Diagnosis of Insulation Condition of MV Switchgears by Application of Different Partial Discharge Measuring Methods and Sensors

Abstract

Partial discharges (PD) measurement provides valuable information for the condition assessment of the insulation status of high-voltage (HV) electrical installations. During the last three decades, several PD sensors and measuring techniques have been developed to perform accurate diagnostics when PD measurements are carried out on-site and on-line. For utilities, the most attractive characteristics of on-line measurements are that once the sensors are installed in the grid, the electrical service is uninterrupted and that electrical systems are tested in real operating conditions. In medium-voltage (MV) and HV installations, one of the critical points where an insulation defect can occur is inside metal-clad switchgears (including the cable terminals connected to them). Thus, this kind of equipment is increasingly being monitored to carry out proper maintenance based on their condition. This paper presents a study concerning the application of different electromagnetic measuring techniques (compliant with IEC 62478 and IEC 60270 standards), together with the use of suitable sensors, which enable the evaluation of the insulation condition mainly in MV switchgears. The main scope is to give a general overview about appropriate types of electromagnetic measuring methods and sensors to be applied, while considering the level of detail and accuracy in the diagnosis and the particular fail-save requirements of the electrical installations where the switchgears are located.

Separation of Partial Discharge Sources Measured in the High-Frequency Range with HFCT Sensors Using PRPD-teff Patterns

“…Thus, in order to evaluate properly the separation method developed, the three PD sources were intentionally placed close to the HFCT sensor, as per Figure 7. It is important to indicate that if the PD sources are not in the same location, the use of previous diagnosis tools that analyse the pulses' amplitude, polarity, frequency or time of flight enable a first separation of sources usually without many difficulties [27,28].…”

Partial Discharge Analysis in High-Frequency Transformer Based on High-Frequency Current Transducer

“…Several PD detection methods have been developed according to the physical properties of the insulation system, which accompany PD activity, such as current pulse method [21], ultrasonic detection, ultra-high-frequency (UHF) detection, and the optical method [22,23]. However, the lower frequency limit of conventional pulse current methods is close to that in the high-frequency transformer, the ultrasonic detection is not sensitive enough because of the complex acoustic impedance, the UHF signals are affected by communication signals, and there is still no known experience with optical measurements in this kind of electrical equipment.…”

Recurrent Neural Network for Partial Discharge Diagnosis in Gas-Insulated Switchgear

“…Various electrical, mechanical, and chemical methods have been used to detect PDs in GISs [7,8]. Some existing electrical methods use ultra-high frequency (UHF) sensors [9][10][11][12][13], while sound measurement methods use acoustic sensors [14,15] and chemical methods use dissolved gas analysis [16,17]. In this study, an electrical method that employs a UHF sensor is used for the PD measurement system.…”