JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III DESIGN ESTIMATION AND COSTING OF ELECTRICAL SYSTEMS Previous Question Paper (February/March - 2022 - R16)
Answer any five questions. All questions carry equal marks.
Main
What are the different types of systems of wiring? List advantages and disadvantages.
Answer
Wiring systems are classified based on the method of installation, the type of conductor used, and the environment. The primary types of wiring systems are:
- Cleat Wiring: Uses porcelain cleats to hold insulated cables. It is temporary, cheap, and easy to install but aesthetically poor and prone to mechanical damage.
- Casing and Capping Wiring: Cables are placed in wooden or PVC casings covered with a cap. It is durable and provides good protection but is a fire hazard if wooden and difficult to inspect.
- Batten Wiring (CTS/TRS): Cables are fixed to wooden battens using brass clips. It is neat, cheap, and easy to install, but cables are exposed to mechanical injury and environmental factors.
- Conduit Wiring: Cables are drawn through metallic or PVC pipes. This is the most popular and safest method, offering excellent protection against fire, moisture, and mechanical damage, though it is expensive and requires skilled labor.
The advantages and disadvantages are summarized below:
| Wiring System | Advantages | Disadvantages |
|---|---|---|
| Cleat | Low cost, easy inspection | Unsightly, high fire risk |
| Casing/Capping | Good appearance, durable | Fire hazard, labor intensive |
| Batten | Low cost, simple installation | Low mechanical strength |
| Conduit | High safety, long life | High cost, complex installation |
With the help of neat sketch, Explain about three phase four wire distributed system.
Answer
A three-phase four-wire distribution system consists of three phase conductors (R, Y, B) and one neutral conductor (N). This system is widely used in low-voltage distribution because it provides two different voltage levels: the phase-to-phase voltage (line voltage) and the phase-to-neutral voltage (phase voltage).
In a star-connected secondary of a distribution transformer, the neutral point is grounded. The phase conductors carry current to the loads, while the neutral conductor carries the unbalanced current back to the source. The relationship between voltages is given by:
This configuration allows for the connection of three-phase loads (like motors) across the three phases and single-phase loads (like lighting and domestic appliances) between any one phase and the neutral. The neutral wire ensures that even if the loads on the three phases are unequal, the voltage across each single-phase load remains constant.
Explain in detail about the location of switches and outlets.
Answer
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Explain how the electrical material cost is estimated for residential installation with suitable examples.
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Discuss in detail about the estimation of material for the electrical installation of commercial building.
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Discuss in detail about the electrical installation of small industries.
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Explain in detail about the type of support required for overhead distribution lines.
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Compare overhead and underground distribution lines in selection.
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What are the factors to be considered in the process of the mechanical design of overhead lines? Discuss.
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Estimate the quantity of materials required for adding 132KV bay at 132KV grid substation.
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State and explain the laws of illumination.
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Explain the functional differences between LED and CFL.
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