by the 3 Phase Associates – Engineering Team
Power Utilities Are Evolving
Since the creation of electric power in the late 1800’s, major technology breakthroughs have evolved that have become necessities for the human race, such as: lighting, telephones, range/microwave ovens, refrigeration, heat ventilation and air conditioning (HVAC), washers, dryers, TV’s, computers, internet, and so on…
These conveniences have greatly improved our standard quality of life, and they continue to progress. None of these necessities and conveniences would have been possible without the formation of electric power. Many times, we take for granted the true importance of electricity and the conveniences it provides until power is interrupted, where these conveniences quickly become major inconveniences and necessities that we cannot live without.
Every time consumers pay their power bill, they are putting their trust in their local power distribution utility to always keep the lights on, ultimately providing reliable electricity. When the lights go out, customer satisfaction goes down. To offset this, distribution utilities focus on upping their game by always striving to provide safe and reliable power to their customers at the lowest possible cost, and without any disruptions. Over the last 30 to 100 plus years, power companies relied on electromechanical devices and analog circuits to properly control and monitor the power flow and to protect against abnormal system faults, overloads, and frequency variations.
Within the last three decades, digital communications and microprocessor-based technologies quickly replaced electric system analog and electromechanical components, allowing them to perform many more functions at greater speeds. These smarter devices allowed more streamlining of physical space requirements, design protection, routine maintenance, and equipment testing.
Improved System Reliability with Newer Technologies
Today, microprocessor devices used by power utilities have evolved into smarter and more intelligent devices, known as intelligent electronic devices (IED’s). These IED’s aid power operators, technicians, and engineers in better system decision making, offering more tools for controlling and monitoring power flow that can perform routine maintenance testing via remote control and automated functions. IED’s can detect and protect against various power fault and system disturbance scenarios along with providing power flow waveforms, metering data, and supervisory control and data acquisition (SCADA) functionality. These smart microprocessor-based components and relays can perform numerous functions that cannot be duplicated with electromechanical devices. IED’s have greatly increased power system reliability for power utilities by reducing the number and durations of customer interruptions, ultimately improving customer satisfaction. The use of IED’s has also aided utilities in better reliability metric tracking during unplanned power outages. Utilities are capable of tracking reliability improvements or reliability declines by using major reliability metrics; such as, the ones taken from the IEEE Standard 1366: CAIDI, SAIDI, SAIFI, MAIFI, etc.
Wikipedia defines CAIDI as “the customer average interruption duration index”, which provides the average outage duration (minutes or hours) that a customer would endure or can also be interpreted as the time for an average power restoration. The following expression shows the relationship between CAIDI, SAIDI, and SAIFI.
CAIDI = Sum of all customer interruption durations = SAIDI
Total number of customer interruptions SAIFI
SAIDI is power interruptions lasting more than five minutes or non-momentary. Interruptions lasting less than five minutes would be momentary interruptions, in which MAIFI, as explained by Wikipedia, is “the momentary average interruption frequency index”, which is “the average number of momentary interruptions that a customer would experience during a given period.” Power utilities use these reliability metrics and other metrics to track the progress of power delivery daily, weekly, monthly, and yearly for comparing the number of customer outages and average time for restoration, in hopes of improving reliability. Power interruptions and disturbances are caused by many factors that can affect or hinder power reliability and customer perception. Major power disturbances are caused by: storms and extreme weather events, overgrown vegetation, encroaching animals/wildlife, aging equipment failures, human error, etc. As SAIDI increases, the customer’s outage duration rises, and power restoration time escalates, thereby, creating unhappy customers. As more power interruptions occur for customers, SAIFI rises, which produces an overall negative impact for CAIDI, diminishing both reliability and customer gratification. Therefore, it’s important for power utilities to perform routine maintenance on equipment, including upgrading aging equipment to newer technologies to improve reliability and obtain better metric results for CAIDI, SAIDI, and SAIFI. Other important factors to consider include keeping overgrown vegetation neatly trimmed and keeping animals/wildlife from invading power systems. Strategically adding fuses and auto-reclosers on the power system will also improve grid reliability.
Today’s intelligent devices offer major advancements in communications. These devices can communicate with multiple digital devices and power control centers via a combination of communication protocols. Continued advancements in telecommunications have paved the way for power utilities to take advantage of more high-speed, real-time communications, and vigorous automation in order to ensure their electric grids are more robust and reliable. A major tool provided by IED’s, DA, and SCADA systems that utilities are benefiting from is fault location, isolation, and service restoration (FLISR). Smartgrid.gov defines FLISR as “technologies and systems that involve automated feeder switches and reclosers, line monitors, communication networks, distribution management systems (DMS), outage management systems (OMS), SCADA systems, grid analytics, models, and data processing tools”, all working together for reliability improvements by automating power restoration, ultimately reducing the number and duration of customer outages. FLISR can reconfigure a permanent faulted power grid in order to restore the most customers as quickly as possible (usually within 60 seconds or less) by redirecting or modifying the flow of electricity through complex coordination with other IED’s, SCADA, protection & controls (P&C), software, and real-time communications.
With the collection of these IED’s working in harmony to form the power grid into a smarter and more intelligent grid, known as Smart Grid (SG), they provide more data and control for better, faster decision making.
The Smarter Grid
SG is an electric power grid involving a combination of digital and smart devices functioning in harmony within an automated capacity, while providing large amounts of power flow data to utility owners and power users. SG allows system operators better control and measurements via smart devices such as IED’s, SCADA Remote Terminal Units (RTU’s), smart switches, smart meters, renewable energy, energy efficiency, smart appliances, etc.
SG is simply a continuous data flow of digital processing information required to properly operate the electric power grid safely, securely, reliably and responsibly. SG engages power utilities to implement more automation for better productivity and improved efficiency in order to perform more functions accurately and with less staff.
The Energy Independence and Security Act of 2007 (EISA-2007) is a US policy that defines SG with ten characteristics. These are: “
- Increased use of digital information and controls technology to improve reliability, security, and efficiency of the electric grid.
- Dynamic optimization of grid operations and resources, with full cyber-security.
- Deployment and integration of distributed resources and generation, including renewable resources.
- Development and incorporation of demand response, demand-side resources, and energy-efficiency resources.
- Deployment of ‘smart’ technologies (real-time, automated, interactive technologies that optimize the physical operation of appliances and consumer devices) for metering, communications concerning grid operations and status, and distribution automation.
- Integration of ‘smart’ appliances and consumer devices.
- Deployment and integration of advanced electricity storage and peak-shaving technologies, including plug-in electric and hybrid electric vehicles, and thermal storage air conditioning.
- Provision to consumers of timely information and control options.
- Development of standards for communication and interoperability of appliances and equipment connected to the electric grid, including the infrastructure serving the grid.
- Identification and lowering of unreasonable or unnecessary barriers to adoption of smart grid technologies, practices, and services.” (Wikipedia, Smart Grid)
One distribution utility that has led the charge and helped pave the way to a smarter grid is the electric municipality of Chattanooga, TN, known as, the Electric Power Board (established in 1935) or simply EPB. EPB was awarded a grant of over $100 million from the Department of Energy (DOE), in 2010, with the sole purpose of transforming their electric grid into a smarter, more sophisticated power system by deploying distribution automation (DA) functions for reliability improvements, better power quality, improved customer service, and energy efficiency. Their goal was to create an electric grid for customers that was both collaborative and self-healing. EPB’s customers, located in Chattanooga and the surrounding areas, gained enormous benefits from EPB’s SG investment. Additionally, EPB added fiber optics (FO) services to its power delivery portfolio in hopes of promoting economic expansion and advancing the quality of life for its customers. EPB was successful in implementing their SG system due to initially installing several miles of FO in their service territory for their backbone communications.
With the implementation of their complex FO network, it allowed them to connect several intelligent switches with voltage and current sensors across their power grid. EPB’s sensors, smart devices, and smart switches were implemented in both their 46kV and 12kV distribution networks, providing communications with each other intelligently. EPB also has a complex automatic meter reading (AMR) system and an advanced metering infrastructure (AMI) network as part of its SG scheme, capable of delivering remote control functionality and power quality to nearly two-hundred thousand smart meters.
Continuous Reliability Improvement
Power utilities will continue improving their reliability with the use of better tools and improved technologies; such as: IED’s, SCADA, FLISR, DA, SG, AMI, AMR, etc. As more utilities implement SG systems, end users will benefit the most with increased reliability and added collaboration. Better grid infrastructure will also aid in renewable or green energy interconnections to distribution substations for data intensive monitoring, equipment protection, and controlling power flow.
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