A thesis submitted in partial fulfillment of the requirements for the award of the degree of. This is to prove that the thesis entitled, "Simulation of partial discharge in high voltage equipment" presented by Mrs. Asima Sabat in partial fulfillment of the requirements for the awarding of the Master of Technology Degree in Electrical Engineering with specialization in.
In submitting my thesis report on “Simulation of Partial Discharge in High Voltage Equipment”, I would like to express my gratitude and sincere thanks to my honorable supervisor Prof. I thank all the faculty and non-faculty members of the department for their help directly or indirectly during the course of my thesis work. Insulation of the HV power equipment gradually breaks down inside the insulator due to the cumulative effect of electrical, chemical and thermal stress.
In this study, efforts were made to investigate the maximum PD magnitude, number of PDs and other PD-related parameters such as PD distribution, frequency content of the obtained PD pulse using phase-resolved partial discharge (PRPD) measurement technique. Ca residual insulation capacitance without residual solid insulator discharge.
Introduction 1
Selection of void parameter 14
According to [7], parameters are chosen to find out the relationship between the empty parameter and the apparent charge. The behavior of internal discharges under alternating voltage can be interpreted using the well-known a-bc model shown in Fig.
Partial discharge measurement system 15
A high voltage supply - High voltage supply has a low degree of background noise to pass the discharge magnitude to be measured for a specific applied voltage. Input impedance is the most determining factor for the waveform of the PD impulse. A high voltage filter - This is used for reducing background noise from the power supply.
Ca corresponds to the capacitance of the residual discharge-free insulation of the rest of the solid insulator Cb corresponds to the capacitance of the residual series insulation with cavities (Cc). Electrical equivalent circuit model of cylindrical cavity in solid insulation together with high voltage equipment. In the equivalent circuit model, the capacitance Cc corresponds to the cylindrical cavity inside the solid insulation, Cb corresponds to the capacitance of the remaining series insulation with cavity (Cc) and Ca corresponds to the capacitance of the remaining discharge-free insulation of the rest of the solid insulator .
Capacitance of the gap Cc is charged which is responsible for the occurrence of breakdown. Apparent charge measurable at the high voltage terminal A and ground terminal B can be calculated from [3]. 3.3) where, S is void geometry factor, V is volume of cylindrical void and is given by πr2h, (where, r.
Partial discharges are electrical discharges confined to a localized region of the insulating medium in high voltage (HV) power equipment. The PD electrical detection method is based on the display of PD current or voltage pulse across the test object for fundamental investigation, which can be either a simple dielectric test object or a large HV power apparatus. In order to estimate the fundamental quantities of the PD pulse, a simple solid insulator equivalent capacitor circuit having cylindrical voids is considered for this work.
In the equivalent circuit, the capacitance Cc corresponds to the cylindrical void present in the solid insulation, Cb corresponds to the capacitance of the remaining series insulation with void (Cc) and Ca corresponds to the capacitance of the remaining discharge-free insulation from the rest of the insulation. the fixed insulator. Depending on the size of the void in the insulation sample (epoxide resin), in this model a cylindrical void with a height of 4 mm and a radius of 2 mm is used in a cubic sample (30 mm x 30 mm x 5 mm) . In this study, the value of the cavity model and the other high-voltage equipment for measuring PD were determined according to Table 1 and Table 2, respectively.
Results and Discussions 22
The relationship between the apparent charge and the height of the cylindrical void is shown in the figure. Another study done in this work is the relationship between apparent charge and void volume. It is noted that the apparent charge is also a function of the volume geometry of the cylindrical void model.
The amplitude of the PD pulse changes with the size of the void, as shown in figure. Similarly, it is found that by changing the height of the void and keeping the radius of the void constant (2 mm), the amplitude of the PD pulse also changes and it is shown in figure. Therefore, increasing the height of the void also increases the amplitude of the PD pulse because the apparent charge of the same void changes.
It has been studied that by increasing the height and radius of the void, the amplitude of the PD pulse increases in positive half-cycle and decreases in negative half-cycle. It is observed that the PD pulse is almost 90 degree phase angle in positive half cycle and almost 270 degree phase angle in negative half cycle of the 5 kV applied voltage which is shown in the figure. It is noted that with the application of the applied voltage of 5 kV, the observed PD signals contain seventy-one (71) PD pulses, of which thirty-nine (39) numbers of PD appear in the positive half and thirty-two (32) numbers of PD pulse appears in the negative half of the applied voltage.
It shows that the PD pulse frequency plot observed with an applied voltage of 5 kV. It is also observed that the maximum frequency amplitude of the same PD pulse appears at 5 kHz, 8 kHz and 125 kHz which is shown in Fig. It is clear that with the increase of the high voltage the amplitude of the PD is also increased.
On the other hand, to observe the characteristics of the PD pulse, the analysis considered the pulse rise time, fall time and its pulse width for an applied voltage of 5 kV. Four PD pulse numbers were taken to calculate the rise time (tr), fall time (tf) and pulse width for b. positive and also for the negative half cycle to study the PD characteristics shown in the figure. It is observed that the rise time and fall time of the PD pulse are in the order of microseconds in both the positive half and the negative half of the cycle.
The pulse width of the measured PD pulse is the addition of the rise time and fall time, i.e. further analysis is also done to calculate the rise time and fall time of negative half cycle of the applied voltage.
Conclusion and Scope for the Future Work 41
Conclusion 41
Partial discharges are a major source of insulation failure in a high voltage power system that must be continuously monitored to avoid the onset of failure in the power system network. To understand the PD activity inside the solid insulation, a MATLAB-based simulink model was developed in this work. The PD activity within the solid insulation depends greatly on the entire geometry of the void presence within the solid insulation model (epoxide resin sample).
Moreover, the PD increases with the increase of the applied voltage within the solid insulation. In this study, attempts have been made to investigate the maximum PD magnitude, number of PDs and number of other PD related parameters such as PD distribution and frequency content of the acquired PD pulse by using the Phase Resolve Partial Discharge (PRPD) measurement technology. Based on the developed SIMULINK model and the calculated parameters used for epoxide resin samples, the characteristic of PDs has been studied.
This study will ensure that energy engineers can predict the quality of insulation used for high-voltage equipment. The current work will be extended for further research on various high voltage equipment such as current transformer (CT), potential transformer (PT), switchgear and circuit breakers.
Scope for future work 42
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