2330 level 3 smartscreen questions/answers

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#SmartScreen

Level 3 Certificate in Electrotechnical Technology Unit 3 Sample questions answers

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#Unit 3: Installation (Buildings and Structures): Fault diagnosis and rectification

Sample questions

Answer guide

1. List six areas where faults can occur in an electrical installation.

Solution

Wiring

Cable terminations

Accessories

Connections

Luminaries

Switch gear

(any other) (6 marks)

2. Describe three situations which may affect rectification of a fault in an installation.

Solution

1. Access to the area where the fault is eg on an oven that is too hot to work on.

(2 marks)

2. Provision of an emergency supply eg in a hospital or similar situation.

(2 marks)

3. Client demand for a continuous supply eg fault in an IT installation therefore emergency supply needs to be verified before disconnection. (2 marks)

3. Describe special precautions that need to be taken when:

a. handling sensitive electronic components

b. working on equipment having large capacitive circuits

c. terminating fibre optic cables.

Solution

a. Take precautions against damage when handling due to electrostatic electricity.

(2 marks)

b. Isolate from the supply and discharge capacitors.

(2 marks)

c. Follow manufactures termination procedures and take extra care to avoid cuts and damage to eyes from glass shards and splinters. (2 marks)

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4. a. State the procedures to be carried out before starting fault diagnosis in terms of:

(i) procedures for isolation

(ii) proof of voltage testing equipment

b. State procedures regarding functional checks on completion of the rectification process.

Solution

a. (i) Ensure loads are disconnected using switches and circuit breakers designed to open circuits on load, switch off the isolator and lock in the off position.

(2 marks)

(ii) Prior to testing, check voltage test equipment against a known source to ensure correct operation and calibration. (2 marks)

b. Check polarity, continuity and insulation tests before connecting the supply and earth fault loop impedance tests with the supply connected, check operation of all circuits and equipment. (2 marks)

5. a) List three sources of information that may be referred to when commissioning an installation.

B) Identify three building materials which may need replacement/making good after fault finding.

Solution

a)

IEE wiring regulations

contract specification

wiring diagram

distribution drawings

manufactures instructions

statutory regulations

(any three from six) (3 marks)

B) Brickwork, plaster, decoration or suitable alternatives (3 marks)

6. Name the type of instrument with typical range to be used for the following tests

a. continuity of protective conductors

b. RCD testing

c. Measurement of current on load.

Solution

a. A low reading ohmmeter with a range typically 0

 

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4. (1.4)

You are called to a factory to rectify a fault on a piece of equipment which has a recorded history of regular breakdowns.

Identify the logical steps to be taken in tracing the fault.

Solution

a. Information on events leading up to fault including talking to staff. (2 marks)

b. Information from verbal and written reports. (2 marks)

c. Analysis of evidence and use of tests to diagnose cause of faults (2 marks)

5. (1.6. a-c)

Describe, for each of the following, the typical symptom of

a. complete loss of supply at origin

b. localised loss of supply

c. overload or fault current devices operating.

Solution

a. The whole building or local area has a loss of supply. (2 marks)

b. An area or floor of a building has a loss of supply. (2 marks)

c. A single circuit is not working. (2 marks)

6. (1.7. a-c)

An item of machinery in a process sequence develops a fault. The machine is eight years old and out of warranty.

Identify three factors which would influence the decision to repair the machinery.

Solution

a. Availability of replacements. (2 marks)

b. Downtime under fault conditions. (2 marks)

c. Costs. (2 marks)

Or alternative suitable answers.

7. (1.6. d-f)

For each of the following faults, identify a possible cause.

a. Transient voltage

b. Insulation failure

c. Component failure

Solution

a. Caused by switching of inductive or capacitive loads. (2 marks)

b. Mechanical damage to insulation by a nail, overheating of cables etc. (2 marks)

c. Caused by overloading, failure of contacts, damage by mechanical forces, strain.

(2 marks)

8. (1.8)

Work is to be carried out in the storage area of a large supermarket which is operational 24 hours a day, even when the shop is closed. Members of the staff need lighting and access to the area to reach refrigeration storage.

Identify three factors which may affect rectification.

Solution

a. Access to system/equipment. (2 marks)

b. Provision of emergency/standby equipment. (2 marks)

c. Client demand for a continuous supply. (2 marks)

9. (2.1. a-e)

List relevant sources of information to help recommissioning with respect to

a. setting of controls on an industrial heating system

b. checking test values with published data

c. determining cable runs and control equipment for installed equipment.

Solution

a. Manufacturer