In Search of 100% - The Meter Communication Conundrum

The digitalisation of the grid will only push reliability and security for meter data communication further up the agenda.
Published: Wed 28 Oct 2015

100% stable communications will be required by utilities in the not too distant future. This is driven by a number of factors, primarily the need to receive reliable meter readings for various purposes not least of which is accurate and trusted billing to customers.

As smart meters get more intelligence built-in, the reliability and security of communication becomes even more critical as these devices will provide edge intelligence which needs to be reliable and trusted for grid operations.

Business needs before technology

In a recent interview with Carsten Nielsen, Head of Product Management – Smart Grid Solutions, Kamstrup, he explained that in this new world, the business needs  and performance level is key and utilities should consider defining these requirements first. Once this is defined and clearly articulated, the responsibility for delivering the performance to the required service level can be left to the solution vendor.

This approach will ensure that the right technology is chosen to deliver the service. This is crucial as, depending on the use case, a number of communication transmission technologies can be applied, and putting the technology choice first can have serious implications on the service delivered as well as the future proofing of the communications architecture.

Communication noise and barriers to stability

There are a number of communication technology options from power line communication (PLC), mobile broadband to radio. Each by their nature will suffer from communication noise particularly in the extreme environment of meter data which has to navigate its way through domestic noise, electric noise and all forms of radio noise.

All carrier options have the same goal: to communicate meter data in a reliable fashion. But, with the ever increasing noise levels, technology solutions need to be found to block this interference particularly as the noise is often created outside of the power plants’ and utilities’ control.

Assessing the technologies for data transmission

As the primary function for power lines is the delivery of electricity – which is unlikely to change – this complex and noisy environment causes various forms of interference in PLC which can result in unstable communications. For PLC, electrical noise is created by various in-home devices and gadgets like TVs and fridges and these will impact the noise level on communication lines. As the level of in-home technology increases, more noise will be generated. Therefore, solutions must be able to accommodate for this type of noise in general since it is bound to increase in the future. The interference factors include:

Huge load-impedance variations: Load-impedance changes will affect PLC signal voltages coupled onto the power lines, which directly impacts the transmission distance. Changes in power factor and location of power loads will change load impedances dynamically over time.

Attenuation on selective PLC carrier frequencies: The random switching of electrical devices on a power distribution network may lead to changes in power parameters, resulting in attenuation on PLC signals on selective frequencies. At the same location and instance, this impact may vary across different PLC carrier frequencies. When certain frequencies are unsuitable for PLC, changing to different frequencies for communication might yield better results.

Strong noise interference:  Electrical equipment on the power grid, such as switched-mode power supplies and inverters, can produce significant amounts of interference on multiple frequencies that vary randomly.

PLC-based solutions rely on low noise-levels on the distribution grid, and while utilities are unable to switch off gadgets that are creating high noise levels, they are equally reliant on products that filter out unwanted noise, at the expense of either the utility or its customers.

Radio-based solutions, including mobile and broadband can be blocked by wireless noise carried on the same frequency as the communication to the meters, and the radio-based solutions must be able to overcome these challenges. The primary challenges include:

Channel sharing: The wireless medium needs to be shared among multiple transceivers which need mechanisms for not accessing the channel at the same time.

Interference: Wireless receivers may be affected by interference from external noise or communication on nearby frequency ranges. These sources of interference need to be mitigated when designing wireless protocols.

Range: The range of the wireless signal is limited by the physical nature of the channel. Factors affecting the range include frequencies, transmission power, receiver sensitivity, and path loss (mainly physical barriers in the environment such as concrete walls or metal cabinets).

Security: Eavesdropping on a wireless channel is easy and cannot be detected, so data must be kept secret using methods such as encryption.

Mr. Nielsen points to a number of solutions that help resolve the rising noise level issue.

For those who use radio, frequencies can be dedicated to specific usage such as smart meters or even licensed to a vendor like Kamstrup. This approach is also applied for mobile broadband solutions.

Mr. Nielsen explains that radio in the experience of Kamstrup can be seen to provide near-100% stable communication to each and every meter. Kamstrup see an additional benefit as, through radio, you are able to remove the noisy powerline environment from the communications architecture.

In further exploring the difference between these carrier technologies Mr. Nielsen explains “One of the main characteristics – and strengths – of a radio based solution is that air is the communication media. We have designed our solution to be redundant so an alternative communication path is always available if something happens to the primary communication path. With PLC, there is only one line to each meter so when the line is noisy, disrupted or damaged, redundancy will not be possible at all and communication with the meter is deteriorated or lost.”

Currently, the European region is working to harmonise a frequency range which is going to be used for radio communication to smart meters. This is one way of eliminating or reducing noise within the communication channel that is being used for meter communication. This will of course be a highly cost effective solution for utilities.

A technology agnostic approach

The increasing complexity and variety of meter data especially with the move to increased edge intelligence will drive the industry further towards the need for five nines reliability.

“We believe that by now the technology and its suppliers ought to be mature and developed enough to guarantee a performance level and it is this desired performance level only which should determine the choice of carriers as each use case and each utility’s technology road map will be different,” says Mr. Nielsen.