Welcome to PSP keys training academy My name is Graham van Brunt. And the subject of this course is per unit system analysis. I am an electrical engineer with over 35 years experience and I started my career off in protection parole with a company called Ontario hydro. In about 1996. It split up into hydro one and OPG and a couple of other splinter groups. But during that time, I had a lot of hands on training in protection and control, including training of the technicians, technologists and engineers in Canada as well as internationally.

I am the founder and lead instructor for PSP T which stands for Power Systems Protection training. And I put together this course for two reasons. In power system analysis, you You are going to run into a series of difficulties. First difficulty you're going to run into is that most systems are three phase in nature that is the voltages and currents are three phase. Next you are going to run into transformer ratios where the transformers are used to step the voltage up from generation to transmission and then stepping it down to distribution and ultimately to the individual user at the end of the transmission line. Then there's also the complexity of transformer connections.

In other words, how a transformer is connected and its configuration. For example, you could have a y two Delta or a delta y transformer or you could have y two y delta delta or even as zigzag transformer. This would add another level of difficulty to system analysis. Finally, you could run into an unbalanced condition for the first three difficulties. The analysis is not that hard if the system is balanced. However, once the system becomes unbalanced, again, you're at another level of difficulty, and you need to develop tools for that process as well.

Fortunately for us, there are solutions for the difficulties that have just been presented. In the case of a balanced system, you can reduce it to a single phase system by the use of per phase analysis. Next, you can use per unit normalization to reduce the complexity that Transformers introduce into the analysis of the system. Then you can use your basic circuit theorems for the analysis of the system. And finally, there is a thing called symmetrical components which is another course however, It deals with asymmetrical quantities and reduces the asymmetrical system to a system of three symmetrical systems which then can be dealt with by per unit analysis and per phase analysis and your basic circuit theorems. So, what are these solutions look like in a typical setup, what you see before you is a typical setup of a three phase system you have the generator connected to two Transformers which step the voltage up to two different voltage levels which are connected to transmission lines and then ultimately connected through to Transformers that step it down for distribution purposes to a couple of loads that you see here.

The first thing you want to do if this system is balanced is do a per phase analysis on the system. Once you do a per phase analysis, the system will be reduced to single phase quantities and would look a lot simpler and would look something like this. As you can see, the system is much, much simpler. However, there is still four Transformers that are in our system. And doing the analysis will be that much more difficult depending on the ratios of the Transformers as well as their connection configurations. So, we would like to remove that complexity introduced by the transformers.

And we do that by using a tool called per unit analysis. And per unit analysis. We'll take all of the voltages and currents and impedances of the system and we run them through a process called normalization Once that takes place, the system will then be reduced to look like this. And you have to admit that this system is much easier to analyze it is a single phase circuit now, with no Transformers in the system or at least the transformer ratios and and connection configurations to worry about. We simply have impedances and generators and loads to worry about. And the system then can be analyzed using our basic circuit theorems.

And that would be much easier task for us in the end. This ends the introduction