Seismic qualification of high-voltage equipment
The present report deals with the seismic qualification of High-Voltage (HV) equipment intended for electrical substations (Report No. 2 of Task 6 of Cascade Project). Earthquakes cause remarkable and costly damages to power systems. Past earthquakes showed that a broad range of equipment is especially vulnerable to damages: instrumentation transformers, circuit breakers, disconnect switches and transformer. Occasionally HV substation equipment is damaged also by low ground accelerations, i.e. less than 0,1 g. Damages of substation equipment can cause system outages of various duration. An earthquake can have higher costs: direct losses due to equipment damage and additional costs for lost revenue due to service disruptions. For these reasons, the dynamic qualification of HV equipment becomes an important step in the earthquake risk mitigation. The approach to HV equipment qualification is faced in this document taking into account the different points of view of all the involved actors, mainly: the Manufacturer, the Qualification Operator and the End User (Industry). A harmonized approach to qualification can provide benefits and cost reduction. Chapters 1 to 3 introduce to the HV equipment qualification with general considerations about the product qualification and the main related difficulties. The most widely used Standards are listed and analysed in Chapter 4. Different qualification approaches allowed by the Standards are described in Chapter 5 (i.e., experimental procedures, numerical procedures, mixed procedures and past experience qualification): critical aspects are highlighted and comments and suggestions are provided. Finally, in Chapter 6 a case history of actual qualification processes, based on different approaches, is presented and discussed. The main requirements of the applicable Standards are reported in the Appendix A, using the same form for all the Standards in order to make easier their comparison. Appendix B lists the most common terms used in the dynamic qualification. The reference documents used in this report are listed in Appendix C.