The current transformer (CT) is an important component in electrical metering, providing a high-accurate way to measure the current that passes through the circuit. A CT has primary and secondary windings (multiple turns of wire around an iron core). The voltage drop across the secondary is proportional to the current passing through the primary. CTs come in a wide variety of forms and sizes, each designed to handle specific electrical applications. For example, window-type CTs have a split-core design and can be easily installed around an existing conductor. Bar-type CTs have a cylindrical shape and are often used in low-current applications. Rogowski CTs have a flexible coil that can wrap around a conductor, making them well-suited for use in irregularly-shaped conduits.

The CT is connected to a meter, which measures the number of kilowatt hours of electricity that has been consumed. Traditionally, a mechanical disk or dials were used to display the reading. Modern electric meters may also feature a digital LCD screen or a small LED display. These displays provide a much more convenient and accurate representation of energy usage, making them ideal for residential use.

Electricity meters can be installed either outdoors or in a meter box inside the customer’s premises. They can be single phase or three-phase and may or may not include a transformer to step down the voltage from higher utility lines. Single phase meters are often used for residential and small commercial customers, while three-phase meters are more commonly found in larger industrial installations.

The main components of an electricity meter are the power supply, the metering engine and the processing and communication engines. The metering engine receives inputs from the power supply, samplers and quantisers, then converts these to digitised values. The processing and communication engine is responsible for calculating the various metering parameters based on these digital values. It is also capable of communicating using a variety of protocols with other addon modules that are connected as slaves to it.

Another important function of the metering engine is to manage the logging process, which records the amount of electricity that has been used. These logs can then be accessed by the electric company to verify that no illegal activity has taken place and to determine if a consumer is overusing the power supply.

In many countries, a single electricity meter can be used to measure both the consumption of power by a consumer and their energy production from solar panels or other renewable sources. The meter may also supply contact closures to KYZ outputs which can be attached to a totaliser relay that feeds a power grid monitoring system or to programmable logic controllers for demand side management.

A prepayment meter is an electronic device that allows customers to pay for their electricity before the start of their monthly billing cycle. It is commonly used in homes, businesses and commercial establishments to improve electricity efficiency. It also helps reduce fraud and theft since it provides a clear record of the exact amount of energy that is being consumed by the user.