SMART METER: 101 COMPREHENSIVE GUIDE

A smart meter is an electronic device that keeps a record of energy consumption, and electrical parameters like voltage levels, current, power factor, etc. These meters have a built-in communication channel through which it can communicate both ways between the meter and a central system. This communication can be via cellular level or via power line communication PLC. The meter can be remotely accessed for collecting data or events, programming the meter for select parameters via these communication channels.

Components of the smart energy meters

The smart meter itself is a component of Advance Metering Infrastructure AMI, and the functional zones are discussed below.

Metering:

The current flowing through a load line is made to pass through a resistance for the purpose of measuring it. The voltage measurement is done by using a resistance voltage divider in the circuit. These resistances for current and voltage measurement are of high precision and low-temperature coefficient. For a better and cost-efficient reading system, the analog signal is converted to digital via an analog-to-digital converter ADC at discrete instances of time. This data is then processed in the digital signal processor in the microcontroller unit of the meter, ready to be displayed at the In-Home Display IHD and further transmitted via the communication channel to the head end system HES.

The In-home display IHD facility

The IHD’s should have two display facilities

• Auto-scroll
• Scroll with the push button

A typical single-phase smart meter’s IHD functions are listed below:

Load Switch:

The smart energy meters are equipped with switching elements, integral within the meter enclosure, to control the flow of electricity to the load at the instance of connect/disconnect commands fed by the Head-end System of the utility via the communication channel. For single-phase smart meters, two load switches are provided one in the phase and the other in the neutral of the circuit. The status of the load switch is conveyed to the IHD and HES and all the switching operations are logged as events.

DISCONNECTION MECHANISM

The load switch will get disconnected under the following conditions

• Overcurrent of minimum 105% of I_max in any phase persisting for a predetermined time.
• The load is beyond the programmable set limit, set by the power utility.
• Pre-programmed factory set events related to faults at load or source side.
• Disconnection signal received from the utility control center, HES
• In the case of the pre-paid facility exhaustion of available or usable units.

RECONNECTION MECHANISM

• Local reconnection after the disconnection due to over-current or load limit proceeds as follows:
• Load switch re-connection is decided by the meter locally. The meter attempts to reconnect the load up to a predefined number of times, with predefined intervals (the number of times and intervals are programmable by the utility). If consumption is within the set load limit, the meter will remain in normal connection mode.
•  If the load consumption is still more than the programmed load limits, the meter will lock out for 30 minutes, the lockout period. After this period, the meter will attempt a reconnection, and if consumption is still above the set load limit, the above procedure is repeated with a status update to the utility’s HES.
•  In all conditions other than the over-current and load limit, reconnection is done from HES. In case of failure of communication with HES, reconnection is done through the optical port locally with specified security.

Communication module:

The data from the smart meter is collected to the data concentrator unit via neighborhood area network NAN and then to the head end system HES of the utility via a wide area network WAN over carrier frequency. The communication technology for NAN may be via power line communication PLC or Radiofrequency RF and cellular technology or optical fiber communication OFC. However, the most commonly used technology for WAN communication is 4G/5G cellular networks.

Components of smart meter infrastructure

Smart meters:

It meters various parameters set by the relevant authority and is capable of having two-way communication with the HES, the head-end system of the power utility.

LEGEND

• A – Metrology Optical port
• B – Load switch for control
• C – Metering protocol
• C1 – IHD Connectivity IHD (optional)
• C2 – NAN Connectivity DCU
• D – Communication

Communication infrastructure:

The communication infrastructure can either be based on radio frequency, PLC, cellular networks, or optical fiber communication OFC for compliance with the NAN and WAN standards. This infrastructure is responsible for providing two-way communication between meters and HES, essential for the system.

Head end system HES:

It is the component of the advanced metering infrastructure which collects data from the field meters without human intervention. It is capable of sending commands or programs to the field meters for relevant updates.

Meter Data Management System MDMS:

It centrally stores all the data collected by the HES from the meter as well as makes data available for billing, settlements, demand forecasting, consumer information, network planning, outage management, etc.

Web application or Mobile application:

This is the portal for the power utility supported by MDMS available to consumers who want to see the real-time consumptions, cost, past usage daily/weekly/monthly, tariffs, etc. This can also be used for peak load management by showing the consumers, incentives, and participation benefits.

Advantage of smart meters to consumers

• Smart metering o­ffers various potential benefits to consumers which include the following:
•  Total elimination of the estimated bills, a major reason for consumer disputes.
•  More accurate and timely billing process
• Empowering consumers with real-time data usage promotes efficient energy management and energy purchase.
• Giving customers greater control over their electricity use, coupled with time-based rates that enable savings
• Promoting informed decisions by providing highly detailed information
• Providing real-time alerts to consumers about power availability and outages
• Enabling faster outage detection and restoration of service
• Ensuring consumer privacy by billing with no human intervention
• Metering electricity generated from domestic microgeneration, enabling consumers to be financially rewarded for their contributions.

Advantages of smart energy meters to utilities

• Reduced meter reading costs as meters are remotely read.
• Improved revenue management with timely billing.
• Allowing system faults to be notified and located quickly.
• Increasing load management during peak load times, ensuring efficient use of grid resources
• Improved ability to deploy advanced tariff­ regimes and other demand-side management initiatives, thus optimizing power procurement costs and improving load management
• Easy energy accounting, leading to more accurate measurements of distribution losses.
• Efficient load forecasting with the MDMS data.

General safety and care of smart meters

• The smart meter should not be installed near the floor which remains waterlogged or wet.
• The installation location should be away from gas or water pipelines
• The meter box should be effectively fixed to the wall with metallic fasteners and should not hang loose in a tilted position.
• Service wires or cables must enter the meter box via glands
• The height of the meter should be between 750 to 1800 mm for accessing the IHD.
• The space between two meters must be at least 300mm
• A proper earthing arrangement should be available at the site for load limits above or equal to 10KW.
• The seals should be easily visible and accessible.

FAQ’s