Overview
IEC TS 63346-2-3:2025, published by the International Electrotechnical Commission (IEC), specifies the design criteria for low-voltage (LV) AC auxiliary power systems (APSs) for substations. This technical specification outlines the common rules and requirements for designing LV AC APS with nominal voltages up to 1 kV AC, focusing on key aspects such as system configuration, wiring, protection, equipment selection, and physical layout. IEC TS 63346-2-3:2025 is vital for professionals involved in substation design, operations, and maintenance, offering standardized guidance to ensure reliable and efficient auxiliary power in substations.
Key Topics
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System Function and Requirements
- The LV AC APS is designed to supply critical auxiliary loads within substations, such as forced cooling devices, motor-operated equipment, heaters, pumps, and control systems.
- Ensures continuous, stable, and reliable power supply to substations’ auxiliary devices to maintain safe and uninterrupted operation.
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Load Classification and Calculation
- Loads are categorized based on importance (essential and non-essential) and operational characteristics, helping to prioritize reliability and backup for critical systems.
- Load calculations are necessary to determine the proper sizing of key equipment like station service transformers and auxiliary circuits.
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System Structure, Wiring, and Protection
- Requirements for the configuration and selection of power sources (main, standby, UPS, diesel generators) and principles for system wiring.
- Clear guidelines for protective devices, system earthing, over-voltage protection, and fault management to enhance safety and uptime.
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Equipment Selection and Physical Layout
- Criteria for selecting transformers, distribution boards, conductors, and auxiliary devices to align with operational and environmental conditions.
- Recommendations for physical arrangement of equipment to facilitate operation, maintenance, and safety.
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Environmental and Safety Considerations
- Guidance to account for temperature, humidity, altitude, electromagnetic interference, and local environmental factors.
- Safety measures for personnel and equipment, including insulation, grounding, arc flash protection, and compliance with relevant IEC safety standards.
Applications
IEC TS 63346-2-3:2025 is applicable for:
- Design of New Substations: Ensuring modern auxiliary AC power systems comply with current international best practices and safety regulations.
- Retrofit and Upgrade Projects: Supporting engineers and maintenance professionals in updating legacy substations to meet contemporary operational and reliability standards.
- Operational Reliability: Assisting operators in implementing systems that guarantee minimized downtime, optimal performance, and swift fault response.
- Regulatory Compliance: Providing a clear framework for meeting both IEC standards and local codes in international and regional projects.
By following this standard, utilities and engineering firms can deliver substations with robust LV AC auxiliary power solutions-critical for the safety, automation, protection, and efficient operation of electrical distribution networks.
Related Standards
For comprehensive substation auxiliary power system design, consider these related IEC and ISO standards:
- IEC 60038 - IEC standard voltages
- IEC 60076 series - Power transformers
- IEC 60364 series - Low-voltage electrical installations, including protection, safety, and equipment selection
- IEC 60909 series - Short-circuit currents in three-phase AC systems
- IEC 61439 series - Low-voltage switchgear and controlgear assemblies
- IEC 62040 series - Uninterruptible power systems (UPS)
- IEC 61936-1 - Power installations exceeding 1 kV AC
- ISO 8528 series - Reciprocating internal combustion engine driven AC generating sets
- IEC TS 63346-1-1 - Terminology for low-voltage auxiliary power systems
Adhering to IEC TS 63346-2-3:2025 alongside these related standards enables substation projects to achieve high safety, resilience, and reliability in auxiliary AC power systems.