Electricity is the lifeblood of our digital world. Access to reliable, safe and renewable energy can impact entire economies and there is extensive research showing the substantial economic losses caused by power outages. This is one of the key reasons why smart grid technology is being deployed by power utilities around the world–improve energy security and grid reliability and keep our digital world running.
Smart Grids are also giving us a glimpse into the much talked about Internet of Things (IoT). Power utilities are demonstrating the critical role of resilient communication networks that enable millions of devices to talk with one another. IoT is often defined as connecting any object with an IP address and some intelligence to any other object over the communications network.
This is essentially what happens when tens of thousands of intelligent electronic devices (IEDs) share critical information about the operating conditions of the grid around them. Communication networks link these devices creating a machine to machine conversation without direct human intervention that enables functions such as remote sensing and control of substation equipment.
Embedding communications and intelligence in the distribution network allows utilities to monitor and manage their power networks, decreasing outages and reducing operational costs. More than 70 percent of the utilities responding to a Utilities Technology CouncilKPI benchmarking survey with information on their overall grid communications investment plans indicate they will include new communications systems.
While the IoT future and associated improvements in resiliency and reliability offer a strong case for the modernization of utility communication networks, utilities are looking to understand the benefits these investments can deliver today. How do they measure the actual benefits of network investments?
The Institute of Electrical and Electronics Engineers (IEEE) has developed 13 metrics to help quantify the reliability of power delivery achieved by electric distribution utilities. The most commonly used grid reliability metrics–CAIDI, SAIFI and SAIDI–are summarized in table 1.
A recent white paper published by Bell Labs describes a way to quantify the impact of communication networks on these three distribution grid reliability metrics that are universally tracked and reported by distribution utilities and regulators.
Using assumptions representative of large distribution utilities, the impact of extending communication networks on the three grid reliability metrics listed in the above table can help reduce the duration of customer outages (CAIDI) by approximately 30 percent, reduce the frequency of customer outages (SAIFI) by about 15 percent, and reduce system-wide average annual outage minutes (SAIDI) by approximately 40 percent. These figures exclude major events such as hurricanes and ice storms.
The three metrics are related mathematically as shown in figure 1 below.
The relationship suggests that by quantifying the impact of communication networks on SAIFI and CAIDI, we can show the impact on SAIDI. The paper provides two scenarios to demonstrate how CAIDI and SAIFI are impacted by communications networks.
To quantify the impact of communication networks on CAIDI, a baseline of 120 minutes from failure and outage to service restoration is used. Table 2 below highlights the differences in outage timelines and shows about a 30 percent reduction in CAIDI as the intelligent network transmits data among networked devices, operations centers and repair crews.
To quantify the impact of communication networks on SAIFI, two important factors are considered:
· The frequency of underlying random events, which trigger network faults
· The ability of the distribution grid to automatically isolate faults and self-heal
While communication networks do not have a direct impact on reducing the frequency of interruptions due to things such as lightning strikes, tree falls or animals, they do play an essential role in reducing equipment failures. Recent research has shown that the collection of detailed power quality data made possible by communication networks can be used to identify failing equipment before a catastrophic fault occurs.
Consumers Energy, which operates a large distribution network on Michigan’s Lower Peninsula, analyzed outages from 2006 to 2010 and identified the top three causes of outages: trees (22 percent), equipment failures (19 percent) and lightning and weather (17 percent). While equipment outages will vary from utility to utility, we can assume that about 20 percent of outages are caused by equipment failures.
Communication networks help reduce SAIFI by enabling the collection of monitoring data from networked grid elements, sensors and other devices. Utility operations staff can use data analytics to identify faulty equipment and replace it before the equipment fails. If we assume 80 percent of the outages can be prevented with proactive maintenance, the net impact of this capability is about a 15 percent reduction in SAIFI.
In addition, the ability to network reclosers with communications to create self-healing distribution networks can help limit the number of customers that experience a power outage from random events such as a falling tree.
If we use the assumptions presented above, a 40 percent reduction in SAIDI can be achieved through the use of communication networks as shown in figure 2 below.
Intelligent communication networks provide high value today by reducing outages and enabling proactive maintenance supported by data analytics. Tomorrow holds even more capabilities with the Internet of Things.
While much has been written about IoT, most of the focus has been on the billions of small consumer-oriented devices such as wearable items, appliances and even connected cars talking to each other. What’s often not mentioned is the critical role communication networks serve as the foundation enabling these devices to connect and share information.
Smart Grids are specialized examples of IoT and the role of intelligent communication networks is critical. Resilient and secure networks not only meet the demanding needs of power utilities today, they will enable a future connected world of everyone to everything. IoT is about this transformation and expanding human possibilities to improve peoples’ lives.
About the author: David Christophe is Director of Utility Solutions Marketing at Nokia, where he focuses on helping distribution utilities modernize the communications networks that support their grid operations.