Martin David Judd

• BSc 1st Class Hons (Hull), PhD (Strathclyde)
• Principal Engineer at HFDE Ltd

This paper is a joint contribution from members of the IEEE DEIS Technical Committee for Diagnostics that highlights selected trends, challenges, and techniques in diagnostics and monitoring of high-voltage electrical insulation. Especially important are broad application areas including traditional generation, transmission and distribution, and re...

Ultra-high frequency (UHF) partial discharge (PD) measurement is a well-accepted technology to assess the quality of the insulation system of power transformers. For successful PD measurements, sensors and systems must be designed for the foreseeable measurable signals. Although 25 years ago the first publications on the UHF frequency spectra of PD...

Although partial discharge (PD) measurement is a well-accepted technology to assess the quality of the insulation system of power transformers, there are still uncertainties about which frequency range PDs radiate and which frequency range should be evaluated in a measurement. This paper discusses both a UHF PD frequency range obtained from studies...

The Technical Brochure (TB) of Joint Working Group JWG A2/D1.51 deals with possible improvements to partial discharge (PD) measurements for factory acceptance test (FAT) and site acceptance tests (SAT) of power transformers. In the joint working group, it is common understanding that a sensitive PD measurement is in the best interest of both, the t...

Modeling of electromagnetic wave propagation inside a gas-insulated switchgear structure can be helpful for understanding and improving the utilization of partial discharge detection by providing information to help determine more optimal positioning of ultra-high frequency sensors. This paper studies the effect of insulating spacers, L- and T-type...

The main improvement for FAT and SAT acceptance tests provided by this brochure is the possibility to provide repeatability and comparability for UHF PD measurements using systems from different manufacturers. As with conventional electrical measurements to IEC 60270, these requirements must be met for the test method to be standardized. It must be...

High-voltage direct current (HVDC) cables are increasingly being installed to connect new offshore wind farms. Unplanned outages of these connectors can cause high economic impacts. Hence, there are requirements for condition-based maintenance that can improve operational reliability. Partial discharge (PD) is indicative of insulation defects. PD m...

Partial Discharge (PD) occurs when insulation containing voids is subjected to high voltage (HV). If left untreated PD can degrade insulation until, eventually, catastrophic insulation failure occurs. The detection of PD current pulses, however, can allow incipient insulation faults to be identified, located and repaired prior to plant failure. Tra...

Partial discharge (PD) testing of high-voltage (HV) cables and cable accessories has been implemented predominantly using high-frequency current transformers (HFCTs) as PD sensors. PD currents initiating at PD sources are coupled onto cable conductors. They travel away from the PD sources and are detected by HFCTs installed at cable terminations. I...

Optimal selection of features of Partial Discharge (PD) signals recorded from defects in High Voltage (HV) cables will contribute not only to the improvement of PD pattern recognition accuracy and efficiency but also to PD parameter visualization in HV cable condition monitoring and diagnostics. This paper presents a novel Random Forest (RF)-based...

It is a great challenge to differentiate Partial Discharge (PD) induced by different types of insulation defects in high voltage cables. Some types of PD signals have very similar characteristics and are specifically difficult to be differentiate, even for the most experienced specialists. To overcome the challenge, a Convolutional Neural Network (...

In this paper, we compare results of sensor characterizations in air and mineral oil to investigate the influence of the dielectric medium on frequency response and sensitivity of the UHF sensors. The results of this comparison, together with supporting theoretical analysis, lead us to propose an empirical scaling procedure for determining the resp...

Partial discharge is a well-established metric for condition monitoring and assessment of high-voltage plant equipment, such as switchgear, transformers and transmission lines. Traditional techniques for the detection of partial discharge pulses involve physical connection of sensors to the device under observation, requiring separate sensors for e...

A useful technique to estimate the degradation of insulation in high voltage (HV) installations is the measurement of partial discharge (PD). Free-space radiometric (FSR) detection of PD is a relatively new technique. Several types of PD emulator sources have been constructed: two internal PD emulators and a floating electrode emulator. The emulato...

Monitoring of partial discharge (PD) activity within high voltage electrical environments is frequently used for the assessment of insulation condition. Traditional measurement techniques employ technologies that require either offline installation or high power consumption and cost. A wireless sensor network is proposed that utilizes only received...

The measurement of partial discharge provides a means of monitoring insulation health in high-voltage equipment. Traditional partial discharge measurements require separate installation for each item of plant to physically connect sensors with specific items. Wireless measurement methods provide an attractive and scalable alternative. Existing wire...

This paper details testing conducted on selected void defects in dielectric insulation samples under various HVDC voltage conditions. The aim of this work is to illustrate the type of PD activity that could be observed in HVDC insulation systems. Initially the samples were subject to HVAC excitation to confirm the defect type and establish the PD i...

Continuous measurement of partial discharge plays a vital role in monitoring the status of high voltage equipment in electricity substations. This requires a comprehensive supervisory system to detect, monitor, collect and locate partial discharge activities. Most of the sensors developed so far require a dedicated software and hardware platform to...

Continuous measurement of partial discharge plays a vital role in monitoring the status of high voltage equipment in electricity substations. This requires a comprehensive supervisory system to detect, monitor, collect and locate partial discharge activities. Most of the sensors developed so far require a dedicated software and hardware platform to...

Monitoring of PD activity within high-voltage electrical environments is increasingly used for the assessment of insulation condition. Traditional measurement techniques employ technologies that require either off-line installation or have high power consumption and are hence costly. A wireless sensor network is proposed that utilizes only received...

The present study addresses the calibration of four types of partial discharge (PD) emulators used in the development of a PD Wireless Sensor Network (WSN). Three PD emulators have been constructed: a floating-electrode emulator, and two internal PD emulators. Both DC and AC high-voltage power supplies are used to initiate PD, which is measured usi...

Monitoring of partial discharge (PD) activity within high voltage electrical environments is frequently used for the assessment of insulation condition. Traditional measurement techniques employ technologies that require either offline installation or high power consumption and cost. A wireless sensor network is proposed that utilizes only received...

High frequency current transformers (HFCTs) are widely employed to detect partial discharge (PD) induced currents in high voltage equipment. This paper describes measurements of the wideband transfer functions of HFCTs so that their influence on the detected pulse shape in advanced PD measurement applications can be characterized. The time-domain m...

This study investigates possible advantages in pulsed over continuous 405-nm light-emitting diode (LED) light for bacterial inactivation and energy efficiency.

Partial Discharge (PD) in cable systems causes deterioration and failure, identifying the presence of PD is crucial to Asset Management. This paper presents methods for interference signals rejection and for PD interpretation for five types of artificial defect in 11 kV ethylene-propylene rubber (EPR) cable. Firstly, the physical parameters of the...

This paper presents an effective, Rough Set (RS) based, pattern recognition method for rejecting interference signals and recognising Partial Discharge (PD) signals from different sources. Firstly, RS theory is presented in terms of Information System, Lower and Upper Approximation, Signal Discretisation, Attribute Reduction and a flowchart of the...

Partial discharges may occur in defective insulation systems of high voltage equipment such as gas insulated substations and power transformers. These discharges generate electromagnetic waves that can be detected using ultra-high frequency (UHF) sensors. UHF sensors must meet certain sensitivity criteria over a wide frequency range so as to be cap...

A useful technique to estimate the degradation of insulation in high voltage (HV) installations is the measurement of partial discharge (PD). Free-space radiometric (FSR) detection of PD is a relatively new technique. Several types of PD emulator sources have been constructed: two internal PD emulators and a floating electrode emulator. The emulato...

Objective: This study investigates possible advantages in pulsed over continuous 405-nm light-emitting diode (LED) light for bacterial inactivation and energy efficiency. Background: Alternative nonantibiotic methods of disinfection and infection control have become of significant interest. Recent studies have demonstrated the application of sys...

Two effective partial discharge (PD) measurement techniques are used; a galvanic contact measurement technique similar to the IEC 60270 standard measurement and free-space radiometric (FSR) measurement. Several types of PD sources are specially constructed: two internal PD emulators and an emulator of the floating-electrode type. An AC power supply...

Partial discharge is measured simultaneously using free-space radiometry (FSR) and a galvanic contact measurement technique based on the IEC 60270 standard. Several types of PD (Partial Discharge) sources are specially constructed: two internal PD emulators and an emulator of the floating-electrode type. The excitation applied to the source is AC a...

Partial discharge (PD) is measured simultaneously using free-space radiometric (FSR) and a galvanic contact measurement technique based on the IEC 60270 standard. The PD source is an emulator of the floating-electrode type. The radiated signal is captured using a biconical antenna. A method of estimating absolute partial discharge (PD) activity lev...

Partial discharge is measured simultaneously using free-space radiometry (FSR) and a contact measurement approach based on the IEC 60270 standard. The PD source is a specially constructed emulator of the floating-electrode type. The power supply applied to the source is DC. A biconical antenna is used to capture the radiated signal and the frequenc...

This paper presents an analysis of energy partition among various physical processes during the formation of an electrical arc. The experimental work was conducted to accurately determine the energy delivered into the discharge. The transient voltage and current waveforms have been measured. An analytical model was developed that allows estimation...

Current techniques used for monitoring the levels of contamination on high voltage insulators, such as leakage current and infrared, are not effective in dry conditions since they require the surface of the insulator to be wetted by fog, rain or snow. If a buildup of contamination occurs during a prolonged dry period prior to a weather change there...

This paper introduces a novel method for monitoring contamination levels on high voltage insulators based on microwave radiometry. Present contamination monitoring solutions for high voltage insulators are only effective in predicting flashover risk when the contamination layer has been wetted by rain, fog or condensation. The challenge comes where...

Measurement of partial discharge (PD) is an important tool in the monitoring of insulation integrity in high voltage (HV) equipment. PD has traditionally been detected by galvanic contact (especially IEC 60270) and capacitive/inductive coupling methods. The free-space radiometric (FSR) detection of PD is a relatively new technique. The work that wi...

Measurement of partial discharge (PD) is an important tool in the monitoring of insulation integrity in high voltage (HV) equipment. PD has traditionally been detected by galvanic contact (especially IEC 60270) and capacitive/inductive coupling methods. The free-space radiometric (FSR) detection of PD is a relatively new technique. The work that wi...

This paper describes partial discharge (PD) phenomena in HVDC insulation, including diagnostic methods that are being developed. PD detection and analysis is used to assess the condition of electrical insulation in many types of HV equipment during manufacture, acceptance testing and condition assessment of equipment in the field. In HVAC systems,...

Hydraulic structures constitute the most vulnerable elements of transportation infrastructure. Recent increases in precipitation have resulted in severe and more frequent flash flooding incidents. This has put bridges over waterways at higher risk of failure due to scour. This study presents a new sensor for measuring scour depth variation and sedi...

A wireless sensor network (WSN) with the potential to monitor and locate partial discharge (PD) in high-voltage electricity substations using only received signal strength (RSS) is proposed. The advantages of an RSS-based operating principle over more traditional methods (e.g., time-of-arrival and time-difference-of-arrival) are described. Laborato...

Two partial discharge (PD) measurement techniques, a contact measurement technique (similar to the IEC 60270 standard measurement) and a free-space radiation (FSR) measurement technique, are compared for the case of a floating electrode PD source. The discharge pulse shapes and PD characteristics under high voltage DC conditions are obtained. A com...

Two partial discharge (PD) measurement techniques, a contact measurement technique (similar to the IEC 60270 standard measurement) and a free-space radiation (FSR) measurement technique, are compared for the case of a floating electrode PD source. The discharge pulse shapes and PD characteristics under high voltage DC conditions are obtained. A com...

Two partial discharge (PD) measurement techniques, a contact measurement technique (similar to the IEC 60270 standard measurement) and a free-space radiation (FSR) measurement technique, are compared for the case of a floating electrode PD source. The discharge pulse shapes and PD characteristics under high voltage DC conditions are obtained. A com...

HubNet Position Paper

Build-up of surface contamination on high voltage insulators can lead to an increase in leakage current and partial discharge, which may eventually develop into flashover. Conventional contamination level monitoring systems based on leakage current, partial discharge, infrared and ultraviolet camera are only effective when the contamination layer h...

A range of experimental and field measurements of partial discharge (PD) activity under high voltage direct current (HVDC) conditions have been conducted with the goal of developing effective monitoring techniques for PD in HVDC cables and ancillary equipment, particularly in offshore renewable energy HVDC grid installations. Laboratory measurement...

This paper introduces a novel method for monitoring contamination levels on high voltage insulators based on microwave radiometry. The microwave radiometer described measures energy emitted from the contamination layer and could provide a safe, reliable, contactless monitoring method that is effective under dry conditions. The relationship between...

Microwave radiometry is a novel method for monitoring contamination levels on high voltage insulators. The microwave radiometer described measures energy emitted from the contamination layer and could provide a safe, reliable, contactless monitoring method that is effective under dry conditions. The design of the system has focused on optimizing ac...

A novel method for long-range detection and potential location of arcing faults on electrical distribution networks is described and investigated. When a network fault induces an electrical arc it is accompanied by the radiation of electromagnetic transients that can be detected remotely as a radio frequency signal. By capturing its wavefront at mo...

Electrical arc flash hazard mitigation techniques focus on the reduction of hazard levels in an electrical power system. Analysis of arc incident energies pre- and post-mitigation to reduce hazard levels shows that risk control measures can lead to significant reductions in potential harm and damage should an arc flash occur. However, mitigation me...

This paper presents a prognostic framework for estimating the time-to-failure (TTF) of insulation samples under electrical treeing stress. The degradation data is taken from electrical treeing experiments on 25 epoxy resin samples. Breakdown occurs in all tests within 2.5 hours. Partial discharge (PD) data from 18 samples are used as training data...

This paper describes some recent developments in the practical application of UHF techniques for partial discharge (PD) detection and location in power transformers. UHF sensors are increasingly being fitted to transformers because they offer an effective method of investigating internal PD. A valuable characteristic is the method's immunity to int...

Measurements are reported that suggest partial discharge sources might be detected and located using amplitude-only free-space radiometric measurements. The measurements are made in two locations with similar measurement protocols by three collaborating research groups. One measurement set is more encouraging than the other but a likely explanation...

The location of partial discharge (PD) sources by free-space UHF detection is an attractive approach for condition monitoring of high voltage equipment in substations. A low-cost, radiometric, PD wireless sensor network (WSN) has been proposed to provide continuous real-time coverage for an entire substation (. A novel ultrawideband (UWB) printed m...

Scour action is one of the main climate change impacts to civil infrastructure due to more frequent and severe flooding incidents. It is the leading cause of bridge failures worldwide and it is expected to occur at most of the hydraulic structures during their service life. Scour process also leads to excessive excavation of the surrounding seabed...

Pre-breakdown phenomena in liquid nitrogen (LN2), often referred as streamers, are the precursor of total breakdown due to the more conductive nature of density-change channels compared to the liquid. The paper characterizes streamer behavior in LN2 under AC voltages using ultra high frequency (UHF) and radio frequency current transformer (RFCT) me...

Partial discharge (PD) measurement is an established high voltage insulation monitoring technique used to facilitate the detection of incipient faults in high voltage apparatus. Based on the great importance of the power system, is constant the research about the nature and characteristics of PD sources. A low-cost, free-standing, radiometric, part...

Energy harvesting is increasingly enabling the expansion of wireless sensor networks in challenging applications by replacing batteries in low power sensors. Many forms of energy harvester suffer from low output voltage that can be partially compensated for by the use of a Cockcroft-Walton voltage doubler ahead of a dc-dc converter. Impedance match...

One of the main challenges in the design and operation of offshore wind turbines arises from the uncertainty about maximum scour depth around their foundations. Scour action can lead to excessive excavation of the surrounding seabed and is being considered as a major risk for offshore wind farm developments. An ability to gather information concern...

The work reported here is part of a PhD research relates to the development of a new type of radiometric system applied to detection of partial discharges signals. A simulation model for the radiometric transmission of a partial discharge pulse is presented. The model is based on a replay model, which acts as a source, which is based on real data t...

Ultra high frequency (UHF) partial discharge sensors are widely used for condition monitoring and defect location in the insulation systems of high voltage equipment. Designing sensors for specific applications often requires an iterative process of manufacture, test, and mechanical modifications. This paper demonstrates the use of finite-differenc...

Partial discharge (PD) monitoring is an established method for insulation health monitoring in high-voltage plant. A number of different approaches to PD defect diagnosis have been developed to extract defect-specific information from PD pulse data in both the time and frequency domains. Frequency-based PD pulse analysis has previously been demonst...

Condition monitoring is playing an increasingly important role within electrical power networks, where its use can help to reduce maintenance costs, improve supply reliability and permit increased utilization of equipment capacity by providing a measure of actual operating conditions as an alternative to relying on more stringent ‘worst case scenar...

On-line Partial Discharge (PD) monitoring is being increasingly adopted in an effort to improve asset management of the vast network of MV and HV power cables. This paper presents a novel method for autonomous recognition of PD patterns recorded under conditions in which a phase-reference voltage waveform from the HV conductors is not available, as...

This paper presents early results from an experimental study of electrical treeing on commercially available pre-formed silicone samples. A needle-plane test arrangement was set up using hypodermic needle. Partial discharge (PD) data was captured using both the IEC60270 electrical method and radio frequency (RF) sensors, and visual observations are...

This paper presents a case study on fault location, characterization and diagnosis in a length of shielded 11 kV medium voltage ethylene-propylene rubber (EPR) power cable. The defect was identified on-site as a low resistance fault occurring between the sheath and the core. A 43 m section was removed for further analysis. The fault resistance was...

Power transformers can exhibit partial discharge (PD) activity due to incipient weaknesses in the insulation system. A certain level of PD may be tolerated because corrective maintenance requires the transformer to be removed from service. However, PD cannot simply be ignored because it can provide advance warning of potentially serious faults, whi...

The smart grid paradigm is set to revolutionize electrical energy delivery over the next two decades. The advantages will be manifold but the challenges to realization will be correspondingly great and the cost will be large. The probable structure of the smart power grid is reviewed and contrasted with that of the traditional grid. The requirement...

This paper describes a novel approach to the powering of small, autonomous wireless sensors for potential use in condition monitoring applications on high voltage equipment and power systems. Paradoxically, while vast quantities of electrical power flow through such systems in comparison with the power requirement of a sensor, the cost of providing...

The pre-breakdown phenomena, have been studied with the aim to further understand the use of liquid nitrogen as a part of insulation system in High Temperature Superconducting (HTS) devices. Previous studies have shown that streamer discharges in liquid dielectrics can appear in the form of pulse trains which are thought to be the results of densit...

In this paper a novel design of a downhole, three-phase optical voltage sensor for monitoring electrical submersible pumps (ESPs) is presented. In the proposed approach, voltage applied across a piezoelectric transducer is converted to strain that is measured using a fiber Bragg grating sensor. A novel design introduces strain amplification at the...

Bridges constitute the most vulnerable element of transportation infrastructure systems. Recent increases in precipitation attributed to climate change have resulted in severe and frequent flooding incidents. This has put bridges over waterways at high risk of failure due to scour. Flood-induced scour has caused the sudden collapse of several bridg...

The topology design and optimization of the capacitive energy scavenging converter will directly determine the performance of the whole device. The optimization of the energy harvesting efficiency could be translated into optimization of the topology parameters under volume restriction. An improved converter topology with the spherical cap was prop...

This paper explores a means of quantifying the relationship between transient earth voltage (TEV), ultra-high-frequency (UHF) and IEC60270 partial discharge (PD) measurements on a pulse-by-pulse basis for well-defined, laboratory-based discharge sources. Since each technique responds differently to the same PD event, there is no theoretical relatio...

Ultra high frequency (UHF) partial discharge sensors are important tools for condition monitoring and fault location in high voltage equipment. There are many designs of UHF sensors which can detect electromagnetic waves that radiate from partial discharge sources. The general types of UHF PD sensors are disc, monopole, probe, spiral, and conical t...