Following are the Typical safe ability of Transformer, Generator and Cable to withstand Isc – short circuit fault current in multiple of its In – rated current, without damage to the equipment.
| Device / Equipment | Isc Fault Current as multiple of In | Safe Withstand Duration without damage |
|---|---|---|
| Transformer | Isc = 25 x In | 300 Sec |
| Generator | Isc = 30 x In | 5 Sec |
| Cable | Isc = 25 x In | 1000 Sec |
HRC – Hazard Risk Category is determined by amount of Incident Energy released upto defined boundary from the source of Arc Flash Point.
Circuit Breaker with Short Time withstand Icw capacity are Calassified as Category B (eg. ACB), and without Icw are Category A (eg. MCCB, MCB).
Electrical joints of Dissimilar metals – Aluminium and Copper suffer from Galvanic Corrosion and thermal expansion effects.
In Practice there wiill always difference in phase displacement between primary and secondary currents, Allowed limits are defined in IEC 61869-2.
Pollution factor can be solid, liquid, gaseous foreign matter which may reduce the dielectric strength accordingly Pollution Degree defined IEC 60664.
Load dispatch center is a coordinating agency for state electricity boards for ensuring a mechanism for safe and secure grid operation.
Arc Flash is light and heat produced as a result of Arc Fault, due to low impedance path, which causes electrical explosion or discharge.
LOTO – Lockout/Tagout, is set of procedures to ensure Equipment is properly Shutdown, Isolated, De-Energized and Tagged.
Electrical Panel Assemblies needs good understanding of GAS laws, PV=nRT, which relates Pressure, Volume, Temperature and Amount of GAS inside the ASSEMBLY.