Utilities have owned and maintained their own private networks for decades, long before there were public wireless carriers which came into existence in the early 1990s. Utilities have historically used private wireless networks for land mobile radio communication and for wireless Supervisory Control and Data Acquisition (SCADA) functionality.
The Federal Communications Commission (FCC) historically have made some narrowband spectrum available for utilities to allow for private communication without interference. While this spectrum was sufficient for utility applications in the past, as data needs have grown exponentially the availability of spectrum has decreased and the FCC no longer has a classification of spectrum for utilities. This puts utilities in a challenging position to meet the demands of grid modernization, requiring communications to exponentially more devices, retrieving exponentially more data than on SCADA networks in the past.
Many utilities have deployed fiber substations and field devices when financially and technically feasible. However, reliable wireless communication is still needed to many downline devices and in rural areas, where fiber connectivity to substations is financially prohibitive.
Utilities need to be able to communicate to many of their devices and field workers during storm situations when power has been out for hours – and potentially days. There are four criteria that utilities typically need for their mission critical communication networks:
While 100% availability is unrealistic, utilities typically require at least 99.999% availability, which equates to between five minutes and 52 minutes of downtime per year.
Communication with devices and personnel must always go through, whether in urban areas that may be highly congested or in rural and remote areas.
When a command to open or close a switch or circuit breaker is sent, the signal needs to be delivered and confirmation sent back to the operator in a few seconds. If the network is used for protective relaying when faults occur, the signals need to be sent even faster, within a few hundred milliseconds.
Protection and security are critical on a network since extreme harm can occur if a utility network is hacked. Access to the network needs to be restricted so unauthorized personnel cannot access it. Data needs to be encrypted to prevent tampering, theft, or acts of terrorism or sabotage.
Commercial networks cannot meet the stringent requirements that utility networks require. The LTE standard used by commercial providers tries to address some of this by allowing prioritization. However, most commercial providers do not employ prioritization on their networks. Commercial network operators may have battery plants on premises that provide four to eight hour back up capacity, but few employ generators at their sites. If power is out for long periods of time, commercial networks typically fail.
With utility owned and operated networks, generators are typically deployed at all sites and technicians are on call 24/7 to repair networks.
There has never been a major natural or man-made disaster in which commercial networks have continued to operate at 100% capacity. In August 2017, Tropical Storm Harvey, one of the costliest hurricanes in U.S. history, caused major damage in 55 Texas counties. The FCC’s Impact Report showed up to 94.7% wireless outages throughout the counties.
The local utility who owns, operates, and maintains their own communication networks for land mobile radio and SCADA maintained 100% communication connectivity–with the exception of one substation which sustained major flooding.
Similarly, Hurricane Michael caused outages to the commercial wireless network in 100 counties throughout Alabama, Florida, and Georgia in 2018. The FCC’s Impact Report showed some counties with 88.9% availability, with one county being entirely without wireless service. Commercial wireless service continued to be spotty several days after the storm made landfall, with the FCC reporting significant outages in areas two weeks later.
Public wireless site outages are frequently caused by a loss of power. Critical infrastructure services that rely on public wireless networks will not be able to communicate once the battery power of a site is lost after 4 or 8 hours. Wireless providers will tell you they have generator backup, but in actuality they have a generator port on a building where a generator can be brought to the site if needed. However, generators cannot always be delivered during disaster within the time they are needed, and fuel needs to be delivered to run the generators. In some disasters, fuel is in short supply. Utilities, on the other hand, typically have their own generators on site with significant fuel supply.
Commercial wireless networks do not typically meet the needs of availability, reliability, low-latency, and security mission critical utility networks require. Utilities must continue to build, operate, and maintain private networks for their mission critical communications. Utilities will need to acquire private, licensed spectrum that allows them to build private networks.
Unfortunately, acquiring that spectrum can be challenging as the FCC does not provide a spectrum allocation for utilities and have been pushing spectrum sharing the past several years. Shared, unlicensed spectrum also puts a utility at risk for interference. Does this mean that commercial wireless networks cannot be used for any utility communications? Absolutely not. It means utilities need to build private networks for communications that must go through for the protection of life and property.