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US 5,621,309 AGranted
Method for detecting a failed ZnO disk in a surge arrester network
AssigneeElectric Power Research Institute, Inc.
InventorJames M. Feldman
Life of this patent
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AssigneeElectric Power Research Institute, Inc.
InventorJames M. Feldman
Estimating the term…
A method of detecting failed disks in power-system surge arresters comprising a network of at least two parallel-coupled stacks of series-coupled ZnO varistors includes measuring differential current flow through each pair of stacks during surge voltage conditions, and comparing the current so measured with a fixed fraction of the total current carried by the arrester. Because each stack contains a like number of substantially identical varistors, current flow through the stack containing a failed disk will measurably exceed current flow through each non-defective stack. If the measured current flow through a stack is excessive relative to current flow through the remaining stacks, the excessive current flow stack is presumed to contain a defective disk. In today's technology, precision Rogowski coils or fiber-optic current sensors provide the high-bandwidth, high dynamic-range transducers necessary for the measurement of both total and differential current.
In a varistor network comprising M.gtoreq.2 parallel-coupled stacks of varistors, each stack containing a plurality of disks, a method of detecting a defective disk in one of the M stacks, the method comprising the following steps:
Dependencies are inferred from the claim text.