The feasibility of identifying and locating thermal mechanisms in large machines by remote sensing

Abstract

In order to obtain an early warning of any over-heating problem within large electrical machines, instruments have been designed and are now commercially available, called ‘Condition Monitors’ (C.M.). Their function is to produce an electrical signal when any particles/materials, i.e. as emitted by over heated insulation, pass through the sensitive ion chamber. In the USA, considerable success has been claimed in preventing catastrophic failure of machines by responding to the condition monitor signals and removing the machine from load. However, electricity suppliers are generally cautious in responding to any condition monitor signal, resulting in either load shedding or desynchronisation of the machine. At present a condition monitor signal will not indicate to the operator the cause for the alarm, nor its location within the machine, even if it is an over heating problem. If the cause for the alarm can be identified and it is a thermal process which can be related to a particular material, then the relative importance of the alarm can probably be assessed. However, these processes are time consuming and often interpretation of the results is difficult and inconclusive. Certain techniques will be discussed, together with promising new developments.