# Detection Method of Partial Discharge on Transformer and Gas-Insulated Switchgear: A Review
## 6 Conclusions  
Monitoring the PD phenomenon in high-voltage power systems and equipment is considered a necessary measurement for the preventive maintenance of equipment that is under operation or for the performance assessment of new equipment manufactured by the industries. Hence, the capability and suitability of the use of appropriate sensors with certain properties and methods of PD measurement in obtaining reliable outcomes of PD measurement on power transformers and GIS is the gap that potentially can be gratified and included to be the critical concerns in extending the research in the future. Based on the collective review of PD detection on power transformers and GIS, it has been found that advanced online monitoring technology was preferred in PD detection, especially the technique that uses directly integrated sensors on high-voltage equipment. This is because the online monitoring technique allowed the PD detection to be conducted without the need of isolating the power system and giving out realistic results based on the equipment's actual peripherals. Therefore, the research on designing and improving the capability of sensors can be summarized as an impactful study for future research on PD detection, including the technique to enhance sensitivity and accuracy in obtaining high precision of PD data collection.  
The UHF detection approach is currently an excellent tool for identifying PD in power transformers and GIS. Capturing and analyzing the electromagnetic signals released by PD occurrences is required for UHF detection. It employs UHF antennas that are purpose-built to detect and receive these signals. The advantage of UHF monitoring is its capacity to detect PD actions early on, allowing for timely maintenance and prevention of future deterioration. To ensure effective detection, UHF sensors can be carefully placed near crucial portions of the equipment. UHF detection has a number of advantages, including high sensitivity, a broad frequency bandwidth, and the ability to detect PD in both power transformers and GIS. It is a widely accepted and reliable method for PD detection in these types of electrical equipment. However, it is interesting to note that the UHF PD detection method is affected by electromagnetic interference and could be a source of pollution for the power grids and equipment. Therefore, non-electrical measurement methods are gradually attracting more attention because they are not prone to electromagnetic interference. Please note that the choice of PD detection method should consider the specific requirements and characteristics of the equipment being monitored. Consulting industry standards and experts in the field is recommended to determine the most suitable method for a particular application.  
Conceptualization, F.Z. and Z.F.; methodology, F.Z. and Z.F.; software, F.Z. and M.J.; validation, F.Z., N.M.S. and Z.F.; formal analysis, F.Z., Z.F. and N.M.S.; investigation, Z.F. and F.Z.; resources, F.Z. and Z.Y.; data curation, Z.F; writing--original draft preparation, Z.F. and F.Z; writing--review and editing, F.Z. and N.M.S.; visualization, Z.F. and Z.Y.; supervision, F.Z. and M.H.A.; project administration, O.A., H.A.M. and M.K.A.R.; funding acquisition, F.Z. and Z.Y. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors would like to acknowledge the sponsorship from the Higher Institution Centre of Excellence (HICOE), the Ministry of Higher Education Malaysia through the Wireless Communication Centre (WCC), Universiti Teknologi Malaysia (UTM) Vot. No. RJ090301.7823.4610. This work was also supported by the Universiti Teknologi Malaysia (UTM) under the UTM Encouragement Research grant (20J65), UTMShine Batch 6 Grants (09G97), and partially sponsored by the Faculty of Engineering. Multimedia University, Cyberjaya (MMU).  
The authors declare no conflict of interest.