Mojtaba Rostaghi

• PhD Student
• Research Assistant at Mississippi State University

This study aims to classify and compare AC and DC partial discharge (PD) based on PD pulse waveform analysis. To achieve this goal, we designed a testbed that enables precise measurements of individual PD pulses. The testbed is used for collecting data from four different types of PDs including cavity, surface, corona, and floating potential discha...

In this paper, a testbed is designed and constructed for the investigation of DC PD pulses. The testbed is equipped with a $50\ \Omega$ transmission line (TL) that terminate to an oscilloscope for measuring the charge displacement current generated by PD pulses. Besides the oscilloscope measurements, two types of electromagnetic field sensors (D-...

Accurate measurement circuit and high-frequency sensors with sufficient bandwidth are necessary for the analysis of individual partial discharge (PD) pulses. In this paper, a testbed is designed and constructed for the investigation of DC PD pulses. The testbed is equipped with a 50 ohm transmission line (TL) that terminate to an oscilloscope for m...

Understanding the damage mechanisms of fiber-reinforced polymer matrix composite materials under high voltage conditions is of great significance for lightning strike protection and high voltage insulation applications of composite structures. In this paper, we investigated effects of the lightning impulse (LI) voltage and high voltage alternating...

Partial discharge (PD) is a common, yet undesirable, phenomenon in high voltage components and systems. Due to its high frequency and low amplitude characteristics, detection and recognition of PD requires sensitive and optimally responsive measuring sensors. For phase resolved (PRPD) analysis in AC applications, existing systems are well establish...

Carbon fiber composites are paving the way for light weight, high strength structures in the aerospace industry. While the benefits of carbon fiber composites are undeniable, they also have their drawbacks. Crippling damage due to lightning strikes is one of them. The current solutions to reducing the damage due to lightning includes adding expensi...

For high voltage impulse testing, a standard lightning impulse is defined in IEEE Std. 4 and IEC 60060-1 as a double exponential waveform having a front time T1 = 1.2 μs ± 30% and time to half-value T2 = 50 μs ± 20%. It has been noticed that for a given specimen, it is possible to successfully pass a flashover test at one end of the T1 tolerance ra...

Porcelain insulators have a long history and wide application range in power systems, but just like any other insulator, they can fail. A number of pole fires occurred on lines utilising porcelain suspension insulators. In some cases, the insulators appeared to be visually intact with no external signs of degradation or abnormal stress. This prompt...

High-current impulse experiments were performed on volcanic ash samples to determine the magnetic effects that may result from the occurrence of volcanic lightning during explosive eruptions. Pseudo-ash was manufactured through milling and sieving of eruptive deposits with different bulk compositions and mineral contents. By comparing pre-and post-...

One of the most important parameters to provide safety for personnel and test equipment in high voltage laboratories is a reliable grounding system. The main characteristics of a reliable grounding system include low resistance at low frequency tests (power frequency test) and low potential rise at high frequency tests such as an impulse test. Also...

The transient electric and magnetic fields radiated by the discharge of a high voltage impulse generator have well-known effects of creating serious interferences with the measuring and recording equipment. These effects may result in the mis-operation, or in the worst case, may damage the electronic circuitry of the measuring system. Measurements...

Environmental and electrical stresses have deterioration effects on Silicon Rubber (SIR) insulators. In coastal areas due to high amount of salt, humidity and dust suspended in the air, the deterioration process is intensive. In this paper, based on IEC 60507 the leakage current (LC) of 20kV SIR insulators has been investigated in clean-fog and sal...

The usage of polymeric insulators is common due to their advantages in comparison with porcelain insulators. Environmental and electrical stresses have got deteriorating effects on polymeric insulators. Thus, knowing about behaviour of these types of insulators under various stresses is necessary. Till now, various electrical tests have been perfor...