Ohio Substation Technician Exam

Ohio Substation Technician Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2025|2026 Q&A | Instant Download Pdf

• What is the primary purpose of a substation?
• To generate electrical power
• To step up or step down voltage levels for transmission and distribution
• To store electrical energy
• To measure electrical loads

Rationale: Substations adjust voltage levels between transmission and

distribution systems to ensure efficient power delivery.

• Which type of transformer is commonly used in substations to measure

current?

• Power transformer
• Current transformer
• Potential transformer 1 / 4

• Step-up transformer

Rationale: Current transformers reduce high currents to a measurable level

for metering and protection.

• What is the main function of a circuit breaker in a substation?
• To increase voltage
• To reduce harmonics
• To interrupt fault currents
• To stabilize frequency

Rationale: Circuit breakers protect systems by interrupting abnormal or

fault currents.

• What is used to ground substation equipment?
• Aluminum rods
• Plastic conduits
• Copper grounding grid
• Steel beams

Rationale: Copper grounding grids provide low-resistance paths for fault

currents and ensure safety.

• Which gas is commonly used in high-voltage circuit breakers?
• Oxygen
• Nitrogen
• SF6 (sulfur hexafluoride)
• Argon 2 / 4

Rationale: SF6 gas has excellent insulating and arc-quenching properties,

making it ideal for high-voltage use.

• What is the typical frequency of power systems in the United States?
• 60 Hz
• 60 Hz
• 50 Hz
• 100 Hz

Rationale: The U.S. electrical grid operates at a standard frequency of 60

hertz.

• Which device protects equipment from lightning surges?
• Circuit breaker
• Transformer
• Lightning arrester
• Ground switch

Rationale: Lightning arresters divert high-voltage surges safely to ground.

• What type of current is transmitted through power lines?
• Direct current
• Alternating current
• Pulsed current
• Filtered current

Rationale: Alternating current is used for efficient long-distance

transmission and easy voltage transformation. 3 / 4

• Which unit measures electrical power?
• Volt
• Ampere
• Watt
• Ohm

Rationale: Electrical power is measured in watts (W), derived from volts ×

amps.

• What is the function of a potential transformer?
• Measure current
• Reduce high voltage for metering
• Increase low voltage
• Store energy

Rationale: Potential transformers reduce high voltages to safe, measurable

levels for meters and relays.

• What is the most common substation voltage class for distribution?
• 13.8 kV
• 13.8 kV
• 230 kV
• 500 kV

Rationale: 13.8 kV is a standard distribution-level voltage used across

many utility networks.

• / 4