Primary metering in electrical circuits requires which types of transformers?

Primary metering in electrical circuits effectively relies on current transformers (CTs) and potential transformers (PTs). Current transformers are used to measure the flow of electric current in a circuit, allowing for the safe conversion of high currents into a lower, measurable amount without disrupting the primary circuit. This is critical for accurate measurements and for protecting equipment and personnel from high voltage levels.

Potential transformers, on the other hand, are utilized to step down high voltage levels to safer, measurable levels. They ensure that the voltage measurement taken by the metering system is accurate and manageable, which is essential for monitoring and controlling the electrical system.

Using both CTs and PTs in combination allows for comprehensive monitoring of electrical parameters in primary metering applications. This enables system operators to ensure that the system is operating efficiently and safely while facilitating billing and operational analysis based on the measured values. The other option combinations listed do not correspond to the types of transformers that would be used for primary metering in electrical circuits.