Abstract
The New Zealand Electricity Department has purchased a number of high voltage circuit breakers with prestressed porcelain columns on which the manufacturers have carried out shock and vibration tests to determine strength and damping characteristics and to make some estimate of earthquake resistance. This paper presents a detailed study of the behaviour of such circuit breakers when subjected to earthquakes and steady-state sinusoidal forging functions. The system, assumed to be single-degree of freedom, has a bilinear force-deflection relationship. The system parameters that varied in this study were: natural period, damping, yield strength and elastic characteristics. All investigations were conducted with the aid of an IBM 360/40 and an IBM 1130 digital computer using Jenning's Pseudo-Earthquakes.
Highlights
The New Zealand Electricity Department has in recent years specified that the high voltage circuit breakers it purchases shall have a breaking strength at least twice that necessary to withstand a horizontal seismic load of 1 . 5 times its weight or some lesser value may be accepted if evidence is submitted as to the amount of equivalent viscous damping inherent in the equipment
The requirements are based on a set of standard response spectra ' a n d are quite satisfactory for many items of equipment but become rather indefinite for structures with non-linear characteristics^
The Department has purchased a number of high voltage circuit breakers which have a high earthquake strength because their porcelain columns are prestressed by an inner insulating tension member as indicated in Fig, 1* The makers had subjected the breaker to shock tests which induced accelerations up to 1 . 6 g at the top of the breaker and this was judged to provide a satisfactory degree of earthquake resistance
Summary
The preceding analysis of test results provides approximation of the force-deflection and damping characteristics of the circuit breaker. Using the vibration test results together with information provided by the manufacturers on the masses of various components the values of these parameters were calculated for the 3 3 0 kV version of the circuit breaker and were deduced for the 2 2 0 kV version.
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