Low-voltage switchgear and controlgear - Part 6-1: Multiple function equipment - Transfer switching equipment
1Key Takeaways
This Final Draft International Standard is an up to 6 weeks' pre-release of the official publication. It is available for sale during its voting period: 2025-12-19 to 2026-01-30. By purchasing this FDIS now, you will automatically receive, in addition, the Redline version of the final publication. IEC 60947-6-1:2026…
2Expert Interpretation
This in-depth analysis of IEC 60947-6-1, 4th edition, covers the technical requirements, testing methods, and latest technological advancements for transfer switchgear. It focuses on key technologies such as automatic transfer switches, bypass isolation devices, and closed-loop transfer functions, providing professional guidance for power system design, equipment selection, and operation and maintenance.
IEC 60947-6-1 Standard Framework and Technology Evolution Analysis
The 4th edition of IEC 60947-6-1 (FDIS edition 2025), published by the International Electrotechnical Commission (IEC), marks a significant milestone in the technical specifications for low-voltage switching equipment. As a key component of the IEC 60947 series of standards, this standard specifically specifies switching equipment (TSEs) used to ensure power supply continuity and achieve energy management. With the global energy structure transformation and increasing demands for power reliability, the importance of switching equipment in modern power systems is becoming increasingly prominent.
Standard Development Background and Evolution
Since its initial publication, the IEC 60947-6-1 standard has undergone several technical revisions to adapt to evolving market demands and technological advancements. Compared to the 3rd edition published in 2021, the 4th edition of the standard has significantly expanded and improved its technical content.
Key technical changes include: **scope clarification**, **terminology definition optimization**, and the addition of several normative appendices. These changes reflect the expansion of application scenarios and increased technical complexity of switching equipment. The main drivers of standard evolution include: increased electricity demand due to global population growth, the widespread adoption of electronic devices, the development of electric vehicle charging infrastructure, energy cost pressures to address climate change, increased access to renewable energy, and higher user expectations for grid reliability. These factors collectively drive the increased demand for innovation and standardization in switching equipment technology. This standard establishes a complete terminology system for switching equipment, providing a unified language foundation for equipment design, manufacturing, and application. Key terms include:| Term Category | Core Terms | Definition Highlights | Application Scenarios |
|---|---|---|---|
| Equipment Type | Transfer Switchgear (TSE) | Complete Equipment for Transferring Loads Between Power Sources | General Power Conversion Applications |
| Operating Mode | Automatic Transfer Switchgear (ATSE) | Equipped with a controller that automatically monitors power supply status and performs transfers | Critical Load Power Supply Assurance |
| Structural Configuration | Bypass/Isolation Transfer Switchgear (BTSE) | Provides Maintenance Bypass and Electrical Isolation Functions | Situations requiring online maintenance |
| Conversion mode | Closed-loop conversion capability (ATSE) | Conversion method supporting uninterrupted power supply during conversion | Loads with extremely high requirements for power supply continuity |
Equipment is classified into three categories according to its operation method: Manually Operated Switchgear (MTSE), Remotely Operated Switchgear (RTSE), and Automatically Operated Switchgear (ATSE). Each type is designed for different application needs and operating scenarios, reflecting the standard's ability to cover diverse application scenarios.
Key Technical Requirements and Performance Parameters
Rated Values and Limiting Parameters
The standard specifies the main rated parameters of the switching equipment, including: rated voltage (AC not exceeding 1000V, DC not exceeding 1500V), rated operating current, rated frequency, and breaking capacity.
These parameters form the basis for equipment selection and application, directly affecting the safety and reliability of the equipment. The rated operating current $I_{\Theta}$ of the transfer switchgear needs to be verified under specific ambient temperatures to ensure that the equipment can safely carry the load current under nominal conditions. Rated breaking capacity testing verifies the switching performance of the equipment under normal and abnormal conditions and is a key indicator for evaluating the functional integrity of the equipment. Usage Categories and Performance Verification The standard defines several usage categories, each corresponding to specific operating conditions and performance requirements. The classification of usage categories is based on the expected application scenario of the equipment, such as resistive loads, motor loads, etc. Verification tests include:| Test Sequence | Test Purpose | Key Parameters | Acceptance Criteria |
|---|---|---|---|
| Sequence I | General Performance Characteristics | Temperature Rise, Dielectric Properties | Complies with Limits in Table 13 |
| Sequence II | Operating Performance Capability | Number of Operating Cycles, Rate | Specified in Table 11-12 |
| Sequence III | Short Circuit Performance Capability | Short Circuit Making and Breaking Capability | Specified in Table 5-6 |
| Sequence V | DC Critical Load Current | Performance under DC Conditions | Table 14-16 Specifications |
Structural Requirements and Safety Design
Mechanical Structure and Operating Mechanism
The standard sets forth detailed requirements for the structural design of transfer switchgear, including material selection, indicating devices, isolation suitability, and main contact opening and closing mechanisms. Especially for equipment suitable for isolation, clear requirements for disconnection visibility and operational safety must be met.
Requirements for clearances and creepage distances ensure the insulation reliability of the equipment in environments with varying pollution levels. Protective grounding provisions ensure the safety of operators and equipment, particularly under fault conditions.
Energy Storage Operation and Dedicated Housing
For equipment employing energy storage closure, the standard requires that the design of the energy storage mechanism prevent accidental release and ensure operational controllability.
The design of the dedicated enclosure needs to consider heat dissipation, protection level, and ease of installation, while providing appropriate protection and connection methods for communication interfaces. Electromagnetic Compatibility Requirements Changeover switching equipment needs to meet stringent electromagnetic compatibility requirements, including immunity and emission limits. Immunity testing covers various interference types such as electrostatic discharge, radio frequency electromagnetic fields, fast transient bursts, surges, voltage dips, and interruptions, ensuring reliable operation of the equipment in complex electromagnetic environments. Emission limits comply with CISPR 11 standards, controlling electromagnetic interference generated during equipment operation and reducing the impact on surrounding electronic equipment. These requirements are particularly important for modern, highly electronic power systems. Test Methods and Verification Procedures Type Testing and Routine Testing The standard specifies a complete testing system, including type testing, routine testing, and environmental testing. Type testing verifies the conformity of the equipment design, covering a comprehensive evaluation of performance characteristics. Routine testing ensures the basic functionality and quality consistency of each piece of equipment leaving the factory. The test circuits are designed to simulate real-world application conditions, as shown in Figure 2 for the source I and source II power supply connection test circuit, and Figure 3 for the switching capability verification test circuit. These standardized test methods ensure the comparability of equipment performance from different manufacturers. Special Equipment Test Requirements For special types of transfer switchgear, the standard appendices provide specific test requirements: Bypass/Isolation Transfer Switchgear (BTSE): Requires verification of interlocking functions, full assembly testing, and maintenance bypass operation sequences. Appendix C provides examples of operation sequences for five typical circuit configurations, covering different structural types such as fixed and withdrawable types. Closed-Circuit Switching Capability (ATSE): Requires verification of timing control and fault handling capabilities during closed-circuit switching. Appendix D details the requirements for operating mechanisms, control sequences, and operating limitations to ensure the safety and reliability of the switching process.Standalone ATS Controller: As a standalone device, it needs to meet specific structural, performance, and EMC requirements. Appendix E specifies the controller's product information, operating instructions, and test methods, including special requirements such as wire bending tests.
Product Information and Labeling Requirements
Chapter 6 of the standard details the product information that manufacturers need to provide, including equipment markings, installation, operation, and maintenance instructions, decommissioning and removal guidelines, and environmental information. Complete markings should include key information such as the manufacturer's name or trademark, equipment model, ratings, usage category, and year of manufacture.
Operating instructions need to cover normal operation, maintenance procedures, troubleshooting, and safety precautions. For devices containing electronic controllers, software version information and parameter setting guidelines are also required.
Standard Implementation Recommendations and Application Guidance
Equipment Selection Considerations
In practical applications, the following factors should be comprehensively considered when selecting transfer switchgear: load characteristics, power quality requirements, transfer time requirements, ease of maintenance, environmental conditions, and cost-effectiveness. For critical applications, it is recommended to select equipment that has passed full type testing and ensure that the equipment markings comply with standard requirements.
Installation and Commissioning Precautions
The installation process should follow the manufacturer's installation instructions and standard safety requirements. Special attention should be paid to:
- Ensure proper ventilation and heat dissipation conditions
- Correctly connect the protective grounding conductor
- Verify the correctness of the interlocking function
- Tighten the connection terminals to the specified torque
- Perform comprehensive functional testing and timing verification
Maintenance and Testing Plan
Establish a regular maintenance and testing plan, including: visual inspection, mechanical operation testing, electrical performance verification, controller function checks, etc.
For automatic transfer switchgear, it is recommended to periodically simulate power failure conditions to verify the reliability of the automatic transfer function.
Technology Development Trends and Future Prospects
With the development of smart grids and distributed energy systems, transfer switchgear is developing towards intelligence, integration, and networking.
Possible future technological evolutions include:| Technology Direction | Development Trends | Standard Impact | Application Prospects |
|---|---|---|---|
| Intelligent Control | Integrated Energy Management Functions | Possible New Use Cases | Microgrids and Virtual Power Plants |
| Cybersecurity | Compliance with IEC 62443 Requirements | Referencing IEC 63208 Guidelines | Critical Infrastructure Protection |
| Environmental Resilience | Consideration of Carbon Footprint and Circular Economy | Referencing IEC 63058 | Sustainability Requirements |
| Functional Safety | Integrated Safety-Related Functions | May Require a New Appendix | Safety-Critical Applications |
The standard has reserved space for future expansion, such as specifying TSE configuration types not currently covered, including overlapped neutral TSE, multi-source TSE, TSE with load shedding function, bus tie TSE, and hybrid TSE. Technological developments in these areas may drive future revisions and improvements to the standard.
Compliance and Certification Considerations
Manufacturers must ensure compliance with all applicable requirements of IEC 60947-6-1 when designing and manufacturing transfer switchgear.
The following measures are recommended: Establish a complete quality management system covering the entire process of design, procurement, production, and testing. Conduct comprehensive type testing, including all applicable test sequences. Maintain the integrity and traceability of technical documentation. Regularly update products to reflect standard revisions and technological advancements. Consider regional differences in requirements, such as the harmonization of the UL 1008 standard in the North American market. When selecting equipment, users should verify that it conforms to IEC 60947-6-1 and check the accreditation of the certification body. For specific applications, such as fire pump control equipment, additional requirements in Annex F must also be met. IEC 60947-6-1, 4th edition, provides comprehensive technical specifications for the design, manufacture, and application of switching equipment. By understanding the requirements and intent of the standard, manufacturers can develop safer and more reliable products, users can select more suitable equipment, and designers can create more optimized systems. As technology continues to develop and application demands become increasingly complex, standards will continue to evolve, providing guidance and support for industry development.