CSCS Electrical Safety 1

Question 1

What voltage supply is required for portable electrical equipment used on construction sites under BS 7671?

Accepted Answer

110V via centre-tapped earth transformer

Answer

BS 7671 and HSE guidance require 110V supply via a centre-tapped earth transformer for portable tools on construction sites. This limits the maximum voltage to earth to 55V, significantly reducing the risk of fatal electric shock.

Question 2

What is the primary purpose of a Residual Current Device (RCD) on a construction site?

Accepted Answer

To detect earth leakage current and disconnect the supply rapidly

Answer

An RCD detects an imbalance between live and neutral conductors caused by earth leakage current and disconnects the supply within milliseconds. Under the Electricity at Work Regulations 1989, RCDs provide additional protection against electric shock but are not a substitute for reduced voltage systems.

Question 3

What is the safe exclusion zone distance for work near 400kV overhead power lines as specified by HSE guidance?

Accepted Answer

15 metres

Answer

HSE guidance note GS6 specifies a minimum safe distance of 15 metres from 400kV overhead power lines. For lower voltages, smaller distances apply — for example, 6 metres for lines up to 33kV. These distances account for potential electrical arcing and the swing of cables in wind.

Question 4

How often must portable electrical equipment on a construction site undergo PAT testing as a general guideline?

Accepted Answer

Every 3 months

Answer

HSE and IET guidance recommend that portable appliances on construction sites are formally PAT tested every 3 months due to the harsh working environment. Additionally, users should carry out visual checks before each use. The frequency is more stringent than for office environments due to the higher risk of damage.

Question 5

Under the Electricity at Work Regulations 1989, who has a duty to ensure electrical systems are safe?

Accepted Answer

The duty holder — employers, self-employed persons, and employees

Answer

The Electricity at Work Regulations 1989 place duties on employers, self-employed persons, and employees (collectively 'duty holders') to ensure electrical systems are constructed, maintained, and used so as to prevent danger. This means everyone from site managers to operatives has a legal responsibility.

CSCS Green Card Practice Test

CSCS Green Card Practice Test

CSCS Electrical Safety 1