These standards cover 99% of what needs to be known to perform a lightning or switching surge insulation coordination study. However, as a good first approximation, system performance can be modeled using the formulas presented in IEC 60071-1, 6. This coordination task as well as the task of selecting and locating arresters can be simple while at other times complex, requiring computer simulation. The task of coordinating insulation withstand with the desired performance levels of the system can be significantly different if arresters are applied versus not applied. Insulation coordination has become a well-developed engineering practice and one where the characteristics of the system in terms of insulation and arresters cross paths. This carefully selected combination of insulators and arresters is then referred to as insulation coordination. An intermediate solution that requires some reasonable investment in insulation and protective equipment is therefore the compromise most often taken.
Similarly, it seems equally unreasonable to insulate for all transient events, even if this were possible. Clearly, it would not be reasonable to insulate only for the operating voltage and thereby allow any transients to trigger insulation failure. How the insulation on any power system is protected is basically an economic issue. While arresters can be used to effectively control the most frequent type of such overvoltages, namely those caused by switching operations, transients due to lightning are more difficult to mitigate. Transient overvoltages occur on all power systems.
0 kommentar(er)
