Introduction To Power Systems and Power Quality

Often times, we turn on the lights with very little thought about all of the mechanisms in place that actually make that light work. We take for granted all of the people, processes, and technology that make that glowing bulb a reality. Moreover, at times, we even are dissatisfied when the bulb doesn’t glow strong enough or flickers. It isn’t until the bulb doesn’t come on when we start to appreciate that the challenges (weather, fire, animal, vegetation, etc) of the power system. In reality, the grid has become far more complex in recent years. There are new risks and challenges in a more connected world.

First, let’s consider the power system. Historically, power moved from large generation plants through a network of transmission and distribution to end up at the consumer’s light switch.  There was no storage on the grid, which meant that grid operators had to carefully balance available generation with every new load (light bulbs) that came on the system. 

Today, the grid is far more complex. Solar generation is everywhere from rooftops to large solar farms. Batteries are in consumer homes and even at scale on the power system. The result is that power flows in all sorts of directions. Imagine having to drive your car only in reverse half of the time! There have been many unforeseen consequences as a result of this dramatic change in the grid.

Sadly, we cannot directly see electricity. Thankfully, we see its effects on things (eg. making lightbulbs glow).  However, we can measure it. In fact, many devices on the power system measure the power flowing through the grid. So, what is actually made?  Electricity is delivered to our homes as 60 Hz sinusoidal waveforms. In fact, nearly 5.7 billion of these waveforms pass by the outlets in our homes every year!

The waveforms above are idealistic. In reality, there is noise on the power system that causes them to be less than perfect. Consider the picture below.  This is actual data recorded from the power system. The red box outlines roughly the same time frame as the perfect ones above. Notice how different they look!

The further the waveforms get from perfect, the more likely it is for equipment to misoperate. In homes, lightbulbs may not glow as strong or flicker. Air conditioning units may not function. In commercial settings, computers may not work correctly.  Finally, in industrial settings, machinery may not operate correctly or at all.

Fortunately, there are numerous standards that detail how to measure, manage, and manipulate these waveforms.  Ensuring that all of the instruments that record these waveforms do so in a consistent way is important.  Once measured, it is imperative to understand what is normal and what is not.  Finally, there are standards that suggest ways to get the abnormal waveforms to look more normal.  In a nutshell, this is power quality, or PQ, making sure that the waveforms have the right size and shape.

To learn more, I would suggest getting a copy of IEEE 1250.  This standard from the Institute of Electrical and Electronics Engineers serves as a primer for Power Quality.  It also serves as a directory to the numerous other standards that helps folks better understand specific PQ phenomenon.