Accurate measurements, easy communication and extra functionality.

The development of smart power grids, renewable energy sources or the growing popularity of electric cars are just some of the factors increasing interest in modern electricity meters. It is also a commonly used device, installed in residential and industrial buildings to settle accounts with energy suppliers, so it is worth knowing what the latest solutions in this area offer. The wide variety on the market means that designers should have no trouble finding the optimal device for their project.

Modern electricity meters

The main function of an electricity meter is to measure the energy used. The basic measurements include the current energy used, stated in watts, and the consumed energy, stated in kilowatt-hours. This primary task traditionally used to be performed by induction, or old-style meters. They consist of a round metal disc placed between two coils. The rotation of the disc is proportional to the instantaneous power used by the load point. These devices are still in use, but due to limited possibilities in terms of communication, additional functions or programming, they are giving way to their digital successors. For the new generation of meters, the measurement of the consumed energy is only the starting point for many new and interesting functionalities supporting the management of electricity consumption.

Digital meters do not contain any mechanical components, no meter reading is required, and additional functionalities allow the user to better manage energy consumption. These types of meters rely on electronic circuits that generate pulses at a frequency that is proportional to the current flow. This method of measurement is much more accurate than in the case of an induction meter. Another advantage of digital meters is the calculation and presentation of additional grid parameters such as active and reactive energy, frequency, voltage and current harmonics or active power. The result is not only presented on the display, but also automatically sent to the electrical energy distributor (especially in the latest models). The device can communicate using such standards as PLC (Power Line Communication), Wi-Fi, Bluetooth or GSM. Thanks to the communication with the energy supplier, the user can pay for the actual usage and not only in a lump sum or based on consumption forecasts. For the distributor, the benefits are also significant, as more accurate power consumption statistics allow for the continuous monitoring of energy demand and better management of the energy system, while constant monitoring of the meter status allows for immediate reaction in case of a failure or for remote upload of a new software version.

How to choose the right energy meter

At the outset, it should be noted that induction meters are practically no longer offered, and purchasing involves the need to make a choice among numerous models of digital meters with varying degrees of sophistication and functionality. First of all, the selection should begin with the basic parameters of current and type of electrical installation. With regard to the number of phases they can be connected to, meters can be divided into single-phase or three-phase devices. The former are mainly used in households with a low connection power (voltage up to 230V). Three-phase meters are dedicated for three- or four-wire grids, with a voltage up to 400V. These devices contain three meters in a single casing, each of which counts the consumption of a given phase, and the display presents the total result. Traditionally, three-phase meters were installed in industrial facilities, where due to the energy needs, three phases were used. Today, they are increasingly often used in residential buildings, where the use of induction hobs or air conditioning requires the connection of more power. The phases should usually be connected in the order indicated by the manufacturer, and modern smart meters signal this fact with a blinking diode or an appropriate message displayed on the screen in the case of incorrect installation.

When choosing a meter, you must also choose whether it is to carry out measurement in a direct or indirect mode. In the former case, the current circuits of the device are directly connected to the circuits of the measured installation, as well as the supply voltage. This solution is used for a low power demand. For higher power installations, appropriate voltage and current transformers are used.

Another important parameter is the meter accuracy class as defined by the Measuring Instruments Directive (MID), which replaced the previous requirements of IEC 62053-21. The current A, B and C accuracy classes correspond to the previous classes 2, 1 and 0.5. Class A applies primarily to municipal applications, while the higher class B applies to commercial and industrial consumers. Class C meters are required in some special, justified cases. If the meter is to be used for billing purposes, the meter must be checked for certification before purchase.

Many meters offer bidirectional measurement, which is especially dedicated to those clients that are producers of energy based on renewable energy sources – they count both the energy consumed by the customer and the energy returned to the grid.

Other aspects of choosing the meter relate to ergonomics and ease of installation. Casing dimensions, degree of protection against environmental factors, mounting method (on the panel or on a DIN rail) – all those features are described in the documentation provided by the manufacturer. It is worth paying attention to additional options such as the possibility to measure various electrical values, communication functions or software supplied.

Electricity meters offered by TME

Popularity of digital meters encouraged manufacturers to extend the functionality of these devices with the components unavailable in traditional induction-based solutions. Modern meters are equipped with digital communication interfaces, measurements of additional electrical values, rich configuration capabilities or a user-friendly interface. An example can be meters by Lumel, including NMID30-1 and NMID30-2 models. Both products are certified as compliant with the MID and enable the measurement of active energy consumed and returned with Class B accuracy in single- and three-phase grids. In addition, it is possible to measure 16 different values and present the result on a clear display. Among the measured electrical parameters are active and reactive energy, frequency, voltage and current harmonics and active power. All these functions allow for the continuous monitoring of energy consumption and grids status, and thanks to the use of Modbus RTU communication protocol, data can be easily sent to an external device. The main difference between the two models is the method of measurement. The NMID30-1 operates in an indirect mode and has three inputs of 1A or 5A nominal power to work with current transformers. The NMID30-2 is a meter for direct measurement, up to 100A. Model No.10 is a version designed for measurements in single-phase grids which provides the same high functionality with the added advantage of smaller casing dimensions.

Controlin GMBH meters

Modern electricity meters increasingly tend to look like small computers with many additional functions, an example of which is the SKD series, developed by Controlin GMBH. This series is dedicated to customers who, in addition to accurate energy measurement (bidirectional and MID-compliant), expect additional information about the status of the grid. The measured parameters include frequency, reactive power, active power, apparent power, AC voltage, AC current or power factor. Communication with external devices can be performed using the pulse output or Modbus protocol, which is becoming a standard in this class of devices. What distinguishes the SKD series on the market is undoubtedly the high quality backlit display. In the SKD-500-M model, beside the meter status, graphical elements showing the current load are also displayed, which facilitates quick assessment of the grid status.

Lovato Electricity meters at TME

Another manufacturer whose products are available at TME is Lovato Electric, who launched the DMED series of meters, including devices from single-phase meters for direct connection to a 40A line to three-phase modules able to work with currents of up to 10000A (through current transformers). All meters are MID-certified, making them suitable for use in financial billing. The strength of DMED series are rich metering and communication functions, and thanks to the included software the user is able to remotely monitor and configure the meters.

Astec meters

Another option is the PRO380 series by Astec. It is a series of modular meters for three-phase grids, with direct metering up to 100A or indirect metering via a current switch. This is an example of a device that, in addition to very accurate measurement of consumed and returned energy, MID-certified in class B accuracy, integrates a number of additional functionalities. The meter is able to measure more than 60 other parameters and, depending on the model, use pulse communication, Modbus or M-bus.

Algodue offer at TME

The UEC series from Algodue stands out for its large number of possible product versions, making it easy for the user to find the optimal meter for the target application. The meters in this family are available in single-phase or three-phase options, for direct and indirect measurements in grids with a maximum current of 6A, 40A and 80A. Communication with external control software can be performed according to Modbus, M-Bus or Ethernet standards. Each model is available in a MID-compliant version. Their common feature is the ability to measure a number of values simultaneously, and depending on the model the device can measure up to 30 different electrical parameters at the same time. Algodue provides dedicated software to improve the analysis of the collected data.

Simet meters at TME

Simet is a Polish supplier with more than 50 years of experience in manufacturing electrotechnical equipment. It is appreciated on both domestic and foreign markets. Simet offers the Simlic series of meters: LS1-F and LS3-F, which are respectively single-phase and three-phase digital meters with the possibility of mounting on a bus and with the option of connecting to a counting device. The series has been designed with user-friendliness in mind – the compact casing makes it easy to install, LEDs inform about the correct operation of the device, and the backlit screen ensures convenient reading. LS3-F model allows partial data reading to be reset, while of course retaining the full value of the energy consumed.

Electricity meters by Trumeter

AMP meter by Trumeter is a meter in which the manufacturer has combined ergonomics with high functionality. The device allows for measurement of more than ten different electrical parameters in single- and three-phase grids, and thanks to dedicated software the user has the possibility of extensive parametrisation of the meter, both in terms of electrical characteristics of the grid, as well as configurable alarms signalling anomalies in the operation of the grid. The large, easy to read display attracts attention, it can be backlit in three different colours, including red in the case of an alarm.

Carlo Gavazzi – electricity meter

EM330 and EM340 from the offer of Carlo Gavazzi are three-phase DIN rail-mounted electronic meters, operating in the accuracy class B, adjusted for current measurement in the range of 6A and 65A respectively. Both models have a backlit display with touch keyboard. Users can read the consumed energy and a number of other parameters. Apart from the pulse output, communication can be carried out in Modbus and M-Bus standards. The meters are characterised by high resistance to difficult environmental conditions, overvoltage and network disturbances.

Selec meters

Selec is an experienced supplier of electricity measuring equipment, known for its commitment to precision and quality workmanship. You can see this clearly in the EM368 series, which includes a three-phase energy meter which can measure reactive, active and apparent power, enclosed in a neat casing. Communication in the MODBUS standard allows for data transmission over a distance of up to 500m. The company also offers single-phase meters with a similar functionality.

Electricity meters by Gossen Metrawatt

Meters by Gossen Metrawatt are designed for commercial and industrial customers, but can also be used in residential buildings with increased energy requirements. They are MID-certified, support multiple tariffs and offer advanced configuration options. Depending on the model, the meters are capable of tracking dozens of different metrics with the option to present the result on the display. In order to facilitate installation, the meters are pre-calibrated at the factory, and connection errors are indicated on the unit panel.

ABB – wide range of electricity meters

The wide range of meters offered by ABB includes devices with a wide range of parameters, designed for both industrial and individual customers. Their products meet IEC and MID requirements, support the measurement of a range of electrical quantities, store an event log and allow for the configuration of individual alarms. The meters are enclosed in a rugged industrial housing with compact dimensions, and with the communication interfaces integration into automation systems is made much easier.

Text prepared by Transfer Multisort Elektronik Sp. z o.o.

The original source of text: tme.eu