Energy meters are revenue registers for utilities. Energy meters have evolved significantly, especially in the past two decades, from electromechanical to smart meters, in line with the development of electronics and communications technology. Nowadays, energy meters not only measure electrical parameters, but also calculate various other parameters as well as tamper conditions, events, load patterns, etc. and log all of these in their memory registers. Meter readers can download all these logged parameters, conditions, etc. through a wired connection.
In the present era, communications technology has evolved and data download technology has also changed. Now, meters are capable of transferring their data to the control room at five-minute to 60-minute periods with alerts as and when they occur. Hence, smart meters can be easily called minicomputers.
All stakeholders (electrical utilities, manufacturers and the Bureau of Indian Standards) should relook at existing energy meters to identify the components that have become redundant and may be eliminated. With this, the cost of meters will decrease and they will become simpler.
Earlier, energy meters were electromechanical in nature and could measure only energy consumption (either in kWh or kVArh or any other single parameter) with a high level of errors. Since then, electronic technology has evolved, which has changed energy meters completely. Now, they can measure multiple electrical parameters and store them under different categories. Also, energy meters can compute derived electrical parameters and store them. Based on various system conditions, energy meters capture specific tamper conditions and log the same.
Now our meters have become smart and comply with IS 16444, IS 13779 or IS 14697 and IS 15884, and IS 15959, with all their amendments. IS 15959 standardised the list of parameters and their OBIS code, etc.
Smart meters and their architecture
Smart meters become fully smart only when the complete AMI system is in place, otherwise they are merely electronic static meters. As per the architecture given below, smart meters send instantaneous, block profile, load profile and billing profile data at a predefined periods of 1 hour to 24 hours, which is configurable. The HES is responsible for data exchange with meters, converting the data into engineering value and transferring it to the meter data management system (MDMS), as well as receiving commands from the MDMS and sending them to the respective smart meters.
The MDMS’s main functionality is to receive data from the HES, and validate, estimate, and edit it and keep all the data in a single repository for other applications. Smart meters have all the functionalities that are available in static energy meters with the addition of communication modules and load switches.
Electrical parameters as per IS 15959 – Part 2
As per IS 15959, three-phase whole current meters should measure/calculate the parameters given in the accompanying table as well as store the same. Also, the meter should keep the load profile data for 35-45 days.
Some electrical parameters are being derived from the quantity of energy measured by energy meters, and therefore the meters need a high computation speed processor. All tamper logic calculations (current bypass, overvoltage, overcurrent, undervoltage, unbalance load, neutral disturbance, etc.) are done by meters based on various measured electrical parameters.
- The calculation part should shift to the HES server from the energy meter. The energy meter should transfer the basic electrical measured parameters to the server within five minutes.
- All different profiles need to be merged into two categories – electrical parameters and billing energy. Time-of-day-based computation should also be done at the HES server only.
- The data for the two suggested categories should be stored for 5-10 days only, instead of 35-45 days.
All smart meters have a display unit as per an old provision so that consumers can see the various electrical parameters. The smart meter architecture provides data to consumers on a mobile app or web portal where all data is available. In such a scenario, the display unit becomes redundant and can easily be eliminated. Also, the display unit is prone to electrostatic discharge and needs a lot of protection.
The display unit should be removed from smart meters if it does not have any functionality.
Meter technology and communications technology have evolved significantly during the past two to three decades. Users are also continuously adding new requirements for meters. All stakeholders, therefore, need to relook at energy meters in the context of smart meter architecture and its complete value chain.
In light of all these requirements, which may or may not be important, the cost of smart meters is going up. Therefore, if we reduce the overhead expenses of smart meters, these meters may become affordable and help achieve the government’s target of smart prepaid meters for all consumers.