Boring But Critically Important – Electric System Reliability
By Tom Butz, Utility Planner/Senior, Minnesota Power
In the arena of emerging technologies, there are a number of very boring but necessary requirements to maintain a reliable electric power system. The core principles defined stand the test of time like the laws of physics, regardless of whether the system is a small single-generation source to a local load or an entire electric utility grid covering thousands of square miles.
The first principle is that electricity is generated, transmitted and utilized simultaneously, across thousands of square miles. In a micro-grid application, the boundaries of matching the electricity generation and usage are the same, unless there are energy storage resources on the system. From a utility-scale perspective, this principle is also true, which makes electricity a modern miracle of keeping the system in balance across thousands of square miles. Electricity travels at roughly the speed of light. In order to gain perspective on this constraint, electricity travels from New York to Los Angeles CA 30 times per second. If the generation is slightly less than the load, the nominal 60 hz frequency is lowered. There are protection relays on a system that closely monitor the system frequency, There are defined frequency points that are designed to suddenly open a switch to reduce the system load in 10% increments. System operators are closely watching the generation and load balance, and typically realize tight system conditions, and avoid the need for an automatic system to be deployed. If the operating margins are getting too tight, that is where load shedding events are ordered, such as during the Feb 14-17, 2021 Winter Storm URI in Texas. Power outages due to a lack of generation are very rare, and typically make the news as a major event such as extreme winter storm conditions such as Winter storm URI.
It is important to acknowledge these basic principles that keep the lights on, and provide the power to charge everything else we need charged.
The second principle is that the electric generation system is comprised of a wide range of generation types, including nuclear, coal, natural gas, wind, solar, storage, and hydro. Most of the emphasis of electric generation is on the removal of all fossil fuel generation from the system, and the replacement with wind, storage, and solar. Replacing generation resources from coal, oil, and natural gas requires a much more sophisticated evaluation of the system to determine if the moment by moment (typically evaluated on an hourly basis) balance can be assured to continue. The typical trend when adding a larger amount of wind and solar is to end up with thousands of hours a year where the generation is much higher than the load, and thousands of hours when the generation is lower than the load, thereby showing the need for other types of resources. Currently, the resources effectively “work together” by providing the right balance of generation to match the load, when some purchases and sales from adjacent power systems occur. Suppose all other systems, mainly coal and natural gas, are removed from the system, and only wind and solar remain. In that case, it is virtually impossible to keep the system in balance, and the outcome is that there will be a system blackout.
The third principle is that the electric system planning must properly reflect the real-time delivery constraints of the system. The responsibility is GREAT for planners to clearly evaluate the expected system conditions, system load, and generation availability so that the real-time operations of the system will remain reliable. All this must include considerations of the very large amount of power expected to be needed for AI servers and data servers, as well as the move to more and more electric usage for EVs and other household usage. Boring, stuff, snore and nod off with all the blur, but if we don’t pay attention, shut down all the coal plants, blindly replace it with wind and solar, we will be bluntly faced with a shortage of electricity – and be in the dark.
What are some specifics to avoid such a dark outcome? Glad you asked. First, we need to clearly think in terms of 8760 hours a year of operations, and not an annual renewable percentage target. Second, we need to understand the challenges in maintaining the balance of electric generation and load, and that the resource mix needs to be changed in step with a clear understanding of the resource portfolio requirements to maintain reliability. Third, the policy goals and statutory mandates must be met with a clear path of transformation that is both technically viable and economically acceptable to consumers. We can cover these areas in more detail at a later time, but for now, it is important to acknowledge these basic principles that keep the lights on, and provide the power to charge everything else we need charged.
About Author:
Tom Butz has been in the electric utility planning space for nearly 40 years, and has an incredibly strong passion for electric system reliability. Desiring to take complicated technical concepts into the mainstream thinking, hopefully this information is useful.