FAULT DIAGNOSIS AND RECTIFICATION 1
Fault finding and rectification, test instrument settings, readings, test procedures, typical faults - 8 questions from a bank of questions
Answer ALL questions. Look for any feedback given if you get an answer incorrect. Keep choosing an answer until you get it correct. CORRECT or INCORRECT answers are indicated at the TOP of the page. A score is given at the TOP of the page when the exercise has been completed. © K.Brown 2018
With reference to GS38, what is the recommended maximum length of exposed metal 'tips' on voltage indicating devices?
- 1mm
- 2mm
- 3mm
- 4mm
If you isolate and lock-off a distribution board, where should any padlock keys be kept?
- with the padlock
- in a key cupboard
- with the supervisor for safe keeping
- in your pocket
Which one of the following will a circuit breaker provide?
- over voltage protection
- over current protection
- excess frequency protection
- protection against direct contact only
Under which ONE of the following conditions should an 'off-load device' be operated?
- only when current has been switched off
- only when low current values are flowing
- at any time when equipment is running
- only when a 'permit to work' has been completed
The 'rating' of a protective device should fulfil which ONE of the following conditions?
- it should be equal in value to the lowest rated item of equipment served by that circuit
- it should be equal to or less than the rating of the cable
- it should be a minimum rating of 6A
- it should be equal to the short-circuit current value of the circuit
Which one of the following symbols represents the current rating of a protective fuse or mcb?
- It
- In
- Iz
- Ib
Which one of the following is the description of a 'short-circuit fault'?
- "a high fault current which flows to the general mass of earth"
- "a fault current resulting from negligible impedance between live conductors"
- "a fault current that exceeds the current carrying capacity of the cable in a circuit that is electrically sound"
- "a fault current between the phase conductor and main equipotential bonding conductor"
Which ONE of the following is representitive of an 'overload fault'?
- multiway adaptors plugged into 13A socket outlets
- excess current flow when large motors start up
- a fault current that flows to the general mass of earth
- plugging a 110v AC lamp into a 230v AC circuit
Which ONE of the following is representitive of an 'over voltage fault'?
- multiway adaptors plugged into 13A socket outlets
- excess current flow when large motors start up
- a fault current that flows to the general mass of earth
- plugging a 110v AC lamp into a 230v AC circuit
Which ONE of the following is representitive of an 'earth leakage fault'?
- multiway adaptors plugged into 13A socket outlets
- excess current flow when large motors start up
- a fault current that flows from a live conductor to the MET of an installation
- plugging a 110v AC lamp into a 230v AC circuit
How can 'transient' start-up currents on large motors be prevented from 'tripping' an MCB?
- only double-pole MCB's are to be used
- the use of a 'B' type MCB
- using an MCB with a higher fusing Factor
- the MCB must be rated for the maximum starting current
Which one of the following would NOT be representitive of a typical short-circuit fault in an electrical circuit?
- poor conductor terminations
- insulation failure
- severed live conductors
- incorrectly connected wiring
Which ONE of the following would NOT cause a 'transient' voltage on the 'mains' supply?
- REC fault on the supply
- Heavy current switching
- Lightning strike
- faulty MCB