Earthing and Bonding Flashcards
6 cards from real ECS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Earthing and Bonding flashcards as text
What is the primary purpose of earthing (grounding) in an electrical installation?
Answer: To provide a safe fault current path and facilitate overcurrent device operation
Earthing provides a low-impedance path for fault currents so that protective devices operate quickly, disconnecting the supply and preventing dangerous touch voltages.
What is the difference between protective earthing and protective bonding?
Answer: Earthing connects electrical equipment to earth; bonding connects extraneous conductive parts together and to earth to equalize potential
Protective earthing connects the exposed metalwork of electrical equipment to earth, while protective bonding connects extraneous conductive parts (pipes, structural steelwork) to prevent dangerous potential differences between them.
What color is the protective earth conductor required to be in a fixed electrical installation?
Answer: Green and yellow stripes
Protective earth conductors must be identified by green and yellow striped insulation as required by electrical standards to prevent misidentification.
What is the minimum cross-sectional area (CSA) of a main protective bonding conductor where the installation is supplied via a TN-S system with a 35mm² meter tail?
Answer: 10mm²
Main protective bonding conductors must be at least half the CSA of the supply neutral up to a maximum of 25mm², so a 35mm² supply typically requires at least a 10mm² bonding conductor.
Which of the following is an example of an 'extraneous conductive part' that requires main protective bonding?
Answer: An incoming gas pipe entering the building
An incoming gas pipe is an extraneous conductive part — it is not part of the electrical installation but could introduce a potential from outside the building and must be bonded.
What instrument is used to test the continuity of a protective earth conductor?
Answer: Low-resistance ohmmeter or continuity tester
A low-resistance ohmmeter or continuity tester measures the resistance of the earth conductor to confirm it provides a low-impedance fault current path.