Unlike a low voltage installation which is generally designed and constructed in accordance with technically prescriptive requirements, most high voltage installations are unique to their application and are designed according to electrical engineering safety principles. As a result, the Regulations that apply set fundamental safety requirements only.
High voltage installations require planned ongoing maintenance and are often designed as a part of or closely interact with the supply or distribution of electricity. As a result, the Regulations implement explicitly a number of measures that apply the same principles and practices across the supply systems/installations interface.
Reflecting the engineered installation philosophy, the Regulations achieve control through identifying the factors that need to be addressed during design and construction and by defining characteristics that are considered to be unsafe.
Stage by stage safety requirements for high voltage installations
High voltage installations require a certified design.
- General safety requirements as explained in Regulation 14
- Technical rules: Safety requirements relating to overhead lines, earthing systems, isolation from supply of electricity, conductors and notices (Reg 41 to 46).
- Certification is required
- Inspection: All high voltage installations are subject to testing (Reg 38) and third party inspection (Reg 70 to 72)
- Safety check as explained in Regulation 73(4)
- In service safety verification as explained in Regulation 41(1)(2)
Defining unsafe works and installations
Regulation 20(external link) defines electrically unsafe works and installations. Works and installations are unsafe if:
- the characteristics of any fittings are impaired
- the connections are not secure and reliable
- cooling conditions are impaired
- there is a risk of ignition (e.g. fittings subject to high temperature are unguarded)
- cables are not protected against the risk of damage or are bent beyond their design criteria
- there is insufficient space to work on the installations safely.
In addition, measures must be put in place to do at least one of the following:
- prevent accidental contact with exposed parts
- provide automatic disconnection of power if a fault arises that would cause injury
- prevent or limit (International Electrotechnical Commission shock current Standards) electric current passing through the body of a person on contact of any part of the works or installations.
There is a requirement to implement a safety checking system (Regulation 40(external link)) that must:
- verify compliance with all the requirements
- occur periodically at reasonable intervals
- ensure records of results are being kept.
Design, construction and inspection of high voltage electrical installations
Regulations for the design, construction and inspection of high voltage electrical installations take into account the fact that each installation will be different, and are designed according to electrical engineering safety principles.