By 2020 as many as 78 million electricity smart meters will need to use AC latching and power relays to manage the supply and measurement of electricity to the user, writes Steve Drumm
Manufacturers are working to improve the efficiency of relays where the key characteristics of switching capacity, switching endurance, coil type, load isolation and physical construction can have a notable impact on the overall energy efficiency.
Smart meters typically require control relays to manage the supply of electricity. Utility companies will want to control the ability to connect or disconnect the AC supply to the smart meter by PLC or by wireless M2M communication such as SMS, GSM or LW.
A latching, single pole electro-mechanical relay with a maximum current rating of up to 120A at 250V AC would meet the needs of a smart meter employed in a commercial, residential or light industrial environment.
Local energy management
Switching relays will play a central role of efficient energy management in the smart meter, ensuring that all of, or part of the system is fully powered down and consuming no energy when not in use. For local load switching and time of use functions, a latching relay is required, as it will stay in the ‘on’ position even when the supply is disconnected, so that power is restored immediately and automatically on reconnection.
Some relay manufacturers are extending their latching relay offerings to address this, reducing the profile of their latching relay devices and offering devices capable of handling the potentially high inrush currents. Silent versions are also desirable where meters are installed in cupboards of small flats, for example.
Local load control
Ripple Control (RC) or local load control is a technology used to control and provide quick and direct influence on the network load without any network limitations. Tariff switching and monthly demand reset can be implemented along with the control of storage and direct control heaters.
Ripple control receivers can be implemented directly within the smart electricity meter. The RC receiver will respond to RC control signals transmitted on the electricity grid by a load control centre.
Relay developments for domestic ripple control receivers include the use of silver-tin-indium (Ag-Sn-In) contacts, which can deliver double the standard switching performance.
The smart meter will also need to ensure tamper proof operation. If the meter is subject to tampering this must be detected and acted upon. The meter should have the ability to safely and securely disconnect the AC supply.
To provide the necessary anti-tamper detection, designs can use sub-miniature switches which incorporate roller or hinge lever and pin plunger actuators which are ideal for detecting unauthorised opening.
The design and implementation of smart meters and new energy management systems needs to provide tangible benefits that will reduce energy consumption and give cost savings. They can also give the user greater control and knowledge of their energy consumption. The systems and component technology is available to produce smart energy management systems and smart meters.
Steve Drumm, market development manager at Omron Electronic Components Europe