Patent ID: 9726708
Date: 2017-08-08
CPC Classifications: G01R

Claim:
1. A device for detecting partial discharge for a power transformer, comprising: an antenna unit receiving an electromagnetic wave; an insulating sealing unit disposed in a drain valve and comprising the antenna unit and protecting an antenna cable; a metal sealing unit connected with the insulating sealing unit and a metal handle; the metal handle sealing a connector connecting the metal sealing unit and a coaxial cable; and the coaxial cable extracted to an outside of the metal sealing unit, wherein a shield line of the antenna cable connecting the coaxial cable and the connector of the metal handle contacts the metal handle which is an end portion of the metal sealing unit, wherein the device further comprises a flange, in a single tube form, attached to the drain valve to enable a space between the drain valve and the flange to be increased, wherein the metal handle seals the connector connecting the metal sealing unit and the coaxial cable and is covered with a waterproof tube to enable a regular measurement, and wherein a length (d2) of the metal sealing unit is adjusted such that a total length (d1+d2) of the length of insulating sealing unit (d1) and the length of the metal sealing unit (d2) is proportional to a wavelength for a resonant frequency, when a phase of the wave by the length (d1) is defined as β1×d1 and the phase of the wave by the length (d2) is defined as β2×d2, the length (d2) is defined by the following equation: d2=1/β2(2π−β1d1), wherein β1 is a propagation constant of a first medium which is contained in the drain valve and β2 is a propagation constant of a second medium which is contained in the metal sealing unit.