Introduction to Short Circuit Current Analysis

In Introduction to Short Circuit Current Analysis, you'll learn ...

• Why short circuit current studies should be done
• Physical phenomena that determine the magnitude and duration of short-circuit currents
• How to determine the type of short-circuit analysis that is required
• How to detect and mitigate the effects of excessive short circuit currents

Overview

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Credit: 4 PDH

Length: 40 pages

Short-circuit studies are done to determine the magnitude of the prospective currents flowing throughout a power system at various time intervals after a fault occurs. The magnitude of the currents flowing through the power system after a fault varies with time until they reach a steady-state condition.

This behavior is due to system characteristics and dynamics. During this time, the protective system is called on to detect, interrupt, and isolate these faults. The duty imposed on this equipment is dependent upon the magnitude of the current, which is dependent on the time from fault inception. This is done for various types of faults (three phage, phase-to-phase, double-phase-to-ground, and phase-to-ground) at different locations throughout the system. The information is used to select fuses, breakers, and switchgear ratings in addition to setting protective relays.

This course presents the subject of short-circuit analysis in a very structured fashion. First, a simple equivalent circuit is developed for a generic power system, system impedances are recalculated to common base and fault are calculated at various locations throughout the system. A detailed explanation is offered for calculation at various locations throughout the system. A detailed explanation is offered for calculation of three phase faults. The computational techniques presented in this course can be verified by any commercial power system software package.

Learning Objectives

Upon completion of this course, participants will be able to:

• Explain the scope and requirements of short-circuit studies.
• Describe AC decrement and the effects of rotating machinery.
• Explain fault-current DC decrement and system impedances.
• Analyze electrical system impedances using symmetrical components.
• Compare time-domain and quasi-steady-state short-circuit current assessment methods.
• Identify industry standards for short-circuit current calculations.
• Describe the four duty types specified in IEC 60909.
• Distinguish significant differences between IEEE C37 and IEC 60909 short-circuit calculation standards.
• Explain bus admittance and bus impedance matrices.
• Describe system modeling and computational techniques.
• Explain selection guidelines for short-circuit current calculation software.
• Identify models of branch elements.
• Analyze factors affecting the accuracy of short-circuit studies.
• Apply short-circuit current study methods to a practical industrial power system example.

   

Certificate of Completion

You will be able to immediately print a certificate of completion after passing a multiple-choice quiz consisting of 35 questions. PDH credits are not awarded until the course is completed and quiz is passed.