Reliability in Power
This is the Fifth episode in this series called ‘Understanding Power’.
This episode’s topic is all about understanding the cost of your utility bills.
This video and blog covers two topics
- Reliability in Power
- Reliability in Transmission
Relability in Power Generation
on January 13, the Alberta Electrical System Operator (AESO) released two notices, each more serious than the other: The grid was at risk of having province wide blackouts. What caused this? Well, it was two-fold:
- High Demand: because it was winter and it was extremely cold (-30C), there was a lot of extra load. In fact, Alberta hit an all time high record that week.
- Limited Power Generation: Alberta has a large percentage of wind power capacity(shown in pie chart on left below) but the thermal gradients that create wind are limited in very cold weather meaning there was very little wind power being generated (shown in pie chart on right below)
this created the perfect storm where we had an elevated load and an undersupplied grid almost resulted in calamity.
Ensuring Sufficient Power Generation
It is probably very clear that a territory needs to ensure that there is more power generation capacity than there is load, what may not be as straight forward is how the different types of power generation operate throughout the day and respond to load variability.
above is a fictitious example of a typical 24 hour day within an example jurisdiction. What this chart is aiming to show is how throughout an average day, most grids see dramatic load change with two main spikes: the first in the morning as people get up and get ready for work, and the second at nighttime when people leave work and start cooking.
Our grid power generation mix is made up of 3 main groups: (Get more information on power generation technologies)
- Baseline power: Power generation capacity that cannot easily be ramped up or ramped down.
- Variable Power: Power generation systems that produce power when available such as solar (during sunlight hours) and wind (when the wind blows)
- ‘Agile’ Power: Power generation systems that can easily be ramped up or ramped down to allow for overall grid load response.
In the chart shown above, you can see how the baseline power (Nuclear, Hydro and Large thermal) remain relatively consistent throughout the day. Additionally, you will notice how solar comes on during sunlight hours. Though wind appears to be consistent, Wind power is a function of wind and can be unreliable as seen above. Finally you can see how the major load variability is responded to by small and responsive thermal plants which operate using engines and aero derivative turbines. The benefit of these types of systems are that they can be easily turned on, ramped up and then turned off as necessary.
This mix of generation capabilities allows the grid to quickly respond to load changes ensuring reliability of power supply.
Reliability in Transmission
The second part of this topic is about reliability in the transmission systems we employ to transmit power from the point of generation to the eventual location of where the load is, whether that is our house or a facility.
It is straight forward to understand that we need to have adequate power generation for the load of our grid at any given time; but equally, we need to ensure that this transportation infrastructure can supply the amount of power to the locations required. The major portion of our system is the transmission lines, whether that’s the transmission portion, or the distribution portion, the power lines play a huge role in the reliability of our power system.
Transmission Reliability Problem 1: Capacity Overload:
The first thing we need to make sure is that we are never in a scenario where our load exceeds the capacity of our transmission lines. In scenarios where the load of the system exceeds the capacity of the power lines or transformers, we end up in scenario where we will have system wide power failure. Want more information how the transmission system works?
Transmission Reliability Problem 2:
The second scenario that we see a lot with power lines is power lines are highly susceptible to weather: They’re above ground, easily exposed to flying debris, for example, in hurricanes, and also susceptible to easily sparking fires and we’re seeing this happen quite a bit in California these days.
In 2019 act, we actually saw a utility actively choose to turn off their high voltage power lines, because of fears that their lines would cause fires and that resulted in massive power outages and failures within the the Northern California region.
How can we increase reliability in transmission?
Well, one of the ways that a utility can increase the reliability of the grid, is by generating power closer to the load, and ont he distribution side of the transmission system. This is called distributed generation. By moving the generation closer, the likelihood of line failure between generation and load has been dramatically reduced.
Onsite Power Generation
So let’s say you lose power at your facility and there is no distributed power generation or in fact, the power outage is right outside of your building, how are you going to ensure that you have reliability? this is where standby generation or on site power generation support power reliability.
Below is an example of a backup diesel generator installed at a hospital to provide backup power in the case of grid power failure. Want more information?