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The correct answer is option 4): (Rust)

Concept:

• Cathodic protection (CP) is a method used to resist the corrosion (forming rust) of a metal surface by making it the cathodic side of an electrochemical cell.
• The main purpose of cathodic protection is to protect steel structures buried in soil or immersed in water which have higher chances of being affected by rust.
• The technique of providing cathodic protection to steel preserves the metal by providing a highly active metal that can act as an anode and provide free electrons. By introducing these free electrons, the active metal sacrifices its ions and keeps the less active steel from corrosion.

The correct answer  is option 4):(STATCOM)

Concept:

• The term FACTS stands for flexible AC Transmission systems

• By the usage of the series and shunt compensation, the fact devices are utilized to  increase power transfer capability, stability, and controllability of the power system

• STATCOM stands for static synchronous compensator

• A static synchronous compensator is a shunt-connected FACTS device that is used primarily for reactive power control

• The STATCOM capability is similar to that of a rotating synchronous condenser or static VAR compensator (SVC) which controls reactive power for voltage support.

• STATCOM is a voltage source converter (VSC)-based device, with the voltage source behind a reactor. The voltage source is created from a DC capacitor and therefore a STATCOM has very little active power capability.

• The reactive power at the terminals of the STATCOM depends on the amplitude of the voltage source.

• If the terminal voltage of the VSC is higher than the AC voltage at the point of connection, the STATCOM generates a reactive current.

• On the other hand, when the amplitude of the voltage source is lower than the AC voltage, it absorbs reactive power.

Correct option 2

Concept:

Suspension type insulator

Definition: A suspension-type insulator protects an over headed transmission line like a conductor. Generally, it is made up of porcelain material that includes a single or a string of insulating discs hung over a tower. It operates at above 33KV and overcomes the limitation of pin-type insulators like the following.

1. Its size and weight increase above 33KV
2. It is difficult to handle and replace a unit insulator
3. The replacement of a damaged insulator is costly

Properties of Insulator Material

The following are the properties of any insulating material they are,

1. They should be mechanically strong.
2. The dielectric strength of the material should withstand high-voltage stress
3. The electrical insulating resistance should be high.
4. The material should be free from impurities, have no cracks, and be non-porous
5. The physical properties and electrical properties of an insulator should not be affected due to changes in the environment

Suspension Insulator Construction and Working :

It consists of two main parts

1. they are the cross-arms and the insulators (also called disc insulators) with a number of metallic links.
2. A suspension insulator or suspension string is developed by connecting a number of insulators in series with the help of metallic links, where the conductor is suspended by the bottom-most insulator and the top end of the insulator is secured by cross-arms 

The correct answer is option 4): (Schottky diode)

Concept:

• The Reverse recovery time is the amount of time the current flows in the reverse direction when the forward current instantaneously switches directions due to residual stored charge.
• Schottky diodes are used for their low turn-on voltage, fast recovery time and low-loss energy at higher frequencies. These characteristics make Schottky diodes capable of rectifying a current by facilitating a quick transition from conducting to blocking state
• Because the Schottky diode is a majority carrier device. At forward bias, there is no diffusion capacitance, which makes the Schottky diode a higher-frequency device than the PN junction diode.
• At reversed bias, there is no minority carrier stored charge, which makes the switching process: forward bias to reverse bias or reverse bias to forward bias), very fast.
• Since there is no minority carrier storage time, the reverse recovery time is nearly zero in the Schottky diode.

The correct answer is option 1): (voltage regulation)

Concept:

• The Zener diode is a semi-conductor diode which is specifically designed for operating at the reverse biased condition

• Zener Diodes can be used to produce a stabilised voltage output with low ripple under varying load current conditions

• It is used to regulate the voltage level. It generates a fixed output voltage that remains constant for any changes in load conditions or input voltage, i.e. it regulates or maintains a constant dc output voltage in spite of the fluctuations in ac input voltage or load current.

• The circuit diagram of the Zener diode as voltage regulator is drawn as

• It is a PN junction (silicon PN junction) diode and has a low specified reverse voltage which takes advantage of any reverse voltage applied to it.

• Unlike a normal diode (Schottky diode, varactor diode, tunnel diode) that blocks any flow of current through itself when reverse biased. From the I-V characteristics curve above voltage across the diode in the breakdown, the region is almost constant.

• In the breakdown region, it can be used as a voltage regulator application.

The correct answer is option 4):(to provide insulating and cooling)

Concept:

• The oil in the transformer is used for insulation and cooling purposes
• Transformer oil is used in oil-filled electrical power transformers to insulate, stop arcing and corona discharge, and dissipate the heat of the transformer
• The transformer is wholly immersed in the oil
• Transformer oil is also used to preserve the transformer’s core and windings
• The insulating oil has the ability to prevent oxidation of the cellulose-made paper insulation.
• The transformer tank shown as

The correct answer is option 1):(zero)

Concept:

A balanced three-phase voltage or current is one in which the size of each phase is the same, and the phase angles of the three phases differ from each other by 120 degrees.

A balanced three-phase network is one in which the impedances in the three phases are identical.

Positive sequence component:

It represents three equal phasors with a phase displacement of 120° and has a phase sequence the same as the original phasors. It specifies that the current is flowing through the source to load.

Negative sequence component:

It represents three equal phasors with a phase displacement of 120° with each other and has a phase sequence opposite to that of the original phasors. It specifies that current is flowing from load to source.

Zero sequence component:

It represents three equal and parallel phasors with zero phase displacement. It specifies that current is flowing from source to ground. In a balanced three-phase system operating in normal conditions, only a positive sequence component exists and hence zero sequence currents are zero.

The correct answer is option 2

Concept:

Service lines:

The overhead line or U.G cable connecting the supplier's distributing line to the consumer's premises is called service mains or service connection or service line.

Feeder:

• A feeder is a conductor which connects the sub-station or local generating station to the area where the power is distributed.
• Generally, no tapping is taken from the feeder, so the current is remain same throughout.
• The main consideration in the design of a feeder is current-carrying capacity.

Distributor:

A distributor is a conductor from which tapping is taken for supply to the consumer. While designing the distributor, voltage drop along its length is the main consideration.

Concept:

In series, resistance and voltage get added while in parallel, resistance and voltage remain the same.

In series, no. of batteries connected = 5

E = 5 × 1.5 = 7.5V

R = 0.2 × 5 = 1 Ω

\({V-7.5\over 1}+{V-7.5\over 1}+{V-7.5\over 1}+{V-7.5\over 1}=0\)

V = 7.5

The correct answer is option 3): (180°)

Concept:

• An ideal transformer is a theoretical model of a transformer with no energy losses in it
• The advantages of the ideal transformer include the following.
• There are no losses like hysteresis, eddy, and copper.
• Voltage & current ratios are perfectly based on the twists of the coil.
• There is no flux leakage.
• It doesn't depend on the frequency
• the phase difference between primary voltage and secondary voltage is i180 degrees in the case of an ideal transformer.
• In a practical transformer, it deviates away from 180 degrees.
• At full load, the deviation is negligible. At lower loads, the deviation is more.