What is the main function of a lightning arrester in a power system?
B
To store electrical energy
C
To protect equipment from high voltage surges
D
To regulate voltage under normal conditions
Analysis & Theory
Lightning arresters protect electrical equipment by diverting high-voltage surge currents safely to the ground.
Where is a lightning arrester typically installed in a power system?
A
Inside the transformer winding
B
Between circuit breaker contacts
C
At the entry points of substations and near transformers
D
At the neutral point of the generator
Analysis & Theory
Lightning arresters are installed near equipment entry points to prevent surge voltages from entering the system.
What type of surge is a lightning arrester primarily designed to handle?
C
Lightning-induced voltage surges
Analysis & Theory
Lightning arresters are designed to protect against lightning-induced voltage surges.
Which of the following materials is commonly used in modern lightning arresters?
Analysis & Theory
Zinc oxide is used in metal-oxide varistor (MOV) type lightning arresters due to its excellent non-linear voltage-current characteristics.
How does a metal-oxide lightning arrester behave under normal operating conditions?
A
Acts like a closed circuit
B
Acts like an open circuit with high resistance
D
Heats up and trips the system
Analysis & Theory
Under normal voltage, metal-oxide arresters offer high resistance and do not conduct. They conduct only when a surge occurs.
What happens when a voltage surge exceeds the rated capacity of a lightning arrester?
B
The surge is allowed to pass through the system
C
The arrester conducts and diverts the surge to ground
D
The arrester switches off the system
Analysis & Theory
When a surge exceeds a certain level, the arrester becomes conductive and safely directs the surge to the earth.
Which of the following is an important parameter in selecting a lightning arrester?
A
Short-circuit current rating
C
Breakdown voltage or discharge voltage
Analysis & Theory
The breakdown or discharge voltage determines when the arrester will conduct and protect the system.
Lightning arresters are usually connected between:
Analysis & Theory
Lightning arresters are connected between the phase (line) and earth to safely discharge surges.
What is the role of the ground connection in a lightning arrester?
B
To stabilize system frequency
C
To provide a low-resistance path for surge current
Analysis & Theory
The ground provides a low-resistance path for surge currents to flow away safely from equipment.
Which of the following problems can occur if a lightning arrester is not grounded properly?
A
Improved voltage regulation
C
Failure to protect equipment from surges
D
Increase in system power factor
Analysis & Theory
Without proper grounding, the surge current will not be safely diverted, causing equipment damage.