Low voltage directive

J W Molyneux-Child of Surrey Management Consultants explains why designers should be interested in the Low Voltage Directive, which came into effect on the 1 January this year

European legislation harmonising the rules on electrical equipment safety has been around for a couple of decades. The Low Voltage Directive (LVD) itself came into effect as long ago as September 1974. But it has recently been amended to make it consistent with the other CE marking Directives in the European Union. Its incorporation with other `New Approach’ Directives and the requirements for CE marking means that it became mandatory from the 1 January 1997.

As a result, manufacturers of electrical equipment will need to ensure and demonstrate that their products conform to the requirements of the Directive. This will allow them to be CE marked and supplied into the European market.

The LVD itself applies to all electrical apparatus or devices that are designed or adapted for use between 50 and 1000Vac, or between 75 and 1500Vdc. This includes domestic, professional and industrial products.

There are some exemptions, including equipment covered by other Directives. These include electrical equipment for radiology and medical purposes, electricity meters, electrical parts for goods and passenger lifts, electric fence controllers and plugs and socket outlets for domestic use. Equipment manufactured for supply outside the European Economic Area is also exempt from the requirements.

In the UK, the Low Voltage Directive and CE marking are incorporated into British Law through the Electrical Equipment (Safety) Regulations 1994. Implementing the requirements of the LVD, the UK regulations also take into account the need to protect users against potentially unsafe second-hand and hired electrical equipment.

Manufacturers of electrical equipment are required by the directive to take all reasonable steps in the manufacturing process to minimise the risks that might arise from the use of the product. Such risks include the danger of death and injury to animals and property, as well as to personnel. The LVD does exclude risk from improper installation or maintenance, but not abuse of the manufacturer’s equipment by the user.

These provisions go further than many might realise. Any requirements for the safe use of the electrical equipment, for example, should be marked up on the equipment, or (if a label is impracticable), supplied on an accompanying form or instruction booklet. And the manufacturers brand name or trademark should be included on the equipment or on the packaging.

Establishing compliance

The Low Voltage Directive requires that the electrical equipment is manufactured in line with the best acknowledged engineering practices. Equipment must be constructed in accordance with the principal elements of the safety objectives that are laid down in Annexe I of the Directive.

Electrical equipment that complies with the safety provisions of a harmonised standard will be presumed to comply with the safety requirements of the regulations.

Within the LVD, many safety test standards are applicable to different types of electrical equipment. For example, EN60335 is the specification for the safety of household and similar electrical appliances, EN60950 applies to information technology equipment and EN60065 covers those products such as brown goods. Others of interest include EN60204, which is for machinery, EN60598 for luminaries and EN61010 for electrical test and measurement equipment.

Each standard includes a series of electrical safety tests with specific test parameters and limits appropriate to the category of equipment. The standards typically include earth bond testing, insulation testing, high voltage testing, residual voltage, earth leakage current, and earth leakage differential.

All are designed to ensure the safe operation of the equipment by a user. In some case, abnormal operation tests are required to test the performance of the equipment. Should faults occur, mechanical safety, stability and the enclosure of moving parts are also covered in the standards.

Technical Documentation

Before a product is placed on the market, the manufacturer must produce technical documentation. This allows the electrical equipment to be assessed with regards to the requirements of the Directive.

Like other Directives, the LVD requires a technical file. The contents of the file must identify the product and describe the means that have been employed to meet the safety aspects of the directive.

Technical documentation must cover the design, manufacture and operation of the electrical equipment. It should include a general description of the electrical equipment, conceptual design and manufacturing drawings plus details of components and sub-assemblies.

In addition, it should include a listing of the standards that have been applied in full or in part, and descriptions of the solutions adopted by the manufacturer to satisfy the safety aspects of the Directive, where standards have not been applied. Full design calculations and test reports are also required. Finally, it should include a Declaration of Conformity.

Holding a test report as part of the technical documentation is a requirement of the LVD and this will form part of the defence if there is a challenge.

Having designed and developed a product that conforms to the essential safety requirements of the LVD, some form of end of production line system capable of testing products before distribution should be sufficient to confirm that the initial design specification remains intact.