Primary metering requires which types of transformers?

Primary metering involves measuring the electrical parameters of a power system at or near the distribution or transmission level. To accomplish this effectively, two types of transformers are essential: potential transformers and current transformers.

Potential transformers are used to step down high voltages to a lower, manageable level that can be safely measured by metering equipment. This is crucial because the operating voltage in primary metering scenarios can be extremely high, and direct measurement would be unsafe and impractical.

Current transformers, on the other hand, are used to reduce high currents to a lower value that can also be safely measured. They provide a scaled-down representation of the current flow, allowing for accurate measurement and monitoring.

Together, potential and current transformers give a complete picture of the power being handled in the system, enabling effective metering, control, and management of electrical energy distribution.

The other choices do not fully capture the necessary components for primary metering. For example, while step-up transformers can raise voltages, they are not typically used in metering applications where reducing and measuring voltage and current is the priority.