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 and travel away from the PD sources and will be detected by HFCTs installed at cable terminations. In this paper, based on combining finite-difference time-domain (FDTD) modeling and transfer function theory, a hybrid modeling approach is proposed to investigate the processes of PD coupling and detection involved in HFCT-based PD testing of HV cables. This approach allows exciting a PD event anywhere in FDTD models of the cables and predicting output from HFCTs some distance away. Implementation of the method is illustrated using an 11 kV XLPE cable. Moreover, a “direct measurement” method to obtain original PD pulses as the excitation source waveform is presented. The modeling approach introduced here will facilitate studies on the relationship between measured PD signals and those excited at PD sources, which can potentially give useful insight into the basic mechanisms behind PD detection in cables.

Partial discharge (PD) is indicative of insulation defects in power cable joints. Cross-bonding cable joints have a break in the joint shield that interrupts the screen of the jointed cables. It is possible for radio frequency (RF) signals of PD in the joints to emit from the shield break. This paper presents the use of off-the-shelf RF sensors at the shield break for non-intrusive PD detection. Measuring results from a 35 kV XLPE cable joint sample with artificial defects suggest that PD-induced electric and magnetic fields can be detected simultaneously with this approach. Typical pulses measured are limited to approximately 500 ns in duration, and the FFT spectrum of the pulses is mainly distributed at frequencies below 200 MHz. Average pulse magnitude ranging from about 6–22 mV can be measured between 10–15 kV. Increasing the measuring distance can cause the measured pulse magnitude to decease exponentially. Additionally, numerical simulations show that reducing the length of the shield break can cause the pulse magnitude recorded at the shield break to decrease gradually. The presented approach can potentially be used for cost-effective and non-intrusive detection of PD in cross-bonding cable joints.

Inappropriate manufacturing of cable joints can cause defects in the joint insulation. During operation, partial discharge (PD) may occur at these defects. The development of PD can cause accelerated aging even breakdown of the insulation, resulting in faults in the electric grid. In this paper, for radio frequency (RF) detection of PD in cable joints, a finite-difference time-domain (FDTD) model of a 35 kV XLPE cable joint is established, an excitation source is defined in the model to represent PD of different defects, and then propagation characteristics of RF electromagnetic signals induced by PD in cable joints are studied through the established model. Transfer functions (TF) of RF PD signals obtained with the FDTD model show that both magnitude and shape of the TF are closely related to the location and direction of the excitation source in the model. Two peaks in the magnitude, locating at 380 MHz and 790 MHz, respectively are present in the obtained TF regardless of the excitation source settings. Moreover, the TF magnitude for the excitation source defined in the radial direction of the cable joint model is found to be generally more than one order larger than that of the same source defined in the axial direction. The effectiveness of the FDTD model in representing high frequency properties of the cable joint has been checked against both time domain reflectometry (TDR) and S ₂₁ measurements on a cable joint made in laboratory. The TF results from this work are expected to be helpful for applications of radiometric PD detection to cable joints, e.g., enabling improvement of the detection sensitivity through optimizing frequency responses of RF sensors.

In this paper, a novel algorithm was proposed to subtract power line interference (PLI) from contaminated ECG signal. Firstly, some PLI values were calculated from ECG signal in linear segment. Secondly, using nonlinear regression and least squares estimation, sinusoidal parameters such as frequency and phase were estimated from the calculated PLI values. Thirdly, the PLI values in the nonlinear segment closest to the linear segment were determined by the sinusoid function with the estimated parameters. Lastly, PLI was subtracted from the contaminated ECG signal in nonlinear segment. The method's performance was tested in ECG databases in www.physionet.org. The experiment results show that the proposed method can more effectively remove PLI from ECG signal than other algorithms even when PLI frequency fluctuates, and do not distort the shape of ECG signal.

Partial discharge (PD) detection effectively identifies insulation defects in power equipment. Radio frequency (RF) methods for PD detection offer promising advantages due to their non-invasive measurement capability and ability to locate discharge sources. However, microstrip antennas used as RF sensors for PD detection suffer from narrow bandwidth and limited installation flexibility. To address these limitations, this paper presents a novel flexible microstrip antenna design. By incorporating a partial ground plane and oblique-cut meandering techniques and optimizing the structural parameters using an improved whale optimization algorithm (I-WOA), the operating bandwidth is expanded from 0.612–0.625 GHz to 0.346–2.0 GHz, while the overall size is reduced to 75.3% of its original dimensions. The antenna’s performance was validated through GTEM cell measurements and PD calibration pulse tests, confirming its suitability for RF detection of PD in power equipment such as transformers and cable joints. Notably, when the antenna was conformally wrapped around a cable joint, the response amplitude increased by 14%. This study contributes to the development of a low-cost, broadband, and flexibly installable RF sensor for partial discharge detection.