Effect of Hydrogen Inlet Pressure Analysis on open Voltage of Proton Exchange Membrane (PEM) Fuel cell by using Periodogram

Proton Exchange Membrane Fuel cell (PEMFC) is one of the renewable energy system that was recently highlighted by researchers. PEM fuel cell generates electricity through the electrochemical reaction of hydrogen and oxygen. Finite changes in the reactant inlet properties leads to unique operating changes within the fuel cell stack. The effect of hydrogen inlet pressure to the operating voltage has been detailed before using a variation of monitoring techniques. Identification analysis is required to monitor every factor that influences the performance characteristic of PEMFC. Periodogram monitoring technique applies a frequency domain waveform signal capable of tracing small changes in the phase behaviour of electrical operations as external parameters are varied. The use of this technique is provided in this paper within the scope of monitoring the signal changes in the open voltage of a 30Watt (W) PEM fuel cell stack as the hydrogen inlet pressure is varied from 0.1 bar to 0.5 bar. The open voltage increases with rise in hydrogen inlet pressure and the Periodogram amplitude signal increases accordingly. Then, the magnitudes of total tolerance voltage, the signal characteristic of direct current voltage (VDC), root means square voltage (VRMS), and alternating current voltage (VAC) were calculated from the voltage waveform where losses could be identified. Therefore, the Periodogram technique has been proven useful and practical in monitoring operation changes of a PEM fuel cell stack

Understanding SFRA Results using Transformer Model with Simulated Faults

Sweep Frequency Response Analysis (SFRA) is well known power transformer diagnostics device which capable on detected faults/changes either electrical or mechanical. However the challenges are on understanding the SFRA results for the newcomers’ engineers. If wrong, mislead interpretation of SFRA results would arise. Inline of this matter, five transformers model with simulated faults have been developed. The faults are; Core Damage, Shorted Turns, Open Circuit, Radial Deformations (Hoop Buckling) and Axial Displacement. These faults are designed to imitate the actual faults occurred in power transformer. Hence, the SFRA is then applied to the models to visualize the changes of SFRA results. In fact it create a clear understanding of the SFRA results changes with referring to which faults occurred

MECHANICAL CONDITION ASSESSMENT OF TNB IN-SERVICE DISTRIBUTION TRANSFORMERS USING SWEEP FREQUENCY RESPONSE ANALYSIS (SFRA)

Distribution transformers in TNB (Tenaga Nasional Berhad) are exposed to the thermal and electrical stresses. Those stresses are effecting to the main mechanical active parts in transformer such as core and winding. In field, lightning strikes and cable faults may cause problem due to transformer core and winding. Sweep Frequency Response Analysis (SFRA) is an off-line diagnostic tool used for finding out any possible winding displacement or mechanical deterioration inside the transformer especially core and winding. SFRA diagnosis is made based on the comparison between two SFRA responses and any significant difference in low, middle and high frequency sub-bands region would potentially indicate mechanical or electrical problem to the winding and core of transformer. The aim of this paper is to assess the condition of TNB in-service distribution transformers by using SFRA method

Effect of repeated electrical breakdowns on mineral and natural ester insulating oils

Transformer insulating oils are exposed to repeated electrical discharge or breakdowns inside power transformers. Durability tests are conducted to analyze the ability of oil to resist decomposition due to such high electrical stresses. With the increasing demand for alternative insulating oils for oilimmersed transformers, it is worthy to compare the performance of different types of insulating oils (conventional mineral-based insulating oil and natural ester-based insulating oil) under repeated electrical breakdown. In this paper, the AC breakdown voltage of different mineral-based and natural ester-based insulating oils is reported. Durability tests were conducted based on the AC breakdown voltage behavior of insulating oils after 50 electrical breakdown shots. The AC breakdown voltage of each insulating oil sample was assessed according to the ASTM D1816 standard test method. Based on the results, it can be concluded that the dissimilarity in chemical composition of the insulating oils has a significant effect on the AC breakdown voltage behavior of these oils under repeated electrical breakdowns

Diagnosis of OLTC via Duval Triangle Method and Dynamic Current Measurement

Power transformers studies have shown that the main cause of power transformers failures is the On Load Tap Changer (OLTC). OLTC failure occurs due to the insulation degradation and contacts failure inside it. Other than that, contacts wear influences the OLTC performance and this phenomenon has not been deeply investigated. The worn contacts will cause hotspots in the OLTC tank and cause the insulating oil to degrade faster. Consequently, this will lead to the damage of complete transformer unit. Thus, the research work that has been carried out applied three different stages related to the diagnosis of OLTC. Firstly, fault detection of power transformer's OLTC is done mainly based on the results of the DGA interpretation by using the latest Duval Triangle method. Then, the results that obtained from latest Duval Triangle method are compared with the results carried out from Dynamic Current Measurement (DCM). Finally, research validation through visual inspection is applied to validate the results obtained from both DGA and DCM

Comparative study of electrical test methods on detecting transformer faults

Condition monitoring of distribution and power transformers is of utmost importance to utilities due to cost effectiveness concerns. The common faults that occur in transformers are short circuits and winding deformation. To date, there are many established test methods used to detect these faults. In this study, three test methods (insulation resistance (IR), transformer turn ratio (TTR), and frequency response analysis (FRA)) were compared to assess their effectiveness in detecting short circuit and winding deformation in a three-phase transformer. Based on the results, the three test methods were found to be capable of detecting short circuits. However, only TTR and FRA can detect winding deformation, and FRA can further indicate which phase is faulty. Therefore, it is concluded that FRA is more effective in detecting short circuit and winding deformation of a three-phase transformer

Transformer Core And Winding Conditions Evaluation From Sfra Measurement Results Using Cross-Correlation Coefficient Function For Tnb Distribution Transformers

Distribution transformers in TNB (Tenaga Nasional Berhad) Malaysia arc exposed to the thermal and electrical stresses. Those stresses are effecting to the main mechanical active parts in transformer such as core and winding. In field, lightning strikes and cable faults may cause problem due to transformer core and winding. SFRA diagnosis is made based on the comparison between two SFRA responses md any significant difference in low, middle and high frequency sub-bands region would potentially indicate mechanical or electrical problem due to core and winding of transformer. instead of using graphical comparison, numerical technique such as Cross-correlation Coefficient Function (CCF) can be used to interpret the SFRA results in n proper say. The aim of this paper is to assess the condition of TNB distribution transformer by using SFRA method in line with the interpretation from the CCF technique

DIAGNOSIS OF OLTC USING DGA AND STATIC WINDING RESISTANCE TEST

On Load Tap Changer (OLTC) failure occurs is due to the insulation degradation and contacts failure inside it. Other than that, contacts wear influences the OLTC performances. The worn contacts will cause hotspots in the OLTC tank and cause the insulating oil to degrade faster. As a result, this will lead to the damage of complete transformer unit. Thus, the research work that has been carried out applied the Dissolved Gas Analysis (DGA) via latest Duval Triangle method during the diagnosis of OLTC rated at 33/11kV, 30MVA at the first stage to provide early indication of OLTC�s breakdown. The Static Winding Resistance Test is then applied at the second stage to figure out any increase of contact resistances for all phases. In addition, it is expected to have a relationship between both results. The results showed that it was proven that by performing DGA via latest Duval Triangle method, the early indication of OLTC�s breakdown can be obtained. Besides, this paper revealed that the Static Winding Resistance Test was capable to provide any sign of bad contacts in fixed condition as well as looses connections

Condition Monitoring of Distribution Transformer's Mechanical Parts Using Sweep Frequency Response Analysis (SFRA)

Distribution transformer is the key element in the electricity transmission throughout the nation. Hence, serious attention for the transformer condition monitoring is a crucial. With an occurrence of short-circuit in the power system, the transformer active parts such as core and winding will experience a mechanical movement created by the electromagnetic forces. There are various types of transformer condition monitoring measurement in market, but the monitoring of the mechanical movement in transformer is still lacking. Therefore, Sweep Frequency Response Analysis (SFRA) has been introduced to assess any mechanical movement especially of the transformer's core and winding. The frequency response of the transformer provides mechanical information of core and winding conditions. The SFRA measurement results were validated using the actual transformer untanking process