An improved method for estimating temperature rise of a bushing loaded above nameplate rating

We have developed an accurate but sinple m e w to estimate the tenperature rise ( r e f d to as \\risen hereafter) of a bshirg amiwtor under any load amditim. This methcd aonsists of me equation and two predetermined rise pmfiles F,(z) and F, (2) . F,(z) is the incremntal rise pmfile at the rated current and F,(z) is the nonmlized rise profile at zero current. Fl(z) and F,(z) canbe abtained fran tho base tkmnal. tests. The proposed metbod allows us to estimate the rise pmfile of the bshing under any given load conditicm. Therefore the rise and the locaticn of the hottest spot can be debmined fran this profile. We have successfully applied this mthod to various~, rmchaslxlahirrgswithandwithcrut oil circulatim, bottan CQnneCted and draw-lead axmected-, and Sam? special bushhgs w i t h two cxxdwtom. We exarmʹ ned this mthod w i t h a t h e r m 4 circuit mdel and verified that the thermal rtpdel supports the newmthod.