Development of enhanced fault-tolerance for a 600 kV impulse generator

A Marx Bank is a voltage multiplication system utilized for generation of high voltage impulses. The system under study is a six stage Marx, of low impedance design for AC and DC transmission line surge testing. Six 100 kV, 0.5 μF capacitors are charged in parallel and discharged in series to produce a single shot “lightning-like” 5 to 1000 microsecond duration impulse waveform with peak voltage of 600 kV, along with 15 kJ of energy. Resistor elements in the Marx, used for charging and voltage equalization, were being destroyed when the 600 kV, impulse generator was discharged into a faulted load, particularly after a sequence of repetitive firings that ended in load breakdown. A new type of a bulk ceramic tube resistor was developed through industrial participation, to eliminate resistor breakdown. There have been no further instances of resistor damage using the bulk ceramics. The methods and results of inductance determination of these units is presented. Through a diagnostic sequence of experiments, it was determined that each OEM resistor consisted of two wire wound coils that were concentrically counter-wound, supposedly to attain a low inductance. In fact, the inductance varied from tens to hundreds of microhenries for the same resistance unit value. HVR Advanced Power Components developed a very low inductance high energy bulk ceramic tube resistor with a resistance rating of either 50 Ohms or 100 Ohms