Per Westerlund

A review of methods for condition monitoring, surveys and statistical analyses of disconnectors and circuit breakers

There is a need for a new survey of condition-monitoring methods for circuit breakers and disconnectors, since during the last two decades less than ten surveys have been carried out. The paper presents several statistical surveys and analyses. The methods of condition monitoring found are reviewed and classified according to the different types of failure identified in the surveys. Some research gaps are identified, such as the prediction of the degradation of the contacts, the signal processing of coil and motor currents and the switching.

Condition monitoring of disconnectors in the electric power transmission grid with temperature sensors

In the electrical substations there are disconnectors, which can be opened to disconnect equipment from high voltage parts. As the disconnectors are normally closed and transfer current owing to th ...

Prediction of current in a substation in order to schedule thermography

It is important to predict the current in a line in the electrical grid for example when planning thermography or handling dynamic rating. This paper takes data from a Swedish substation from 10 years and applies analysis of variance (ANOVA) to construct a linear model. The factors are the time of the day, the day of the week and the week number. About two thirds of the variance in the data can be explained by the model, but the means are too low to attain a current of at least one third of the current for which the equipment is rated. Thus the model is not good enough to plan thermography for the studied bay in the substation. However the model is able to predict the current and can also be used to predict power flows in the electric network.