenditure for replacement. The complex nature of transformers requires synergy of multiple systems and regular maintenance to operate at full capacity. Every transformer with time needs proper preventive maintenance procedures for a safe and reliable operation of the system. “Regular maintenance and diagnostic tests help in detecting the issue at an early stage and prevent in further deterioration. Preventive maintenance such as oil sampling and analysis (oil quality, moist level, etc.) and electrical measurements such as (insulation resistance, winding resistance, etc.) should be monitored periodically,” asserts Agrawal from Uttam (Bharat) Electricals.

In order to prevent failure, Kundu emphasises that industry needs to carry out right application engineering to offer the right product for our utility environment using right material, adopting right manufacturing practices and complying with quality demand whereas utility must practice the philosophy of life cycle cost added with asset management philosophy. “Not doing so would only hamper our national growth at the cost of our industry growth. It would be contradicting ‘win-win’ proposition for ‘Make in India’ and rather lead to ‘lose lose’ dictum that we cannot afford,” he adds.

Vijaykumaran lists out the following measures:
• Selection of vendor.
• Place order only on qualified reputed reliable vendors for the transformer.
• Vendor shall have SC tested experience for supply of short circuit proof transformer.
• Conduct design review to ensure that the transformer is designed to customer specification.
• Check the manufacturers design rule and tool and have detailed manufacturing quality plan.
• Only select a material and components from approved manufacturer.
• Outsourcing of parts and components shall be with purchaser approval.
• Rigorous factory acceptance test.
• Pre-commissioning test in front of manufacturer.
• Have periodical condition-based maintenance and replace the transformer after prefixed life.
• Policy guidelines.
• For better fire safety use ester oil instead of mineral oil.
• Better to use dry type transformer for higher reliability.
• Introduction of HRC fuses at HT &LT fuses.
• Purchase new transformer conforming to IS 1180 only.

With the advent of new technology, progression of new energy efficiency level and strict quality checks, the distribution transformer industry is expected to increase substantially. “Increase in generation capacity of both conventional and non-renewable sources and new avenues like electric vehicle charging stations etc will also become one of the major growth drivers for the transformer industry,” states Agrawal.

Kundu asserts that the growth of renewable energy especially solar energy in the national energy portfolio will give substantive boost to DT sector but challenges like harmonics or DC injection will make DT more vulnerable unless we are careful in right prescription, design, procurement, installation and usage.