Substation cellular connectivity MultiTech

Substation automation - the problem of offline RTUs

How can you ensure remote terminal units are always communicating? Engerati asks experts in the field to share their view.
Published: Fri 02 Feb 2018

Distribution utilities are fully aware of the benefits of remote terminal units (RTUs) for their low voltage networks.

At the substation level, these monitoring devices help boost reliability and power quality of networks up to 1,000V. Research reports suggest that the RTU market is nearing saturation, a marker of success of their effectiveness in controlling and monitoring automated systems.

However, the powerful monitoring impact of RTUs within substations relies on one major factor – connectivity between the unit and the control point used for supervisory control and data acquisition (SCADA) traffic.

The value of data from a RTU is only as good as its connection - typically through a wired (such as telephone line or Ethernet) or a wireless connection (like cellular).

But what happens if the communication technology infrastructure is lacking at one of your substations? This is not uncommon, says Darrell Jones, Technical Sales Manager at UK network installation company Cherry & White.

Jones, who works with major UK distribution network operators (DNOs) to deploy field networks, says companies can have difficulty communicating with RTUs.

“We see many examples of this when working with DNOs, not just in remote rural areas but also urban areas such as London.”

Communication companies MultiTech and Stream Technologies explain their connectivity technology offerings for the utility sector and use cases - from water metering to preventive maintenance. 

Jones explains the difficulty that DNOs have with the connectivity of their RTUs/substations is whether connectivity is available.  

He says: “Sites that have been installed with fibre or copper lines for example do not pose such a problem as remote sites where there is no fibre or copper cables installed.”

In the latter instance, Jones says, the DNO has to decide which is the most efficient and reliable way of connecting the site and transmitting the data, whether that is to install fibre or copper cables, microwave or cellular radio or satellite such as very small aperture terminal.  

The knock-on effect for the DNO of not having their network connected is to lose sight of the substation.

 Jones says: “If there is an outage, for example, the DNO needs to know the state of the switching gear. If they could not connect to the site they would have to dispatch engineers to investigate.”

The practice of truck rolling for site visits in such situations is a scenario that DNOs everywhere in the world are trying to reduce.

“If we can help DNOs enable their network to be self-sustaining and self-recovering as much as possible, then this aids them significantly.

He adds: “Engineers having to visit sites in remote areas for example is not only time consuming but also costly so the need for the DNOs to reduce these is paramount.”

Connecting substations - backup solutions

From experience in the field, Jones views the solution as robust connectivity with a viable backup or a redundancy option.

“DNOs can use a cellular router as backup or secondary communications platform. If their primary means of communication is affected, whether that be satellite communication or something else, then the cellular router can establish a connection over the cellular network. This then keeps the sites visible and manageable for the DNO.”

Richard Stamvik, Managing Ecosystem and Partnerships at IoT communication device provider MultiTech, agrees that DNOs should select the right communication technology for the use case.

MultiTech, which supplies the connectivity technology for Cherry & White’s network deployments, offers a range of cellular solution to support industrial internet of things use cases from 2G/3G/4G cellular including HSPA, LTE and NB-IoT, operating in licensed radio spectrum, and Low Power Wide Area (“LPWA”) including LoRa, operating in unlicensed radio spectrum.

 Stamvik says: “The various technologies have their technical and commercial pros and cons, such as physical range, energy consumption, quality of service level, and CAPEX versus OPEX-based business model, and in many cases complement each other.”