Understanding the Use of PD Measurements in High Voltage Hydro-Generators

On-Line Partial Discharge Detection and Monitoring of a 110 kV/6 kV Power Transformer in a Refinery

During routine on-line partial discharge (PD) spot testing of high-voltage (HV) cables in a European refinery, unexpected PD activity was detected from a connected 110 kV/6 kV, 63 MVA power transformer. Follow-up investigations and on-line PD monitoring identified multiple PD activities originating from the active part of the transformer. This paper presents the measurement methodology, permanent sensor installation, comparison with dissolved gas analysis (DGA), and benefits of on-line monitoring for predictive maintenance of aged transformers. Results demonstrate that continuous PD monitoring provides superior insight into the insulation status and supports effective asset management in industrial facilities.

Electricity Theft Detection and Protection in a Power Distribution System: A Modeling and Analysis Approach

Facing a Challenge: Partial Discharge Measurements and Monitoring in Electrified Vehicle Assets Under PWM Supply

Increasing power density of electrical devices in electrified transportation is an irreversible trend which involves power electronic-type supply, higher voltage and temperature. However, fast converter-switch rise times, high modulation and carrier frequencies, harmonics, and increased design field and temperature constitute potential causes of accelerated electrothermal aging of insulation, especially if harmful phenomena, as partial discharges (PDs), incept. This paper focuses on solving issues related to PD monitoring under power electronics waveforms, dealing with effective and automatic tools for noise rejection and for the identification of the type of source generating PD, the latter being fundamental for quality control, diagnostic and condition maintenance. It is shown that innovative techniques are available, which allow PD to be measured even under fast switching (rise time) and high frequency, separating, in the time domain, PD pulses from switching noise. This approach can be carried out automatically by the PD detector software presented here, not requiring experts for measurement management and, thus, making it a feasible tool also for on-line PD monitoring and condition-based maintenance. PD monitoring results from accelerated aging tests on a motor under pulse-width modulation (PWM supply) are presented. In order to assess the insulation health condition, progressive degradation of the motor is quantified using a dynamic health index (DHI), primarily based on key PD parameters, i.e., PD magnitude, repetition rate, and likelihood of discharge type (surface or internal). The proposed DHI approach not only provides meaningful metrics for translating PD data into a diagnostic tool, but it also offers insights into residual life estimation and failure risk prediction.

Panov obtained dependences of the breakdown voltages of transformer oil on the distance between the electrodes (up to a maximum distance of 50 cm) Volt-time curves of oil-filled power transformer insulation Survey of 100 years of research – Part II

The second part of the article examines the data of Soviet scientists on the dependence of the electrical strength of insulation of power transformers on time in historical development. Where possible, the scatter values of break-down voltage and/or partial discharge initiation voltage have been extracted from the publications under consideration for data collection to optimize insulation design and possible future statistical coordination of the internal insulation of transformers. The article is intended for young transformer engineers and for teaching transformers to undergraduate and postgraduate students in universities.

Analytical Investigation of the Humidity Effects on Repetitive Partial Discharge Inception Voltage in Inverter-Fed Motor Windings

Inverter-fed motors are exposed to high dv/dt surge voltages that can initiate partial discharge (PD) in winding insulation, particularly under humid operating conditions. This study examines the effects of humidity on the repetitive PD inception voltage (RPDIV) using twisted-pair samples and a SiC-MOSFET-based pulse power supply. Experimental results show that RPDIV decreases with increasing humidity. Analysis based on the volume-time theory indicates that this reduction is primarily caused by an increase in the electron emission from the insulation coating, while the influence of electron detachment from negative ions in air is negligible even in the high-humidity environment.

Reducing Pipeline AC Interference by Phase Permutation

High-voltage power lines can induce alternating current (AC) voltages on nearby gas pipelines, creating safety and corrosion risks. This article presents a French case study involving three gas pipelines exposed to severe interference from a 225 kV dual-circuit line over 17 km (10.6 mi).A Initial simulations predicted voltages approaching 200 V in the steady state; nine earthing systems were installed to reduce them, but these were not sufficient to meet design criteria. A further study examined conductor arrangement and led to phase permutation on the power line. Field measurements confirmed a major mitigation effect, with voltage levels reduced by about a factor of four and AC current densities significantly lowered.