IEC 61439-5 Low Voltage Switchgear and Control Devices - Part 5: Devices for Power Distribution in Public Networks

The standard “IEC 61439-5 Low-voltage switchgear and control devices – Part 5: Devices for power distribution in public grids”, published by the International Electrotechnical Commission (IEC), defines specific requirements for public electricity grid distribution devices. These devices have the following criteria:

• It is used for the distribution of electrical energy in three-phase systems with a nominal voltage not exceeding 1.000 Volts AC and in DC systems with a nominal voltage not exceeding 1.500 Volts DC.
• Still.
• Open-type installations are not covered by this standard.
• They are suitable for installation in locations accessible only to qualified personnel, but outdoor types can be installed in locations accessible to ordinary people.
• It is designed for use in energy distribution in public electricity networks.
• Indoor use: systems for installation inside electrical substations.
• Outdoor use: systems including an enclosure suitable for outdoor installation.

The purpose of this standard is to define the distribution systems of the public electricity grid and to specify their service conditions, structural requirements, technical specifications, and testing. Higher performance level tests may be applied with certain grid parameters.

Public electricity grid distribution systems may also include control or signaling devices associated with the distribution of electrical energy.

Control and monitoring devices can be used in smart grid applications or in the transmission of smart grid data.

This standard applies to all public electricity grid distribution systems, whether they were designed and manufactured as a one-off event or are fully standardized and mass-produced.

Production or assembly may be carried out by a person other than the original manufacturer.

This standard does not apply to individual devices and standalone components such as motor starters, fuse switches, and electronic equipment that conform to relevant product standards. If the substation is owned or operated by a public distribution system operator, public electricity grid distribution devices used as LV distribution panels in substations fall within the scope of this standard.

This standard does not apply to certain types of assemblies listed in other parts of the IEC 61439 standard series.

In the world of electrical engineering, standards ensure safety, reliability, and interoperability. The International Electrotechnical Commission (IEC) plays a key role in developing these guidelines, particularly for low-voltage systems. The IEC 61439-5 standard is a specific standard focusing on low-voltage switchgear and control device assemblies designed for power distribution in public electricity grids.

This standard addresses the demands of public infrastructure where disruptions can have widespread impacts. It is based on the fundamental rules described in IEC 61439-1 and adapts the requirements to public grid distribution assemblies.

The IEC 61439 series of standards replaces the older IEC 60439 standard, offering a more flexible and stringent framework for low-voltage assemblies (up to 1.000 Volts AC or 1.500 Volts DC). Unlike the older standard, which distinguished between fully type-tested and partially type-tested assemblies, this standard emphasizes design verification through a combination of testing, calculation, and comparison.

The IEC 61439-5 standard targets public electricity grid distribution groups that are critical for the distribution of electrical energy in three-phase systems. The characteristics of these groups are as follows:

• Voltage and phase limits: In three-phase configurations, the rated voltage must not exceed 1.000 Volts AC.
• Application: Priority is given to public grids, such as those managed by public utilities for urban or rural electricity distribution.
• Accessibility: Suitable for installations accessible only to qualified personnel during normal operation. Outdoor types may be open to the public, but must include protective measures.
• Exclusion: Open groups are excluded; the standard focuses on closed systems for safety.

Public electricity grid distribution groups are used in substations, pole-mounted cabinets, or underground boxes to handle medium to high distribution level loads. The latest update to this standard confirms that testing on the most demanding public electricity grid distribution groups can validate similar groups and facilitate certification for manufacturers.

The IEC 61439-5 standard includes specific construction, performance, and environmental criteria to ensure that public electricity grid distribution units can withstand general grid voltages, variable loads, weather exposure, and fault conditions. The basic requirements are as follows:

• Structure and materials:
• Enclosures: Must provide IP (ingress protection) ratings suitable for indoor and outdoor use (e.g., IP54 or higher for dust and water resistance). Materials must be resistant to corrosion, UV rays, and mechanical impacts.
• Separation forms: Functional units must be separated to prevent accidental contact between live parts (e.g., Form 2b or higher).
• Terminals and conductors: Minimum capacitances for copper protective earthing conductors and clear markings for interfaces.
• Technicial Specifications:
• Rating specifications: Assemblies must declare the rated current (up to thousands of amperes), voltage, frequency, and short-circuit withstand capability (e.g., 25-50 kA for 1 second).
• Temperature rise: To prevent overheating in ambient temperatures between -25 and +40 degrees (or -40 degrees for arctic designs), it is limited to 70 K (Kelvin) under full load.
• Dielectric properties: Withstands 2,5 kV impulse tests to ensure insulation integrity.
• Environmental and mechanical durability:
• Impact resistance: IK ratings for resistance to mechanical impacts (e.g., IK08), arctic variants specify precise force directions and timing.
• Static load: Cabins must support weights such as snow accumulation without deformation.
• Climate adaptation: Specific provisions for extreme conditions, including thawing and seismic zones.

These requirements are consistent with public safety requirements by mitigating risks such as arc flash or unauthorized access.

IEC 61439-5 standard compliance covers two manufacturers: the original manufacturer for the assembly system and the assembly manufacturer for the final product.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its customers, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services to businesses in accordance with the “IEC 61439-5 Low-voltage switchgear and control devices - Part 5: Devices for power distribution in public networks” standard.