Bài giảng Kỹ thuật điện: Chương 3 - Phạm vi bảo vệ của kim thu sét

Generated by Foxit PDF Creator © Foxit Software<br /> http://www.foxitsoftware.com For evaluation only.<br /> 12/9/2012<br /> <br /> Ph m vi b o v c a kim thu sét<br /> • Ph m vi b o v c a m t kim thu sét<br /> <br /> 4:13 PM<br /> <br /> Ph m vi b o v c a kim thu sét<br /> • Ph m vi b o v c a m t kim thu sét<br /> <br /> 0.8h<br /> <br /> h<br /> <br /> 2h/3<br /> hx<br /> 1.5h<br /> <br /> 0.75h<br /> <br /> 0<br /> <br /> 0.75h<br /> <br /> 1.5h<br /> <br /> rx<br /> 0<br /> <br /> 4:13 PM<br /> <br /> 1<br /> <br /> Generated by Foxit PDF Creator © Foxit Software<br /> http://www.foxitsoftware.com For evaluation only.<br /> 12/9/2012<br /> <br /> Ph m vi b o v c a kim thu sét<br /> • Ph m vi b o v c a m t kim thu sét<br /> 0.8h<br /> <br /> h<br /> <br /> 2h/3<br /> <br /> hx<br /> 1.5h<br /> <br /> 0<br /> <br /> 0.75h<br /> <br /> 0.75h<br /> <br /> 1.5h<br /> <br /> rx<br /> 0<br /> <br /> 4:13 PM<br /> <br /> Ph m vi b o v c a 1 kim thu sét<br /> • Xaùc ñònh baùn kính baûo veä rx<br /> 0.8h<br /> <br /> h<br /> <br /> +N u<br /> <br /> 2h/3<br /> hx<br /> 1.5h<br /> <br /> 0.75h<br /> <br /> 0<br /> <br /> 0.75h<br /> <br /> rx<br /> 0<br /> <br /> 1.5h<br /> <br /> thì<br /> +N u<br /> <br /> thì<br /> <br /> 2<br /> h<br /> 3<br /> rx = 0 . 75 (h − h x )<br /> hx ><br /> <br /> hx ≤<br /> <br /> 2<br /> h<br /> 3<br /> <br /> rx = 1.5(h − 1 .25 h x )<br /> <br /> 4:13 PM<br /> <br /> 2<br /> <br /> Generated by Foxit PDF Creator © Foxit Software<br /> http://www.foxitsoftware.com For evaluation only.<br /> 12/9/2012<br /> <br /> Ph m vi b o v c a 1 kim thu sét<br /> <br /> 0.8h<br /> <br /> *. Tính toaùn chieàu cao kim h<br /> + N u h > 2.67 r<br /> x<br /> <br /> h<br /> <br /> 2h/3<br /> hx<br /> 1.5h<br /> <br /> 0.75h<br /> <br /> 0<br /> <br /> Thì<br /> 0.75h<br /> <br /> rx<br /> <br /> 1.5h<br /> <br /> +N u<br /> <br /> 0<br /> <br /> Thì<br /> <br /> h =<br /> <br /> x<br /> <br /> rx<br /> + hx<br /> 0 . 75<br /> <br /> hx ≤ 2.67 rx<br /> h=<br /> <br /> rx<br /> + 1 .25 h x<br /> 1. 5<br /> <br /> 4:13 PM<br /> <br /> Ví d<br /> Ta có chi u cao kim: h = 10 + 3 = 13m<br /> <br /> 3m<br /> 4m<br /> 5m<br /> <br /> 10m<br /> <br /> Chi u cao công trình c n b o v : hx = 10m<br /> <br /> 2<br /> 2<br /> h = ´ 13 = 8.67m<br /> 3<br /> 3<br /> <br /> hx ><br /> <br /> 2<br /> h<br /> 3<br /> <br /> ⇒ Bán kính b o v th c t c a kim<br /> <br /> rxtt = 0.75(h - hx ) = 0.75(13 - 10)<br /> 4:13 PM<br /> <br /> rxtt = 2.25m<br /> <br /> 3<br /> <br /> Generated by Foxit PDF Creator © Foxit Software<br /> http://www.foxitsoftware.com For evaluation only.<br /> 12/9/2012<br /> <br /> Ví d<br /> 3m<br /> <br /> Bán kính b o v yêu c u c a kim: rxyc<br /> 4m<br /> <br /> 5m<br /> <br /> 42 + 52<br /> = 3.2m<br /> 2<br /> <br /> rxyc =<br /> <br /> 10m<br /> <br /> rxyc > rxtt ⇒ Kim không b o v đư c<br /> công trình<br /> <br /> 4m<br /> <br /> 2.25m<br /> 5m<br /> <br /> 4:13 PM<br /> <br /> Ph m vi b o v c a kim thu sét<br /> • Ph m vi b o v c a 2 kim thu sét cao b ng nhau<br /> 0.8h<br /> h0<br /> <br /> hx<br /> <br /> hx<br /> 1.5h<br /> <br /> 0.75h<br /> <br /> h<br /> <br /> 01<br /> <br /> 03<br /> <br /> a<br /> <br /> 02<br /> <br /> 0.75h 1.5h<br /> <br /> 0.5a<br /> <br /> rx<br /> <br /> rx<br /> bx<br /> <br /> 01<br /> <br /> 03<br /> <br /> 02<br /> <br /> 4:13 PM<br /> <br /> 4<br /> <br /> Generated by Foxit PDF Creator © Foxit Software<br /> http://www.foxitsoftware.com For evaluation only.<br /> 12/9/2012<br /> <br /> Ph m vi b o v c a kim thu sét<br /> • Ph m vi b o v c a 2 kim thu sét cao b ng nhau<br /> 0.8h<br /> <br /> h0<br /> <br /> hx<br /> <br /> hx<br /> 1.5h 0.75h<br /> <br /> h<br /> <br /> 01<br /> <br /> 03<br /> <br /> a<br /> <br /> 02<br /> <br /> 0.75h 1.5h<br /> <br /> 0.5a<br /> <br /> rx<br /> 01<br /> <br /> rx<br /> <br /> bx<br /> 03<br /> <br /> 02<br /> <br /> 4:13 PM<br /> <br /> Ph m vi b o v c a 2 kim thu sét cao b ng nhau<br /> <br /> * Tính toaùn baùn kính baûo veä bx<br /> Ta coù:<br /> +N u<br /> Thì<br /> <br /> +N u<br /> Thì<br /> 4:13 PM<br /> <br /> h0 = 4h -R = 4h - 9h 2 + 0.25a 2<br /> <br /> 2<br /> h0<br /> 3<br /> b x = 0 .75 (h0 − h x )<br /> hx ><br /> <br /> hx ≤<br /> <br /> 2<br /> h0<br /> 3<br /> <br /> bx = 1.5(h0 −1.25hx )<br /> <br /> 5<br /> <br />