Young Zaidey Yang Ghazali

Formation and Effect of Moisture Contents to Kraft Paper’s Life of In-Service Power Distribution Transformer

Examples of solid and liquid electrical insulations for power transformer are mineral oil and cellulose based paper. As transformers performed their function to step-up or step-down voltage level, its’ insulations will be degraded. Paper insulation is considered the most critical component in a transformer insulation system because it is not easily replaced if compared to oil where it is easily reconditioned in-order to remove water and contaminants. Studies show that temperature, moisture contents and oxygen contributed to paper insulation degradation. Moisture and furanic compound were produced from these deterioration processes. This paper is focused on the formation and effect of moisture to Kraft paper’s life. Levels of moisture contents were obtained from in-service power distribution transformers. These data then is used to assess the Kraft paper’s life by means of Weibull plot. This study shows that level of moisture contents can be used to assess the life of Kraft paper insulation.

Comparative Study of Worldwide Standards for Interpreting Frequency Response Analysis (FRA) Results of Distribution Transformers

Distribution transformer in Malaysian electricity network is categorized as major element on delivering electricity throughout the nation. Advanced diagnostic tools are used to monitor any technical problem of transformer to sustain its capability in the long run. One type of it which is currently being used in worldwide is Frequency Response Analysis (FRA). The reliability from this method is proven worldwide in diagnosing transformer condition especially a mechanical movement. FRA technique is done by comparing the response result in transformer initial condition to its current condition. The interpretation of transformer condition from the response is based on frequency sub-bands. Each frequency sub-bands are indicating any movement parts of transformer and electrical faults. Currently, there are three worldwide standards established for interpreting the FRA results but both of them are different in frequency sub-bands range. Up to now, there are no research papers comparing the fault detection capabilities from frequency sub-bands range for both standards. In this paper, comparative study is done to visualize and interpret the capabilities from three standards (IEEE Std C57.149 2012, DL/T911-2004 and Cigre WG A2/26); by focus on the frequency sub-bands range.

Application of Weibull-Bayesian for the reliability analysis of distribution transformers

With the certification of PAS 55 in 2013, there is a need for Tenaga Nasional Berhad (TNB), an electric utility company in Malaysia to further enhance the systematic assessment methods to evaluate asset performance in order to sustain the certification. Among the vital assets in TNB are the distribution transformers, which are used to transform voltage and supply electricity to end customers. Failure of distribution transformers will result in power interruption which not only reduces the utilitys revenue, but also causes loss of customer confidence towards the utility. Therefore, it is imperative for TNB to ensure the reliability of distribution transformers is not compromised throughout the years. This paper discusses the application of Life Data Analysis using Weibull-Bayesian statistical distribution to evaluate the reliability of distribution transformers. The evaluation is performed on distribution transformers supplied from 3 different manufacturers in TNB.

On-site OLTC monitoring using duval triangle and DWRM

Generally, the insulation degradation and contacts failure happened inside the On Load Tap Changer (OLTC). Besides, the OLTC performance can be dropped due to contact wear. Hence., the worn contact creates hotspots inside OLTC tank and affects the insulating oil. Due to this phenomenon, the insulating oil will degrade faster. Consequently, the whole unit of the transformer will be affected as well. Therefore, it is important to find new ways to detect the contacts wear inside the OLTC as it impacts the insulation oil and the age of the transformer. Thus, this paper demonstrates the application of Duval Triangle method during the diagnosis of OLTC to provide any significant indication related to the breakdown of OLTC. Besides, this paper introduced the advanced technique, Dynamic Winding Resistance Measurement (DWRM) to figure out the types and locations of faults occurred inside the OLTC. Finally, visual inspections will be carried out to validate the both results obtained from DGA and DWRM respectively. The analysis in this paper revealed that the findings from Duval Triangle method were similar to the outcomes carried out by DWRM.

Reliability analysis of premature failed 11/0.433kV hermetically sealed distribution transformers

There were around 450 units of 11/0.433kV distribution transformers which have found to fail prematurely over the past 15 years. These distribution transformers are vital to power utilities as they supply electricity to respective customers in industrial, commercial or domestic areas. Failure of distribution transformers will result in power interruption which not only reduces the utilitys revenue, but also causes loss of customer confidence towards the utility. Hence, it is imperative that power utilities, such as Tenaga Nasional Berhad (TNB) to perform studies to assess the reliability of distribution transformer. The reliability analysis is supported by the internal inspection which was guided by a standardized procedure. This paper presents a reliability analysis method called Life Data Analysis which utilizes statistical distribution, Weibull distribution to analyze and compare the reliability of distribution transformers from 3 different manufacturers. It has been found that the findings of the reliability parameters are consistent with the nature of incipient faults in the transformer.