Oil Immersed Outdoor Type Distribution Transformers have become an important part of today’s
electricity distribution systems to efficiently transmit electricity. Such types of transformers are
designed with mineral oil as the insulating medium, which not only helps them maintain their
temperature but also increases their efficiency and life expectancy. As these devices are
responsible for playing an important role in power distribution systems, they need to meet all
kinds of standards for reliable performance.
Under IS 1180 (Part 1): 2014, outdoor type oil-immersed distribution transformers with a
maximum capacity of up to 2500 kVA and with a rated voltage of 33kV should conform to
specified technical requirements relating to various aspects like insulation characteristics,
permissible temperature rise, energy efficiency, short circuit withstand capability, materials for
winding and overall quality of construction. In order to comply with the applicable BIS QCO
standard, the certificate of compliance should be issued under this standard. ISI mark on a
distribution transformer indicates conformance with Indian Standard specifications for
distribution transformers and guarantees the reliability and longevity of these products.
What is IS 1180 (Part 1): 2014 for Oil Immersed Distribution
Transformers up to 2500 kVA?
This is the Indian Standard for outdoor type oil-immersed distribution transformers up to and
including 2500 kVA, 33 kV class, using mineral insulating oil. It mentions the safety and
performance requirements to ensure reliable power distribution in electrical networks. As per the
BIS (Bureau of Indian Standards), these transformers are:
- Checked for voltage regulation
- Evaluated for thermal performance
- Assessed for insulation strength
- Tested for short-circuit withstand capability
Why ISI Mark Certification is Important for Oil Immersed
Distribution Transformers?
The ISI Mark Certification for Outdoor Type Oil Immersed Distribution Transformer is to confirm
that the equipment complies with the relevant IS 1180 (Part 1): 2014 specifications and satisfies
all the necessary safety and quality parameters. As transformers are important components of
electrical network infrastructure, ISI certification would ensure safe and effective functioning of
the equipment throughout its service life.
- Compliance with IS 1180 (Part 1): 2014 specification
- Confirmation of electrical safety and insulating quality
- Assurance of proper performance even under loads, heat and fault conditions
- Certification required for BIS QCO compliance
- Increases confidence among utility companies, industries and consumers
- Improves marketability and credibility of the transformer business
- Enables ISI Mark for the sale of the Oil Immersed Transformer in India
Who must apply for ISI Mark Certification for Oil Immersed
Distribution Transformers?
BIS certification under IS 1180 (Part 1): 2014 is required for businesses involved in
manufacturing, importing, or supplying Oil-Immersed Power Transformer in India.
Applicable to:
- Manufacturers (India) - Must get BIS approval if the Transformer up to 2500 kVA is covered under QCO.
- Foreign Manufacturers - Need certification to export the product to India.
- Importers/Brand Owners - Must ensure that the products are BIS-certified before sale.
- Sellers/Distributors - Should only sell certified Electrical Transformers.
BIS Testing Requirements for Oil Immersed Distribution Transformers under IS 1180 (Part 1)
To ensure efficient performance of outdoor type oil-immersed distribution transformers used in power distribution networks up to and including 2500 kVA, 33 kV class, the Bureau of Indian Standards outlines the minimum requirements under IS 1180 (Part 1): 2014. This certification ensures that manufacturers produce transformers with high electrical efficiency, strong insulation systems, and safe thermal performance for long-term grid operation.The BIS testing parameters and quality checks for the transformers are listed below:
| Test Group | What is Covered | Purpose |
| Transformer Tank & Mechanical Construction | Tank welding, bolts, nuts, washers, and structural assembly | Ensures mechanical strength and durability of the transformer body |
| Dimensional & Design Compliance | Minimum air clearances, core-coil design, flux density, layout drawings | Ensures correct electrical design and safety margins as per IS 1180 |
| Electrical Routine Tests | Winding resistance, voltage ratio, insulation resistance, load/no-load losses | Ensures correct electrical performance and operational reliability |
| High Voltage & Withstand Tests | Induced voltage test, separate source voltage test, impulse test | Ensures insulation strength and safety under high-voltage conditions |
| Thermal Performance Test | Temperature rise of oil and windings | Ensures safe heat dissipation during continuous operation |
| Leakage & Pressure Test | Oil leakage test, tank pressure test | Ensures transformer is leak-proof and mechanically sealed |
| Efficiency & Loss Evaluation | No-load loss, load loss, impedance measurement | Ensures energy efficiency and controlled power losses |
| Special Performance Tests | Sound level, paint adhesion, BDV & moisture content of oil | Ensures operational performance, durability, and oil quality |
| Safety & Clearance Verification | Phase-to-phase and phase-to-earth clearances, mounting arrangement | Ensures electrical safety and safe installation conditions |
| Core & Winding Verification | Core material type, winding material (Cu/Al), assembly quality | Ensures correct internal construction and performance stability |
How to get BIS License for Oil Immersed Transformers in India?
The certification procedure of BIS guarantees that the Outdoor Type Oil Immersed Distribution Transformers having capacity up to and including 2500 kVA and voltage up to and including 33 kV as per IS 1180 (Part 1): 2014, comply with the necessary specifications regarding their safe and efficient performance. The BIS is a certification body which makes sure that the transformers meet the necessary quality specifications. The process includes the following stages:
- Online Registration :- Manufacturers register on the BIS Manak portal by submitting company, factory, and product details. Foreign manufacturers must appoint an Authorized Indian Representative (AIR).
- Testing at BIS-Approved Laboratory :- Product samples are tested in BIS-approved laboratories for electrical performance, insulation resistance, temperature rise under load, dielectric strength and energy efficiency.
- Application Submission :- The application is submitted along with test reports, technical documents, and factory details. Foreign manufacturers must also submit AIR-related documents.
- Factory Inspection :- BIS officials carry out an on-site inspection of the manufacturing unit to verify the production process, safety measures, and quality control system.
- Grant of BIS License :- Once all compliance requirements are successfully verified, BIS grants the certification license under Scheme-I.
- Use of ISI Mark :- After approval, the manufacturer is authorized to use the ISI Mark on the product along with a valid CM/L number, confirming that the product meets BIS standards.
List of Documents for IS 1180 (Part 1): 2014 License
| Document Category | Documents Required |
| Basic Details | GST Certificate, Email ID & Contact Number, Factory & Office Address, Rent Agreement / Lease Deed (if applicable), Partnership Deed (if applicable for partnership firms) |
| Manufacturing Details | List of Machinery, Process Flow Chart, Factory Layout Plan |
| Raw Material Details | List of Raw Materials, Supplier Details, Raw Material Invoices, Raw Material Test Certificates |
| Testing & Quality Control | List of Testing Equipment, Calibration Certificates, QC/Lab In-charge Appointment Letter & Qualification |
| Production Details | Annual Installed Capacity, Last Year Production Value |
| Product & Packaging Details | Quantity per Package, Nature of Packing, Product Printing / Marking Details |
| Management Details | Top Management Details, BIS Communication Contact Person |
| Brand & Certification Documents | Trademark / Brand Certificate, Consent Letter from BIS Recognized Laboratory |
| Additional Documents | Weekly Off Details, Hygiene Document (if applicable), Relaxation Letter (if applicable), Any Other Relevant Document |
| Foreign Manufacturer Requirements | Agreement with AIR (Authorized Indian Representative), [Aadhaar Redacted], AIR Nomination Form, Required Undertakings, Scope of License |
The Foreign manufacturers must designate an Authorized Indian Representative (AIR) in India. The representative is the local point of contact for the Bureau of Indian Standards (BIS) and manages all compliance and regulatory requirements in India.
BIS ISI Marking Requirements for IS 1180 Oil Immersed Distribution Transformers
After the manufacturer obtains a BIS license, the ISI Mark for Oil-Immersed Distribution Transformers must be clearly and permanently marked on its packaging or on the product. Along with the ISI Mark, important details such as the manufacturer’s identification and licence number (CM/L) must be mentioned. This ensures the product complies with all safety and quality standards. Further details are mentioned below:
| Requirement | Details |
| ISI Mark | Indicates that the product is BIS certified and conforms to standards |
| Standard Number | IS 1180 (Part 1): 2014 |
| CML Number | Certification Marks Licence (CML) number issued by BIS |
| Manufacturer Details | Name of manufacturer or registered trademark |
| Batch / Date | Batch number, heat number, or manufacturing date for traceability |
Note: Marking is typically applied using durable stamping, tagging, or permanent printing to ensure clear identification during handling, storage, and transportation, as per BIS marking requirements.
BIS License Validity for Oil Immersed Distribution 2500 kVA Transformer
| Particulars | Details |
| Validity | Typically 1 to 2 years, depending on BIS approval conditions |
| Renewal | Must be renewed before expiry by submitting the application along with the prescribed fee and updated documents |
| Surveillance | Includes periodic factory inspections and market sample testing conducted by BIS |
| Compliance | Continuous following to standard and applicable Quality Control Orders (QCOs) is mandatory |
| Risk | Non-compliance or failed sample testing may lead to suspension or cancellation of the BIS license |
BIS Certification Cost for Oil Immersed Transformers in India
The cost of BIS Approval for a mineral oil-filled distribution transformer includes charges for application, inspection, license, testing, and marking. These fees are paid to BIS as per Scheme I guidelines.
| Charge Type | Indian Manufacturers | Foreign Manufacturers |
| Application Fee | INR 1,000 | USD 15 |
| Audit Charges | INR 7,000 | USD 3,200 - 5,900 |
| License Fee | INR 1,000 | USD 15 |
| Marking Fee | As applicable | As applicable |
| Testing Charges | As applicable | As applicable |
| EVTL India Consultancy Fee | As per actual | As per actual |
Note:
- Application fee for foreign manufacturers is payable via SWIFT (SAARC countries may pay in INR with applicable GST).
- Audit charges for foreign manufacturers vary based on country/location.
- The marking fee is determined based on the product category and production volume (MSME benefits may apply).
- Testing charges are to be paid directly to BIS-recognised laboratories.
- Consultancy fees can vary depending on product type and factory location.
BIS QCO Penalties for Non-Compliance with IS 1180:2014 Oil Immersed Transformers
Failure to comply with IS 1180 (Part 1): 2014 and failure to certify products by obtaining BIS Certification (ISI Mark for transformers) may attract serious punitive measures based on the BIS QCO (Quality Control Order for transformers) and the BIS Act.
- Ban on sale: Prohibited from selling or marketing non-compliant and non-certified products without a valid BIS License for transformers / ISI Mark
- License withdrawal: Withdrawal of BIS Certification for distribution transformers in case of consistent breach of compliance or testing for IS 1180
- Recall by BIS: Recall of the non-complying products under the BIS QCO for outdoor oil immersed transformers
- Legal Action by BIS: Fine and other legal action in case of violation of ISI Mark requirements for transformers
- Goods Seizure by BIS: Confiscation of non-licenced product for outdoor oil immersed transformers violating BIS standards of certification for transformers
Conclusion
Oil-Immersed Distribution Transformers are very crucial for effective and dependable power distribution for industries. Such types of transformers use mineral insulating oil to cool and insulate, ensuring that the transformer functions effectively, is energy-efficient, and lasts longer. The standard for these transformers should be IS 1180 (Part 1): 2014 which applies to transformers of capacities up to and including 2500 kVA and voltages up to and including 33 kV, with provisions on insulation levels, temperature rise, energy efficiency, and short circuit withstands.
The BIS Certification for these transformers, according to the IS 1180 (Part 1) is a requirement that ensures compliance with the relevant BIS QCOs and ISI mark application. Professional BIS consultants provide certification assistance for transformers such as EVTL India.
