New water tree monitoring technique

The design philosophy is given for producing image currents depicting water motion during water treeing. A diagnostic for water treeing in polyethylene (PE) is being developed from a successful one for prebreakdown studies in liquids. The basic technique is to stress a dielectric between two electrodes and observe image currents in the ground electrode. Direct measurement of motion appears to be feasible if one looks at the changes that occur in the measuring instrumentation in response to the transport. Presented are results on test cell design and setup, detection electronics and circuitry, and some preliminary tests on detected pulses in the equipment that might be attributable to motion inside the water tree. Preliminary DC tests produced observable pulses, but subsequent examination of these samples revealed some cracks produced in the needle-printing process. It is not yet known if the pulses were from the actual water tree at the end of the crack or from the motion of water within the crack