Thibaut Billard

On the nature of the discharges in samples fed by bipolar pulse like voltage and its possible impact on the detection of partial discharge in machines fed by inverter

This paper deals with Partial Discharge (PD) detection in a twisted pair fed by a bipolar square shape voltage using a non-intrusive sensor. These discharges are hardly detected, yet harmful, in such an environment and it may be caused by the nature of the discharge itself. Thus, the aim of this work is to investigate the nature of the discharge using an intensified CCD camera to follow the temporal evolution of the light distribution on a controlled sample.

Numerical signal processing methods for partial discharge detection in more electrical aircraft

In forecoming “more electrical aircrafts”, aircrafts will become more compact and lighter. Hydraulic, pneumatic or mechanical systems will be replaced by electrical ones thus leading to an increased demand of electric power. The network voltage is expected to increase far above Paschens minimum, thus increasing the risk of partial discharges. Furthermore the use of inverter drives will be generalized and PD detection on square voltage powered equipments will become a mandatory challenge. The purpose of this study is to propose a method to denoise partial discharge signals embedded in the electromagnetic noise induced by switchings. This denoising is performed using the wavelet decomposition.

Non-intrusive partial discharges investigations on aeronautic motors

The present paper reports on a study of non-electrically intrusive partial discharge investigations on an aeronautic motor. Relevancy, robustness and repeatability of partial discharge testing procedures, both on insulating materials characterization and on operating aeronautic equipment are essential to ensure reliability of the aircraft systems. The aim of this paper is to be the very first step of defining such procedures and the associated test equipments. To do so, the paper will start by providing an understanding of partial discharge phenomena and will review typical more electrical aircrafts architectures and their key characteristics causing partial discharge risk to increase. The impact of harness length, high performance power electronics and increase of voltage level on insulation system is demonstrated. Then, an analysis is conducted from motor design point of view to find out which test procedures are relevant to each insulation system performance both at atmospheric pressure and reduced pressure. The study helps to realize the benefits of using multiple test samples and procedures to assess insulation system performance levels through the design process of the motor. It is shown that a good agreement is find out between the stator and representative samples. This paper will also review the ability of the non-intrusive test method used to detect partial discharge with a full scope of voltage signal from AC to impulse voltage and under different pressure. The paper is concluded with analysis of results and thoughts about future work regarding motor design taking into account partial discharge risk and evolution of proposed procedures.

Partial discharges in aeronautics: the last frontier?

This paper presents the recent advances made in the field of Partial Discharges detection and analysis in the field of aeronautics. More particularly, it intends to present the influence of the voltage waveform on the type of detection method, the role of the assembly process on the PD Inception Voltage and finally an on line PD detection under PWM voltage. The influence of the pressure on the type and nature of the discharges is also discussed.

Partial discharges monitoring in twisted pair fed with PWM inverter using non-intrusive sensors

This paper deals with partial discharge measurements in twisted pair fed by a PWM inverter. Measurements are carried out using antenna sensors. Both D-Dot sensor and self-made sensors are compared when it comes to detect partial discharge in a PWM environment. High-pass filter performance is tested as well with these sensors. Finally, a innovative noise suppression method is demonstrated using two identical antenna sensors. This method could be a useful and simple mean to improve signal to noise ratio before signal processing.

Influence of pressure on partial discharge spectra

In the near future, the aircrafts will become more compact and lighter, since hydraulic, pneumatic or mechanical systems will be replaced by electrical ones. The network voltage is expected to increase far above Paschens minimum, thus increasing the risk of partial discharges. These discharges, also known as silent enemies, may affect the reliability of the systems. Moreover, some electrical equipments are located in unpressurized areas so their operating conditions (temperature, pressure) may change in a large range. These environmental parameters (and their cycling) have a large impact on discharge inception voltage and may even modify its nature. This paper deals with the influence of the pressure on partial discharges and more particularly on the modification of partial discharges spectra with pressure. Twisted pairs of enamel wires were subjected to repetitive square voltage waveform and sinusoidal voltage at various pressures.

On-line non intrusive PDs' measurements on aeronautical systems

In aeronautics, the concept of the “more electrical aircraft” emerged during the recent years thanks to the evolution of power electronics, the increase of power density, which has considerably spread the use of power converters for Adjustable Speed Drive (ASD) applications. In parallel, due to the power demand, increasing the voltage of the on-board network has been mandatory. Last but not least, some of these equipments work in depressurized areas of the aircraft. All these conditions put together made possible the existence of Partial Discharges (PD) in systems not designed to endure them. One of the main questions to address is the development of an approach for PD detection in machines supposed to be PD free. Their detection under PWM is therefore a key issue in this new field of applications. Recent advances made in the related different topics i.e on line PD detection under PWM voltage on real industrial test benches will be presented and discussed regarding their consequences.

Recent advances in on-line PDs'detection in power conversion chains used in aeronautics

At the dawn of this new millennium, transportations facing a much greener approach, the main aircrafts manufacturers have to change their paradigms: to replace the combination of hydraulic, pneumatic, electrical and mechanical power by a « More » (and “All” in the future) Electrical Aircraft approach consisting in drastically increasing the power density of electrical power systems without compromising on reliability. The increasing demand for more on board electrical power has led to increase the voltage and/or to change its shape. Such an increase may lead, depending on many parameters related to the electrical characteristics of the power chain (power converter, voltage waveform (dV/dt, frequency, …), the cables length, the type of machine driven) or to the environment (pressure, temperature, relative humidity) to the Partial Discharges Ignition in systems which were not supposed (and have not been designed) to endure them.

Advanced Partial Discharge Testing of 540V Aeronautic Motors Fed by SiC Inverter under Altitude Conditions

The present paper reports non-electrically intrusive partial discharge investigations on an aeronautic motor fed by SiC inverter drive under variable environmental conditions. A representative test procedure and experimental set-up based on operating aeronautic conditions are essential to ensure the accuracy and reliability of partial discharge test on aircraft systems to make informed decisions on insulation system design choice. The aim of this paper is to demonstrate the feasibility of partial discharge test of the insulation system on a typical aeronautic motor under such conditions, both electrically and environmentally. To do so, the paper will start by detailing the innovative experimental set-up to be used in the study. It mainly consists in a high-voltage (1000V) inverter drive using SiC components to provide fast rise time surges and associated with phase-by-phase surge filtering. A vacuum chamber is used to simulate altitude while the association of non-intrusive sensors and wavelet based signal processing provided partial discharge detection. Optical detection is also used to reinforce partial discharge inception level accuracy. Then, an analysis is carried out on a 540V motor to find out which combination of switching frequency, harness length, rise time by phase and voltage magnitude is the worst case scenario. The study helps to realize the benefits of using an inverter based test method to find the limits of the insulation system under various pressure and electrical conditions. It is shown that a representative insulation system performance diagram could be built experimentally and used to enhance insulation design and manufacturing choices. This paper will also review the ability of the non-intrusive test method and the associated numerical signal processing to detect partial discharge in a motor fed by fast-rise time surge and under different pressures. The paper concludes with an analysis of results and thoughts about future work regarding advanced test procedure.

Partial discharge testing in aeronautic environment on magnet wire and feeder cables

Rationalization of energy sources aboard aircraft and improvements in more electric technologies are pushing the aeronautic industry to meet the all-electric aircraft challenge. As a result, onboard power has been steadily increasing, reaching 1MW for B787. AC and HVDC network voltage have followed reaching 230VAC and 540VDC increasing the likeliness of partial discharge. In the future, this shift will lead to the complete redesign of the architecture of onboard power systems. The aim of this study is to characterize the partial discharge inception voltage, with the aforementioned constraints in mind, on two components of the electromechanical chain: magnet wires used in electric actuators and feeder cable used in harness.