Last October, Southern California Edison (SCE; Rose-mead, California) completed installation of a first-of-kind neighborhood distribution circuit referred to by The New York Times as “the circuit of the future.” The emerging solutions deployed on the 5-mile circuit east of Los Angeles have stemmed from industry best practices and SCE subject experts in transmission and distribution automation, distributed generation and communications, working on system reliability and security, and workforce safety.
Far from a self-serving collaboration, third-party stakeholders in the circuit project include the Department of Energy (DOE), Oak Ridge National Laboratory, the Electric Power Research Institute, the Consortium for Electric Infrastructure to Support a Digital Society/IntelliGrid, the California Energy Commission and KEMA Consulting.
Suppliers and manufacturers were challenged to provide innovative equipment and expertise. After design competition among the stakeholders, the final plan and the future circuit was named “Avanti,” the Italian word for ahead or advancement. These worldwide partners have high expectations for improved system reliability, security and superior distribution circuit delivery. But at the heart of the Avanti Circuit is another set of expectations that has given the men and women who will work on the system high hopes for the future.
Shortening the Gap
When linemen hear about a new tool or device that will save them time or make their job safer, their first response is, “When can we get it?” However, they have learned to brace themselves for the answer, which is usually, “Oh, it's several years away.”
The benefits of many new technologies remain unrealized because of the time involved and the cautiousness associated with deploying new innovation responsibly and in a timely manner. Linemen hope this will change.
There are good reasons why development of new technologies can take what seems like forever to be realized in the field. The high demand for reliability in the electric industry has made testing in the field a risky environment to prove the capability of new technologies. And, in addition to bench testing and field trials, there are consensus building and compliance issues to consider.
One of the underlying premises of the Avanti Circuit is the hope that the gap between the testing of a new system device and deployment can be significantly shortened. Linemen see the Avanti Circuit as a way to take test beds and demonstration projects to the next level, where smart devices and equipment work together in the real world. Combining these demonstration projects will more quickly help build momentum and acceptance for the solutions while reducing the perception of risk.
Ganging of Emerging Devices
Another big advantage for those who work on SCE's distribution systems is having all of the field-testing gathered in one neighborhood circuit. Most of the advanced communications and control technologies are in various prototype stages. They are also more complex and, in some cases, they are new to the distribution workforce. Rather than having field trials scattered randomly across SCE's 50,000-sq-mile distribution system and risking the possibility of linemen running into new devices on which they are not fully trained, Avanti centralizes the next-generation solutions for proof of concept in one real-world neighborhood.
The 12-kV circuit, which originates in the Shandin substation, will actually be comprised of three adjacent distribution feeder tie circuits using a radial topology with a mix of overhead and underground facilities. Having the innovations in one service area enables a focused crew of line workers to more confidently maintain the neighborhood system. All SCE staff will benefit from the experience and information gained from the host of emerging and advanced systems and equipment used on this circuit. However, only those linemen who work on the circuit need to receive additional maintenance and troubleshooting training.
The field crews also are an integral part of the proof-of-concept process. One of the criteria of all future equipment deployment is that it be lineman friendly and easy to work on by all field personnel. If a device does not meet the performance criteria or a better solution emerges, plug-and-play architecture is included in the circuit design. This allows it to be flexible enough to test a variety of equipment types, communication strategies and protection schemes. Disconnect points at various stations make it easy to upgrade and re-engineer the switches, reclosers and sensors staged on bolt-on platforms on the system. As new devices are added and improvements are made, the line crews in the service area are schooled to work on the new equipment.
Once an innovation has been proven on the Avanti Circuit and it is ready to be deployed to other parts of SCE's system, the line crews working on the neighborhood circuit will train other linemen in the company. This train-the-trainer model makes learning new technology easier for linemen as they receive practical schooling from their peers who have been working with the new technologies.
Technology at Your Fingertips
Another plug-and-play innovation that will affect linemen and trouble-call technicians is the use of temporary distributed generation. Avanti has been provisioned with interconnection sites for SCE's portable skid-mounted distributed energy resources and future storage technologies. Portable step-up transformers can be hooked up to these interconnection points. In the case of a weeklong heat storm, it can be grueling for a lineman to try to find a solution to backfeed a system and relieve load off the circuit. Instead, technicians can dispatch a step-up transformer predesigned for the 12-kV circuit and the appropriate portable generator rented from a vendor or in SCE's inventory. A SCE task force has been developing temporary generation solutions for a variety of circuits.
One lineman-sensitive initiative on Avanti is the use of composite poles and crossarms. The concept of creating a nonconductive fiberglass utility pole is a maturing technology in both transmission and distribution. These poles have proven to be as strong as or stronger than a comparable wood pole with a fraction of the weight. SCE is installing composite poles on the Avanti Circuit because of their ease of handling and life-cycle maintenance cost.
Composite poles are manufactured in modular sections. In the event that a car runs into a pole, the crew unbolts the bottom section, lifts the pole off the platform and replaces it. Because the composite poles are hollow, they are much lighter than wood, and can be manually carried by a crew and installed much faster without heavy equipment.
Mitigating Fault-Current Dangers
One of the actual plug-and-play innovations incorporated into the design of the Avanti circuit is a pre-engineered and installed connection point, which will allow the quick connection of temporary distributed generation.
From an overall design perspective, the circuit is a 5-mile-radial, 12-kV line with a normal load rating of 8 MW and a peak load capacity of 12 MW. Toward the far end of this line, provisions have been made to allow the quick connection of up to 3 MW of temporary generation or energy-storage devices. This connection is done through a skid-mounted portable substation including a step-up transformer and associated metering, control and protective apparatus.
In the case of an extended heat storm or during the maintenance or replacement of critical circuit components, it can be difficult for utility system operators to find a solution to relieve the load the circuit must serve. With interconnection provisions and a location prearranged and preinstalled, technicians can dispatch a portable interconnection facility designed for the 12-kV circuit. Local generation capacity reduces the loading on critical circuit components, such as the underground “get-away” cables used to connect the circuit to the substation transformers. SCE engineers and technicians have been developing temporary generation and energy-storage solutions for a variety of circuits for load support purposes. If successful, this distributed generation innovation can be cost-effectively implemented in retrofitting connection points across SCE's 4300 distribution circuits.
Hot Spot Dangers
Another safety feature that SCE linemen are hopeful about on the future circuit is the deployment of fiber-optic temperature sensors. Hot spots on power lines indicate an equipment malfunction, premature cable aging or some other anomaly. In most cases, they are undetectable to the naked eye and can be dangerous to workers in the area if undetected. Distributed fiber-optic temperature sensing technology offers a way to find these hot spots before they find the linemen.
SCE was the first utility in the United States to monitor 69-kV transmission circuits using dynamic circuit thermal line ratings. Thermal rating of the cable ducts will measure both current temperatures and detect the location of significant hot spots on the transmission lines that can more easily be corrected. On the Avanti Circuit, the sensors have been installed in the 12 get-away conduits at the Shandin substation. This technology helps to determine the temperature of the conductor along the entire length of the transmission and distribution feeders. During peak load seasons, when air conditioners are running full tilt and businesses are working overtime, the controller must decide if circuits can handle the load or if load needs to be dropped to protect equipment. The fiber-optic sensors measure the temperature of cable in the ducts and help the controller calculate load distribution without risk of overheating the circuit. They also give linemen on maintenance and trouble calls the added assurance of the location of the hot spots.
More Work to Do
During the past five years, SCE has invested more than $5 billion in distribution infrastructure expansion and replacement to keep pace with a growing service area and to retire aging components. The circuit of the future cost about $3.5 million, about 10% more than a traditional circuit. In addition, the DOE provided nearly $1 million in research and development assistance. The philosophy behind the Circuit of the Future is it is not the end state, and many other new devices and solutions will still need to be considered.
SCE plans to invest another $9 billion over the next five years in system upgrades and improvements. Avanti provides an environment to install and demonstrate these distribution technologies in a safe and systematic way and more quickly prove the validity of new technologies. And for the linemen on the project who hope for a safer workplace, they may see improved reliability sooner rather than later.
SCE's Avanti Circuit is a 1400-customer neighborhood study platform featuring the most advanced distribution circuit technology currently available. It is located in the Inland Empire region of Southern California, east of Los Angeles in San Bernardino County, which is one of the fastest-growing U.S. urban areas. Key technologies include modular hybrid poles with molded crossarms, vacuum fault interrupters, automatic reclosers, remote-controlled switches, duct-bank temperature sensing and distributed generation/ VAR resource connect points.
Additional devices to be installed include a distribution-level static VAR system, RFID tags, automated meter interfaces and a fault-current limiter, which will be installed at a premounted pad and bypass disconnect switch at the Shandin substation.