Background
A number of electrical phenomena corresponding to abrupt variations in the electrical variables of a system or a grid can be grouped together under the category of "electromagnetic transients". Here one can include phenomena such as resonance, ferroresonance, overvoltages with various front speeds such as the transient voltages established at the terminals of a circuit breaker or those following a lightning strike, and even the impact of transformer inrush currents.
These phenomena, such as ferroresonance, may be non-linear, electromagnetic phenomena being able to appear under certain conditions on electricity grids containing transformers that can be saturated (potential transformers, in particular) and capacitances (stray capacitance on the cables, compensation banks, etc.).
Requirement
Any of these phenomena may cause damage to electrical grids and systems through over-currents and overvoltages (dielectric breakdown). Ferroresonance, for example, can generate large-scale overvoltage in stabilized regimes, which has the ability to destroy potential transformers.
Further, in certain cases, insulation coordination within the grids requires a detailed analysis by means of simulation of the main electromagnetic transients which may occur.
Service principle
Capsim uses numerical simulation tools such as PSIM, EMTP, Matlab-Simulink, PSCAD and PowerFactory EMT to identify and eliminate the risks associated with electromagnetic transients. When certain parameter values having an influence on the risk are not identifiable, Capsim carries out parametric studies which are able to sweep a sufficiently broad range of values to cover any risk. Additional risk limiting systems (circuit damping, lightning protection, etc.) can be sized and evaluated by simulation.
Results
In this way, it was possible to do the following :
- To check if a structure, already in existence or part of a project, contains risks associated with electromagnetic transients
- To highlight a problematic case (for example ferroresonance) reported in such a way as to detect the influential parameters and hence propose a remedial solution
