There are three operating technologies used in electric meters. Historically, induction meters were the standard, but in recent years there have been increasing installations of advanced hybrid and solid state meters. According to data from the U.S. Energy Information Administration (EIA), by the end of 2018 only 17% of the meters in the U.S. were still induction meters. Around the world meter standards differ by country. Some countries such as Italy and Sweden have standardized on solid state meters while others such as Brazil, China, Germany, and Mexico only began widespread implementation of advanced meters in 2019. Consultant Wood Mackenzie estimated that the number of advanced meters in the world will double from 665 million to 1.2 billion between 2017 and 2024.
An induction meter employs the oldest technology, simply a mechanical meter with a rotating disk. The faster the disk rotates, the more power that is being consumed. In actuality, the meter is a small electric motor whose spins are proportional to the amount of electricity flowing through it.
The meter includes a mechanism that counts the disk revolutions, or the number of times the disk has rotated. This data is then displayed on a register that consists of dials that are turned by a gearing system. The gearing system converts the number of rotations to a number indicating the amount of energy, or kWh, that has flowed through the meter.
This technology has been used since the early part of the last century and has several advantages. It is a low-cost, known technology, and it is relatively accurate over a long period of time. The disadvantage of the induction meter is that the data that can be recorded is limited. Most induction meters register only kWh, and are limited to indicating how much energy has been used since the last time the meter was read. They do not tell when the power was used, the maximum demand, or other useful quantities. Some induction meters have been designed to allow for time-of-use billing by including a timer and a separate register that shows energy usage during a peak time period. But again, this data is limited when compared to other meter types.
Solid state meter
A solid state meter, commonly called a smart meter, is the newest revenue meter technology used in the electrical industry. These meters are completely electronic and have no moving parts to wear out. In essence they are small microprocessor-based electronic data recording and communications systems. Smart meters measure and quantify electrical pulses that are then stored in the meter’s memory. They have the ability to record, store, and retrieve large amounts of information such as electrical usage, demand, and other electrical quantities such as power factor (%), reactive power (kVAR), total power (kVA), and voltage. They can also record and track outages and other events. An onboard communications system using wired or wireless technology also provides the ability to either remotely read the data from the meter or stream the data in real time to other devices or systems. Some meters are also able to communicate with home area networks (HANs), building management systems, and load control devices. Utilities can remotely read solid state meters by connecting them to an automated meter reading (AMR) infrastructure.
The smart meter’s ability to correlate electrical usage with a time stamp provides useful information for both the customer and utility that the induction meter historically was not able to provide. If connected to an advanced metering infrastructure, the meter can directly report power outages to the utility and may also include a remote disconnect switch that allows the utility to connect or disconnect service without dispatching a crew to the site. Many utilities and meter manufacturers are working to develop new services enabled by smart meter technology such as market-based pricing, price-based demand response programs that offer customers credits or payments in return for curtailing power usage during high-price times, and the ability to remotely control and manage smart appliances behind the meter. The smart meter has allowed the convergence of revenue metering and information gathering in one device.
The primary advantages of smart meters include the ability to measure and record multiple quantities and large amounts of information plus the simplicity and ease of data retrieval. This includes the ability for utilities to implement automated meter reading and enable new services. The primary disadvantages of the solid-state meter to date include high initial capital costs and reduced reliability compared to induction meters. In addition, large voltage spikes and lightning transients can degrade the meter’s electronic components quickly resulting in metering failures and more frequent replacements than with the rugged induction meters. And even without degradation due to spikes or transients, the life of electronic components is much shorter than the mechanic components used in an induction meter.
A hybrid meter combines a mechanical meter with a solid-state register. Here’s how this works. A small electric motor connected to the rotating disk is interfaced with a pulse initiator to produce pulses that are stored in memory. This data can then be downloaded over a telecommunications system.
The advantage of this technology is that it combines the ruggedness of the induction meter with the data storage and remote communications capabilities of the solid state meter. While hybrid meters do cost more than induction meters, they cost less than a solid state meter.