On-line partial discharge monitoring system for distribution networks

Abstract

Partial discharges (PD) occur as a result of dielectric breakdown in electrical insulation under high voltage stress. PD activity, once initiated, causes chemical and physical degradation of insulating material and can lead to catastrophic failure. Early warning of PD activity and localisation is considered essential to ensure the reliable operation over the long term of high voltage equipment including cables, cable accessories and switchgear. PD detection in high voltage cable and cable accessories is usually carried out with test objects offline, requiring potentially significant interruption of service. An online detection system is preferable but difficult to calibrate apparent charge magnitudes due to changes in real distribution network loading and topologies. An online PD detection system with continuous calibration has been developed to determine the apparent charge magnitudes of PD activity and locations in a section of in-service distribution network with high monitoring frequency and no requirement to take cables off line. Results of the on-line PD monitoring system in a typical urban distribution network in Spain are presented. System components including the online calibration pulse injector, capacitive sensors for high frequency PD pulse detection, and data acquisition, processing and communication components at each monitoring site are presented.

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

“…As mentioned before, this method is inapplicable for on-line PD measurements because the electrical noise on-site is normally very high. However, the acquisition system through a coupling capacitor, plugged into the cable terminals within switchgear cable compartments, can be used to perform on-line measurements when the signals are processed in the HF range [ 29 , 30 ].…”

Continuous online monitoring of PD activity in the medium voltage distribution network

“…However, for asset management and preventative maintenance purposes the trending of these parameters over time [4,5,6] is a key indicator of when assets may fail. This paper presents continuing observations from a monitoring system installed as part of trials in a typical Spanish urban distribution network [7] SYSTEM ARCHITECTURE An overview of the system architecture employed in this trial can be seen in Figure 3 Using in-house developed capacitive coupling units, installed directly into T-junction cable end-plugs within the switchgear enclosure, it is possible to simultaneously capture both high frequency and voltage signals due to the integrated quadripole. This simultaneous measurement allows for PRPD patterns to be easily represented.…”

Modelling and simulation of online partial discharge measurement for medium voltage power cable

“…2, April 2020 : 427 -435 428 bridges the insulation between the conductor and may or may not occur adjacent to the conductor [10]. The high precision of the PD measurement system is essential for capturing PD activity as it occurs in the short duration of current pulses, usually for only a few nanoseconds [11][12][13]14]. PD usually occurs before the breakdown indicates that PD monitoring can be a good system to install, with reference to data from [15].…”