WorksheetsSession 3 Symptoms of electrical faults.
Total questions: 20
Worksheet time: 10mins
Regarding Electrical Faults every installation shall be divided into circuits as necessary to:
avoid hazards and minimise inconvenience in the event of a fault.
reduce the cost of the job.
protect circuits against overload fault.
protect circuits against mechanical damage during a fault.
Which of the following would be a common example of a loss of supply?
Smell of burning coming from a two-way switch.
The supply company’s protective devices operating.
The sound of arcing coming from a socket outlet.
Loose cpc in a consumer unit in a domestic house.
Which of the following would be classed as a overload?
Insulation breakdown
Arcing at a two-way switch.
Motor starting current not accounted for on motor circuit.
Breaking of live circuit by nail or similar.
Which of the following could lead to an earth fault or short circuit?
Faulty switch.
Faulty socket outlet.
Extra loads places on an existing circuit or installation
Breaking of live circuit by nail or similar.
Which of the following would not be classed as causing a high resistance?
Poor or loose connections
Cross-sectional area of cable too large.
Cross-sectional area of cable too small.
Long cable runs.
When equipment that contains inductors and capacitors are regularly switched then a short-term voltage spike is injected onto the system. What term is this known as?
Overload
Transient voltage
Earth fault.
High resistance joint.
Which of the following would best describe a open circuit?
Cables with a low insulation resistance value.
Cables connected with a torque screwdriver.
Cables not connected properly.
A low R1+R2 reading.
An immersion heater element has a direct fault to earth. Using an insulation resistance tester the fault will show itself as
an infinity reading between L and N
a zero reading between L and N
a zero reading between L and E
an infinity reading between L and E
A fault between the phase conductor and the surrounding metalwork of an appliance may not operate a protective rewirable fuse if the
Zs value is too high
Ze value is less then 0.5 ohms
Ze value is higher that 0.5 ohms
Zs value is too low
An insulation resistance test is carried out on an MI cable. A low insulation resistance value is recorded. The reading is probably caused by
unsuitable environment
a short circuit caused by twisted conductors
unsuitable cable
moisture absorbed into the insulation
You are called to an office and told that some of the socket outlets are not working. One of the office workers tells you that because she was cold she plugged in an old fire that she found in a cupboard. The information she offers you is
evidence
invalid
not important
a schedule
One terminal of the power factor correction capacitor becomes disconnected in a fluorescent luminaire. This will
cause the heaters in the tube to glow
not affect the operation at all
cause the tube to flash on and off
cause the fuse to blow
Which of the following is the most likely of implications caused from fault diagnostics
Arcing
Open circuit
Loss of power
Short circuit
Which of the following would be most important to be discussed with the client prior to any fault diagnostics being carried out.
Cost of the work
Isolation timing
The Earthing system
The breaking capacity of the main protective device
Which of the following could cause an SPD to operate
Short circuit
Lightning stikes in the area
Overload in the circuit
A damaged light switch
Which of the following could cause an SPD to operate
Short circuit
Overload in the circuit
Switching of large induction motors
A damaged lamp
Which of the following would be the most likely cause of the final light in a lighting circuit not working when the other lights do
Short Circuit at the origin
Open Circuit at the origin
Open circuit in the last leg of the cable
Short Circuit in the last leg of the cable
If equipment plugged into a socket outlet is not working which of the following is the likely cause
Loose Earth cable
Faulty Switch
Earth leakage
One of the Line conductors has become loose
Which of the following is likely to cause a transient voltage spike
Switching surge from large induction motors
High resistance joint
Short Circuit
Earth fault
Which of the following would most likely cause a motor to not work if the circuit is healthy
High resistance joint in the isolator
Equipment malfunction
Too many capacitors causing a leading effect
Lightning strike
