What device steps down transmission voltage to distribution voltage?

What device steps down transmission voltage to distribution voltage?

• A. Recloser
• B. Substation transformer
• C. Distribution panel
• D. Circuit breaker

Answer: (B)

Transformers in substations change voltage levels between transmission and distribution networks. The device that lowers high transmission voltage to distribution voltage is the substation transformer, which uses turns ratio to step the voltage down while delivering the needed current to feeders. This works because a transformer transfers energy magnetically between windings: the high-voltage side (primary) provides the input, and the lower-voltage side (secondary) supplies the distribution feeders. Transmission lines carry power at very high voltages to minimize losses, and the substation transformer brings that voltage down to distribution levels for local delivery. After this, further step-down can occur locally for customer voltages, but the key device at the substation is the transformer. The other options serve protective or distribution roles rather than changing voltage levels. A recloser automatically restores service after interruptions but does not change voltage. A circuit breaker interrupts current to protect equipment, not to convert voltage. A distribution panel routes power to loads and provides protection, but it does not step high transmission voltage down to distribution voltage.

Transformers in substations change voltage levels between transmission and distribution networks. The device that lowers high transmission voltage to distribution voltage is the substation transformer, which uses turns ratio to step the voltage down while delivering the needed current to feeders.

This works because a transformer transfers energy magnetically between windings: the high-voltage side (primary) provides the input, and the lower-voltage side (secondary) supplies the distribution feeders. Transmission lines carry power at very high voltages to minimize losses, and the substation transformer brings that voltage down to distribution levels for local delivery. After this, further step-down can occur locally for customer voltages, but the key device at the substation is the transformer.

The other options serve protective or distribution roles rather than changing voltage levels. A recloser automatically restores service after interruptions but does not change voltage. A circuit breaker interrupts current to protect equipment, not to convert voltage. A distribution panel routes power to loads and provides protection, but it does not step high transmission voltage down to distribution voltage.