Martin D. Judd

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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(More)
Ultra-high frequency (UHF) methods for detecting and locating partial discharges (PD) are well established for gas insulated equipment. This paper provides an overview of their application to power transformers, discussing practicalities, capabilities and challenges. In recent years, UHF PD detection has proved helpful to manufacturers as a tool for(More)
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-difference(More)
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 demonstrated to(More)
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 matching of(More)
The effect of rates of lime and nitrogen on the growth of ryegrass (Lolium perenne) was measured in a pot experiment using two yellow-brown earth steepland soils (pH 5.1 and 5.3). Nitrogen or raising the soil pH above 5.8–6.0 markedly increased growth on both soils. Negative lime×N interactions on both soils together with other data indicated that an(More)
A pressure-controlled test facility has been set up that allows the PD behaviour of polymer insulated twisted pair samples exposed to 50 Hz AC voltages in the range of 0 to 10 kV to be characterised. Resulting PD activity is quantified using the methods defined in IEC standard 60270 and by using a simple monopole antenna to detect the RF signals excited(More)
Measuring partial discharge (PD) activity in high voltage plant using radio frequency (RF) equipment is a well-established technique used to monitor insulation integrity. This paper presents a study of partial discharge behaviour involving gaseous, liquid and solid dielectrics typical of insulation defects that may occur in practice. Discharge pulses with(More)