Precision digital filters for high voltage impulse measurementsystems

This paper reports the design, testing and practical applications of two types of high order FIR digital filters for noise reduction and data smoothing of high voltage impulse waveforms. Particular attention is paid to the estimation of the error limits introduced by the digital filters. The error estimation involves the analysis of the frequency components of the impulse waveforms, the ripple calculation of the filters and testing of the filters with simulated and real impulse waveforms. The relationships between the filter parameters and the required filter accuracies are established     

The evaluation of impulse divider response parameters

The expression of the transfer characteristic of a HV impulse divider by a limited number of response parameters is considered. The response parameters under consideration for introduction into the revised standard for HV impulse tests are summarized, and the errors in the evaluation of the response time, and time standard rise time, are discussed. A method is proposed for determining the correct settling level of the step response to reduce the great uncertainty in the evaluation of the rise time. The method proved to be effective for three different types of impulse dividers     

Interlaboratory comparison of high direct voltage resistor dividers

A 150-kV divider from the National Measurements Laboratory of Australia was used as a travelling standard in comparison tests against standard dividers maintained at the Korean Research Institute of Standards and Science and the National Research Council of Canada. Results are presented in terms of the relative ratio changes between these dividers and the transfer standard under high voltages. In addition to establishing the relative agreement in high direct voltage measurements, the comparison tests were shown to be especially valuable for evaluating the ratio drifts of the dividers under prolonged application of high voltage     

The interpretation of radio-influence voltage profiles

A method for obtaining a radio-influence voltage (RIV) versus applied voltage profile is described. Typical results are presented and suggestions are made for their interpretation. The pass/fail levels given by various national standards and methods for applying atmospheric corrections are discussed. The RIV extinction voltage is directly proportional to the air density. Failure to apply a density correction can result in incorrect interpretation of test results.     

Electrostatic charging in transformer oils. Testing and assessment

This review outlines the charging tendency test methods that have been used in the electricity supply industry especially as applied to large transformers. Methods that have been used to generate charge and to measure charge are discussed and the results of various experiments are presented     

Electrical insulating oils. I . Characterization and pre-treatmentof new transformer oils

It is of fundamental importance that appropriate oil purity be preserved for all applications in electrical equipment. Oil purity can be maintained if good oil handling and testing procedures are provided. Trace contaminants and very small particle contents have recently received more attention because of improved measurement techniques. As delivered, new oils require pre-treatment by the users, but most often this is only drying and filtering, although mixing and additive treatments are also used. Care has to be taken, as problems with the miscibility of the compounds can be experienced