Detection of high resistance earth faults in medium voltage networks using higher harmonics

2017 ◽  
Author(s):  
Lubomir Marciniak ◽  
Mateusz Piatek
Keyword(s):  
High Resistance ◽  
Higher Harmonics ◽  
Medium Voltage

scholarly journals The influence of the network asymmetry on the settings and sensitivity of an earth fault protection using higher harmonics

2019 ◽  
Vol 84 ◽  
pp. 02008
Author(s):  
Lubomir Marciniak ◽  
Mateusz Piątek
Keyword(s):  
Reactive Power ◽  
Higher Harmonics ◽  
Medium Voltage ◽  
Earth Fault ◽  
Power Setting ◽  
Zero Sequence ◽  
The Asymmetry ◽  
Supply Voltages ◽  
Zero Sequence Voltage

Detection of high resistance earth faults in medium voltage networks is an important problem due to ineffectiveness of traditional earth fault protections. Such short circuits can be detected by the criterion of a reactive power of higher harmonics for zero sequence current and voltage. The main problem is determination of the power setting value in the protection, which depends on the asymmetry of phase-to-earth capacitances and higher harmonics in supply voltages, which are generated by non-linear loads. The intensive tests of the asymmetry of the zero sequence currents and voltages for harmonics and their reactive power have been carried out in 15 kV compensated network as a function of all relevant parameters, i.e.: maximum capacitance deviation of the network and protected line, percentage content of harmonics in supply voltages, capacitive current of the network and the line. It has been shown that third harmonics of the zero sequence voltage and current are the best suited for practical use, since the asymmetry reactive power of these components is the smallest among the considered harmonics and the protection sensitivity will be the highest.

scholarly journals Why Should We Test the Wideband Transformation Accuracy of Medium Voltage Inductive Voltage Transformers?

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4432
Author(s):  
Michal Kaczmarek ◽  
Ernest Stano
Keyword(s):  
Low Power ◽  
Magnetic Core ◽  
Sinusoidal Voltage ◽  
Higher Harmonics ◽  
Medium Voltage ◽  
Phase Displacement ◽  
Secondary Voltage ◽  
Instrument Transformers ◽  
Multiple Frequencies ◽  
Limiting Values

In this paper the results of the tests of the wideband transformation accuracy of medium voltage (MV) inductive voltage transformers (VTs) in the frequencies range from 50 Hz up to 5 kHz are presented. The values of voltage error and phase displacement for transformation of the harmonics of distorted primary voltages are determined. In the case of a typical 50 Hz-type inductive VT with a rated primary voltage equal to (15/Ö3) kV and (20/Ö3) kV manufactured by an international company the limiting values of the accuracy classes extension for quality metering required by the standard IEC 61869-6 for the Low Power Instrument Transformers (LPIT) were not exceeded. While, in the same test other MV inductive VTs show poor accuracy and even resonance at multiple frequencies. Unfortunately, this problem also arises from nonlinearity of the magnetization characteristic of their magnetic core. Therefore, for transformation of the sinusoidal voltage in the secondary voltage significant but not easily detectable values of the low order higher harmonics are present. Moreover, for transformation of harmonics of distorted primary voltage the influence of connected capacitance on the obtained values of voltage error and phase displacement was tested.

scholarly journals General earth fault protection for MV networks using wavelet decomposition and Bayesian criterion

2019 ◽  
Vol 84 ◽  
pp. 02007
Author(s):  
Lubomir Marciniak
Keyword(s):  
High Resistance ◽  
Wavelet Decomposition ◽  
Harmonic Distortion ◽  
Sampling Frequency ◽  
Selective Detection ◽  
Medium Voltage ◽  
Bayesian Criterion ◽  
Fault Protection ◽  
Probability Criterion ◽  
Short Circuits

For selective detection of earth faults in medium voltage networks, the general protection can be used, which unlike individual protections controls earth currents in all lines supplied from the substation. To detect high-resistance and arc faults, it is possible to use in such protections the details from wavelet decomposition of earth currents and the Bayesian conditional probability criterion. The paper presents a protection model using details of earth currents and the Bayesian criterion. Significant parameters of the model were determined: sampling frequency, wavelet types and decomposition levels, parameters of the probability density function and decision conditions. The effectiveness of the protection in the case of non-stationary high-resistance short-circuits in the network with natural asymmetry and harmonic distortion was also assessed.

Applying High-Resistance Neutral Grounding in Medium-Voltage Systems

2011 ◽  
Vol 47 (3) ◽  
pp. 1220-1231 ◽  
Author(s):  
L J Kingrey ◽  
R D Painter ◽  
A S Locker
Keyword(s):  
High Resistance ◽  
Medium Voltage

Prospects for convergent beam electron diffraction with a 200kV cold field-emission transmission electron microscope

1991 ◽  
Vol 49 ◽  
pp. 466-467
Author(s):  
J W Steeds ◽  
R Vincent
Keyword(s):  
Field Emission ◽  
High Performance ◽  
Small Diameter ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
Medium Voltage ◽  
Transmission Electron ◽  
Good Crystallinity ◽  
Special Modification ◽  
Convergent Beam

We review the analytical powers which will become more widely available as medium voltage (200-300kV) TEMs with facilities for CBED on a nanometre scale come onto the market. Of course, high performance cold field emission STEMs have now been in operation for about twenty years, but it is only in relatively few laboratories that special modification has permitted the performance of CBED experiments. Most notable amongst these pioneering projects is the work in Arizona by Cowley and Spence and, more recently, that in Cambridge by Rodenburg and McMullan.There are a large number of potential advantages of a high intensity, small diameter, focussed probe. We discuss first the advantages for probes larger than the projected unit cell of the crystal under investigation. In this situation we are able to perform CBED on local regions of good crystallinity. Zone axis patterns often contain information which is very sensitive to thickness changes as small as 5nm. In conventional CBED, with a lOnm source, it is very likely that the information will be degraded by thickness averaging within the illuminated area.

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