scholarly journals Behavior of Residual Current Devices at Frequencies up to 50 kHz

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1785
Author(s):  
Stanislaw Czapp ◽  
Hanan Tariq
Keyword(s):  
Electric Shock ◽  
High Frequency ◽  
Pulse Width Modulation ◽  
Low Voltage ◽  
Residual Current ◽  
Indirect Contact ◽  
Additional Protection ◽  
Operating Current ◽  
Low Voltage Circuits ◽  
Frequency Components

The use of residual current devices (RCDs) is obligatory in many types of low-voltage circuits. They are devices that ensure protection against electric shock in the case of indirect contact and may ensure additional protection in the case of direct contact. For the latter purpose of protection, only RCDs of a rated residual operating current not exceeding 30 mA are suitable. Unfortunately, modem current-using equipment supplied via electronic converters with a pulse width modulation produces earth fault currents composed of high-frequency components. Frequency of these components may have even several dozen kHz. Such components negatively influence the RCDs’ tripping level and, hence, protection against electric shock may be ineffective. This paper presents the results of the RCDs’ tripping test for frequencies up to 50 kHz. The results of the test have shown that many RCDs offered on the market are not able to trip for such frequencies. Such behavior was also noted for F-type and B-type RCDs which are recommended for the circuits of high-frequency components. Results of the test have been related to the requirements of the standards concerning RCDs operation. The conclusion is that these requirements are not sufficient nowadays and should be modified. Proposals for their modification are presented.

scholarly journals Testing Sensitivity of A-Type Residual Current Devices to Earth Fault Currents with Harmonics

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 2044
Author(s):  
Stanislaw Czapp
Keyword(s):  
Power Systems ◽  
Electric Shock ◽  
Low Voltage ◽  
Wide Spectrum ◽  
Residual Current ◽  
Motor Speed ◽  
Earth Fault ◽  
Fault Currents ◽  
Wide Range ◽  
Sinusoidal Waveform

In many applications, modern current-using equipment utilizes power electronic converters to control the consumed power and to adjust the motor speed. Such equipment is used both in industrial and domestic installations. A characteristic feature of the converters is producing distorted earth fault currents, which contain a wide spectrum of harmonics, including high-order harmonics. Nowadays, protection against electric shock in low-voltage power systems is commonly performed with the use of residual current devices (RCDs). In the presence of harmonics, the RCDs may have a tripping current significantly different from that provided for the nominal sinusoidal waveform. Thus, in some cases, protection against electric shock may not be effective. The aim of this paper is to present the result of a wide-range laboratory test of the sensitivity of A-type RCDs in the presence of harmonics. This test has shown that the behavior of RCDs in the presence of harmonics can be varied, including the cases in which the RCD does not react to the distorted earth fault current, as well as cases in which the sensitivity of the RCD is increased. The properties of the main elements of RCDs, including the current sensor, for high-frequency current components are discussed as well.

scholarly journals Shock safety modelling of indirect contact with low-voltage electric devices

2011 ◽  
Vol 60 (3) ◽  
pp. 303-315
Author(s):  
Włodzimierz Korniluk ◽  
Dariusz Sajewicz
Keyword(s):  
Ventricular Fibrillation ◽  
Electric Shock ◽  
Low Voltage ◽  
Indirect Contact ◽  
Probability Of Occurrence ◽  
Electric Device ◽  
Shock Protection

Shock safety modelling of indirect contact with low-voltage electric devices The article presents a shock safety model of an indirect contact with a low-voltage electric device. This model was used for computations and analyses concerning the following: the probabilities of appearance of the particular shock protection unreliability states, electric shock states (ventricular fibrillation), contributions of the unreliability of different shock protection elements to the probability of occurrence of these states, as well as the risk of electric shock (and the shock safety), and contributions of the intensity of occurrence of damages to different shock protection elements to this risk. An example of a possibility to reduce the risk of an electric shock through changing the intensity of occurrence of damages to the selected protection elements was provided.

scholarly journals Improving sensitivity of residual current transformers to high frequency earth fault currents

2017 ◽  
Vol 66 (3) ◽  
pp. 485-494 ◽  
Author(s):  
Stanislaw Czapp ◽  
Krzysztof Dobrzynski ◽  
Jacek Klucznik ◽  
Zbigniew Lubosny ◽  
Robert Kowalak
Keyword(s):  
High Frequency ◽  
Low Voltage ◽  
Current Transformer ◽  
Residual Current ◽  
Fault Current ◽  
Earth Fault ◽  
Fault Currents ◽  
Proper Operation ◽  
Current Device ◽  
A Current

Abstract For protection against electric shock in low voltage systems residual current devices are commonly used. However, their proper operation can be interfered when high frequency earth fault current occurs. Serious hazard of electrocution exists then. In order to detect such a current, it is necessary to modify parameters of residual current devices, especially the operating point of their current transformer. The authors proposed the modification in the structure of residual current devices. This modification improves sensitivity of residual current devices when high frequency earth fault current occurs. The test of the modified residual current device proved that the authors’ proposition is appropriate.

scholarly journals Harmonic Reduction in Multilevel Inverter Based on Super Capacitor as a Storage

2015 ◽  
Vol 16 (3) ◽  
pp. 520
Author(s):  
Mohammed Rasheed ◽  
Rosli Omar ◽  
Marizan Sulaiman
Keyword(s):  
Distribution System ◽  
High Frequency ◽  
Pulse Width ◽  
Pulse Width Modulation ◽  
Low Voltage ◽  
Harmonic Distortion ◽  
Multilevel Inverter ◽  
Super Capacitor ◽  
Harmonic Reduction ◽  
Ieee Standard

Cascaded H-Bridge multilevel inverter has become more attractive to generate high power in an electrical distribution system. This paper discusses the control of five level cascaded H-bridge multilevel inverter with super capacitor as a Dc energy storage. The control of the multilevel inverter using PI and space vector pulse width modulation (SVPWM) controllers based on the modelling and Simulink of cascaded H-bridge can observe the effectiveness of the proposed control to reduce harmonic contents of the multilevel inverter output. High frequency ripple from the inverters can be removed from the system using low voltage filter. Total harmonic distortion (THD) for both current and voltage is quite low to meet the IEEE standard. Modelling of the system has been done using MATLAB/Simulink.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

Resonant BLDC Motor Drive System for Medical Applications

2019 ◽  
Vol 14 ◽  
Author(s):  
C. Vidhya ◽  
V. Ravikumar ◽  
S. Muralidha
Keyword(s):  
High Frequency ◽  
Pulse Width Modulation ◽  
Power Converter ◽  
Low Power Consumption ◽  
Motor Drive ◽  
Medical Applications ◽  
Bldc Motor ◽  
Three Phase ◽  
High Frequency Ac ◽  
Motor Drive System

: The objective of this paper is to implement an ac link universal power converter controlled BLDC motor for medical applications. The ac link universal power converter is a soft switched high frequency ac link converter, created using the parallel combination of an inductor and a capacitor. The parallel ac link converter handle the ac voltages and currents with low reactive ratings at the link and offers improved power factor, low power consumption, more efficiency and less weight on comparison with the traditional dc link converter. Because of the high throughput, BLDC motors are preferred widely medical applications. A modulation technique called Space Vector Pulse Width Modulation (SVPWM) is used to generate the three phase power for the BLDC motors from the input DC supply. To validate the proposed system, simulations are performed in MATLAB – Simulink and an experimental prototype is constructed to supplement the simulation results.

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