Water as an insulator in pulsed facilities (Review)

Abstract

Transmission lines with distributed parameters are often used as electrical energy storage units and high-voltage (high-current) pulse shapers in electrophysical facilities. To increase the pulse power and reduce the dimensions of the equipment, deionized water, purified from mechanical impurities and gas, is used as an insulator in lines. Water has a high breakdown strength ((BS) ~ 130 kV/cm) at pulses with a duration of ~1 µ s and electrode areas of up to tens of square meters, a large value of the relative permittivity (~80), and a small loss tangent in the frequency range 0-1 GHz. Water also possesses a number of characteristics needed to achieve the above aims. We review here the data on the electrical properties of water and the studies of it published over the last three decades; the methods for increasing the water BS and the influence of numerous factors on the BS; the physical mechanism of water breakdown and the basic regularities of the BS in strong electric fields; the BS in the most frequently used electrode systems; formulas for calculating the water BS under different conditions and over the surfaces of solid dielectrics; the characteristics of mixtures of water and ethylene glycol or methanol; water purification systems for electrophysical facilities; the comparative parameters of coaxial energy storage units having various insulators, etc. The summary generalizes the brief and predominantly reference information on the electrical properties of water and its applications for researchers, engineers, and the users of the equipment having water insulation; it can help to solve related problems more quickly and reliably.

DC electrical breakdown of water in a sub-micron planar gap

“…The observed 3 Volts water breakdown voltage is low and the 300 nm gap is small compared with previous breakdown experiments [1,2,6,7,8]. Furthermore, the applied DC field is uniform across the gap, which is different from the field distributions in spherical geometries.…”

“…Due to its high permittivity and high dielectric strength, water is a good dielectric medium for pulsed power systems [1], for which water dielectric properties, including electrical breakdown properties, are of great interest. The study of such properties started more than a century ago, yet there are still ongoing efforts to understand them.…”

Nanoscale Corona Discharge in Liquids, Enabling Nanosecond Optical Emission Spectroscopy

“…Considering existing theories of discharge initiation in liquids [13][14][15] and our current experiments, there are several factors that contribute to the reasons why the NCDP is different from the streamer coronas previously observed in liquid and specifically why the two initial stages of the negative corona are observed. This study is the first which simultaneously combines 1) short rise-time voltages, 2) nanosecond-duration pulses, 3) high temporal resolution emission spectra, and most importantly 4) nanoscale tips.…”

A System for Monitoring the Energy Characteristics of an Electron Beam during the Generation of High-Power Bremsstrahlung Pulses

“…The target fully absorbs the accelerated electrons. Under these conditions, it is advisable to measure the electron beam characteristics using noncontact instruments that do not alter the bremsstrahlung field being formed [5].…”