BIS Revises IS 398 Standard for Aluminium Alloy Power Conductors: A2-A3 Wires, Corona Tests and Grid Safety Explained

Why is IS 398 (Part 4):2026 in News?

The Bureau of Indian Standards organised a Manak Manthan programme at its Chennai Branch Office on 18 September 2026 to discuss Draft IS 398 (Part 4):2026.

The draft concerns aluminium-alloy stranded conductors used for overhead electricity transmission and represents the fourth revision of this Indian Standard.

The development is relevant to India's rapidly expanding electricity network because transmission infrastructure must safely carry increasingly large volumes of electricity while maintaining mechanical strength, electrical efficiency and reliability.

What is BIS?

BIS stands for Bureau of Indian Standards.

It is India's National Standards Body and functions under the Department of Consumer Affairs, Ministry of Consumer Affairs, Food and Public Distribution.

BIS develops Indian Standards for products, processes and services and also performs conformity-assessment and certification-related functions under the applicable legal framework.

BIS Act, 2016

The present statutory framework for BIS is provided by the Bureau of Indian Standards Act, 2016.

The legislation strengthened India's standards and conformity-assessment framework and replaced the earlier BIS Act of 1986.

For competitive examinations, students should remember that BIS is a statutory organisation rather than a constitutional body.

What is IS 398?

IS denotes an Indian Standard.

IS 398 is associated with aluminium conductors for overhead transmission purposes.

The standard has different parts dealing with different conductor configurations and materials. The September 2026 discussion specifically concerned Part 4 and aluminium-alloy stranded conductors of the aluminium-magnesium-silicon type.

What is an Overhead Transmission Conductor?

Electricity generated at a power station often needs to travel over considerable distances before reaching consumers.

High-voltage transmission lines carry this electricity through conductors suspended from transmission towers or poles.

These conductors must combine good electrical conductivity with adequate mechanical strength because they are exposed to wind, temperature variations, mechanical tension and other environmental conditions.

Why is Aluminium Widely Used?

Aluminium is widely used in overhead electricity conductors because it combines relatively good electrical conductivity with low density.

Its lower weight compared with several alternative conducting materials can be advantageous for long overhead spans.

However, the precise conductor design must balance electrical performance, strength, sag, durability and cost.

Why Use Aluminium Alloys?

Pure electrical conductivity is not the only requirement for a transmission conductor.

A conductor must also withstand mechanical loads during installation and operation.

Alloying aluminium with selected elements can improve mechanical properties while maintaining useful electrical characteristics.

Aluminium-Magnesium-Silicon Alloy

The standard discussed by BIS concerns aluminium-magnesium-silicon alloy stranded conductors.

Magnesium and silicon can be used in aluminium alloys to obtain useful combinations of strength and conductivity.

The detailed chemical composition and performance requirements are controlled through technical standards rather than being left entirely to individual manufacturers.

What Does Stranded Conductor Mean?

A stranded conductor is formed from multiple individual wires arranged together rather than a single large solid wire.

Stranding can provide flexibility and suitable mechanical characteristics for overhead transmission applications.

The quality of individual wires and their assembly therefore affects the performance of the complete conductor.

Fourth Revision of the Standard

BIS stated that the fourth revision incorporates updated requirements in response to technological developments and the needs of Indian utilities.

Standards require periodic revision because materials, manufacturing processes, testing technologies and operating conditions change over time.

A technical standard that is not periodically updated may eventually fail to reflect contemporary engineering requirements.

Type A2 and Type A3 Wires

An important feature of the fourth revision is the inclusion of two types of aluminium-magnesium-silicon alloy wires designated Type A2 and Type A3.

BIS stated that these classifications are incorporated in accordance with IEC 62641.

This is important because alignment with relevant international standards can support technical consistency and interoperability.

What is IEC?

IEC stands for International Electrotechnical Commission.

It is an international standards organisation dealing with electrical, electronic and related technologies.

IEC standards are widely used as technical references across the global electrotechnical industry.

What is IEC 62641?

IEC 62641 is the international reference specifically mentioned by BIS in connection with the Type A2 and Type A3 aluminium-magnesium-silicon alloy wires incorporated into the revised Indian Standard.

For examinations, the important connection is that the revised IS 398 Part 4 aligns these alloy-wire designations with IEC 62641.

Dimensions and Tolerances

The revised standard modifies requirements concerning dimensions and tolerances on nominal sizes.

Engineering components cannot be manufactured with unlimited variation. Standards specify acceptable dimensional ranges so that components perform predictably and are compatible with system requirements.

Tolerance therefore refers to the permitted variation from a specified nominal value.

Electrical Resistance

Electrical resistance is a fundamental property of a transmission conductor.

When electric current passes through a conductor, resistance causes energy losses in the form of heat.

For a given operating condition, excessive resistance can increase transmission losses and reduce efficiency.

Why Resistance Testing Matters

Testing verifies whether a conductor's electrical resistance remains within specified limits.

This is important not only for energy efficiency but also for predictable system design.

Utilities must know the electrical characteristics of transmission assets when calculating line performance and system losses.

DC Resistance Test on Stranded Conductor

The fourth revision includes a DC Resistance Test on the stranded conductor.

DC means Direct Current.

The test helps assess the electrical resistance characteristics of the complete stranded conductor against the requirements specified by the standard.

Breaking Load

Breaking load refers to the mechanical load at which a material or conductor fails.

Overhead conductors experience mechanical forces from their own weight, tension, wind and environmental conditions.

Minimum mechanical-strength requirements therefore form an essential part of transmission-line safety.

Ultimate Tensile Strength Test

The revised requirements include an Ultimate Tensile Strength Test on the stranded conductor.

Tensile strength measures the ability of a material to withstand pulling forces before failure.

This test helps verify whether the complete conductor possesses the required mechanical integrity.

Elongation

Elongation describes how much a material can extend under tensile loading before failure under specified test conditions.

A material's strength alone does not completely describe its mechanical behaviour.

Elongation provides additional information about ductility and how the material responds when subjected to mechanical stress.

Wrapping Test

The fourth revision includes a Wrapping Test among its additional testing requirements.

Such testing can help evaluate the behaviour of conductor wire when subjected to bending or wrapping deformation.

This is relevant because conductor wires undergo mechanical handling during manufacturing, installation and service.

Joints in Wires

The revised standard elaborates requirements concerning joints in wires.

Joints can become mechanically or electrically vulnerable locations if they are not produced correctly.

Standardised joint requirements therefore contribute to reliability and quality control.

Procedure Qualification Test for Welded Joints

The fourth revision includes a Procedure Qualification Test on welded joints of aluminium-alloy strands.

The purpose of procedure qualification is to verify that the method used for producing a joint is capable of consistently achieving the required performance.

This shifts attention from merely inspecting a finished joint to validating the process used to create it.

Surface Condition Test

A Surface Condition Test is also included among the enhanced requirements.

The physical condition of a high-voltage conductor surface can influence electrical performance.

Surface defects may also provide evidence of manufacturing or handling problems.

What is Corona Discharge?

Corona discharge is an electrical phenomenon that can occur around high-voltage conductors when the electric field becomes strong enough to ionise the surrounding air.

It can result in energy loss, audible noise, visible glow under certain conditions and electromagnetic interference.

Controlling corona is therefore an important consideration in high-voltage transmission engineering.

Corona Test

The revised standard includes a Corona Test.

This test evaluates conductor behaviour under high-voltage conditions relevant to corona performance.

Its inclusion illustrates that conductor quality involves more than mechanical strength and ordinary electrical resistance.

Radio Interference Voltage Test

The fourth revision also includes a Radio Interference Voltage Test.

Electrical activity associated with high-voltage equipment can produce electromagnetic interference capable of affecting communication systems.

Testing helps ensure that conductor performance remains within prescribed technical requirements.

Mechanical and Electrical Performance Together

A transmission conductor must simultaneously satisfy several engineering requirements.

A material with excellent electrical conductivity but inadequate mechanical strength would not be suitable for long overhead spans.

Similarly, a mechanically strong conductor with poor electrical characteristics could create excessive transmission losses.

Standards therefore consider both electrical and mechanical performance.

Packaging and Marking

The fourth revision also updates provisions concerning packaging and marking.

Packaging protects conductors during storage and transportation, while appropriate marking supports identification and traceability.

Traceability becomes particularly important when utilities need to identify the manufacturer, product specifications or production batch associated with installed equipment.

Why Traceability Matters

If a technical defect is identified after deployment, traceability can help determine which batch or manufacturing process may be affected.

This allows corrective measures to be targeted more effectively.

Traceability is therefore a quality-management tool as well as an administrative requirement.

What is Manak Manthan?

Manak Manthan is a BIS stakeholder-engagement initiative focused on discussion of Indian Standards.

It creates a forum for manufacturers, users of standards, technical experts and other stakeholders to provide practical feedback.

Such consultation helps ensure that standards remain relevant to technological developments and actual industry conditions.

Why Stakeholder Consultation Matters

A standard developed without industry and user feedback may contain requirements that are difficult to implement or may fail to address real operational problems.

Manufacturers can provide information about production processes, while utilities and users can explain field-performance requirements.

Testing organisations and technical experts can contribute knowledge about measurement and conformity assessment.

Role of Indian Utilities

BIS specifically noted that the fourth revision takes into account the requirements of Indian utilities.

Electricity utilities operate transmission and distribution infrastructure under diverse climatic and operating conditions.

Their field experience can therefore provide valuable information for updating conductor specifications.

Standards and Grid Reliability

India's power grid is a complex interconnected system in which failure of individual components can have wider consequences.

Technical standards help ensure that equipment procured from different manufacturers satisfies minimum performance requirements.

This supports reliability, safety and consistency across the electricity infrastructure.

India's Growing Transmission Requirement

India's electricity system is expanding as electricity demand rises and new generation capacity is added.

The growth of renewable energy also creates a need for transmission infrastructure capable of carrying electricity from resource-rich regions to demand centres.

Conductor technology therefore forms an important, though often less visible, part of the energy transition.

Renewable Energy and Transmission

Solar and wind projects are often located where renewable resources are strongest rather than close to major urban demand centres.

Electricity generated in such areas must be transported through transmission networks.

Consequently, renewable-energy expansion requires not only generating equipment but also stronger transmission infrastructure.

Transmission Losses

Some electrical energy is lost when electricity travels through conductors because of resistance and other system effects.

Reducing technical losses is important for improving overall electricity-system efficiency.

Appropriate conductor selection and design form one component of transmission-loss management.

Conductor Sag

An overhead conductor does not remain perfectly horizontal between two towers. It hangs in a curved shape, producing sag.

Temperature, conductor material, span length and mechanical tension influence sag.

Excessive sag can reduce required ground clearance and create safety concerns, which is why mechanical and thermal characteristics matter.

Difference Between Conductor and Cable

The terms conductor and cable should not always be used interchangeably.

A conductor is a material or component designed to carry electric current. A cable can contain one or more conductors together with insulation and other protective layers depending on its application.

High-voltage overhead transmission commonly uses exposed conductors rather than the fully insulated cable arrangements familiar in household wiring.

Standards versus Technical Regulations

A technical standard describes agreed specifications, test methods or performance requirements.

Whether compliance with a particular standard is voluntary or mandatory depends on the applicable legal and regulatory framework.

Students should therefore avoid assuming that every BIS standard automatically imposes a compulsory certification requirement on every product.

BIS Standard Mark

The familiar BIS Standard Mark is commonly associated with products conforming to relevant Indian Standards under applicable certification schemes.

However, different products may be governed by different conformity-assessment requirements.

Standards development and compulsory certification are related but distinct regulatory concepts.

What is Conformity Assessment?

Conformity assessment refers to processes used to determine whether a product, service, process or system satisfies specified requirements.

It can involve testing, inspection and certification.

Reliable conformity assessment gives buyers and regulators greater confidence that products meet the relevant specifications.

Role of Laboratories

Technical standards become practically meaningful only when characteristics can be measured and tested.

Laboratories therefore play an important role in verifying parameters such as resistance, tensile strength and other performance characteristics.

Standardised test methods also improve comparability between results obtained at different facilities.

Why International Alignment Matters

Aligning appropriate Indian requirements with international technical standards can facilitate compatibility and improve understanding across global supply chains.

It can also reduce unnecessary differences in technical specifications where Indian operating conditions do not require a distinct approach.

At the same time, national standards can incorporate requirements reflecting local climatic, infrastructure and utility needs.

IEC and BIS Are Different

IEC is an international electrotechnical standards organisation, while BIS is India's National Standards Body.

The fact that an Indian Standard refers to an IEC standard does not make the two organisations identical.

BIS may adopt, adapt or refer to international standards while developing Indian Standards according to the applicable process.

Digital Initiatives of BIS

The Chennai programme also provided participants with an overview of e-BIS and the BIS Care App.

These initiatives form part of BIS's digital interface for standards-related services and consumer engagement.

Digital access can make information about standards and certification more accessible to businesses and consumers.

BIS Care App

The BIS Care App provides consumers with access to certain BIS-related information and services.

Digital verification tools can help consumers obtain information associated with certified products and lodge relevant complaints where supported.

Such tools illustrate the connection between technical standardisation and consumer protection.

Why This Topic Matters for UPSC

This topic connects infrastructure, energy security, technical standardisation, consumer protection and science and technology.

It also demonstrates that reliable infrastructure depends not only on large projects but on detailed engineering standards governing individual components.

For GS-III, it can be used as an example of the role of standards in strengthening India's power infrastructure and supporting renewable-energy integration.

Potential Prelims Traps

BIS is India's National Standards Body.

The September 2026 programme concerned IS 398 Part 4, not the entire electricity transmission regulatory framework.

The conductor is of aluminium-magnesium-silicon alloy.

The revision introduces Type A2 and Type A3 wires in accordance with IEC 62641.

IEC stands for International Electrotechnical Commission.

Corona is an electrical phenomenon associated with high electric fields; it is not a mechanical failure test.

Important Facts for Competitive Exams

• Organisation: Bureau of Indian Standards.
• Programme: Manak Manthan.
• Date: 18 September 2026.
• Location: BIS Chennai Branch Office.
• Draft standard: IS 398 (Part 4):2026.
• Revision: Fourth Revision.
• Subject: Aluminium Alloy Stranded Conductors for Overhead Transmission.
• Alloy type: Aluminium-Magnesium-Silicon.
• New wire designations highlighted: Type A2 and Type A3.
• International reference: IEC 62641.
• Revised parameters include dimensions, electrical resistance, breaking load and elongation.
• Additional tests include Wrapping Test and welded-joint Procedure Qualification Test.
• DC Resistance Test and Ultimate Tensile Strength Test are included.
• Surface Condition Test is included.
• Corona Test is included.
• Radio Interference Voltage Test is included.
• Packaging and marking provisions have been revised to improve identification and traceability.