On-line diagnostics of reactor and transformer bushings by utilization of overvoltage transients swegrids-logo

SweGRIDS research area Controllable Power Components
SweGRIDS project code CPC15
Project type PostDoc
Status running
Researcher Mahidhar Durga Pawan Gorla   (webpage)
University KTH (EME)
Project period 2021-04-09 to 2021-12-31   
Project supervisor Hans Edin   (webpage)
Industrial sponsors Hitachi ABB Power Grids, Ellevio, Svenska kraftnät


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Project abstract

The project's aim is to develop and evaluate an on-line diagnostic/monitoring system based on transient over-voltages and incipient faults that frequently occur in the power grid.

The main focus is to build up a fundamental knowledge on transients that reactor and transformer bushings in particular are exposed to. Transient stresses may occur in the form of overvoltages from switching, lightning and transients, and from fault currents following earth faults and short-circuits. The motivation for this project is to use such transients as a stimuli for on-line diagnostics of reactor and transformer bushings. The transient by itself may not damage the component directly, but may create transient signals that can indicate a weakness in the insulation or in a mechanical part. The transient may also be the incipient fault of a degradation process that finally leads to a failure. In this sense, on-line monitoring, and in-particular consecutive transients that may follow later on, may be important stimuli for on-line based diagnostics and monitoring that can prevent an unexpected outage.

Remote sensing measurement techniques will be developed based on antennas and acoustical sensors with which one can study the response from the transients in form of partial discharges or acoustical emission from transient mechanical stresses. The measurement techniques intends to be evaluated in the laboratory as well as in the field. The primary intended test objects are shunt reactor bushings, as they frequently are exposed to switching transients, typically twice per day if they are connected during low loads and disconnected during high loads. The measurements should be on-line based and correlate to the transients. Remote sensing devices for measuring the switching transients must also be evaluated, typically in the form of capacitive sensors.[1]

The development of PD measurement techniques that can measure PD in connection to transients has to be developed and evaluated. A standard method could be to use the bushing test tap (F-connector) for PD measurements. However, such solutions should usually be avoided for installations that will operate over a long time. Alternatives could be to use Rogowski-coils around the bottom part of the bushing, but more interesting new alternatives would be to base the measurements on antennas or arrays of antennas [2, 3]. This project will focus mostly on antenna based technologies.

Within the project we aim for evaluating the developed method both in the laboratory and in some field installations. We also expect that the system can be installed on-line for at least 1-2 months during the summer 2021 in order to acquire data for further analysis. As there exists a significant amount of data from existing diagnostic methods around bushings related to gas-in-oil analysis and tan-delta measurements, the following project will analyse and correlate the on-line achieved signatures with these established results.


Summary of work

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Event log

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Project reference-group

Francisco Penayo,  PG
Lars Jonsson,  PG
Nima Sadr-Momtazi,  PG
Anders Eriksson,  PG
Eskil Agneholm,  Ellevio
Niclas Schönborg,  Svenska kraftnät


Publications by this researcher

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Publication list last updated from DiVA on 2021-09-18 22:00.


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Page started: 2021-04-09
Last generated: 2021-09-18