SIST HD 60364-4-43:2023/kFprAA:2026

SIST HD 60364-4-43:2023/kFprAA:2026 is a draft amendment to the CENELEC Harmonization Document HD 60364-4-43:2023 for low-voltage electrical installations. It specifies how to protect live conductors, PEN conductors, PEM conductors and PEL conductors against overcurrent, and it adds rules for where overload and short-circuit protective devices are installed.

What does SIST HD 60364-4-43:2023/kFprAA:2026 specify?

SIST HD 60364-4-43:2023/kFprAA:2026 modifies the overcurrent protection part of Low-voltage electrical installations. It focuses on protection against overload current and short-circuit currents, and on how those protective measures are coordinated in practice.

The amendment is organized as:

• a change to Subclause 431.4 on overload current,
• a change to Subclause 431.5 on short-circuit currents,
• a new normative Annex G on the position of overcurrent protection devices,
• special national conditions and A-deviations in the national annexes.

What are the key requirements of SIST HD 60364-4-43:2026?

SIST HD 60364-4-43:2023/kFprAA:2026 makes the location of overcurrent protective devices part of the requirement, not just their presence. In practice, designers have to check where the conductor changes, where the risk changes, and whether an exception is allowed.

Overload protection follows Annex G

Subclause 431.4 now points to Annex G for the positioning of devices that protect against overload current. This means the device location has to be checked against the conductor route, not chosen only by convenience.

Short-circuit protection also follows Annex G

Subclause 431.5 now points to Annex G for the positioning of short-circuit protective devices. In practice, the short-circuit protective device has to match the conductor’s withstand capability along the circuit.

Devices are normally placed at the origin of each circuit

Annex G starts from the rule that overload and/or short-circuit protective devices are installed at the origin of each circuit unless an exception applies. This gives a clear default for circuit design and panel layout.

Changes in current-carrying capacity trigger overload protection

Where the current-carrying capacity of conductors decreases, overload protection is required at that point unless one of the allowed exceptions applies. The document gives examples such as changes in conductor size, material, insulation, installation method, external influences, or grouping of conductors.

Short-circuit protection follows changes in withstand capability

Annex G requires short-circuit protection at the point where the conductor’s let through energy withstand capability (k2S2) is reduced, unless an exception applies. This helps prevent damage when a conductor segment has lower short-circuit tolerance than the rest of the circuit.

Exceptions are tightly limited

The annex allows exceptions only under defined conditions, such as short protected runs, no branch circuits or socket-outlets in the affected section, and reduced risk of short-circuit, fire, or injury. The text also excludes these exceptions in locations presenting a fire risk or risk of explosion.

Special cases are covered for some systems and supply arrangements

Annex G includes cases where overload or short-circuit devices may be omitted because protection is already provided on the supply side, because the distributor accepts the arrangement, or, in IT systems without a neutral conductor, because a residual current protective device is installed in each circuit. For an engineer, this means the protection concept has to be checked as a whole, not device by device.

What terms does SIST HD 60364-4-43:2023/kFprAA:2026 define?

• Current-carrying capacity - the conductor capability that drives where overload protection must be placed.
• Overload current - current that can heat conductors and create harmful effects over time.
• Short-circuit current - fault current that can create severe thermal and mechanical stress.
• Let through energy withstand capability (k2S2) - the conductor’s ability to withstand short-circuit energy before the protective device clears the fault.
• Special national conditions - national characteristics or practices that cannot be changed even over a long period.
• A-deviations - national deviations due to regulations outside the competence of the CENELEC national member.
• IT systems - a supply arrangement specifically treated in the overload protection exceptions.
• Residual current protective device - a device used in one of the IT system exceptions for overload protection.

Who uses SIST HD 60364-4-43:2023/kFprAA:2026?

This document is used by electrical designers, installers, panel builders, inspectors, quality managers and buyers who need to specify or check low-voltage protection arrangements. It is relevant in buildings, industrial installations and electricity supply systems where conductor protection and device placement must be coordinated.

It is especially useful when deciding:

• where to locate protective devices in a circuit,
• whether a conductor segment needs separate overload or short-circuit protection,
• whether an exception is allowed,
• how national conditions affect the design.

What changed in SIST HD 60364-4-43:2023/kFprAA:2026 from the previous edition?

The underlying HD 60364-4-43:2023 is described as a technical revision that cancels and replaces the 2008 third edition. The scope identifies these main changes:

• the document was restructured,
• automatic disconnection of supply was designated as the preferred overcurrent measure,
• other overcurrent measures were moved to normative annexes for restricted applications,
• a new terms and definitions clause was added,
• new requirements were added for neutral or mid-point conductors, including cases with triplen harmonics.

Which standards are used with SIST HD 60364-4-43:2026?

The national condition for Germany refers to IEC 60364-5-53:2019/AMD1:2020 and HD 60364-5-53:2015/A11:2017. These references matter because they affect how related protection requirements are applied in the German special national condition.

The Italian national condition refers to CEI 0-21 for prospective short-circuit currents at a grid supply point.

What does the SIST HD 60364-4-43:2026 document contain?

The amendment text contains the European foreword, the two modified subclauses on overload and short-circuit currents, and the new normative Annex G. Annex G is the practical core of the document: it gives the general rule, the overload-protection positioning rules, and the short-circuit-protection positioning rules.

It also contains annexes on special national conditions and A-deviations, with country-specific notes. In practice, those annexes are used when applying the document in national implementations and when checking whether a local rule changes the default harmonized requirement.