Keep the lights on with a resilient converged FAN
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- January 29, 2019
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When the lights go out, lives in a modern society stop. The interruption of power service can cause hazards to the public and inconvenience to communities, as well as economic losses to businesses. It also creates revenue losses for power utilities. Consequently, improving grid reliability is a major goal of the power industry.
Self-healing systems need reliable FAN connections
Unfortunately, service interruptions can and will happen. Cable failures, insulator contaminations, broken utility poles, snowstorms, floods, and even heat waves can all disrupt the constant flow of electricity. To mitigate against the impact on grid reliability, utilities are deploying fault location, isolation and service restoration (FLISR) systems (also known as fault detection, isolation and restoration (FDIR)). These systems include intelligent electronic devices (IEDs), such as line switches and reclosers. They work in conjunction with distribution management systems (DMS), supervisory control and data acquisition (SCADA) systems, and grid data processing and analysis tools. Typically, the FLISR operation is supported by a field area network (FAN) that carries grid data, along with command and control messages.
According to a study conducted by the U.S. Department of Energy, FLISR systems can reduce the number of customers interrupted by a disruption by up to 55 percent and the number of customer minutes of interruption by up to 53 percent. In addition, many utilities also deploy volt-VAR optimization (VVO) applications to remedy voltage drops after feeder circuit reconfiguration by FLISR systems during the self-healing process.
While FLISR and VVO are key to grid self-healing and voltage level maintenance, they are only as good as the FAN to which they are connected. If there is a failure in the FAN’s end-to-end communication path, the DMS cannot trigger FLISR applications to resolve circuit faults because fault notifications from remote terminal units (RTUs) or smart meters are not received. A FAN failure also makes it impossible for in-line switches to receive service restoration instructions. In short, if the FAN fails, grid self-healing fails.
Converged FAN maintains reliable connectivity for all applications
A converged FAN, grounded in LTE and IP/MPLS technologies, contains the resilient multiservice network architecture utilities need to maintain reliable power grids.
To provide the reliable and efficient communications network links needed, the FAN should be built on fully redundant end-to-end communication paths, as well as a feature-rich LTE IP/MPLS router that can capitalize on all network protection and restoration measures (Figure 1).
Figure 1: Key elements in a resilient FAN architecture
The key elements of this resilient, converged, FAN architecture include:
- A protected LTE link enabled by an LTE IP/MPLS router that brings IP/MPLS services to all attached IEDs, can detect LTE network faults, and switch traffic to a backup LTE network, when needed
- A multi-fault resilient IP/MPLS backhaul network that connects all the communication nodes in the distribution grid and can intelligently reroute IED and application communication traffic, as required
- A hot duplex LTE packet core that serves as the central gateway for LTE radio traffic
- Multiple headend routers to support all distribution automation application traffic carried over the LTE network and terminating in the active operations center
- A geo-redundant pair of operations centers where utilities can manage the grid from a standby operations center when the active operations center is seriously damaged
- A hot redundant pair of network services management platforms to provision, monitor and operate the FAN
The multiservice capabilities of a converged FAN built with these elements also provide secure and cost-effective segregated broadband connectivity with quality of service (QoS) assurance to support a plethora of smart grid applications. These capabilities also enable open but secure interconnection to other IP networks, if necessary.
Converged FAN strengthens power service reliability
Equipped with end-to-end redundant network protection, a converged FAN built on these six elements harnesses the power of IP/MPLS multiservice capability and offers the scalability to support traffic for multiple distribution automation applications. It significantly reduces network operations costs compared to the discrete FAN paradigm. And it protects grid communications to ensure operations integrity.
Most importantly, a converged FAN provides the necessary resiliency to reliably carry all FLISR, VVO and SCADA communications during service disruptions when keeping the lights on will ensure business continues as usual for the public, communities and businesses.
 Distribution Automation, U.S. Department of Energy, 2016.