NABTEB Electrical Installation Obj & Essay 2024

NABTEB ELECTRICAL INSTALLATION ANSWERS

ELECTRICAL INSTALLATION OBJ:
01-10: CCAAACCCCC
11-20: DCBBACAAAA
21-30: CDCADADACB
31-40: BCBCCCDAAC

Completed!!!
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ANSWER SIX QUESTIONS ONLY
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*PART ONE*
_(ANSWER TWO QUESTIONS ONLY)_

(1a)
Draw the diagram

(1b)
Advantages:
(i) Durable and long-lasting
(ii) Provides excellent protection for wires

Disadvantages:
(i) Heavy and difficult to install
(ii) Expensive to purchase
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(2)
(i) Polarity test
(ii) Continuity of circuit protective conductor (CPC)
(iii) Earth fault loop impedance test
(iv) Insulation resistance test
(v) Functional testing of electrical systems
(vi) Operation of residual current devices (RCDs)
(vii) Verification of protective device settings
(viii) Verification of correct circuit connections
(ix) Verification of earthing and bonding
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*PART II*
_(ANSWER TWO QUESTIONS ONLY)_

(4a)
(i) Ducting is used for ventilation systems, while trunking is used for organizing and protecting cables.
(ii) Ducting can transport air for heating, cooling, or ventilation, while trunking does not carry air flow.

(4b)
(i) Measuring and cutting the conduit to the required length
(ii) Bending the conduit to specific angles
(iii) Threading or deburring the conduit ends

(4c)
Conduit bender
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(5a)
Draw the diagram:

(5b)
MOVING IRON INSTRUMENTS:
Advantages:
(i) They have a low cost of construction compared to moving coil instruments.
(ii) Moving iron instruments have good shock resistance and can withstand high overload current for a short period.

Disadvantages:
(i) They have a lower accuracy compared to moving coil instruments.
(ii) Moving iron instruments have a slower response time compared to moving coil instruments.

MOVING COIL INSTRUMENTS:
Advantages:
(i) They have a higher accuracy compared to moving iron instruments.
(ii) Moving coil instruments have a quick response time, making them suitable for measuring rapidly changing currents.

Disadvantages:
(i) They are more expensive to manufacture than moving iron instruments.
(ii) Moving coil instruments are more susceptible to damage from mechanical shock and overloads.
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*PART III*
_(ANSWER TWO QUESTIONS ONLY)_

(6a)
Draw the diagram:

(6b)
NO-VOLTAGE RELEASE PROTECTION:
(i) Prevents automatic restart of machinery after power restore, reducing the risk of accidents.
(ii) Protects against damage caused by power fluctuations during startup.
(iii) Enhances equipment longevity by avoiding sudden power-ons and potential surges.
(iv) Safeguards against unauthorized access or tampering by requiring manual restart.
(v) Decreases the likelihood of fire hazards due to electrical malfunctions.

OVER-CURRENT RELEASE PROTECTION:
(i) Guards against overheating and potential fires caused by excessive current flow.
(ii) Extends the lifespan of electrical equipment by preventing damage from overloaded circuits.
(iii) Enhances safety for both equipment and personnel.
(iv) Ensures compliance with electrical safety standards and regulations.
(v) Minimizes downtime and maintenance costs associated with electrical failures.
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(9a)
(i) Open Drip Proof (ODP)
(ii) Totally Enclosed Fan Cooled (TEFC)
(iii) Totally Enclosed Non-Ventilated (TENV)
(iv) Explosion Proof (XP)

(9b)
(i) Open Drip Proof (ODP): This enclosure type allows air to flow freely through the motor but prevents dripping water from entering. It is suitable for indoor use in relatively clean and dry environments where there is minimal risk of water splashing on the motor.

(ii) Totally Enclosed Fan Cooled (TEFC): With this enclosure, the motor is entirely enclosed, which protects it from dirt, dust, and moisture. It includes an external fan that helps to cool the motor during operation. TEFC motors are suitable for harsher environments where there is a risk of exposure to contaminants.

(iii) Totally Enclosed Non-Ventilated (TENV): This enclosure type completely encloses the motor and does not have any external ventilation openings. TENV motors rely on convection and conduction for cooling. They are used in applications where the environment is relatively clean and free from excessive heat buildup.

(iv) Explosion Proof (XP): This type of enclosure is designed to contain and prevent any internal explosions from igniting vapors, gases, or dust in the surrounding atmosphere. XP motors are commonly used in hazardous locations where flammable materials are present. They are constructed to withstand and contain internal explosions to ensure safety in volatile environments.
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