Corona ring

Abstract: This paper provides an overview of the electric field (E-field) distribution on transmission line composite insulators applied in alternating current applications. Factors that affect the E-field distribution are discussed as well as the influence of the E-field distribution on the short and long term performance. Modeling and measurement methods are reported and examples of calculated E-field magnitudes determined are presented together with corona ring application information. This paper was developed by the IEEE Task force on electric fields and composite insulators.

Abstract: A method of supplying electrical power to and controlling corona discharge cells used for the generation of ozone employs a single-cycle discontinuous waveform which is characterized by a fixed pulse width and a variable repetition rate. Discrete bipolar pulses are composed of a pair of unipolar pulses of opposite polarity. The bipolar pulse repetition rate is varied to control the average corona power, providing an infinite turndown of ozone output. When powering discharge cells which are asymmetric in their response to pulse polarity, such as those containing a dielectric coated with a conducting surface as a first electrode and a metal as a second electrode, the present invention configures the first pulse of each pair to make the dielectric electrode electronically negative with respect to the metal electrode. This polarity sequence produces a more stable corona and far less electrical noise. Furthermore, to decrease acoustic and mechanical resonances and fatigue to system components and to the human ear, this invention broadens the frequency distribution of the pulse repetition rate by repetitively sweeping or randomly jittering the intervals between bipolar pulses.

Abstract: An electrostatic fluid accelerator having a multiplicity of closely spaced corona electrodes (1). The close spacing of such corona electrodes (1) is obtainable because such corona electrodes (1) are isolated from one another with exciting electrodes (2). Either the exciting electrode (2) must be placed asymmetrically between adjacent corona electrodes (1) or an accelerating electrode must be employed. The accelerating electrode can be either an attracting (13) or a repelling electrode (19). Preferably, the voltage between the corona electrodes (1) and the exciting electrodes (2) is maintained between the corona onset voltage and the breakdown voltage with a flexible top high-voltage power supply. Optionally, however, the voltage between the corona electrodes (1) and the exciting electrodes (2) can be varied, even outside the range between the corona onset voltage and the breakdown voltage, in order to vary the flow of fluid. And, to achieve the greatest flow of fluid, multiple stages (28, 29 and 30) of the individual Electrostatic Fluid Accelerator are utilized with a collecting electrode (31 or 32) between successive stages (28, 29 and 30) in order to preclude substantially all ions and other electrically charged particles from passing to the next stage (28, 29 or 30), where they would tend to be repelled and thereby impair the movement of the fluid. Finally, constructing the exciting electrode (2) in the form of a plate that extends downstream with respect to the desired direction of fluid flow also assures that more ions and, consequently, more fluid particles flow downstream.

Abstract: It is shown that certain regions of commercially available 500 kV non-ceramic insulators have surface electric fields that are above the threshold for water drop corona. Observations made in a full scale accelerated aging chamber, and in service, demonstrate that water drop corona occurs on such insulators. A correlation between the magnitude of the surface electric fields and the condition of the silicone rubber non-ceramic insulator surfaces due to water drop corona is illustrated for two different insulator types in an accelerated aging chamber. Other examples of degradation of nonceramic insulators due to water drop corona are illustrated.