🙄 What is Short Circuit? ·
- Accidental or intentional conductive path between two or more conductive parts forcing
the electric potential differences between these conductive parts to be equal or close to
Why Short Circuit?
- To avoid unnecessary Over design
- To avoid the insufficient rating of equipment’s ·
- To optimize the cost with various possibilities ·
- Selection of Optimal Transformer Impedance ·
- To provide input to Relay Coordination, Motor Starting, Harmonic Analysis, Transient Stability & Arc flash.
🙄 How short circuit occurs? (TYPES OF FAULTS) ·
- Series Fault
- 1. Single Conductor Open
- 2. Two Conductor Open ·
- Shunt Fault Symmetrical Fault
- 1. Three Phase Fault
- 2. Three Phase to Ground
- Unsymmetrical Fault
- 1. Line to Ground
- 2. Line to Line
- 3. Line to Line to Ground
🙄 Standard – IEEE / IEC ·
- IEC 61363-1998 “Short circuit calculation procedure for 3ph. AC system in isolated system” .
- IEC 60909-2016 “Short circuit current in 3ph. Ac system” ·
- IEEE 3002.3-2018 “Recommended practice for calculation of Short circuit current for industrial and commercial power system”.
🙄 Objectives of Short Circuit?
- To find Short Time Rating (STR) of all equipment’s (Transformers, Cables, Transmission Lines, Generators, Motors, Switchgears, CT, CB etc)
- Breaking, Making and DC Breaking Requirements of Interrupting Equipment’s
- To find Voltage Raise during the fault
🙄 Effect of short circuit ?
Short circuit occur even in well-designed power systems, cause large decaying transient
current generally much above load current. Short circuit may lead to ·
- Undesirable current flow.
- Excessive magnitude of current may lead equipment damage.
- Excessive overvoltage.
- Hazardous to working personnel.
- Generator Out of Step (Angular Stability)
- Results electro -dynamic and thermal stress