What Is a Watt-Hour Meter?
A watt-hour meter is an electrical device used to measure the amount of electricity consumed.
By measuring the electricity usage in factories and residences, it helps calculate individual customers’ electricity rates. A watt-hour meter consists of an ammeter and a voltmeter, whose readings are multiplied to calculate the electricity consumed.
Watt-hour meters objectively measure electricity consumption, thus preventing billing disputes and fraud between consumers and electricity suppliers. Their use increases the transparency and reliability of electricity billing.
They also enable regular data collection, aiding in identifying electricity usage patterns and trends. This facilitates monitoring and management of electricity consumption, enabling efficient energy management and demand forecasting.
Uses of Watt-Hour Meters
Watt-hour meters are used in various settings where electricity is consumed. They are commonly installed in the following locations:
1. General Households
In general households, watt-hour meters measure electricity usage. They help monitor household electricity consumption and assist in managing electricity bills. They are also used with private power generation systems, such as solar panels, to measure the electricity generated and consumed.
2. Commercial and Office Buildings
In commercial and office buildings, these meters are used for energy management and monitoring electricity usage. They serve as indicators for implementing energy conservation measures.
3. Manufacturing Industry
In the manufacturing industry, watt-hour meters are used to monitor the electricity consumption of production equipment. This aids in improving efficiency and energy management, reducing production costs and environmental impact.
Principle of Watt-Hour Meters
All watt-hour meters calculate electricity usage based on current and voltage measurements. The current is measured by a current transformer or similar device within the meter, while the voltage is measured by an instrument transformer or similar. These sensors detect fluctuations in current and voltage and output analog signals.
The meters accumulate data on the measured currents and voltages at regular intervals. Current and voltage are measured as instantaneous values but can be integrated over time to determine total electricity consumption.
Types of Watt-Hour Meters
There are several types of watt-hour meters, including:
1. Induction Disc Type
This type of meter consists of a current coil, a voltage coil, an aluminum disc, and a measuring device. Electromagnetic induction generated by the current coil connected to the load causes the aluminum disc to rotate for measurement.
2. Electronic Type
The electronic watt-hour meter uses an internal electronic circuit to measure current and voltage and calculate electricity usage. Compared to the induction disc type, it has fewer mechanical components and thus a lower risk of breakdowns, allowing for longer operation without issues.
3. Smart Meters
Smart meters are advanced watt-hour meters with enhanced functions and communication capabilities. Equipped with communication features, they can transmit electricity data remotely. The digital display of electricity usage can promote energy conservation awareness. Smart meters, integral to Japan’s policy of widespread adoption, do not incur meter replacement costs for households. However, concerns about privacy and the potential inference of personal information from electricity data have been raised.
Other Information on Watt-Hour Meters
Expiry Date of Watt-Hour Meters
Watt-hour meters used in trade have an expiry date set by the Measurement Act: 10 years for stand-alone meters and 7 or 5 years for transformer-connected meters. Trading with expired meters incurs penalties under the Measurement Act. Utility companies, responsible for meter installation, typically attach a sticker indicating the expiry date to the meter.