PD Sensor
UHF Power Transformer Hatch Cover PD Sensor

UHF Power Transformer Hatch Cover PD Sensor

This sensor is designed for the installation in oil-immersed power transformer to do on-line partial discharge measurement and location of the partial discharge source (at least 3 sensors, and better 4 sensors). The frequency rang of this sensor is about 200 MHz to 1.2 GHz.

  Components of flange type sensor  

The sensor of flange type (Fig. 1) is the standard type of UHF sensor, and is designed for the application of the transformer with reserved hatch/manhole. This sensor consists of three parts.

  Transformer interface flange  
In order to connect the UHF transformer sensor to the transformer, an interface flange is needed and PDS will provide the size of interface flange to the transformer manufactory. The hatch/manhole for the interface flange shall be taken into consideration in the design stage of the transformer, and the interface flange is welded to the tank as tank assembly (Fig. 1).

Fig. 1 Standard interface ange

  Dielectric window  

For collecting partial discharge (PD) signals, a non-metal material window is used for PD signal passing through. This dielectric window separates the oil and the air, and thus a flat rubber gasket ring is used as first seal. The dielectric window will be bolted to the interface flange before filling the transformer with oil.

  UHF sensor window  
The UHF sensor is bolted to the dielectric window and is fastened on the interface flange (Fig. 2). There is a second oil seal in case of dielectric window developing a leak due to some uninspected reason. The UHF sensor is removable, and can be replaced with newer design in the future. For special cases (such as in-service transformer), PDS can also design customized UHF transformer sensor.

Fig. 2 The UHF sensor fastened on the flange

  The selection of the sensor location  

The sensors can be installed at any position due to uninfluenced of the electric field distribution. However, for the convenience of locating the PD source, the opposite diagonal lines at different side of the tank wall are recommended as shown in Fig. 3.

Fig. 3 the recommendation for the selection of sensor location