Probabilistic Short-Circuit Uprating of Station Strain Bus System - Mechanical Aspects

Design of strength of station structures and clearances to accommodate forces and motions of strain bus during short circuit faults has been based on an energy method and a pendulum swing out model at Ontario Hydro. The energy method was developed some time ago to calculate the forces in a strain bus at the moment of zero motion following a fault. Several recent extensions of this approach are described in this paper. These include: (i) In-depth comparisons of predictions of peak tension, time of peak tension, and force on the structure with values from experiments on simple bus arrangements. (ii) Studies of insulator static and dynamic properties and incorporation of these values in the program. (iii) Extension of the theory to asymmetric faults and to four conductor busses. This method of calculation has recently been used in the probabilistic analysis of the uprating of Ontario Hydro´s Middleport Transformer Station (TS) as well as a number of other design applications. This study demonstrates the overall accuracy of this relatively simple approach and its potential for application to more complex arrangements of strain bus. This paper and three companion papers present the probabilistic uprating process as applied to Middleport TS.