By Jonas N. Olsen, On-Ramp Wireless, Inc.
Search the term ‘smart grid,’ on the Internet and you’ll get a long list of articles about smart meters. But the smart grid goes far beyond the meters. Often located in underground basements or on impossibly high rooftops, devices associated with operating the smart grid can be hard-to-reach, especially in metro or other challenging environments, where there is no hardwire Internet connection.
Distribution Automation (DA), which has the potential to significantly improve the performance of the smart grid, also struggles to connect these “smart devices.” DA systems strive to improve reliability of the smart grid through situational awareness, outage management, and faster response times when a fault is discovered. A smarter distribution system can also assist in utility capital planning by highlighting changing load conditions over time. Utilities are interested in implementing DA because it improves their bottom line and it is an autonomous project – they don’t need to communicate with their consumers.
Half the battle of optimizing a DA system is connecting these billions of “smart” devices cost-effectively. Utilities need to be able to deploy a secure and reliable wireless remote monitoring system throughout their distribution network to accomplish asset monitoring, fault indication to improve outage restoration, alert to power quality issues, capture power theft and act as a hub for demand-side load management, which ultimately lowers cost of operation and maintenance costs for utilities.
For electric utilities, an added challenge is the advent of distributed generation, where electricity is generated from many small energy sources, and the introduction of Electric Vehicles (EVs), which bring new pressures to utilities’ distribution grids. However, wireless remote monitoring systems can address this too, especially as they become increasingly prevalent.
Wireless Systems for Remote Monitoring
While utilities are increasingly using wireless technology for remote monitoring applications, it should be noted that not all wireless technologies are created equal. There are significant differences, which ultimately determine their applicability (cost and performance) to a specific application.
The key characteristics of a wireless system that determine its overall applicability are:
- Coverage: The system’s ability to transmit a signal over a long distance.
- Capacity: This can be defined in two terms. First, there is the actual application throughput (good put) from a single end device (such as a pressure sensor) in the network. Second, the overall network capacity must also be considered. This refers to the ability of a concentrator (or Access Point) to process data from nodes in the network. This is what we call the overall throughput capacity.
- Power consumption: In remote monitoring applications, many end points must rely on batteries as the main source of power. The preference is for lower power consumption to extend the span between battery replacements. In some installations solar or other renewable sources can be used to supplement a main battery.
- Latency: This term relates to the time it takes for information to move through the system in either direction (from the remote device to a central collection system and the other way around).
- Communication type: Wireless (or any communication system for that matter) operates as either simplex (communication only one way), half-duplex (communication both ways but not at the same time), or full-duplex (same time, bi-directional communication).
Wireless spectrum allocation is another concern that must be addressed. Wireless systems perform over a wide range of frequencies, from a few kilohertz to high frequency gigahertz systems. Many frequencies are licensed and typically bought by private companies through public auctions. Other frequencies are designated unlicensed and can be used free of charge. The unlicensed frequencies, however, are associated with rules and regulations about how the free spectrum can be used by various different private operators. An example of a rule would be guide use of popular technologies such as Wi-Fi and Bluetooth. The rules and guidelines address the amount of power output and the occupied bandwidth that can be applied in the allocated free spectrum. The rules vary from country to country, and operators need to observe and comply with local restrictions. Many remote monitoring applications operate in the free and unlicensed frequencies. This is mainly due to cost concerns, as many of these applications do not warrant the high cost of dedicated frequencies or the monthly recurring fees incurred when renting this spectrum of a third party operator.
It is important to recognize that different wireless systems mix and match these characteristics in various ways. This also means that there isn’t a “one size fits all” wireless system that is ideal for any application. The unique application requirements of a flow measurement system, for example, are very different from a low latency, factory floor SCADA application, which may require millisecond response times. Some applications will require very high data rates, while others just process a trickle of index data throughout the day. Pick any of the above mentioned system characteristics and the same kind of comparisons could be made.
Most remote monitoring applications fall into a category where range and low power consumption is prioritized. Range, in this sense, should be understood as either great distance (e.g. >10 km), or as the ability to penetrate obstacles, like vegetation, building, etc. Low power is key, as many remote devices will require monitoring without access a continuous power source (i.e. battery operated). Relatively small amounts of data are typically transmitted and capacity therefore tends to be a minor concern. What is important, however, is the aggregate data rate at the collectors/Access Points. If a wireless system has great coverage it is likely to provide coverage for many thousands of devices from a single network infrastructure point. This “Access Point” must provide sufficient throughput capacity to, robustly, receive and process data from all of the covered devices. This is where many narrow-band radio systems fail to meet the requirements of utility customers.
Finally, one needs to consider the communication type. Some applications can survive with simplex communication. This would be the case when all the application is intended to do is to collect data from a remote point. For an application where two-way communication is needed (resetting alarms on remote devices or changing configurations) a duplex system must be deployed.
Backhaul Options
An additional concern is backhaul from the remote site to a central data processing site. Most remote operation is far from the main hubs for IT infrastructure. When a private wireless system is installed (as opposed to using public infrastructure like a carrier based GMS network), it is up to the user to provide all connectivity links in the system. A wireless system that uses unlicensed spectrum will typically terminate in a set of wireless access points or gateways, which then need to be connected to the overall company network. This can be done in various was, but the most commonly used methods are a direct connection to the Local Area Network (if available), backhaul via a public cellular network (again, if available), and finally through satellite links. These options are listed both in terms of preference and cost.
Systems Integration
Integration with a process automation platform has to be considered. For a wireless remote monitoring system to be effective, it has to present the collected data in an industry standard format. An end-to-end wireless remote monitoring application will provide every step in the process, from integration of the wireless module with the remote sensor, wireless networking and networking infrastructure and conversion of the data to a standard format, such as Modbus or OPC. This allows for simple integration, both with on-site process automation systems and backend historical data storage.
Conclusion
As electric, cable, and telecom utilities increasingly work to improve their DA systems while having an eye on their bottom line; they should look at wireless remote monitoring solutions. With the right system, utilities should be able to pinpoint a problem exactly where it occurs so that their work crews can go directly to the affected area to fix it, and don’t have unnecessary downtime. In some cases, preventative maintenance system integration will even avoid failures altogether. A system should also be able to integrate fault indicator alarms with work order systems for simple and automated dispatch of workmen. Beyond the workforce, a connected DA system also leads to low power consumption by limiting peak power requirements, better capital planning, and fewer outages.
Lastly, the network should ultimately allow for a low-cost, fully-automated Distributed Grid, which enables e.g. fault indication (above and below ground), transformer monitoring, substation automation and other applications that were previously thought unfeasible to automate. When these applications come “online”, utilities will see significant enhancements in key performance metrics.
Jonas N Olsen is the VP strategic partnerships for On-Ramp Wireless, Inc., which is currently deployed by a Western utility for its wireless communication system.
