Usual causes of failures in HT (High-Tension) Components of an Electrical System – Transformer (A Review)

Vikas Goyal, Vishal Singh

Sr. Manager, Singh Isotech Private Limited, Gurgaon
Director, Singh Isotech Private Limited, Gurgaon

Abstract:According to the various studies and audits, it has been proved that safety of HT (High Tension) electrical Equipments is being compromised many times in production and manufacturing industries. Though the fact HT systems and connections are the roots for the entire electrical system of such unit, but then too neglected all the time. This may be because of avoiding extra expenses, to maximize the manufacturing time, to avoid penalties from civil authorities for extra load, it shouldn’t impact the quantum for production, and many more reasons. Although electricity is the only main soul for any of the production or manufacturing units and these Equipments are those braces which holds up your entire system as spine of electrical system.

Introduction:We work for the awareness of Electrical safety and try to focus that the HT system of such units should stand still even at various crucial circumstances. We have observed many times in our previous audits that, business owners are tirelessly into the revolution of their investment and seeking for higher production so that they can surplus their revenue in the least time. Power Transformer is the heart of your entire electrical system, though it can work robustly in any of harsh conditions but doesn’t mean that it so compulsory to let it happen.
In terms of electrical safety for transformers, they are the most neglected part of every industries. Like our heart needs appropriate flow of fresh blood, transformer requires the same thing that its oil should be filtered at the regular span of time. It should be kept cleaner and safer so that it can pump it up its maximum efficiency to the entire system. Due to over running and doing excess of cardio activities impacts functioning of a human heart, overloading and unbalance load causes excess of vibrations and shivering to the transformer which may cause a huge trauma to entire electrical system leading to various kind of losses.

Factual Study:As per Indian Electric Rules, International standards and IEC guidelines maximum output a transformer should deliver is 85%, crossing this calling upon various casualties to the existing electrical system. As per the Audit Data received from Electrical Safety & Energy Audit team for Singh Isotech Private Limited, Gurgaon it is observed that, some of the mediocre level production and manufacturing units are used to neglect the fact rigorously, and keep on extracting the maximum they wants from the electrical system so that their shouldn’t be any kind of down fall into their production.
They observed that load shedding and imbalance load distribution at units are the usual cause of failures for the transformer, among the several. They also stated that, avoiding recent circumstances of transformer may help in the continuous production in the unit, but the possessor are not aware the amount of money which they are making from this continuous production (by bypassing the maintenance and failure conditions of the transformer) is very less than which is wasted in terms of penalties, surges, voltage instability, losses. Etc in that transformer unit.
It has been observed that ESEA-SIPL is working far better on electrical safety concerns for industries and commercial units. They used to have rich experience and good practice in the HT systems, which gives them actual strength to attain the pure values of audits. They also percept and proved through their recent audits, that electrical safety is least bothered in the industries, safety measures of HT system is mostly neglected.

Results & Conclusion:As per the audits they conducted, they like to share some generic points on transformer in terms of general preventive measures:

  • Never use any kind of direct looping through transformer LV terminals.
  • Always try to accommodate the transformer unit under covered area.
  • Try not to skip the maintenance schedule for the transformer.
  • Always look forward for cleaning and sustaining through all required measures.
  • If there is a change in the connected load, in comparison to the starting days, we recommend to re-exercise on the rating of transformer.
  • Try to opt parallel operation schemes for transformer.
  • The transformer should always consists of separate protection device, to avoid the faults.
  • Earthing should be provided as per IE rules and standards.

They also shared some of the obligation and rules against violation of any IE rule or electrical standard sections –

  • As per the NEC article limiting loading capacity of transformer to 80% – 85% of total capacity.
  • The loading capacity of transformer is calculated as per the Part 3, 4 & 5 of Article 220 of NEC.
  • Overcurrent Violation – Part 1 Article 240.
  • Using overloading on Transformer more than its set capacity of 85%, is the violation of code 110.3(B).
  • According to the IEEE red book section 104.3 – It’s stated that the transformer cannot be loaded above its capacity of 85%.


  1. ESEA-SIPL, Audit Report No. 44, Dated – 28.01.2020 & 29.01.2020 for Hapur location.
  2. Y. Kamata, “Testing Methods for Power Transformer Insulation”, in IEEE Transactions on Electrical Insulation (Volume: EI-21, Issue: 6, Dec. 1986).
  3. Omar Alshear, “Testing And Maintenance Of Power Transformer”, in TESTING AND MAINTENANCE OF POWER TRASFORMER, University of Turkish Aeronautical Association Faculty of engineering EEE department.
  4. Dhruvesh Mehta, Prasanta Kundu, Anandita Chowdhury, “Indian transformer industry gearing up for next-gen green liquids”, 2015 5th Nirma University International Conference on Engineering (NUiCONE), IEEE.
  5. Indian Transformer Manufacturers Association [ITMA], Testing Services “”.