The Most Confusing Part of the Power Grid

There is enough generation to meet demand because that energy still has to be moved to where it is needed through transmission lines. Engineers use a photovoltaic curve to monitor this challenge. It relates the

power

flowing to a load in the system to the voltage it sees.  As expected, the more

power

flows, the more the voltage drops, as more power is lost in the transmission lines on the way to the load. It's the same reason the lights go out in older houses when the air conditioning is turned on: the current goes up, the voltage goes down. If you combine Ohm's law and the power equation, you can see that the power lost in a transmission line is related to the current squared.

Double the amps; quadruple the energy lost in the form of heat. But the further the system goes along this curve, the more dangerous things become. There is a point, the tip of the curve, beyond which increased demand on the system actually reduces the amount of power that can be delivered, all while the voltage continues to fall. Generators may have the capacity to supply more power, but cannot meet the load due to system limitations. Operating under the nose is unstable because the generators lose control of their speed, like a rubber tire losing grip on the road. Infrastructure is expensive, and building new power plants and transmission lines always comes with legal and environmental challenges, so we are often forced to use the

grid

to the limits of its capacity.

But

grid

managers must ensure they operate with enough headroom so that any contingency, such as a generator disconnection or a transmission line failure, doesn't push the system over an electrical cliff. This is where power factor comes into play. Loads with a lower power factor shift the tip of the PV curve downward and to the left. That reduces margin and reduces voltages in the system for a given power demand, making a voltage collapse more likely if any

part

of the system fails. Therefore, we use various ways of supplying reactive power to provide voltage support and shift the curve back up.

Power plants can adjust their operating parameters to supply reactive power, but transmission lines have their own inductance that consumes the reactive power as it travels. Therefore, it is often more efficient to address the problem on the load side, and there are several types of infrastructure that make this possible. Synchronous capacitors are large motors that are not connected to anything.  Instead of converting electrical energy into mechanical energy, they basically spin freely, but with some smart circuitry they can generate or absorb reactive power from the grid. They can also help stabilize fluctuations in the grid with the inertia of their heavy rotating mass, something that is becoming increasingly important as we transition more towards renewable sources that use inverters to connect to the grid.

Another option, and one you are more likely to spot, are banks of shunt capacitors connected across the lines. They can sometimes be seen at substations, but many capacitor banks are installed on poles outdoors so anyone can take a look. Like the capacitor in my demonstration, they increase the power factor and increase the PV curve. This can actually become a problem during off-peak hours by increasing the voltage above where it should be, which is why many capacitor banks turn on or off depending on system conditions. Looking again at the PV curve, you can see how leaving the capacitors off during periods of low demand keeps the voltage within limits, and having them on when demand is high provides more headroom and more voltage.   Some operate on timers that turn on during the highest demands of the day, and many operate at the discretion of a utility company to adapt to different grid conditions.

They are usually either fully on or completely off, so deciding when to flip the switch is important. A third option for reactive power supply, called a static VAR compensator or SVC, addresses that challenge. These use electronic components to quickly turn inductors and capacitors on or off to constantly adjust to system conditions. That change occurs automatically and quickly, making them much more suitable for the dynamic changes that occur on the network. That's why Hydro-Québec installed them in its system in 1989. The long transmission lines between hydroelectric plants in the north and load centers, such as Montreal, in the south, require careful voltage control to avoid instability.

But the geomagnetic storm ruined the process.  Induced currents in the transformers and along those transmission lines seriously increased the system's reactive power demand. The resulting distortions in the voltage and current waveforms had not been considered when the equipment was installed. The SVCs were not configured to handle the dynamic conditions affecting the system, so the relays designed to protect them tripped, taking the equipment out of service. Without SVCs, grid voltage dropped, frequency increased, and chaos ensued. Grid operators were unable to disconnect clients quickly enough to maintain stability, and within seconds the rest of the system collapsed. Many pieces of equipment suffered permanent damage and millions woke up that frigid morning with no real power, reactive power or apparent power, shutting down virtually the entire province for half a day and requiring costly and expensive repairs.

They learned a lot of lessons that day and adjusted a lot of relay setups since then. It's just one of many case studies on the importance of understanding and managing this hopefully less baffling idea of ​​reactive power on the grid. One of the biggest challenges as renewables become a much more significant proportion of electricity sources is controlling voltage swings that can occur when the sun or wind changes suddenly. And one of the countries that is preparing to satisfy, at least for short periods of time, 100 percent of electricity demand using renewable sources is Australia. One idea they are exploring that I thought was really cool is to repurpose old fossil fuel generators into synchronous capacitors that can stabilize those oscillations and keep the reactive power flowing.

A pretty creative solution, a great country. And if you want to see some of the more interesting

part

s, my friend Sam at Wendover Productions just started the next season of Jet Lag, a travel-based game show. They travel across the country trying to claim as many regions as possible by winning challenges. It's a super creative concept in its tenth season and each episode is released early on Nebula. You probably already know Nebula. It is a streaming service created by and for independent creators. There are no studio executives deciding what gets the green light, no ads, and no algorithms directing content to a single style.

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