Background
At any point on an electricity grid, there is a risk of occurrence of short circuits. Such short-circuits immediately cause circulation of large currents originating both from the supply sources and also from some of the loads (motor contribution for example). They can result in serious accidents on industrial sites (personal injuries, fire, etc.).
An upstream modification of the electricity supply network (transmission or distribution grid), or of the electrical installation or the operating configurations, can lead to a variation in short-circuit current levels.
Requirement
It is therefore essential to calculate the short-circuit current values, which could appear at any point on the grid and under all possible configurations in order to be able to size the distribution equipment (cables, transformers, panels, etc.) and to establish the settings for the protection devices.
Service principle
Capsim performs short-circuit current calculations using numerical simulation by modelling the entire grid concerned and considering the various influencing parameters: short-circuit power of the supply, normal/emergency modes, load factor, short-circuit contribution from the motors, feeding configurations, etc. These calculations are carried out with respect to applicable standards and rules, particularly bthe following: IEC 60909, IEC, IEC 61363, NFC 13200, UTE C13-205, ANSI C37 013.
These studies are performed on electrical grids, from the LV to HV level, and possibly including the autonomous generators. They are performed via software such as ETAP, PowerFactory, Cyme, PSS-E, EDSA, CANECO HT and BT...depending on the context and client requirements.
Results
All of the characteristic short-circuit data are calculated :
| Ip | peak asymmetric current |
| I’’k | initial symmetric current, efficient value |
| Ik | continuous current, efficient value |
| Ith | Equivalent thermal current |
| Ib | cut-off current |
| Idc | asymmetric component |
The data are used to size the equipment as well as for adjusting the protection devices ( see Protection coordination study)
Our associated achievements
Short-circuit calculation for a grid
