What is an Watt Hour Meter?

What is an Watt Hour Meter?

Watt-Hour Meter Definition

A watt-hour meter is defined as a device that measures and records the electrical power passing through a circuit over a period of time.

Tampering and Security

A common tampering method involves attaching a magnet to the outside of old energy meters. Using capacitance and inductive loads can also reduce the rotor speed.

The most modern meter can store up the previous value with time and date. So the tampering is avoided. Utilities install remote reporting meters to detect tampering.

Types of Watt Hour Meter

Electromechanical Type Induction Meter

A non-magnetic and electrically conductive aluminum metal disc is made to revolve in a magnetic field in this type of meter. The rotation is made possible with the power passing through it. The rotation speed is proportional to the power flow through the meter.

Gear trains and counter mechanisms are incorporated to integrate this power. This meter works by counting the total number of revolutions, and it is relative to the usage of energy.

A series magnet is connected in series with the line, which comprises a coil of few turns with thick wire. A shunt magnet is connected in shunt with the supply and comprises a large number of turns with thin wire.

A braking magnet, a permanent magnet, is included for stopping the disc at the time of power failure and placing the disc in position. This is done by applying a force opposite to the rotation of the disc.

A flux is produced by the series magnet that is directly proportional to the current flow, and the shunt magnet corresponding produces another flux to the voltage. Because of the inductive nature, these two fluxes lag each other by 90o.

An eddy current is developed in the disc, which is the interface of the two fields. A force corresponding produces this current to the product of instantaneous current, voltage, and phase angle.

A break torque is developed on the disc by the braking magnet positioned over one side of the disc. The speed of the disc becomes constant when the following condition is achieved, Braking torque = Driving torque.

The gear arrangement linked with the shaft of the disc is implemented for recording the number of revolutions. This is for single-phase AC measurement. An additional number of coils can be implemented for different phase configurations.

Electronic Energy Meter

The major feature of the electronic meter other than power usage measurement is that it can display the energy usage on a LED or LCD. In some advanced meters, the readings can be transmitted to remote areas.

It can also record the amount of usable energy in on-peak hours and off-peak hours. In addition, this meter can record the parameters of supply and load like voltages, reactive power used, the instantaneous rate of usage demand, power factor, maximum demand, etc.

Smart Energy Meter

In this type of meter, communication in both directions (Utility to the customer and customer to the utility) is possible.

Customer to utility communication includes parameter values, consumption of energy, alarms, etc. The utility to consumer communication includes disconnect/reconnect instructions, automatic meter reading system, upgrading of the software of the meter, etc.

Modems are implemented in this meter to make communications easy. The communication system includes fiber cable, power line communication, wireless, telephone, etc.

Advantages of Different Types of Watt Hour Meter