For electric power operators today it is crucial to achieve efficient and reliable delivery of power. Technological developments continue to guide the industry towards a smarter grid. One of those developments is the implementation of communication networks in the electric grid. With the right communication network in place, a Smart Grid can reduce peak demand, shift usage to off-peak hours, lower total energy consumption and improve reliability. However, the right communication system is different for each layer of the Smart Grid. At the distribution automation layer, for example, many actions are managed, such as demand for and control over the amount of electricity created/required versus the amount used/delivered to the use point. In order to effectively automate the distribution grid, a reliable communication network is required to balance speed, distance, security and ease of use.
Defining a Communication Network
A wireless communication network consists of broadcast points (transmitters) with receivers and transceivers where both fixed and mobile units can communicate with each other over broad geographic locations using radio waves. In the industrial world, including the Smart Grid, a communication network mostly will be comprised of fixed applications with a radio connected to a Remote Terminal Unit (RTU), Programmable Logic Controller (PLC) or some other intelligent device. Often times, there is an Input/Output (I/O) device in the wireless network communicating to a central location where the Supervisory Control and Data Acquisition (SCADA) network and telemetry is monitored and controlled.
Wireless Technologies for a Communication Network
No single wireless technology can satisfy the requirements and priorities for all applications, especially for a system as complex as the Smart Grid. The first step in determining which technology is the best choice for each layer of the Smart Grid, is to evaluate what is most important to the operator in a communications system and what their individual needs are in advance. For some applications, reliability is critical. In the distribution layer, it is critical to have a highly reliable system with enhanced security features, accurate data and speed of data transmission.
Wireless radios that are industrially hardened, including unlicensed Frequency Hopping Spread Spectrum (FHSS) and licensed frequency radios, are proven to be reliable in the harshest environments and are deployed daily in mission critical industrial and military applications. At the distribution automation layer, these radios often offer the most reliable, economical solution when compared to other options. When compared with fiber, wireless systems are relatively easy to install. In the event that a buried optical cable is damaged to the extent that it requires repair or replacement, the costs can be very high. Some wireless systems provide information regarding a pending maintenance concern and the location or type of maintenance required can be easily detected remotely. Operators only send a technician out for service to precisely the right location if/when they need it, thereby saving time and resources. If designed and installed correctly, wireless systems will last maintenance-free for years. Additionally, when compared to satellite and cellular options, certain wireless radio solutions do not incur monthly fees that make satellite and cellular solutions more expensive over time. In fact, most comparisons show recurring data fees from cellular communications over a two-year period are equal to the cost of all devices for the same network with unlicensed FHSS radios. FHSS radios also offer advanced security features that protect the Smart Grid from attack. For example, a major security concern is Denial of Service (DoS). In a DoS attack, an intruder accesses the network and blocks communication by crippling the network with excessive data. At this point, the utility no longer is in control over what is happening on the grid. This is dangerous. This could mean a variety of risks, from a homeland security issue, to safety of the operators and teams of people working in the field. It is critical to know whether the power is off in a certain area, if it’s working in other areas and the high-level system view in order to keep workers and residents safe. At the distribution automation layer, FHSS wireless systems have proven to be very resilient to DoS by design. These wireless data radios use tiny amounts of radio spectrum at a time and will “hop” to another frequency quickly. Comparing this to standards-based radios (example: 802.11, Wi-Fi) whose radios are available at electronics retail stores, this makes a DoS attacks on FHSS systems very difficult.
Monitoring with Wireless I/O
Also available for electric power operators are wireless I/O radios that use FHSS technology. Wireless I/O offers substantial and measurable cost savings in terms of engineering, installation and logistics as well as dramatic improvements in the frequency and reliability of field data collection. In applications with a central processing device, wireless I/O enables users to extract full diagnostic data and predictive intelligence from the devices which then will automatically notify the appropriate personnel of the precise problem before a costly asset, unit, or plant shutdown occurs. I/O acts as the eyes, ears and hands of the wireless communication network whose overall goal is to deliver more value from the same assets.
As a result, wireless I/O is becoming increasingly popular to help reduce expenditures. The majority of wireless I/O systems being deployed today are used for data acquisition, but increasingly more users are utilizing Wireless I/O in control applications. The electric power and Smart Gird markets, in particular, have many processes that can benefit from wireless I/O.
Wireless I/O for Power Transformer Monitoring
One example of a wireless I/O application in the Smart Grid is power transformer monitoring. Located in distribution substations and throughout the distribution grid, transformers are a critical piece of the grid. Transformers take extremely high voltages from power generation or transmission, and decrease the energy level for proper distribution and delivery. This process is crucial for energy distribution to safely and efficiently power our homes and businesses. With extremely high power levels flowing through the transformers, it is often necessary to use a cooling system to prevent damage, most commonly using oil cooling. A damaged transformer is one of the most visible failures of the grid. These failures are both extremely costly to the utility to repair damages and to the community for the business and residential interruptions. With wireless I/O technology, this is easily prevented. The capacity of oil to carry heat and cool equipment deteriorates with age. The breakdown is accelerated by heat. Transformers can generate large amounts of heat, aging the oil and decreasing its ability to cool effectively. The greater the heat of the transformer, the faster the oil will age. As aging occurs, the oil will quickly loose its ability to effectively cool. Wireless I/O can monitor the overall health of the transformer and cooling oil. Monitoring sensor outputs with wireless I/O devices, the operator has a clear view of the oil condition without the need to have a person on site. New I/O expansion technologies allow the operators to monitor the oil condition at several different places in large transformers by adding a stackable module to the wireless I/O radio. This allows the user to increase I/O points, without needing to purchase additional radios. Wireless I/O also can be used to monitor cooling fans. By using the digital input operators can monitor whether the fan is actually working or if it has failed. This is yet another way to manage the extreme levels of heat caused by energy that passes through the transformer. Furthermore, in locations where transformer oil theft is pervasive, operators can be notified real-time data when oil levels drop to service the site before more serious damage occurs.
Wireless I/O for Variable Frequency Drives
Another unique application for wireless I/O in the electric power industry is control of variable frequency drives. Pumps are used by electric utilities to store energy by pumping water uphill and many utilities use pumps and wells to get fresh water for cooling and protection systems. To store energy pumps force water uphill into a reservoir that is connected to a hydroelectric plant. In the past, pumps have been controlled with on/off control and the water flow has been controlled by restrictive valves to achieve the desired water flow. The valve caused energy loss because it actually dissipated energy that the pump consumed to push the water. The problem is that the pump would still be running at full speed and consuming full power. The amount of energy being put into the water is essentially dissipating in the valve because half of it is being blocked, which becomes wasted energy. Newer installations have variable frequency drives controlled by wireless I/O. Variable frequency drives act as an adjustable speed and power control for pumps, delivering a very specific amount of power to pump the right amount of water. This is much more effective than simply turning on a switch and it acts more like a dimmer light switch. The operator can limit the amount of energy put into the pump and deliver just enough water. The amount of energy put into the pump then equals the amount of energy and water needed. This can save the utility thousands of dollars per pump in lower energy costs.
Decision makers in the electric power industry continue striving towards a grid that eliminates energy waste due to inefficient transmission and distribution systems. With the Smart Grid and all the technologies available to support it, we can see these efforts in action. Wireless communication networks allow operators to become knowledgeable about the health of the grid. FHSS wireless data radios help decrease wasted energy and loss of power by sending critical data to an operator's fingertips. Wireless I/O, in particular, can be utilized to monitor and control critical electric power applications. But, decision makers must understand that communication needs vary from generation, to transmission, to distribution and from the pole-top to the meter to the home area network (HAN). The key to choosing the right technology at each level is to understand each system’s needs before choosing a technology. Then developing a communication network that delivers the right benefits creates a smoothly running system for efficient and effective delivery of power.
Andrejs Rozitis can be reached at email@example.com and Glenn Longley can be reached at firstname.lastname@example.org.