Francisco R. Blanquez

Bio: Francisco R. Blanquez is an academic researcher from CERN. The author has contributed to research in topics: Transient voltage suppressor & Modular design. The author has an hindex of 4, co-authored 10 publications receiving 44 citations.

Evaluation of the applicability of FRA for inter-turn fault detection in stator windings

Abstract: In this paper, the applicability of the FRA technique is discussed as a method for detecting inter-turn faults in stator windings. Firstly, this method is tested in an individual medium-voltage stator coil with satisfactory results. Secondly, the tests are extended to a medium-voltage induction motor stator winding, in which inter-turn faults are performed in every coil end of one phase. Results of the frequency response in case of inter-turn faults are evaluated in both cases for different fault resistance values. The experimental setup is also described for each experiment. The results of the application of this technique to the detection of inter-turn faults justify further research in optimizing this technique for preventive maintenance.

Enhancement of a high speed de-excitation system for brushless synchronous machines by large blocking voltage semiconductors

Abstract: One of the main disadvantage of the synchronous machines with brushless excitation is that the field winding is not accessible for the de-excitation. The de-excitation process is very slow as the field current flows through the rotating diodes which operate in freewheel mode. Therefore in case of an internal fault, despite the correct operation of the protection relays, the machine could have severe damages. A high-speed de-excitation system for these machines was developed. The de-excitation is achieved by inserting a resistance in the field circuit by a static switch semiconductor based, obtaining a dynamic response similar to that achieved in machines with static excitation. This paper presents the improvement in the de-excitation system in the second commercial 20 MVA hydro generator in operation. In this case, high blocking voltage semiconductor was used, making the dynamic response even better, than in the first hydro generator.

Design and construction of a laboratory bench system for the teaching and training of engineers on diagnostics of permanent magnet motors

Abstract: Permanent magnet synchronous motors PMSM are widely used in industry due to their higher torque and higher power to volume ratio. Moreover they have a better dynamic performance compared to the motors with electromagnetic excitation. Despite its robustness electrical, mechanical and magnetic faults has been described. It has led to the development of specific diagnostic systems for such machines. These systems are constantly evolving according to the literature. In this situation of increasing use of PMSM it is necessary to teach and train professionals in diagnostic techniques. This paper describes the design process of an experimental bench on which can be studied all types of faults associated with the PMSM operation. The design of a PMSM prototype, which is the most important equipment of this bench, is described in more detail.

The design and performance of Static Var Compensators for particle accelerators

Abstract: Particle accelerators, and in particular synchrotrons, represent large cycling non-linear loads connected to the electrical distribution network. This paper discusses the typical design and performance of Static Var Compensators (SVCs) to obtain the excellent power quality levels required for particle accelerator operation.

Back-to-Back HVDC Modular Multilevel Converter for Transient Voltage Dip Mitigation in Passive Networks

Abstract: For nuclear research laboratories like CERN, where the exceptionally high power quality conditions are required, the immunity against transient voltage dips is of vital importance. By using the traditional HVDC modular multilevel converter in a back-to-back configuration with properly dimensioned submodule capacitors, voltage dips can be mitigated instantaneously, improving power quality of the network. The dimensioning of the capacitors is shown as one of the key elements of this paper. Firstly, the actual voltage dips statistics recorded at CERN are presented and described. Then, the traditional capacitor submodules dimensioning method is presented and compared to the proposed energy design rule. To validate the energy dimensioning and the mitigation performance, a detailed Simulink model of a 220MVA HVDC modular multilevel converter is described and the main results are presented. The paper concludes with the main conclusions of this study and the future works.

Power Supply Quality ~~provement with a Dynamic Vol ge Restorer (DVR)

Abstract: This paper presents the technical aspects of designing a Dynamic Voltage Restorer to meet the stringent requirements of voltage dips mitigation with respect to the magnitude of voltage dip, fault duration, permissible line voltage deviations and response time. An introduction to the IGCT technology based on latest transparent anode GTO (I-GTO) and gate technology is given. The performance of the DVR based on digital simulations is discussed. A description of a hardware based real time simulator model for performance assessment of DVR in voltage dips mitigation is presented. The results of the real time simulator are compared with the digital simulations. Finally, control and protection concepts for the DVR are highlighted.

Condition monitoring of power electronic converters in power plants — A review

Abstract: In terms of power supplies and power conversion, power electronics based converters have their own advantages. Proper condition monitoring for power electronic converter has become necessary which is now in incipient stage. This paper includes different kinds of failure modes associated with power electronics at the converter as well as device level and recent Condition Monitoring (CM) techniques to detect those faults at the earliest stage. Proper reliability improvement has to be performed on power electronic systems so that they could be more resistive to different aspects such as safety, cost and availability. Power semiconducting devices are considered to be the most sensitive part of the power electronic systems and the main causes of stresses on these devices could be initiated due to the atmospheric conditions as well as short duration heavy loads, which should be considered during power electronic system design and normal operation as the consequences of these can't be felt at the initial stage which demands conservative converter design.

Effects of transmission belt looseness on electrical and mechanical measurements of an induction motor

Abstract: This article explores the impact of belt looseness on electrical and mechanical quantities of a system driven by an induction motor and a belt-pulley transmission. The effects of this defect, for example the belt slipping or the apparition of spectral signatures in some measurements, are first investigated under steady state operation. Transient state tests are then performed to analyse, in the time domain, the system response to a step of the speed reference. The behaviour of different variables (slip, speed, currents, etc.) is studied for different health conditions and the increase of the belt looseness clearly impact the electric and mechanical variables' waveforms. The experimental tests carried out in this study, under steady or transient state, show promising results for the diagnosis of belt degradations. Perspectives of this work are therefore detailed at the end of this paper.

Statistic-Based Method to Monitor Belt Transmission Looseness Through Motor Phase Currents

Abstract: Belt–pulley systems are widely used in the industry due to their high efficiency and their low cost. However, only few works exist about the monitoring of their degradation. This paper details the impact of belt looseness on electrical measurements under steady and transient state in order to identify spectral signatures. This analysis enlightens the advantage of the transient state to detect belt looseness because it exacerbates belt slip. An innovative methodology is then proposed based on the application of a square-wave speed reference in order to monitor belt looseness. A statistical-based indicator is defined from the phase currents in order to automatically detect drifting of the indicator. A normalization process is also applied to increase the detection robustness. The proposed indicator is evaluated on a 30-kW induction machine and a direct-current machine coupled with two trapezoidal belts for three speed and four load conditions. It reaches very good results with almost 90% correct detections for 1% false alarms. These results are way better than those obtained with a classic spectral analysis during the steady state. Moreover, results demonstrate that higher load conditions are more accurate for the monitoring of belt looseness.