• Student and Mentor
• Learning Example
• Basic Example
• Advanced Example

Line faults in a power system are a major concern for Engineers working in power generation, transmission and distribution. Despite the effort to prevent faults within the system, they occur frequently and without warning.  Quick action must be taken to determine the exact nature and location of these faults so that the proper action can be taken to restore the system.  There are many type of faults.  Typical cases are a single line or multiple lines in contact with ground or the lines of two or more phases in contact with one another.  These faults can be temporary and require only a reclosure after a breaker trip or they can be permanent requiring repair crews to be dispatched to correct the problem.

Educational Goals

This web-based tutorial has been designed to demonstrate how a power system’s protection devices respond to a fault. It allows students to examine the sequence of alarms and actions that occur as the result of a fault, use an Intelligent Alarm Analyzer to determine all of the possible locations and types of  faults that resulted in the chain of event alarms and actions, and finally to draw their own conclusion as to the nature and location of the fault. 

Instructional Approach

An interactive approach is suggested as an effective method of teaching a student the concepts of Fault Analysis. This method utilizes a Fault Simulation and Intelligent Alarm Analyzer software package called GAAM to create fault scenarios and an online communications program, Microsoft Netmeeting, to allow the tutor and student to communicate efficiently. 

GAAM

This program can be integrated with a utility control center, and we have prepared some GAAM cases for educational exercise

GAAM is a software package that integrates a one-line diagram of a power system, a sequential event report (SER), a trip summary and an intelligent alarm analyzer into a single screen.  This package is a convenient tool for simulating faults as well as protection system malfunctions in a power system and analyzing the protection system’s response to the fault.  The program can then be used to determine all of the possible locations, types of faults, and protection system malfunctions. 

Features

One Line Diagram

The one line diagram, located in the upper left corner of the screen, shows the entire network of buses, generators, transmission lines and loads of the given system.  To locate a specific bus, the find feature can be used.  For example, in case one we will be looking at a fault in the area of the bus named Castelnuov.  To locate this bus on the one line diagram, click “Find”, then type in Castelnuov and push the enter key. The Castelnuov Bus should now be near the center of the one line diagram window.  To get a closer look at the area of interest, the zoom feature can be used.  Click “Zoom” and select 100%.

Sequential Event Recorder Report (SER Report)

Located in the lower left corner of the GAAM screen is the Sequential Event Recorder Report. As the name implies, the SER is a sequential list of the system alarms that are recorded during a fault. Understanding the SER report is an important part of understanding fault analysis.  The SER report includes information about the status of relay protection devices, and the opening and closing of circuit breakers. Also recorded are communication signals between protection relays and circuit breakers known as telepilots.  The telepilots can be displayed on the one line diagram by clicking “Signals” and selecting “ALL”. 

The program GAAM was developed for an Italian utility so the SER report is written in Italian. It is convenient to use a program to translate the SCR report to English.  This translator file is located in the MMI folder.  To translate the SER report, double click the trans.exe icon (a happy face).  The translator will then create a new text file named “scr_new”.  This file can then be viewed with any text editing program.  

Trip Summary

 The trip summary is located in the lower right corner of the GAAM window.  It lists all circuit breakers that were opened to isolate the fault in sequential order.  This information can be found in the SER report, but because of the importance of the breaker openings it is emphasized in the trip summary. 

Analyzer

The analyzer is located in the Upper right corner of the GAAM window.  This feature takes the data from the SER and determines all possible locations and types of faults, and/or malfunctions that would cause the chain of events.  These results are displayed as “Hypothesis” and it is important to note that there may be more than one hypothesis.  This will likely be the case if there has been a malfunction in the protection system and the SER report is incomplete. 

Lesson Plan

The following cases are a suggested lesson plan developed to be used with Netmeeting and GAAM.  The first two cases are relatively simple cases designed to familiarize the users with the features of GAAM.  The third case is a more challenging case designed to challenge the student’s ability to determine the effects of both a fault and protection system device malfunction.  A sample of the typical communication between the tutor and the student are shown for each of the cases.