Short Circuit Studies

What are Short Circuit Studies?

• The short circuit is an abnormal connection of relatively low impedance between two points of different potentials. Hence, an overcurrent (i.e., short circuit current) will flow into the system which can damage the power system equipment.

• The short circuit can occur in the power system due to lose connection, insulation failure, aging of insulation, voltage or mechanical stress applied to the equipment, lightning strikes, wind storms, presence of animals such as birds.

• Short circuit studies can be used to determine the system behavior under short circuit or fault conditions and it helps to identify the faults in the system.

• This study helps to determine the total fault current and fault current contribution sources such as power grids, generators, and motors.

What is the Importance of Short Circuit Studies?

The main purpose of short circuit analysis is:

• • To determine the maximum possible fault current which helps to determine the protective device interrupting capability.

  • To design the equipment rating of new systems such as bus bars, transformers, cables, and protective devices.

  • To verify the acceptable equipment rating of existing systems.

  • To calculate the incident energy for arc flash studies.

How Do We Perform Short Circuit Studies?

• • Step-1: Data collection such as single line diagram (SLD), data sheet of all the equipment, and system data such as short circuit fault level, X/R ratio, power rating, voltage rating, etc.

  • Step-2: Modeling the study system/substation using PSCAD/EMTDC software.

  • Step-3: Preparation of simulation case studies with the study scenarios accepted by clients.

  • Step-4: Preparation of technical report and submission to clients. 

What Standards can be Referred for Short Circuit Studies?

• • IEEE Std 3002.3™-2018 - IEEE Recommended Practice for Conducting Short-Circuit Studies and Analysis of Industrial and Commercial Power Systems.

  • IEC 60909 - Short-circuit currents in three-phase a.c. systems.

  • IEC 61363-1:1998, Electrical installations of ships and mobile and fixed offshore units—Part 1: Procedures for calculating short-circuit currents in three-phase a.c.

  • IEEE Std C37.010™, IEEE Application Guide for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis.