Electrical Engineering: Surge and Lightning Arresters

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What is the main function of the horn gap arrester?

To ionize the air during a voltage rise
To eliminate the need for grounding
To provide a physical barrier against lightning
To allow fault current to pass through a small air gap (correct)

Which arrester operates based on the principles of an electrolytic cell?

Horn Gap Arrester
Metal Oxide Lightning Arrester
Thyrite Lightning Arrester
Electrolytic Arrester (correct)

What material is the base of the metal oxide lightning arrester?

Copper
Aluminium
Steel
Zinc (correct)

What must be done to minimize the soil resistivity when installing lightning arresters?

Add minerals or a backfill compound (A) Signup and view all the answers

What distinguishes the surge arrester from the lightning arrester?

The lightning arrester primarily protects from outside surges (C) Signup and view all the answers

What is defined as an increase in voltage for a very short time in a power system?

Voltage surge (C), Voltage transient (D) Signup and view all the answers

Which of the following is NOT a cause of external over voltage?

Voltage regulation failure (A) Signup and view all the answers

What potential difference is necessary for a lightning flash to occur between clouds and the ground?

5 to 20 million volts (A) Signup and view all the answers

Transient over voltages can be generated at which of the following frequencies?

High, medium, and low frequency (B) Signup and view all the answers

Which type of lightning stroke is characterized by a direct hit?

Direct lightning stroke (A) Signup and view all the answers

Which of these is a common internal cause of over voltage?

Load switching (D) Signup and view all the answers

What type of over voltages arise from atmospheric disturbances primarily due to lightning?

External over voltages (A) Signup and view all the answers

Electrostatic induced over voltages can occur due to which of the following phenomena?

Presence of charged clouds (D) Signup and view all the answers

What is the primary cause of switching over voltages in a power system?

Faults in the network (D) Signup and view all the answers

Which voltage surge is caused when a no load transmission line is suddenly switched on?

Switching impulse (D) Signup and view all the answers

What effect does a Ferranti effect have on a long unloaded power line?

Increases the voltage at the receiving end (B) Signup and view all the answers

What is a likely consequence of frequent over voltages occurring in a power system?

Damage to electrical equipment (C) Signup and view all the answers

What is identified as a transient voltage or voltage surge in a power system?

Sudden increase in voltage to a high peak (C) Signup and view all the answers

Which overvoltage protection method is commonly used over electrical substations?

Earthing screen (A) Signup and view all the answers

During which operation is over voltage due to current chopping most likely to occur?

Switching off a loaded line (A) Signup and view all the answers

What type of overvoltage is most likely to cause substantial damage in a power system?

Lightning impulse overvoltage (A) Signup and view all the answers

What characterizes the transient nature of voltage surges?

Existence for a very short duration (C) Signup and view all the answers

Why is it important to have protection against abnormal over voltages in a power system?

To eliminate risk of equipment damage (A) Signup and view all the answers

What is the primary function of an overhead earth wire in electrical transmission networks?

To divert lightning strokes to the ground (C) Signup and view all the answers

How does a lightning arrester function during an overvoltage event?

It offers a low impedance path for excess charge to ground (C) Signup and view all the answers

What is a key goal of insulation coordination in electrical power systems?

To localize insulation failures to easily repairable components (A) Signup and view all the answers

What type of lightning arrester is currently most commonly used for overvoltage protection?

Gapless ZnO lightning arrester (B) Signup and view all the answers

Which of the following best describes the term 'Nominal System Voltage'?

The phase to phase voltage for equipment design (A) Signup and view all the answers

What is the primary function of an overhead ground wire?

To intercept and conduct lightning strikes (B) Signup and view all the answers

Which material is commonly used for overhead ground wires due to its lightweight and corrosion resistance?

Aluminium (B) Signup and view all the answers

Why are ground wires placed as the topmost conductor in high voltage transmission lines?

To provide protection against lightning strokes (D) Signup and view all the answers

What is the purpose of grounding the overhead ground wire at substations?

To dissipate lightning energy safely into the ground (C) Signup and view all the answers

What action does a lightning arrester take under normal voltage conditions?

It functions as an electrical insulator (A) Signup and view all the answers

What is a critical angle for the effective shielding of line conductors by ground wires?

30° (B) Signup and view all the answers

What key property must an overhead ground wire possess to minimize voltage stress on phase conductors during a lightning event?

Sufficient conductivity (D) Signup and view all the answers

Which of the following describes the behavior of a lightning arrester when voltage levels rise?

Resistance decreases with voltage (D) Signup and view all the answers

What is the role of the corona ring installed on an overhead ground wire?

To reduce radio interference and corona discharge (C) Signup and view all the answers

What is a characteristic of overhead ground wires in relation to lightning strikes?

They provide multiple pathways to the ground for lightning strokes (D) Signup and view all the answers

Which of the following types of lightning arresters involves a gap between the ends of two rods?

Rod Gap Arrester (B) Signup and view all the answers

What does the spacing between the overhead ground wire and phase conductors ensure?

Provides necessary clearance to prevent flashover (B) Signup and view all the answers

In a lightning arrester, what mechanism is used to discharge high voltage through the ionization of air?

Corona discharge (A) Signup and view all the answers

What does the proper installation of overhead ground wires contribute to in power transmission systems?

Enhanced reliability and safety (D) Signup and view all the answers

What aspect is NOT considered when determining the size of an overhead ground wire?

Seasonal weather patterns (D) Signup and view all the answers

Over Voltage

A temporary increase in voltage in a power system.

External Overvoltage Cause

Overvoltage caused by atmospheric events, primarily lightning.