بررسي نقش جداگرهاي اصطكاكي آونگي در كاهش آسيب‌پذيري لرزه‌يي تجهيزات پست‌هاي فشار قوي

Investigation into the Effect of Friction Pendulum Systems on Seismic Damage Reduction of Substation Equipment

يكي از پرهزينه‌ترين تبعات وقوع زلزله، آسيب پست‌هاي انتقال برق فشار قوي و به تبع آن قطع برق در مناطق آسيب‌ديده است. در مطالعه‌ي حاضر، به‌واسطه‌ي به‌كارگيري جداگر اصطكاكي آونگي (FPS)، عملكرد لرزهيي دو تجهيز آسيب‌پذير ترانس ولتاژ خازني (CVT) و برق‌گير (LA) بررسي شده است. در اين راستا، با اعمال ركوردهاي مقياس‌شده براساس بيشينه‌ي تغييرمكان جنبش زمين (PGD) و طبق روش تحليل ديناميكي فزاينده (IDA)، پاسخ لرزه‌‌يي تجهيزات ارزيابي شده است. به علاوه، با تعريف مقادير مختلف فاصله‌ ميان لغزنده‌ي اصطكاكي جداگر و لبه‌هاي جداگر (فاصله‌ي لغزندگي)، اثر تغييرمكان لغزنده در پاسخ لرزهيي تجهيزات مورد بررسي قرار گرفته است. در پايان نيز مشخص شده است كه نصب جداگر اصطكاكي در پاي برق‌گير، بر نصب آن در پاي ترانس ولتاژ برتري دارد و به‌طور چشم‌گيري پاسخ‌ مجموعه‌ي تجهيزات را كاهش مي‌دهد. همچنين افزايش فاصله‌ي لغزندگي تا مقدار بهينه‌ي آن، بر اثربخشي جداگر اصطكاكي در كاهش پاسخ مي‌افزايد.

Substation damage, and consequently electricity cut-off, have been always one of the costly earthquake disastrous outcomes. In the present study, a 2-item set of equipment, including capacitive voltage transformer (CVT) adjacent to a lightning arrester (LA) known as vulnerable instruments existing in substations, is aimed to seismically strengthen by isolation strategy. The isolator device considered in the present study is a single friction pendulum system (FPS) which possesses sliding and re-centering mechanisms integrated in one unit. In addition, CVT and LA instruments are cable-connected as well. Since interaction of conductors between equipment subjected to earthquakes is a challenge for seismic design of substations, it is prudent to design the cable-connected system with sufficient cable slackness. By taking advantage of incremental dynamic analysis (IDA) and defining an appropriate damage state, equipment seismic response is evaluated. Many measures of earthquake ground motion intensity, rather than PGA, have been examined. Finally, it is decided that the peak ground displacement (PGD) can better represent the equipment seismic response among all other alternative measures. Afterwards, porcelain insulator breakage (which outnumbers any other reported failure modes of CVT and LA) and breakage of conductor terminal pads are taken as the two main failure mechanisms of 2-item set of equipment. Moreover, the influence of the gap between FPS stoppers is one of the most prominent variables considered in the present study. The rationale behind the decision refers to pounding of slider against stoppers, which seemes to be a matter of concern. The IDA curves of the non-isolated 2-item set of equipment revealed that LA is much more susceptible to failure. In order to evaluate the isolation effect on the seismic performance of the 2-item set of equipment, two different cases are supposed: A. Base isolation of CVT while LA is fixed-base; B. Base isolation of LA while CVT is fixed-base. Case A was found to be much more suitable than case B to enhance the seismic performance. Eventually, it is concluded that FPS isolator has the potential to decrease flexural stresses caused by intense ground motions, and this could be enhanced by widening the gap between stoppers of isolator.