Abstract
This paper outlines an investigation by the New Zealand Electricity Department into possible methods of increasing the seismic strength of 220kV airblast circuit breakers. The circuit breaker was idealised as a two mass vibrating system whose behaviour in different earthquakes was examined by the method of direct integration of the equations of motion.
Highlights
This paper outlines an investigation by the New Zealand Electri city Department into po s sible methods of increasing the seismic strength of 2 20kV airblast circui t breakers
The circuit breakers had been purchased under a specif i cat ion requiringa se i smi c de sign factor of 0.25g« earthquake damage to similar breake rs in a number of count rie s together with a more detailed understanding of the response of structures to earthquakes lead to the adoption by the New Zealand Electricity Department of standard design spectrum curves based on a set of single mass response spectra drawn up by Skinner^ ^
Theuppermass repre se nt s the three sets of airblast heads which are mechanically coupled so that they move virtually as one body and the lower mass represents the compressed air tank whi ch forms the base of the circuit breaker
Summary
Several methods of measuring the 'size' of an earthquake have been usedo (a) according to maximum ground acceleration (b) according to the me an value of the velocity re sponse spe ctrum between 0 0 1 and 2.5 seconds natural period for a value of damp-. The two body arrangement representing the circuit breaker is shown in Fig. I 0 The equations of motion governing the systems are: X, = - Z - Mi. The structure was first subjected to the 19^0 El Centro N-S acceleration record and the response of the airblast heads is shown on Fig III for different values of support structure stiffness and damping. The circuit breaker haad response is shown on Fig. IV
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