Introduction to Power Systems



What are Power Systems

Describe what a power system is and link to a better post

Talk about 3 phase power and a short history of it.

Talk about the different voltages and link to the better post.

Blurb about design and interpretation of how a power system reacts using power system studies.

Power System Studies

Power System studies are a group of studies that look at a power system model developed in various software, or by hand, that tell something about how the system operates.

There are various types of these studies, including:

  • Short Circuit Study
  • Time-Current Curve (TCC) Study
  • Load Flow Study
  • Incident Energy Study

These 4 are the most common types and with them an engineer can glean a lot of the information they need to determine the state of the system in a moment in time.  That is a critical distinction, these studies are snapshots in time of how the system is configured, a load change in a motor will change how the entire system behaves.  A competent engineer will be able to determine the worse case set up for the system, especially in the area that they are looking at, to determine what the best group of scenarios are to set up the initial state.  It is a iterative process.

Short Circuit Study

A Short Circuit Study is used to determine if the bracing is proper in the event that there is a solid short circuit (bolted fault) across the phases or a phase to ground.  This creates large amounts of current, and the various magnetic fields that come with them.

TCC Study

A TCC study coordinates the protection on the system such that the closest protection device to the fault will trip. This ensures that the least amount of equipment is affected in the occurrence of a fault on the system. It also helps determine how the system will react during an event in a predictable manner.

There is always an interplay between the TCC and Incident Energy studies. Sometimes we will sacrifice coordination for lower incident energy levels.

Incident Energy Study

This is the study that is also referred to as a arc flash study. This study helps determine the incident energy levels in the case of an arc fault using IEEE or NFPA equations.

Load Flow Study

This is the most fluid and changing study. Here you set up the system with the known loads and determine how the power flow is affected across the system, current, power factor, and voltage.

This study is important in determining if power factor correction is necessary, and how to go about it. If the feeders are sized properly to minimize voltage drop and ampacity.