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The coming into force of the new IEC 61439 series of international standards, adopted in Europe (with possible variations) as EN 61439, has changed the requirements for low-voltage power distribution boards in the European Economic Area. It significantly impacts electrical power distribution in buildings and industrial applications. The entirely restructured series of standards came into force on June 1, 2010. After the end of the transition period, the IEC 61439 series replaced the previous IEC 60439 series of standards.
The new IEC 61439 series of international standards defines clear regulations for low-voltage switchgear and controlgear assemblies. It specifies the safety requirements for the electrical equipment of planners, system engineers, electricians and end users in order to define protection objectives for people and industrial plants with regards to electrical installations.
A low-voltage switchgear and controlgear assembly is defined as the combination of one or more low-voltage switching devices and associated equipment for control, measuring, signaling, protecting and switching.
Low-voltage switchgear and controlgear assemblies includes: Arc fault detection device (AFDD), circuit breakers, miniature circuit breakers, residual current protective devices, cables, terminals, etc.
The standard applies for power distribution boards, switching and control systems, meter cabinets and distribution cabinets in residential and non-residential buildings, distribution boards for construction sites and power distribution cabinets as well as for controlgear assemblies in special areas.
Scope of the standards
The IEC 61439 series of standards  consists of seven parts: five standards, a technical report and a technical specification:
- IEC TR 61439-0: Low-voltage switchgear and controlgear assemblies - Part 0: Guidance to specifying assemblies
- IEC 61439-1: Low-voltage switchgear and controlgear assemblies - Part 1: General rules
- IEC 61439-2: Low-voltage switchgear and controlgear assemblies - Part 2: Power switchgear and controlgear assemblies
- IEC 61439-3: Low-voltage switchgear and controlgear assemblies - Part 3: Distribution boards intended to be operated by ordinary persons (DBO)
- IEC 61439-4: Low-voltage switchgear and controlgear assemblies - Part 4: Particular requirements for assemblies for construction sites (ACS)
- IEC 61439-5: Low-voltage switchgear and controlgear assemblies - Part 5: Assemblies for power distribution in public networks
- IEC 61439-6: Low-voltage switchgear and controlgear assemblies - Part 6: Busbar trunking systems (busways)
- IEC TS 61439-7: Low-voltage switchgear and controlgear assemblies - Part 7: Assemblies for specific applications such as marinas, camping sites, market squares, electric vehicles charging stations
In addition to the current state of technology, the standards contain some new terminology, ratings and verifications. As the successor of IEC 60439, the new standards describe operating conditions, design requirements, technical properties and verification options for all types of low-voltage switchgear and controlgear assemblies.
Significant changes to EN 60439
In 1973 the IEC 60439 standard summarized the various types of power distribution boards for the first time, categorizing them with the terms TTA (type-tested switchgear and controlgear assemblies) and PTTA (partially type-tested switchgear and controlgear assemblies). The new IEC 61439 series of standards replaces the previous categories TTA and PTTA with the term "low-voltage switchgear and controlgear assembly". Also new is the "design verification", which suspends type-testing and the differentiation between TTA and PTTA.
The standards furthermore introduce the so-called "black box concept", which specifies important issues between the manufacturer of the switchgear and controlgear assembly and its user.
In contrast with the previous standard, IEC 61439 uniquely describe the areas of responsibility of all parties concerned. DIN EN 61439 differentiates between the obligations of an original manufacturer and those of a "manufacturer of switchgear and controlgear assemblies".
The "original manufacturer" is the company manufacturing a ready-to-use switchgear and controlgear assembly for customer applications. Siemens AG is an example of an "original manufacturer" and is therefore responsible for design verification.
A "manufacturer of switchgear and controlgear assembly" is any certified electrician, who builds a power distribution using switchgear and controlgear assembly from an original manufacturer. That electrician is responsible for the relevant switching system and therefore obligated to provide a design verification for all changes not included in the design verification supplied by the original manufacturer.
A "user" can be a planner or system operator, who purchases, uses or operates the switchgear and controlgear assembly. Users must request certifications of the complete design verification.
The rating factor has been defined in more detail, the requirements with regards to heat development have been more explicitly described and have been adapted to the current state of technology. New requirements from IEC 62208 standard (empty enclosure for switchgear and controlgear assemblies) have been additionally applied.
Black box concept
The IEC 61439 series of standards specifies the issues to be clarified between the manufacturer of the switchgear and controlgear assembly and its user. It is seen as a so-called "black box" and contacts the installation environment with four defined interfaces:
- Power supply
- Setup and ambient conditions
- Circuits and loads, as well as
- Operation and maintenance.
All these are defined by relevantly unique technical characteristics and properties, e.g. the protection type (IP), rated frequency fn, rated insulation voltage Ui or door locking.
From the viewpoint of the manufacturer, the black box includes the switchgear and controlgear assembly equipment with its internal workings, the implementation of the defined interfaces to installations outside the equipment and the user requirements. For the electrician, the advantages of the black box concept are on the one hand a significant simplification of their work, on the other hand optimized safety due to the use of prefabricated power distribution board systems.
Design and Routine verification
The "design verification" replaces the previous type testing. The original manufacturer provides proof of compliance with the design requirements and with it the basic conformity of the switchgear and controlgear assembly. This requires several individual verifications of the various components, which must be documented in the design verification.
The original manufacturer has various methods for verification available to him to prove that the design complies with the requirements of the relevant switchgear and controlgear assembly standard.
The "routine verification" is the verification process all switchgear and controlgear assemblies must be subjected to during and after manufacture. It detects faults in materials and workmanship and ascertains proper functioning of the manufactured assembly. The results are documented. The manufacturer of the switchgear and controlgear assembly will only have to provide a documented routine verification, if he creates it in accordance with the provisions of the original manufacturer. If that is not the case and the manufacturer of the switchgear and controlgear assembly installs own modifications, then he will be deemed to be the original manufacturer and has to carry out the design verification as well as the routine verification.
The manufacturer of the switchgear and controlgear assembly is faced with new requirements in terms of the extensive documentation obligations of standard EN 61439-1. This may include the verification of sample switchgear and controlgear assemblies or of parts thereof to show that the design complies with the requirements of the relevant switchgear and controlgear assembly standard. Other requirements may include:
- Complete and detailed documentation of the design verifications of the original manufacturer
- Test reports, logs, calculations and records
- Archiving of documentation: throughout the product lifecycle
- Check lists for the verification of compliance with all requirements set out by the standard for the planning and implementation of the switchgear and controlgear assembly
A forwarding of the documentation to the manufacturer of the switchgear and controlgear assembly is not required. Only one design verification is required for multiple identical assemblies. Any modification to the original system, however, will provide additional design verifications (the manufacturer becomes the original manufacturer).
The design verification applies to the assembly and the operating behavior of the manufacturer of the switchgear and controlgear assembly, and must comply with the following criteria:
- Strength of material and parts
- Degrees of protection provided by enclosures
- Creepage distances
- Protection against electric shock and continuity of PE circuits
- Internal electric circuits and terminals
- Terminal connections for external conductors
- Dielectric properties
- Temperature rise limits
- Short-circuit resistance
- Electromagnetic compatibility (EMC)
- Mechanical function
The manufacturer of the switchgear and controlgear assembly bears the responsibility of providing complete and exhaustive documentation for a routine verification. It includes the test report including all data used and the necessary calculations and comparisons applied. The resulting documentation must be archived for the duration of the lifecycle of the products.
The manufacturer of the switchgear and controlgear assembly is required to provide a routine verification with the following content in order to prove the correct function of the finished switchgear and controlgear assembly and to detect any material or manufacturing faults:
- Enclosure protection types
- Air gaps and creepage distances
- Protection against electric shock and integrity of protective conductor circuits
- Incorporation of switching devices and components
- Internal electric circuits and terminals
- Terminals for external conductors
- Mechanical function
- Dielectric properties
- Wiring, operating response and functioning
The various verifications therefore collectively confirm the correct function of the individual components of a controlgear and switchgear assembly.
- List of publications in the IEC 61439 series of standards
- DIN EN (IEC) 61439 Low-voltage switchgear and controlgear assemblies
- "IEC TR 61439-0", "IEC 61439-1", "IEC 61439-2", "IEC 61439-3", "IEC 61439-4", "IEC 61439-5", "IEC 61439-6", "IEC TS 61439-7" at International Electrotechnical Commission
- IEC 61439 – Everything you need to know about the new standard
- Scope of the standard and definition of a low-voltage switchgear and controlgear assembly
- Design and Routine Verifications
- Wikipedia (German) – Die Norm IEC 61439
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