Print this page Introduction to Protective Device Coordination Analysis
Velimir Lackovic, MScEE
Course Outline
The objective of a protection scheme in a power system is to minimize hazards to personnel and equipment while allowing the least disruption of power service. Coordination studies are required to select or verify the clearing characteristics of devices such as fuses, circuit breakers, and relays used in the protection scheme. These studies are also needed to determine the protective device settings that will provide selective fault isolation. In a properly coordinated system, a fault results in interruption of only the minimum amount of equipment necessary to isolate the faulted portion of the system. The power supply to loads in the remainder of the system is maintained. The goal is to achieve an optimum balance between equipment protection and selective fault isolation that is consistent with the operating requirements of the overall power system.
Short-circuit calculations are a prerequisite for a coordination study. Short-circuit results establish minimum and maximum current levels at which coordination must be achieved and which aid in setting or selecting the devices for adequate protection. Traditionally, the coordination study has been performed graphically by manually plotting time-current operating characteristics of fuses, circuit breaker trip devices, and relays, along with conductor and transformer damage curves—all in series from the fault location to the source.
This course reviews the subject of protective device coordination in a very structured fashion. First, modelling technique is shown for a generic power system, protective relays are modelled in details and relay settings are determined based on short circuit current calculations. A detailed explanation of modelling and calculation procedure is offered. Explained techniques can be implemented in any commercial power system software package.
This course includes
a multiple choice quiz at the end,
Learning Objective
At the conclusion of this course, the student will:
- Basics of coordination;
- Computer programs for coordination;
- Common structure for computer programs;
- How to make use of coordination software;
- Verifying the results;
- Equipment needs; and
- Practical example.
Intended Audience
This course is intended for electrical engineers.
Benefit to Attendees
Attendee of this course will be able to understand basic protection principles, equipment used for electrical system protection, ways to selectively coordinate protection devices and how to complete relay protection coordination study.
Course Introduction
Electrical power systems must be designed to serve a variety of loads safely and reliably. Effective control of short-circuit current, or fault current as it is commonly called, is a major consideration when designing coordinated power system protection. In order to fully understand the nature of fault current as it is applied to electrical power system design, it is necessary to make distinctions among the various types of current available, normal as well as abnormal. It is also important to differentiate between the paths which the various types of current will take. Both types of current and current path, as well as current magnitude, will affect the selection and application of overcurrent protective devices.
Course Content
In this lesson, you are required to download and study the following course content in PDF format:
Introduction to Protective Device Coordination Analysis
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Course Summary
The increased popularity of the computer and its availability in most engineering facilities has resulted in liberating the design engineer from the tedious task of manually drawing coordination curves, thereby allowing him or her to be free to design. This courses presents skills that are still necessary to make those critical judgment decisions and to establish the criteria that should not be left to a computer.
Quiz
Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.
DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.
