Water as an insulator in pulsed facilities - (Review)

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 similar to 1 mu s and electrode areas of up to tens of square meters, a large value of the relative permittivity (similar to 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.