EI-604: Electrical Equipment Installation & Safety

• The exam is for Electrical branch, 6th semester, subject code EI-604.
• The subject is Installation and Maintenance of Electrical Equipments.
• The exam has a duration of three hours and the full marks are 70.
• Part A and Part B are compulsory.
• Part A is worth 25 marks.

Electrical Safety

• The safety of electrical appliances and wiring is ensured by insulation, earthing and providing a fuse wire in the electric circuit.
• Painful electric shock is felt when the magnitude of current passing through the human body is from 8 to 15 milliamp.
• Electric shocks are received when the neutral wire comes in contact with the earth wire.
• When current is felt by touching the metal body of any appliance, it indicates an electric shock.

Earthing

• The main methods of lifting electrical machines are pulley blocks, chain hoists, and overhead cranes.
• The material used in pipe earthing is charcoal-salt.
• Inside the earth or pit, the earthing electrode should be placed vertically.
• Coal-salt mixture is preferred for filling around the earth electrode for effective earthing.

Electrical Quantities and Testing

• The range of medium resistance is 1 to 1000 ohm.
• The insulation resistance test is performed on a power line with a Meggar.
• A dirt-free, moisture-free machine should have a polarization index > 2.
• A test lamp is used to find out the polarity of a wire
• A close circuit is not a break in the continuity of the circuit.

Maintenance

• Corrective maintenance is needed when equipment fails.
• Preventive maintenance is carried out to reduce equipment failure.
• Overhaul is done for replacement of parts of electrical equipment.
• Breakdown maintenance is not carried out daily.

Transformer Oil

• To determine the suitability of transformer oil, breakdown test, acidity test, and crackle test are performed.
• Grade B mineral oil is suitable as transformer oil.
• Dehydration and filtration of transformer oil is important.

Tools and Installation

• For holding, twisting, or cutting wires, pliers are used.
• Chisel, Poker, Blow lamp and Screw drivers are used in electrical installation works.
• Motors are tested for commissioning.

Open Questions from Part B

• Draw the diagram of plate earthing and explain it, or describe the points to be considered during earthing installation.
• Discuss why dehydration and filtration of transformer oil is important.
• Enumerate six properties of good insulation.
• What are the reasons for the deterioration of insulating oil, and explain it? Discuss the various tests to determine the suitability of insulating oil instead.
• Name the different types of maintenance.
• Enumerate two advantages of preventative maintenance, or describe the preventative maintenance of a distribution transformer.
• Also, describe the maintenance schedule for a circuit breaker.
• What are the faults that happen in D.C motors, what causes them and how can we fix those?
• What are four of the most likely things to break on domestic electrical appliances.
• What is earthing and what effects can it have?