Partial Discharge Detection In Cables Research Articles

Research on cable partial discharge detection and location system based on optical fibre timing

Partial discharge (PD) is an important index to reflect the running state of cables. According to the characteristics and propagation mechanism of cable partial discharge signal, a cable partial discharge detection and location system based on optical fibre time synchronisation technology and travelling wave double terminal location principle is developed. The system has high detection sensitivity, high reliability, real-time detection, diagnosis and positioning of cable discharge power supply. The experimental results show that the positioning accuracy of the cable partial discharge source can be effectively improved based on the fibre timing and double terminal positioning technology, and the positioning accuracy can reach 1%; the method studied in this paper can meet the requirements of the accurate location of the partial discharge source of the cable, Gil and other equipment.

Research on cable partial discharge detection and location system based on optical fibre timing

Research on cable partial discharge detection and location system based on optical fibre timing

Research on Time-Domain Transfer Impedance Measurement Technology for High Frequency Current Transformers in Partial Discharge Detection of Cables

We focus on the high frequency current method which is widely applied in the partial discharge (PD) detection of cables. Aiming at guaranteeing the accuracy of this method, we study an innovative time-domain technology for effectively measuring the transfer impedance of the high frequency current transformers (HFCTs). The proposed technology called pulse injection method obtains the system response under the excitation of the wide-band instantaneous pulse signal. Firstly, by studying the working principle of HFCTs, we summarize that the bandwidth of the selected signal acquisition device should be at least 100MHz to ensure measurement accuracy. Secondly, Gauss pulse and square wave pulse are generated to determine the effects of different sources. The measurement results indicate that Gauss pulse is more suitable for pulse injection method, and the rise time should be under 10 ns to improve the starting frequency of oscillation distortion. Finally, the transfer impedance curves of five types of HFCTs are acquired by both pulse injection and traditional point-frequency methods. The measurement results show a remarkable consistency between two methods. However, pulse injection method requires the simpler operation and has a higher resolution, obviously improving the measurement efficiency and better displaying the details of the transfer impedance curves.

Modeling of High-Frequency Current Transformer Based Partial Discharge Detection in High-Voltage Cables

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. 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 of obtaining 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.

Study on Partial Discharge Performance Testing of High Voltage Cables for EMUs

EMU high voltage cable partial discharge detection is an important means that is to ensure the reliable operation of EMU. This thesis summarizes the causes of partial discharge of EMU high voltage cable, and the mechanism of its formation is analyzed, then the corresponding cable partial discharge model and its interference model are designed. The main components of the test system are introduced. The partial discharge test system for high voltage cable of EMU is tested on site, and corresponding test data is obtained and then analyzed. At the same time, measures of anti-interference on site are put forward. Partial discharge testing detects the potential risks through state detection, and handles this problem by taking some effective measures to reduce the operational risks of the power supply system and ensure the safety and stability of the vehicle operation.

Research on Charge-Discharge Characteristics and Location of Cable Partial Discharge Detection System Based on Damped Oscillation Wave Voltage

Traditional partial discharge detection methods of linked polyethylene (XLPE) cable have disadvantages about limited applicable conditions, low effectiveness and difficulty of field application. However, partial discharge detection method based on oscillation wave test system (OWTS) is a new type nondestructive testing technique for cable insulation with time short, Portable, flexible, and convenient operation. This paper researches on the charge-discharge principle and location error of cable partial discharge OWTS by using theoretical derivation method, reveals the damped characteristics of over-damped charge and under-damped discharge process, clarifies the influence mechanism of the abnormal insulation of the cable system on the charging failure, and indicates that the accurate value of the cable length and wave velocity can determine the precise location of the partial discharge defect. Therefore, the conclusion obtained from the research has a strong guiding significance for the detection and location of the cable partial discharge based on the damped oscillation wave voltage.

Onsite Detection Technology and its Application for Electric Cable Partial Discharge

This paper introduces the electric cable partial discharge detection technology and elaborates pulse waveform characteristics of cable partial discharge, PD signal’s detection theory and basic method of cable PD source localization. On this basis, application examples of substation cable-site detection are given.

The use of power frequency current transformers as partial discharge sensors for underground cables

Partial discharge (PD) diagnostics can be used to diagnose insulation defects in medium voltage cables and thereby inform required maintenance planning to extend the lifespan of ageing assets. High frequency current transformers (HFCT) installed on the earth strap at the cable termination are widely used to detect the fast varying pulses resulting from PD. Due to constructional reasons earth strap accessibility in underground cables is often limited. Furthermore in three core cables, phase angle dependency of pulses resulting from PD sometimes fails to induce pulses in the earth screen. This paper investigates an alternative method of PD detection using conventional power frequency current transformers (PFCT) principally used for protection and measurement purposes. This investigation assesses the feasibility of this approach by conducting a magnetic study of the transformer core, frequency response analysis (FRA), and finally capturing and analyzing onsite PD measurements using conventional PFCTs and the developed PD data acquisition/interpretation system. Based on the laboratory and on-site measurement results, PFCTs can be considered for detecting PD. This approach does not require retrofitting additional PD sensors and can also be applied to older switchgear design without any outage. Hence this approach can be considered as a low cost and noninvasive method of PD detection in cables.

Wavelet packet denoising for online partial discharge detection in cables and its application to experimental field results

Partial discharge measurements taken online are severely corrupted by noise due to external disturbances. In this paper a powerful noise reduction technique, based on a wavelet packet denoising algorithm, is employed to isolate the signals from the noise. This methodology enables the denoising of partial discharges that are heavily corrupted by noise without assuming any a priori knowledge about the partial discharge features. A brief description of the wavelet packet theory as an extension of the multi-resolution analysis is given. Results of the application of this algorithm to simulated data of low signal-to-noise ratio are presented, demonstrating substantial improvement in signal recovery with minimum shape distortion. Finally, the capability of this technique is highlighted by applying it to experimental field data taken from three-phase 11 kV cables.

On-line partial discharge detection in cables

This paper describes an on-line PD (partial discharge) detection technique applicable to power cables. The method can be applied to both wire screen and solid shielded cables. In wire screen shielded cables, PD components with frequencies <100 MHz can be detected at distances over 150 m from the source, PD activity with levels as low as 20 pC can be detected within 100 m. However, in the case of solid shielded cables, PD levels of /spl ges/50 pC can be measured within 60 m in the frequency range <50 MHz. This method also can be utilized to check cable accessories such as splices and terminations. PD pulses with frequencies to /spl sim/300 MHz can be measured near the joints and terminations. The suitability and the sensitivity of the VHF technique were checked against two other alternative PD detecting techniques (pulse phase analyzer and high speed digital oscilloscope) by performing PD measurements in standard air gap and defects induced in EPR-insulated cable under laboratory-controlled conditions. The suitability and sensitivity of the VHF method were as good as the two alternative PD detection techniques.