June 19, 2018
Utilities nationwide are relying on wireless networks to connect elements of the smart grid to reduce peak loads for improved operation. The smart grid also provides a means for consumers to reduce their energy costs.
This intelligent utility network features sensors throughout the transmission and distribution grid to collect data, provide real-time two-way communications to move data and electricity between utilities and consumers, and create the computing intelligence to make improvements in reliability and efficiency.
The smart grid integrates multiple networks, including Home Area Networks (HANs), Field Area Networks (FANs), and Wide Area Networks (WANs). A variety is necessary because the multiple smart grid applications have different network requirements in terms of data payloads, sampling rates, latency and reliability. Given the mission-critical nature of the smart grid, it is important to ensure robust signal coverage and avoid potential sources of interference for each of these wireless segments. In this post, we will delve into each network element and the test tools to ensure optimal performance.
Home Area Network (HAN)
A HAN infrastructure is typically open and must be interconnected with the Advanced Metering Infrastructure (AMI) and the Internet via a home gateway to enable high-end services. Smart grid metering and control applications require fast and secured two-way communication. In a HAN, home appliances designed with RF antennas communicate with smart meters, typically using the IEEE 802.15.4-based ZigBee 2.4 GHz communication protocol.
Field-area networks (FANs)
Filling the communication void between the core IP network and devices, and utility personnel in the field is a FAN. Cellular, narrowband and broadband point-to-multipoint (PTMP), and broadband wireless mesh networks are commonly used in a FAN. To support the varied smart grid applications, FANs must be:
- Reliable – FANs must operate even when events disable the electric grid, as communication is most critical during an outage.
- Scalable – In some cases, a FAN must cover a utility's entire service territory, so it must be able to scale according to meet the geography. It must also scale to support up to millions of connected devices.
- High performance – There are some critical applications, such as protection and safety, that are part of a FAN. Therefore, low latency is essential.
Wide Area Network (WAN) – A utility’s WAN will need to cover the entire distribution footprint, including all substations. It will have to interface with distributed power generation, storage facilities, and other distribution assets. The WAN will also be used for substation communication, distribution automation (DA), and power quality monitoring while also supporting aggregation and backhaul.
Because a WAN is the core of the smart grid, as well as the fact it supports mission critical applications and is used for cyber security, its performance is essential. A typical utility WAN is a blend of wireless technologies, as well as high bandwidth fiber optics-based communications technologies such as SONET/SDH, and WDM/DWDM.
Tools to Test the Smart Grid
Because wireless technologies are so integral to the smart grid, there is a great need to verify signal coverage and locate interference sources that will impede successful transmissions. Utilities need to be able to analyze communication problems quickly and insure that their wireless network continues to run under a variety of conditions. To do so, a series of analysis tools should be part of any utility tool box.
Cable and Antenna Analysis - The cable and antenna system serves an important role in the overall performance of the smart grid. Slight variations in the antenna system can affect the signal and coverage area, and eventually cause dropped transmissions. Using portable cable and antenna analyzers, such as the Site Master™, to characterize communication systems can simplify maintenance and overall performance significantly. Return loss/VSWR measurements are used to characterize the system, while distance-to-fault (DTF) measurement can be used to troubleshoot problems, locate faults, and monitor changes over time.
Interference Analysis – Smart grid systems coexist in extremely complicated signal environments. This is particularly true at industrial, scientific and medical (ISM) frequencies, such as the 2.4 GHz band used by WLAN, Zigbee, and Bluetooth. Household appliances, particularly microwave ovens, are also potential sources of interference. Various cellphone frequencies, WiFi and other technologies are also common in today’s home, making signal integrity quite the challenge. To locate causes of interference so they can be corrected, a handheld spectrum analyzer such as the one shown in figure 2 should be used.
Indoor Coverage Mapping - To plan and optimize wireless networks, utilities must identify the coverage their transmissions provide in a given geographical area. For indoor signal analysis, coverage mapping makes it easy to identify coverage quality throughout any facility. With this tool, taking signal strength measurements is as simple as walking through the facility with the appropriate handheld analyzer. Real-time updates of signal quality can be provided, so network planners can identify areas where additional transmitters or repeaters may be needed to insure high signal quality.
Outdoor Coverage Mapping - Outdoor coverage mapping enables the utility to optimize the network by identifying signal coverage in an outdoor environment. Assisted with GPS, areas of relative signal strength can be automatically measured and precisely correlated with location. The analyzer can be set up to take automated measurements either as a function of distance or time, so it can be used by technicians with any level of experience. Data can be displayed later in a variety of formats, including third-party vendors such as GoogleEarth™.
The smart grid has transformed how utilities deliver electricity to consumers, as well as how customers can have greater control of costs. It has also created a variety of considerations for utility managers, the least of which is maintaining high signal quality. Using the proper test tools can help achieve the necessary KPIs for success. To learn which test tools are right for you, visit this dedicated smart grid page.