Partial discharges (PD) are small current pulses that can occur within the insulation of medium and high voltage (HV) electrical assets such as cable accessories, transformers and switchgear. In GIS units, PD's can occur near the high-voltage conductor or at other locations commonly due to metallic particles from the erosion of the switchgear contacts or left behind after maintenance. For that reason, GIS units are usually equipped with multiple embedded UHF sensors in selected compartments that can detect PD in their vicinity.

Partial discharge (PD) detection is a standardized technique to qualify the insulation condition in power equipment. The main purpose of the article is to evaluate the performance of an extra high-sensitivity adapted giant magneto-resistive (xMR) sensor for non-contacting PD detection. First, compensation and signal conditioning circuits of the sensor are designed. Frequency response and time-domain response to fast calibrator pulses of the sensor with the implemented circuit are measured. Besides, PD experiments based on corona and surface models are carried out and compared with measurements using a high-frequency current transformer (HFCT). The results show that the xMR system can measure the magnetic fields produced by the PDs at distances up to 50 cm. The correlation between the HFCT and xMR signals is proportional under different voltages, showing that PDs can be effectively detected and evaluated by this method. PDs in a cross-linked polyethylene (XLPE) cable with an artificial discharging defect are successfully measured, demonstrating the sensitivity and performance of the xMR system.

There are no accepted procedures that quantify the apparent charge of partial discharge (PD) in gas-insulated substations (GIS). This paper proposes a calibration method for PD charge estimation using unconventional electromagnetic sensors: a magnetic loop antenna (inductive coupler) and an electric antenna (capacitive coupler.) The calibration procedure is intended for the voltage double integral method, which is reviewed for magnetic antennas and extended for electric antennas. By injecting low-frequency sinusoidal signals, the calibration constants are determined for two different test setups: the first one being a testbench where the characteristic impedance is matched and the second one a full-scale 420 kV GIS. The calibration method is validated in three ways: with a calibrated pulse in the testbench, a calibrated pulse in a full-scale GIS, and PD defects in the full-scale GIS. The calibration procedure revealed a frequency limit range dependent on the GIS length and the sensor's signal-to-noise ratio. The three validation methods showed low charge estimation errors for the magnetic and electric antennas, demonstrating that the PD calibration method applies to any electric/magnetic detector with a low-frequency derivative response. This research paves the way for better GIS insulation monitoring and PD sensor harmonization.

The authors wish to make the following erratum to this paper [1]: the summation symbol in the Equations (11) and (12) should be a product symbol. The corrected Equations (11) and (12) appear below: The authors apologize for any inconvenience caused and state that the scientific conclusions are unaffected. The original article has been updated.

Space charges are one of the main challenges facing the constantly increasing use of extruded high voltage direct current (HVDC) cables. The Pulsed Electro-Acoustic (PEA) method is one of the most common procedures for space charge measurements of insulation. One issue with the PEA method is distortion due to the crosstalk between the applied voltage pulse and the acoustic sensor. This work analyzed two factors involved in the reduction in this distortion: the influence of the exposed semiconductor distance between the injection electrodes and PEA test cell, and the influence of adding a reactance at the grounding circuit of the PEA test cell. The interaction of these two factors with the distortion was analyzed through a series of experimental testing. Moreover, the performance regarding distortion after applying a developed coaxial injection was compared with the standard non-coaxial injection configuration. It was observed that these two factors had a direct impact on distortion and can be utilized for the reduction in distortion arising from the crosstalk of the applied pulsed voltage. The results can be utilized for the consideration of practical aspects during the construction of a PEA test setup for the measurement of full-size HVDC cables.

The recognition of partial discharge (PD) sources is an important task of the monitoring and diagnostics of high-voltage components. Nowadays, digital PD measuring systems have the capability of extracting features and form scatter plots with such data sets. Part of an unsupervised PD analysis system is to discover clusters within the data sets and link them to particular PD sources. Due to the nature of PD data sets, clusters may appear very close to each other or even merged hindering the separation of sources. Clustering methods based on spatial density such as the density peak clustering (DPC) method and DBSCAN are suitable approaches to discover clusters within PD data sets. However, their accuracy can be reduced due to the proximity among clusters. In this paper, a new method is presented to improve the accuracy of the DPC method. Our method proposes to partition the data set and later pass the resulting subsets to the DPC method. The partitioning is based on the spatial density of data computed by a smoothed density method (SD). SD has the advantage of being fast and not requiring high computational power. As a final step, a routine is applied to group the sub clusters as per the DPC method having a threshold for the data contour distance as a criterion. This method proved higher accuracy to discover clusters in actual PD data sets. However, the threshold for the data contour distance still needs further research.

This paper investigates the triggering and development of partial discharges at artificial defects in the cross linked polyethylene (XLPE) insulated cable with accessories under superimposed voltage. The experiments are conducted on a 4-meter long 6/10 kV commercial XLPE cable sample, which is assembled with a cable joint and terminations. Defects are fabricated on purpose in the cable accessories. The cable sample was subjected to the superimposed voltage of 50 Hz AC with impulse voltage. Partial discharge activities are measured by a HFCT sensor and analyzed by PDflex. The measurement results show that, the impulse voltage could trigger partial discharges, which might be kept sustained by the AC voltage. The partial discharge activities are influenced by the AC voltage level, which is determined by the PDIV and PDEV.

This paper presents a new concept for partial discharge measurements in gas insulated systems (GIS). The proposed technique uses a novel GIS magnetic antenna that measures the magnetic field produced by partial discharges (PD) propagating in GIS. The foundations of the measurement technique and the magnetic antenna design are presented together with laboratory measurements. The magnetic antenna performance and the sensitivity of the acquisition system are studied. The bandwidth of the measurement system is in the high frequency and very high frequency (HF⁻VHF) range. Laboratory experiments demonstrate the suitability of the novel magnetic antenna-based measuring system for PD in GIS for corona, surface discharges, and free moving particles in SF₆.

This paper presents a magnetic loop antenna for partial discharge (PD) measurements on gas insulated systems (GIS). The antenna is based on a single shielded loop inserted in the dielectric window of a GIS that measures the PD currents propagating in TEM mode. The paper describes the relevant parameters of the antenna and the antenna performance in combination with a transimpedance amplifier. A calibration method for charge estimation is presented along with laboratory experiments with free moving particle, surface and corona discharges in SF₆ test cells. The results show the suitability of the magnetic antenna for PD detection and the charge evaluation performance. Under laboratory conditions, the antenna sensitivity is in the order of 1 pC at a few meters from the PD source.

Partial discharge (PD) measurements are an effective tool for insulation assessment of high-voltage (HV) equipment widely used in both HV laboratories and in field tests. This paper presents the design of a test platform for electrical detection of partial discharges that contribute to the understanding of the phenomena. The test set-up comprises a collection of electrodes for the production of artificial PD sources frequently found in HV equipment, such as positive corona, negative corona, surface discharges, internal discharges, floating component and free moving particle. The test set-up has been designed in such a way that the gaps and clearances can be adjusted to modify the discharge characteristics, e.g. the discharge inception voltage, amplitude, repetition rate, etc. Besides, the platform has a symmetrical and radial arrangement of the PD sources around the coupling capacitor of the PD measuring systems with contribute to reduce the effect of the measuring circuit on the measurements. Relevant characteristics of the presented design is that the sensing of the PD signals is done by a high frequency current transformer (HFCT) with a wide bandwidth and the acquisition of the signals by a digital oscilloscope. A software tool was designed for the purpose of processing of the digitalized signals which proved to be an excellent workbench for studying the performance of clustering techniques.

With the availability of modern acquisition systems it has been possible to measure partial discharge (PD) pulses with enough bandwidth as to record its pulse shape. This new approach has made possible to compute new parameters that were not possible with the tradition narrow band measurements guided by the standard IEC60270. However, broader bandwidth also means more chances to measure noise and disturbances. The measuring circuit plays a main role because it may be the cause of resonances that distort the shape of the PD pulses. This paper presents a test set-up design that contributes to control the RLC parameters of the detection circuit and thus reduce the distortions such as oscillations of the PD pulses. The RLC parameters are estimated by means of a simple but novel procedure where a fast pulse from a calibrator is induced in the detection circuit leading to an easy detection of resonance frequencies.