Exam Practice Questions And Correct

Substation Technician Certification Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a substation?
• Generate electricity
• Transform voltage levels
• Store electrical energy
• Convert AC to DC

Rationale: Substations primarily step up or step down voltage levels

to facilitate transmission and distribution.

• Which device protects transformers from overcurrent?
• Circuit breaker
• Relay 1 / 4

• Capacitor
• Disconnect switch

Rationale: Relays detect abnormal current conditions and trip

breakers to protect transformers.

• What type of transformer is commonly used in substations for high-

voltage transmission lines?

• Distribution transformer
• Power transformer
• Instrument transformer
• Isolation transformer

Rationale: Power transformers are designed to handle high voltages

and large loads in transmission systems.

• Which gas is commonly used in high-voltage circuit breakers?
• Oxygen
• Nitrogen
• SF6 (sulfur hexafluoride)
• Helium

Rationale: SF6 gas has excellent insulating properties and is widely

used in high-voltage switchgear.

• What is the function of a busbar in a substation?
• Store energy
• Distribute electrical power within the substation
• Measure voltage 2 / 4

• Convert AC to DC

Rationale: Busbars are conductive bars that carry and distribute

power between equipment.

• Which type of protection device isolates a faulted section of a

substation?

• Transformer
• Circuit breaker
• Capacitor bank
• Lightning arrester

Rationale: Circuit breakers interrupt current flow during faults to

protect equipment.

• What does a PT (Potential Transformer) do?
• Step up voltage
• Step down current
• Step down voltage for metering
• Store electrical energy

Rationale: PTs reduce high voltage to a lower level suitable for

instruments and relays.

8. A CT (Current Transformer) is used to:

• Step up voltage
• Step down voltage
• Step down current for measurement and protection
• Store energy 3 / 4

Rationale: CTs provide a scaled-down current for meters and

protective relays.

• Which component protects substation equipment from lightning

surges?

• Circuit breaker
• Transformer
• Lightning arrester
• Isolator

Rationale: Lightning arresters divert high-voltage surges to ground

to protect equipment.

• Which relay operates when current exceeds a preset value?
• Overvoltage relay
• Overcurrent relay
• Distance relay
• Differential relay

Rationale: Overcurrent relays detect excessive current and initiate

breaker operation.

• What is the main purpose of grounding in a substation?
• Store energy
• Insulate equipment
• Protect personnel and equipment from electrical faults
• Measure voltage
• / 4