BIS Certification for Outdoor/Indoor Type Liquid Immersed Distribution Transformers IS 1180 (Part 3)

In today’s power distribution networks, distribution transformers serve as the final voltage transformation stage before electricity reaches end consumers. With an increasing demand for eco-friendly, safer, and high-performance transformer solutions, liquid-immersed transformers using natural or synthetic ester liquids have gained significant attention due to their enhanced fire safety, biodegradability, and superior insulation properties.

To ensure quality and safety, the Bureau of Indian Standards (BIS) has introduced IS 1180 (Part 3) — a specialized standard for Outdoor/Indoor Type Liquid Immersed Distribution Transformers up to and including 2500 kVA, 33 kV, using natural/synthetic organic ester insulating liquids.

Let’s explore the scope and requirements of IS 1180 (Part 3), the BIS certification process, and why manufacturers and suppliers must comply with this Indian Standard for sustainable and safe transformer deployment.

Indian Standard IS 1180 (Part 3)

IS 1180 (Part 3): 2023 is the Indian Standard that specifies the technical and performance requirements for distribution transformers immersed in natural or synthetic organic ester fluids. These transformers are designed for voltages up to 33 kV and capacities up to 2500 kVA. They are suitable for both indoor and outdoor installations and provide enhanced fire safety due to the high fire point of ester fluids. Additionally, they offer improved environmental performance through biodegradability and efficient insulation due to their excellent dielectric properties. This standard complements the existing IS 1180 series, which covers mineral oil-immersed transformers, thereby expanding India's regulatory framework to incorporate sustainable insulation technologies. The standard outlines stringent construction, performance, and testing criteria for ester-immersed distribution transformers:

  1. Rated Capacity and Voltage: Designed for capacities up to 2500 kVA and primary voltages up to 33 kV, these transformers are suitable for three-phase applications.
  2. Insulating Liquid Requirements: The use of natural esters (vegetable-based) or synthetic organic esters is required, which must comply with IS 16081 or equivalent IEC standards. The ester fluids must have a high fire point (greater than 300°C), high moisture tolerance, and biodegradability.
  3. Cooling and Mounting: These transformers utilize ONAN type cooling (Oil Natural Air Natural) and are suitable for both pole-mounted and pad-mounted installations.
  4. Efficiency and Losses: The transformers must meet the energy efficiency levels defined by the Bureau of Indian Standards (BIS) and comply with minimum loss values for different kVA ratings.
  5. Type Tests and Routine Tests: Required tests include temperature rise tests, lightning impulse tests, short-circuit withstand tests, insulation resistance tests, and dissolved gas analysis of the ester fluid.
  6. Marking and Nameplate Details: Certified transformers must prominently display the manufacturer's name, serial number, BIS license number, standard number (IS 1180 (Part 3)), and the ISI mark.

Why BIS Certification is Mandatory

As part of India’s commitment to electrical safety, quality, and environmental sustainability, BIS certification is mandatory for manufacturers of distribution transformers covered under IS 1180 (Part 3).

BIS Certification Ensures:

● Compliance with safety and energy efficiency norms

● Reliability under Indian grid and climatic conditions

● Eligibility for government and utility tenders

● Usage of BIS-approved natural or synthetic ester liquids

● Long-term durability and reduced risk of fire

The ISI mark signifies adherence to national standards and gives end users, including power utilities and infrastructure developers, confidence in transformer performance and safety.

BIS Certification Process for IS 1180 (Part 3)

Here’s a step-by-step guide for manufacturers seeking ISI certification for ester-immersed distribution transformers:

  1. Application Submission: Submit the completed application form with necessary documentation to BIS.
  2. Document Review: BIS evaluates the submitted documents to verify accuracy and completeness.
  3. Factory Inspection: BIS officials conduct on-site inspections to assess manufacturing processes and quality control systems.
  4. Sample Testing: Product samples are collected and tested at BIS-approved laboratories to verify compliance with Indian standards.
  5. Certification Grant: Upon successful inspection and testing, the BIS issues the certification, allowing the use of the ISI Mark. 

Documents Required for BIS Certification 

To apply for ISI Certification for Fire Doors and Assembly, manufacturers must provide the following documents:

● Completed application form

● Detailed manufacturing process information

● Quality control plans and test reports

● Factory layout and equipment details

● Product specifications and technical details

● Business registration proof

● Declaration of conformity to Indian standards

Additional documentation may be required based on product specifications and environmental regulations.

BIS ISI Mark Certification Costing And TimelineBIS ISI Mark Certification Costing And Timeline

To Know The Process in Detail, Please Visit:

Under BIS Registration Products ISI and CRS

Conclusion

As India moves toward a greener, safer, and more reliable power infrastructure, standards like IS 1180 (Part 3) are critical in ensuring high-performance transformer technology. By obtaining BIS certification for Liquid Immersed Distribution Transformers, manufacturers can demonstrate compliance, unlock new markets, and contribute to sustainable development goals.

The ISI mark is not just a regulatory requirement — it's a badge of quality, trust, and commitment to safety. Need assistance with BIS certification under IS 1180 (Part 3)? Our experts can help with testing, documentation, audits, and licensing. Let’s power progress — safely and sustainably.