The global warming crisis has exacerbated wildfires’ intensity and frequency in recent years, damaging infrastructure and impacting communities in many parts of the world. In the U.S. alone last year, 58,733 wildfires burnt more than 7.13 million acres, resulting in multiple fatalities. Utilities have, unfortunately, been implicated in many of these wildfires, with statistics from California, in 2015, indicating that more than half of the fires were caused by power lines. Power line failures were also implicated in some of Australia’s deadly Black Saturday bushfires of 2009.
Ignitions occur when the array of components making up distribution and transmission networks fail due to either electrical contact and arcing or fatigue failures under high strain conditions usually associated with winds. Overhead power lines and components are exposed to wear and tear due to weather conditions and vegetation growth. As global warming effects continue to bring unpredictable weather patterns, including extended droughts and higher winds, the power utility sector is under the spotlight and must mitigate the danger of wildfires by adapting the grid.
Identifying broken connections
One of the main ways that power utilities can mitigate the global wildfire crisis is by faster detection of falling conductors. Advanced communications technologies such as IP/MPLS and private LTE/5G, are being widely adopted by utilities as part of their smart grid efforts. These advanced communications can also carry real-time synchrophasor and usage data to monitor, detect and de-energize fallen power lines. In less than two seconds, a fallen line can be detected and isolated before it sparks, significantly mitigating the threat of widespread destruction and injury and loss of animal and human life.
When a cable breaks and falls to the ground, in particular when the soil is dry, it may not be detected by most protection systems because it is a “high impedance fault”. The US reports that 30–50% of these downed line faults are not detected by the standard protection systems. When conditions are deteriorating and wildfire risk is on the rise, some power utilities will proactively shut down power to parts of the grid; re-energizing the lines, however, can take several days. Fortunately, there are better solutions emerging.
One of the solutions being considered by several companies and research institutes is to detect falling or broken conductors by correlating local and regional ozone using OMS (Ozone Metering Systems) with Advanced Metering Infrastructure (AMI) data to identify power outages and more precisely locate downed live conductors. Ozone is generated by wildfires, and offers a viable approach, but it is not real time and is cost- and labor-intensive. OMS data collection efforts are often further complicated by difficulty of access, the need for climate-controlled facilities to house instrumentation, and a requirement for a connection to utility-grade (grid) power. Regional ozone is more often analyzed via modeling, so data needs to be processed offline before a good prediction can be made.
A better, real-time approach is to use synchrophasor measurement units to get information on voltage, current and phase angle of all conductors at different ends of the power lines. This data gets sent to a Phasor Data Concentrator where the data is analyzed to look for signatures of broken cables (high impedance faults). When such a fault is detected, commands are sent to control logic in order to open circuit breakers as close as possible to the fault and to de-energize the line. This process needs to happen within 1.3 seconds (for cables on distribution poles with heights of10m/30ft).
One of the keys to making this approach work is a reliable way to relay phasor data throughout the grid. Tolerances for latency and jitter are very low and time accuracy must be within 1µs. Transmission lines equipped with optical-ground wire (OPGW) infrastructure which includes fiber(s) and an IP/MPLS network, can connect phasor measurement units (PMUs) and circuit breakers/reclosers to accommodate these precise tolerances. Microwave radio can be used where fiber isn’t available. The approach for distribution lines is slightly different because they are rarely equipped with OPGW infrastructure. In this case, a private wireless solution, either LTE or 5G can provide the low latency connectivity required.
The advantage of this second approach is the ability to proactively isolate faults and downed conductors before a fire starts. It avoids the many variables involved in ozone detection and leverages the communications network already in place as part of previous smart grid upgrades. The IP/MPLS and private LTE/5G networks support a wide array of use cases for power utilities, so that the cost can be quickly amortized by providing benefits across multiple operational systems.
Global warming demands adaptation, not only to increased wildfires, but to renewable energy sources needing distributed energy resource management — both challenges that can be met with today’s high-speed, low-latency and highly reliable communications solutions.
