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Electrotechnical Unit 302 :
A) A prospective earth fault current test needs to be carried out on a domestic
consumer unit which has type B circuit breakers. Some of the lighting circuits have fluorescent fittings.
1. State which instrument(s) can be used.
2. What precautions need to be taken prior to the test.
3. The minimum allowable value(s).
4. Describe the test.
(6 points)
B. Explain the terms
1. Equipotential bonding
2. Exposed conductive part
C. Draw a star-delta transformer arrangement.
1. Fully label all conductors, voltages and currents for a 25kV/400kV step-up system.
2. State two materials used for conductors in the UK generation, transmission and distribution system and why they are chosen.
Note: electro-technical level 2 and level 3 papers,
you will find quite a few questions which relate to this unit. Here are some examples
of what you may be asked (what is covered in the unit and should be known as underpinning knowledge):
_ Statutory safety regulations and safe working practices.
_ Selection of wiring systems and cable sizes
_ Be able to represent an installation using block, schematic, wiring or layout diagrams
_ Describe the generation, transmission, transformation, distribution and delivery of electricity in the UK
_ Describe single-phase and 3-phase supply types, voltages, currents and terminology
A) A prospective earth fault current test needs to be carried out on a domestic
consumer unit which has type B circuit breakers. Some of the lighting circuits have fluorescent fittings.
1. State which instrument(s) can be used.
2. What precautions need to be taken prior to the test.
3. The minimum allowable value(s).
4. Describe the test.
Answers
A) A prospective earth fault current test needs to be carried out on a domestic
consumer unit which has type B circuit breakers. Some of the lighting circuits have fluorescent fittings.
1. State which instrument(s) can be used.
2. What precautions need to be taken prior to the test.
3. The minimum allowable value(s).
4. Describe the test.
Answer:
1. PFC tester or loop tester with PFC function (as shown). The voltage range the meter will work on is from 50V to 480V, which is taken from the supply it is plugged into. It measures the current between line and neutral across an internal impedance inside the tester: PFC =
I = V/R = 230/0.5 = 460A. The meter will return a value from 0A up to ≈50kA.
The value can also be ascertained by calculation or determined by other means. ( 16th edition 713-12-01, ↔ 17th edition 612.11 )
2. This is a live test, you may be measuring live energised conductors (when using clip-on leads) so be very careful. As this is not the first live test, you will have already informed persons, put up warning signs, informed persons who could be affected by a
A) A prospective earth fault current test needs to be carried out on a domestic
consumer unit which has type B circuit breakers. Some of the lighting circuits have fluorescent fittings.
1. State which instrument(s) can be used.
2. What precautions need to be taken prior to the test.
3. The minimum allowable value(s).
4. Describe the test.
(6 points)
B. Explain the terms
1. Equipotential bonding
2. Exposed conductive part
C. Draw a star-delta transformer arrangement.
1. Fully label all conductors, voltages and currents for a 25kV/400kV step-up system.
2. State two materials used for conductors in the UK generation, transmission and distribution system and why they are chosen.
Note: electro-technical level 2 and level 3 papers,
you will find quite a few questions which relate to this unit. Here are some examples
of what you may be asked (what is covered in the unit and should be known as underpinning knowledge):
_ Statutory safety regulations and safe working practices.
_ Selection of wiring systems and cable sizes
_ Be able to represent an installation using block, schematic, wiring or layout diagrams
_ Describe the generation, transmission, transformation, distribution and delivery of electricity in the UK
_ Describe single-phase and 3-phase supply types, voltages, currents and terminology
A) A prospective earth fault current test needs to be carried out on a domestic
consumer unit which has type B circuit breakers. Some of the lighting circuits have fluorescent fittings.
1. State which instrument(s) can be used.
2. What precautions need to be taken prior to the test.
3. The minimum allowable value(s).
4. Describe the test.
Answers
A) A prospective earth fault current test needs to be carried out on a domestic
consumer unit which has type B circuit breakers. Some of the lighting circuits have fluorescent fittings.
1. State which instrument(s) can be used.
2. What precautions need to be taken prior to the test.
3. The minimum allowable value(s).
4. Describe the test.
Answer:
1. PFC tester or loop tester with PFC function (as shown). The voltage range the meter will work on is from 50V to 480V, which is taken from the supply it is plugged into. It measures the current between line and neutral across an internal impedance inside the tester: PFC =
I = V/R = 230/0.5 = 460A. The meter will return a value from 0A up to ≈50kA.
The value can also be ascertained by calculation or determined by other means. ( 16th edition 713-12-01, ↔ 17th edition 612.11 )
2. This is a live test, you may be measuring live energised conductors (when using clip-on leads) so be very careful. As this is not the first live test, you will have already informed persons, put up warning signs, informed persons who could be affected by a
