Q1. Which symbol represents a Circuit Breaker (CB) in substation single line diagrams?
A. Two parallel lines
B. A break with operating mechanism
C. Zig-zag line
D. Coil symbol
Answer: B. A break with operating mechanism
Explanation: In SLDs, a circuit breaker is shown as a break in the conductor with an operating mechanism to indicate switching under load and fault conditions.
Q2. The symbol of an Isolator (Disconnector) is represented by:
A. Automatic switching device
B. Open switch without arc quenching
C. Coil with contacts
D. Fuse link
Answer: B. Open switch without arc quenching
Explanation: An isolator symbol shows a visible open gap and is used only when the circuit is not carrying load.
Q3. Which symbol is used for a Current Transformer (CT)?
A. Two concentric circles
B. Single circle
C. Triangle
D. Rectangle
Answer: A. Two concentric circles
Explanation: CTs are commonly shown by two concentric circles around the conductor in single line diagrams.
Q4. The symbol of a Potential Transformer (PT or VT) is shown as:
A. Two concentric circles
B. Coil connected to ground
C. Small transformer symbol connected across line
D. Fuse symbol
Answer: C. Small transformer symbol connected across line
Explanation: PTs are connected in parallel with the line to measure voltage, hence shown across the line.
Q5. Which symbol indicates a Lightning Arrester (LA)?
A. Fuse symbol
B. Zig-zag line connected to earth
C. Coil
D. Capacitor symbol
Answer: B. Zig-zag line connected to earth
Explanation: Lightning arresters divert surge voltages to earth, so their symbol includes a zig-zag path connected to ground.
Q6. The Earth (Ground) symbol in substation diagrams is:
A. Single straight line
B. Triangle
C. Three horizontal lines of decreasing length
D. Circle
Answer: C. Three horizontal lines of decreasing length
Explanation: The standard earth symbol consists of three horizontal lines indicating grounding.
Q7. Which symbol represents a Power Transformer?
A. Two parallel lines
B. Two coils separated by core
C. Zig-zag line
D. Fuse symbol
Answer: B. Two coils separated by core
Explanation: Power transformers are represented by two windings separated by a magnetic core.
Q8. The symbol of a Busbar is represented by:
A. Thin broken line
B. Thick straight line
C. Zig-zag line
D. Circle
Answer: B. Thick straight line
Explanation: Busbars carry high current and are shown as thick straight lines in substation diagrams.
Q9. Which symbol is used for a Fuse?
A. Rectangle
B. Small zig-zag or thin line
C. Coil
D. Two circles
Answer: B. Small zig-zag or thin line
Explanation: Fuse symbols represent a weak link that melts under excess current.
Q10. Which equipment symbol is used for Shunt Capacitor Bank?
A. Coil symbol
B. Parallel plate symbol
C. Zig-zag symbol
D. Triangle
Answer: B. Parallel plate symbol
Explanation: Capacitors are shown by two parallel plates and are used for power factor improvement.
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