High voltage instrument transformer and method for partial discharge recognition
A high voltage instrument transformer includes a measuring assembly and isolator, with at least one sensor for partial discharge measurements. A method for partial discharge recognition in high voltage instrument transformers includes a detection of a signal from at least one sensor for partial discharge measurements, particularly a Transient Earth Voltage sensor.
1. A high voltage instrument transformer, comprising:
an isolator,
a vessel attached to the isolator,
a measuring assembly enclosed in the vessel,
a ground screen arranged enclosed by a passage between the isolator and the vessel, and
at least one sensor for partial discharge measurements arranged on or directly arranged on the ground screen.
2. The high voltage instrument transformer according to claim 1 , wherein the at least one sensor is a Transient Earth Voltage sensor.
3. The high voltage instrument transformer according to claim 1 , wherein the at least one sensor is electrically connected to a ground screen.
4. The high voltage instrument transformer according to claim 1 , wherein an outer shield of a bushing of the instrument transformer is electrically connected to a ground screen.
5. The high voltage instrument transformer according to claim 1 , wherein the at least one sensor is arranged on or directly arranged on an outside surface of the isolator.
6. The high voltage instrument transformer according to claim 1 , wherein the at least one sensor is arranged inside of the isolator.
7. The high voltage instrument transformer according to claim 1 , wherein the at least one sensor is connected to a monitoring system, or to a continuous and/or online monitoring system.
8. The high voltage instrument transformer according to claim 7 , wherein the monitoring system, or the continuous and/or online monitoring system, comprises a computer, and/or elements in the cloud, and/or mobile elements, for continuous monitoring and/or monitoring according to service intervals.
9. The high voltage instrument transformer according to claim 1 , wherein the instrument transformer is designed for voltages in a range of a kilovolt up to 1200 kV.
10. A method for partial discharge recognition in high voltage instrument transformers according to claim 1 , comprising:
detecting a signal from at least one sensor for partial discharge measurements.
11. The method according to claim 10 , comprising:
transforming detected signals from time domain to frequency domain,
cutting frequencies above a defined threshold value resulting in truncated signals,
retransforming the truncated signals from frequency domain to time domain, and
determining and comparing of information content of the detected signals and the truncated signals.
12. The method according to claim 11 , wherein signals with comparable information content of the detected signal and the truncated signal are identified as noise, and/or signals with lower information content of the truncated signal compared to detected signal information content are identified as a signal including partial discharge information.
13. The method according to claim 11 , wherein the determination of information content is performed by a calculation of Shannon entropy.
14. The high voltage instrument transformer according to claim 6 , wherein the at least one sensor is arranged directly on a surface of the isolator.
15. The high voltage instrument transformer according to claim 9 , wherein the instrument transformer is designed for voltages in a range of 15 kilovolt up to 1200 kV.
16. The method according to claim 10 , wherein the sensor comprises a Transient Earth Voltage sensor.