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Experiment of Dielectric Frequency Response for Aged ZnO Surge Arrester
(2025-01-01)
Aiamrungruang, Phitthaya
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Methavithit, Winai
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Pannil, Pittaya
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Chuayin, Chaitawat
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Zinck, Matthieu
Condition-based monitoring of surge arresters has gained increasing attention in modern power system asset management, especially for medium-voltage equipment. This paper presents an investigation into the dielectric frequency response (DFR) analysis technique as a diagnostic method to evaluate aging and unhealthy conditions in 21-kV metal oxide surge arresters (MOSA). Four types of simulated defects, excessive number of lightning current stress, cracking, moisture ingress, and tracking, were introduced to represent common field failures. The DFR technique enables frequencydomain interpretation of dielectric properties, providing insight into insulation behavior over a wide frequency range. The test results show a significant variation in capacitance and dissipation factor corresponding to different defect types. Among these, moisture ingress exhibited the most severe deterioration. The findings suggest that DFR is a viable offline diagnostic method that can support preventive maintenance strategies for high-voltage surge arresters.
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Development of a Health Index for Transformer Condition Assessment Using an Online Dashboard
(2025-01-01)
Sripatawasumadee, Kornchet
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Maneerat, Noppadol
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Dechothamsathit, Vorawut
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Kingkham, Sukanya
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Jeenmuang, Siwakorn
Power transformers are critical components in electrical power systems in the transmission and distribution of electricity. Keeping them in good working condition is necessary to prevent power outages and ensure system stability. Traditional maintenance strategies, such as time-based maintenance, may not always be the best way to avoid problems or use resources efficiently. To improve this, the concept of a Health Index (HI) has been introduced as a systematic method for transformer condition assessment. By integrating various diagnostic data - such as load data, oil analysis, maintenance record, and on-load tap changer (OLTC) parts - into a unified HI score, asset managers can make informed decisions regarding maintenance prioritization and replacement planning. Furthermore, this paper proposes the development of an online dashboard system that facilitates the input, storage, and visualization of transformer health data. This user-friendly platform enables engineers to monitor condition trends in real time and supports strategic maintenance scheduling. The integration of Health Index evaluation with an accessible digital interface enhances the efficiency, transparency, and reliability of transformer asset management practices.
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The Experiment of Partial Discharge testing for Low Voltage Motor
(2025-01-01)
Sawangsri, Jaturaphat
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Wiangtong, Theerayod
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Pathanrat, Khomsan
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Ruangwong, Khomsan
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Jeenmuang, Siwakorn
Low-voltage (LV) motors are widely used and highly popular in industrial settings due to their critical role in production processes. Any malfunction or failure of an LV motor can lead to production downtime, resulting in reduced output and potential revenue loss. Therefore, it is essential to conduct diagnostic assessments that evaluate the reliability of the insulation system in LV motors. Partial Discharge (PD) testing is recognized as a highly effective and reliable method for assessing the condition of motor insulation. This paper presents PD testing on LV motors to investigate the behavior of partial discharges using multiple analysis techniques. Additionally, an acoustic camera is integrated into the testing process to accurately identify the discharge locations.
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Dielectric Frequency Response Analysis of 230 kV Service Aged OIP and RIP Bushings: Case Studies
(2025-01-01)
Pattanadech, Norasage
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Jeenmuang, Siwakorn
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Ostria, Elmer
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Suksagoolpanya, Suthat
Transformer bushings are critical components that enable current to pass through the transformer enclosure while providing insulation between the high-voltage conductor and the grounded housing. A failure in the bushing could potentially result in transformer failure. This paper presents case studies on the evaluation of 230 kV Oil-Impregnated Paper (OIP) and 230 kV Resin-Impregnated Paper (RIP) bushings using Dielectric Frequency Response (DFR) analysis. The bushings investigated in this study were service-aged units removed from the field. For the 230 kV OIP bushing, the paper insulation was peeled off starting from the outermost layer. This allowed for DFR testing on individual insulation sections. The results indicated moisture absorption and provided information on the moisture distribution within the paper insulation. Furthermore, a 230 kV RIP bushing suspected of having poor contact between the outermost foil layer and the test tap connection was also investigated. The DFR results from this case revealed the observable impact of such connection issues on the DFR test. In summary, DFR analysis has proved that it is a very useful technique for testing and diagnosing various common bushing degradation mechanisms that can lead to severe failure of the bushings and the transformers.
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Condition Assessment of Rotating Machine Insulation: Case Studies from Power Plants
(2024-01-01)
Pattanadech, Norasage
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Jeenmuang, Siwakorn
Unexpected failure of rotating machines in the power plant can cause unnecessary expense. Thus, appropriate preventive and predictive maintenance should be planned and scheduled, to avoid premature failure of the machines and to ensure the reliability and safe operation of the systems. Besides, the online monitoring technique has an advantage as it can monitor the condition periodically without interrupting the equipment and it can measure even during actual operating conditions while off-line tests can't. Indeed, the most vulnerable part of the equipment is the insulation since it is subjected to several stresses during service which can alter the insulation condition, so-called degradation. Hence, this paper intends to present the experience of insulation condition assessment on generators and motors in power plants in Thailand. Several test techniques were conducted on the machines during the annual outage including the polarization and depolarization current (PDC) analysis, off-line partial discharge (PD) test as well as dissipation factor and capacitance tip-up. Those diagnostic test techniques are useful as effective tools to evaluate the insulation condition of the machines. The experimental results will be introduced and discussed in this paper.
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Partial Discharge Investigation of 22kV Distribution Transformer
(2024-01-01)
Dechothamsathit, Vorawut
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Pannil, Pittaya
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Yamsiri, Thummanoon
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Chumpiboon, Komin
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Jeenmuang, Siwakorn
This paper presents an off-line partial discharge (PD) experiment conducted on a 22 kV/400 V distribution transformer, which was decommissioned after 20 years of service. The study investigates the impact of reduced oil levels within the transformer on PD characteristics that are expected to facilitate PD activity within the transformer. The experiments were performed with reduced oil levels below the top clamp and using both single-phase and three-phase voltage excitations, with PD measurements recorded for each case. The PD signals were measured using High-Frequency Current Transformers (HFCTs) and capturing current pulses of PD in the frequency range of 100 kHz to 20 MHz. Additionally, transformer oil tests were performed, including moisture content, oil breakdown voltage, and oil conductivity. The results of the PD measurements and oil tests are introduced and discussed in this paper.
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Dielectric Response Analysis Characteristic of Service-Aged XLPE Cables
(2024-01-01)
Thongkong, Patchara
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Promphanich, Wiboon
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Udomluksananon, Patt
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Jeenmuang, Siwakorn
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Wiangtong, Theerayod
The main insulation used in plastic underground cables is cross-linked polyethylene (XLPE). The XLPE underground cable which has been utilized in service for a long time, has experienced various stresses, or so-called TEAM stresses. Consequently, the XLPE insulation will be degraded over time and lead to insulation properties degradation. This paper represents the dielectric response analysis technique for characterizing the insulation condition of the service-aged XLPE medium voltage underground cable. The dielectric response analysis was performed on the 22 kV XLPE underground cables that have been in service for more than 10 years and were directly buried. The dielectric response analysis measurement consists of a combination of polarization and depolarization current (PDC) measurement in the time-domain and frequency-domain spectroscopy (FDS) measurement. After that, test results were analyzed to evaluate the insulation condition and compare it to the new 22 kV underground cable. The analyzed dielectric response analysis test results will be reported in this paper.
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Partial Discharge Classification with Transformer Neural Networks
(2024-01-01)
Cheypoca, Thepjit
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Promphanich, Wiboon
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Thway, Aung Ye
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Hankae, Angelina Phimpissada
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Jeenmuang, Siwakorn
This paper introduces an approach with the Transformer Neural Networks model for partial discharge patterns classification, that consists of corona discharge, internal discharge and surface discharge. The PD measuring circuit suggested in IEC 60270:2000 is used to record Partial discharge signals. Independent parameters such as phase and charge of PD patterns were recorded. The phase value will be encoded into the charge array and Transformer Neural Network is constructed using Positional Embedding and Transformer Encoder Layer. 80% of the recorded data will be used as a training data and 20% recorded data was used for testing of the classification models. Impacts of neuron numbers and network architecture on the PD classification performance will be observed
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The Experiment of Dielectric Frequency Response of Serviced Aged Distribution Transformer
(2024-01-01)
Posrimahapoch, Purichaya
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Maneerat, Noppadol
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Daengdee, Danaiwat
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Jeenmuang, Siwakorn
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Pannil, Pittaya
Outdoor Distribution Transformers typically encounter random environments and affect moisture in any ingress ways, e.g., defective breathing, oil leakage, or human error during internal inspection, etc. Such moisture is a very important enemy of the insulation integrity of the transformer. It may cause the failure of the transformer eventually. Therefore, the condition of the transformer insulation needs to be monitored. Dielectric Frequency Response (DFR), also known as Frequency Domain Spectroscopy (FDS), and Polarization and Depolarization Current (PDC) are nondestructive tests providing efficient diagnostic for transformer insulation. The test results can be used to estimate moisture content and oil conductivity. In this paper, the dielectric investigation of a 315 kVA, 22 kV serviced aged distribution transformers, which have been retired for 6 months after being utilized for more than 20 years, was conducted. The experiment results of the DFR and the PDC tests including the investigated mineral oil characteristics (i.e., oil breakdown voltage, moisture content, and tan delta) are reported and analyzed. They should be useful to understand the condition of the transformers.
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The Experiment of Partial Discharge for Cast Resin Transformer
(2024-01-01)
Aiamrungruang, Phitthaya
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Pannil, Pittaya
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Dorkmai, Kritsada
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Maneerot, Sakda
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Jeenmuang, Siwakorn
Dry-type cast resin transformers, utilizing epoxy resin insulation instead of traditional liquid insulation like mineral oil, are designed to prioritize safety, avoid fire hazards, be environmentally compatible, and endure short circuits well. Limitations of dry-type transformers are the installation area by which it should be dry, free from dust, excessive moisture, fertilizers, chemicals, and other corrosive fumes or fumes. This paper investigates the Partial Discharge (PD) phenomena occurring on a 12 kV dry-type transformer surface using HighFrequency Current Transformers (HFCT) with 100 kHz -20 MHz bandwidth as a PD detection device. The simulated PD sources were made from the conductive wire. Moreover, the scheme of winding connections in the dry-type transformer related to cross-talk phenomena between transformer coils is also reported. The recorded Phase-resolved PD (PRPD) and the PD Inception Voltage (PDIV) have been summarized and compared, as described in this paper.

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