Estimation and Costing MCQ Quiz - Objective Question with Answer for Estimation and Costing - Download Free PDF

The correct answer is option 3.

National Electric Code (NEC) 2011

The primary scope of the National Electrical Code (NEC) 2011 is to provide a set of guidelines for the safe installation and use of electrical wiring and equipment. It focuses on minimizing hazards and preventing accidents, injuries, and fires related to electrical installations. 

Safety: The NEC prioritizes safety by outlining general safety procedures, providing recommendations for safe practices, and addressing specific hazards. 

Electrical Installations: The code applies to various types of electrical installations, including those in buildings, industrial sites, and even outdoor locations. 

Equipment and Wiring: The NEC covers the selection, installation, and maintenance of electrical equipment and wiring, ensuring they meet safety standards. 

Hazardous Areas: The code includes provisions for special precautions in areas with explosive or otherwise dangerous atmospheres. 

The correct answer is option 4.

This is indeed the correct and most critical factor because:

• Accurate power calculation ensures the system is appropriately sized and avoids overload. Protective devices (like circuit breakers, fuses, overload relays) are essential to prevent equipment damage and ensure safety.
• Power calculations ensure the motor, cables, and supply system are appropriately sized.

The correct answer is option 2.

Compliance with electrical codes (like NEC, IEC) and safety standards is crucial in any commercial electrical installation. It ensures:

• Safety of occupants and maintenance personnel.
• Legal compliance to avoid penalties, rework, or shutdowns.
• Accurate costing, since estimates include only approved materials and proper labor practices.
• System reliability reduces the chance of electrical faults or fire.

Ignoring these codes can result in failed inspections, costly legal consequences, or dangerous systems.

The correct answer is option 4.

Cogeneration

• Cogeneration (also called Combined Heat and Power, CHP) is a highly efficient process that uses one fuel source (e.g., natural gas) to generate electricity and heat.
• Cogeneration reduces energy waste by simultaneously producing electricity and useful thermal energy, while a well-designed tariff system incentivizes off-peak energy usage, lowering overall costs.
• This results in higher overall efficiency (up to 80–90%) compared to just 30–50% in conventional separate generation.

Tariff system

• A tariff system is a pricing structure for electricity use (e.g., flat rate, time-of-use, or demand-based).
• Tariff systems that are well-designed (like time-of-use pricing) encourage energy consumption during off-peak hours, leading to lower energy bills and better load distribution.

The correct answer is option 1.

In the design procedure for electrical installations in commercial buildings, the first step must be understanding how much power the building will need. This involves:

• Estimating electrical loads: Lighting, HVAC, elevators, office equipment, etc.
• Calculating peak demand: Helps size transformers, panels, and feeders correctly.
• Planning for future expansion: Ensures flexibility without major redesign.

Only after this analysis can an engineer begin selecting conductor sizes, designing protective systems, specifying panel boards, switchgear, and layout. Without a load analysis, you risk installing an unsafe or non-functional system. It can lead to power outages, fire hazards, or legal violations.

The cheapest system of wiring is cleat wiring.

1. Horizontal strip earthing: This type of earthing is used at places which have rocky earth bed.
2. Rod earthing: This system of earthing is suitable for areas which are sandy in character. This system of earthing is very cheap as no excavation work is involved.
3. Plate earthing: It is used for larger stations and transmission lines, where the fault current, likely to be high.
4. Pipe earthing: It is used for ordinary soil or dry and rocky soil. The size of the pipe depends upon the current to be carried and the type of the soil. Usually, the pipe used for this purpose is of diameter 38 mm and 2.5 meters in length for ordinary soil or of greater length in case of dry and rocky soil.

• Pipe earthing is the most common and best system of earthing as compared to other systems suitable for the same earth and moisture conditions.
• Pipe earthing is the best form of earthing and is very cheap in cost.
• In this method the galvanized steel and perforated pipe of approved length and diameter in place upright in permanently wet soil.
• The size of the pipe depends upon the current to be carried and the type of soil.

The correct answer is option 3.

​Earnest money deposit

• It is a small refundable fee collected by the department from each bidder to ensure that a bidder does not submit a dummy bid or back out at the time of tender opening.
• It is returned when all the bids are opened & tender is awarded to another firm.
• It is generally 2% of the tender value.

Security deposit

• It is the amount of money that has to be deposited with the buyer once the tender is awarded to a bidder to ensure that if he does not complete the task as per the work order, the buyer can recover the loss by forfeiting his security deposit.
• It can be in the form of a demand draft or bank guarantee.
• When the contractor completes the project, he gets its security deposit returned.
• ​It is generally 10% of the tender value.

Additional Information Caution money:

• It is the amount of money that someone has to pay when they rent property, use a service, etc. which will not be refunded if they damage something or owe money at the end of their contract.

Bank guarantee:

• It is a written contract given by a bank on behalf of a customer that undertakes to pay or discharge the liability of the debtor in case of any default.

The minimum clearing distance between the equipment for the 750 to 1000 kV line must be 45 feet.

The minimum clearing distance that equipment should keep from the power lines of different voltage levels is:

The desired minimum depth of laying from the ground surface to the top of the cable is as follows:

High voltage cables (3.3 kV to 11 kV rating) = 0.9 m

High voltage cables (22 kV, 33 kV rating) = 1.05 m

Low voltage and control cables = 0.75 m

Concept:

Full Load Current(IFL): A full load current is a maximum current that electrical equipment is designed to carry under rated conditions.

Leakage current(Ilek): A leakage current is an electric current in an unwanted conductive path under normal operating conditions.

Note: According to IE Rule 48 The maximum permissible value of leakage current should not be exceeded beyond the \(\frac{1}{{5000}} \)times of full load current.

Insulation Resistance(IR): An insulation resistance (IR) is the total resistance between any two points separated by electrical insulation.

It is given by,

\(IR = \frac{{Supply\;Voltage}}{{{I_{lekage}}}}\)

Note: IR of a cable is also given as:

\(IR = \frac{\rho }{{2\pi l}}{\log _e}\frac{{{r_2}}}{{{r_1}\;}}\)

Where ρ is the resistivity of cable on Ωm

l is the length of cable in the metre.

r1 is the radius of core in metre

r2 is the radius of cable in metre

Calculation:

Given, P = 2.4 kW, V = 240 V

I_FL = 2400 / 240 = 10 A

According to IE Rule 48:

\({I_{lek}} = \frac{{{I_{FL}}}}{{5000}} = \frac{{10}}{{5000}} = 0.002\;A\)

∴\(IR = \frac{{supply\;voltage}}{{{I_{lekage}}}} = \frac{{240}}{{0.002}} = 120,000 = 0.12\;M{\rm{\Omega }}\)

The symbol of different Transformer is shown below:

Different Type of Tower Design:

1. Three Phase Single circuit two ground wire Tower:

2. Three Phase Single circuit one ground wire Tower:

2. Double Three Phase Single circuit one ground wire Tower:

4. HVDC Bipolar Tower:

Concept:

Full Load Current(IFL): A full load current is a maximum current that electrical equipment is designed to carry under rated conditions.

Leakage current(Ilek): A leakage current is an electric current in an unwanted conductive path under normal operating conditions.

Note: According to IE Rule 48 The maximum permissible value of leakage current should not be exceeded beyond the \(\frac{1}{{5000}} \)times of full load current.

Insulation Resistance(IR): An insulation resistance (IR) is the total resistance between any two points separated by electrical insulation.

It is given by,

\(IR = \frac{{Supply\;Voltage}}{{{I_{lekage}}}}\)

Note: IR of a cable is also given as:

\(IR = \frac{\rho }{{2\pi l}}{\log _e}\frac{{{r_2}}}{{{r_1}\;}}\)

Where ρ is the resistivity of cable on Ωm

l is the length of cable in the metre.

r1 is the radius of core in metre

r2 is the radius of cable in metre

Calculation:

Given, I_FL = 7.5 A

According to IE Rule 48:

\({I_{lek}} = \frac{{{I_{FL}}}}{{5000}} = \frac{{7.5}}{{5000}} = 0.0015\;A\)

∴\(IR = \frac{{supply\;voltage}}{{{I_{lekage}}}} = \frac{{240}}{{0.0015}} = 160,\;000 = 0.16\;M{\rm{\Omega }}\)