Voltage Current Transformers Research Articles

In situ measurement of burdens in instrument transformer test systems

Methods to measure the burdens of voltage transformers (VTs) and current transformers (CTs) in situ in instrument transformer test systems have been developed using non-reactive resistors connected in series with the VT secondary and in parallel with the CT secondary. This development was based on a theoretical analysis of the equivalent circuits of the instrument transformers. The burden values for the instrument transformers are obtained by measuring the ratio error (and phase displacement) with varying resistors. The values of the transformer burdens obtained using this method were consistent, within acceptable tolerances, with those measured using conventional methods.

A T‐LCLC type immittance converter

Abstract“Immittance converter” is short for “impedance–admittance converter.” The immittance converter has an input impedance that is proportional to the admittance of the load connected across output terminals. In this converter, the output current is proportional to the input voltage and the input current is proportional to the output voltage. Consequently, it converts a constant voltage source into a constant current source and a constant current source into a constant voltage source.It is well known that the quarter‐wavelength transmission line shows immittance conversion characteristics. However, it has very long line length for the switching frequency, and is not suitable for power electronics application. Thus, we proposed immittance converters that consist of lumped elements L, C and show improved immittance conversion characteristics at a resonant frequency. In this paper, we propose a T‐LCLC‐type immittance converter, which has the transitive configuration and both advantages of T‐LCL‐ and π‐CLC‐type immittance converters. We show voltage–current transformation characteristics and frequency characteristics and efficiency characteristics of the T‐LCLC immittance converter. These characteristics were determined analytically and experimentally. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(3): 57–63, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10095

Hybrid‐type immittance converter

AbstractThe immittance converter has an input impedance that is proportional to the admittance of a load connected across output terminals. Therefore, in this converter, the output current is proportional to the input voltage and the input current is proportional to the output voltage. Consequently, it converts a constant‐voltage source into a constant‐current source and a constant‐current source into a constant‐voltage source.It is well know that the quarter‐wavelength transmission line shows immittance conversion characteristics. However, it has a very long line length for the switching frequency of converters and is not suitable for power electronics application. Thus, we proposed five types of immittance converters that consist of lumped elements L and C and showed improved immittance conversion characteristics at a resonant frequency.The output characteristics and efficiency characteristics of an immittance converter are the most important parameter when it is used in practical applications in a high‐frequency link. In this paper, we show voltage–current transformation characteristics, current–voltage transformation characteristics, and efficiency characteristics of a hybrid‐type immittance converter which consist of L and C elements with losses. The excellent characteristics were confirmed analytically and experimentally. © 2001 Scripta Technica, Electr Eng Jpn, 138(3): 80–86, 2002

Three-Phase Immittannce Converter

The immittance converter has an input impedance that is proportional to the admittance of a load connected across it's output terminals. In this converter, the output current is proportional to the input voltage and the input current is proportional to the output voltage. Consequently a constant voltage source is converted into a constant current source and a constant current source into a constant voltage source. The immitance converters consist of only the passive elements reactor L and capacitor C are suitable to use in a high frequency link of power electronics.We proposed some types of immittance converters and some applications to power electronics equipment. In this paper, we propose a new 3-phase immittance converter consist of each three L, C elements to obtain an alternating current source from a 3-phase voltage source without control.This paper shows the configuration of the new 3-phase immittance converter that operates on either the anti-phase or the in-phase between the input voltage and the output voltage, and it's voltage-current transformation characteristics and efficiency characteristics.

T-LCLC Type Immittance Converter

The immittance converter is the combined word of the impedance-admittance converter. The immittance converter has an input impedance that is proportional to the admittance of the load connected across output terminals. In this converter, the output current is proportional to the input voltage and the input current is proportional to the output voltage. Consequently, it converts a constant voltage source into a constant current source and a constant current source into a constant voltage source.It is well known that the quarter-wavelength transmission line shows immittance conversion characteristics. However, it has very long line length for the switching frequency, and is not suitable for power electronics application. So we proposed immittance converters that consist of lumped elements L, C and show improved immittance conversion characteristics at a resonant frequency. In this paper, we propose a T-LCLC type immitttance converter, which has the transitive configuration and both merits of T-LCL and π-CLC type immittance converter. We show voltage-current transformation characteristics and Frequency characteristics and efficiency characteristics of the T-LCLC immittance converter. These characteristics were determined analytically and experimentally.

Hybrid Type Immittance Converter

The immittance converter has an input impedance that is proportional to the admittance of a load connected across output terminals. Therefore, in this converter, the output current is proportional to the input voltage and the input current is proportional to the output voltage. Consequently, it converts a constant-voltage source into a constant-current source and a constant-current source into a constant-voltage source. It is well know that the quarter-wavelength transmission line shows immittance conversion characteristics. However, it has a very long line length for the switching frequency of converters and is not suitable for power electronics application. Thus, we proposed five types of immittance converters that consist of lumped elements L and C and showed improved immittance conversion characteristics at a resonant frequency. The output characteristics and efficiency characteristics of an immittance converter are the most important parameter when it is used in practical applications in a high-frequency link. In this paper, we show voltage–current transformation characteristics, current–voltage transformation characteristics, and efficiency characteristics of a hybrid-type immittance converter which consist of L and C elements with losses. The excellent characteristics were confirmed analytically and experimentally. © 2001 Scripta Technica, Electr Eng Jpn, 138(3): 80–86, 2002

プラズマソースイオン注入による３次元立体物へのイオン注入

A plasma source ion implanter (PSII) has been built and used to study nitrogen ion implantation into silicon wafers and titanium substrates. Plasma was generated by rf (13.56MHz) glow discharge. A-20kV pulse bias voltage was applied to the substrate holder for 50μs at a repetition rate of 100Hz and for 10μs at a repetition rate of 500Hz. The substrate bias voltage and current during implantation were monitored using a voltage divider and current transformer. The substrate surface was analyzed using Auger electron spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Results showed that the PSII achieved uniform ion implantation into a three-dimensional substrate and that the Ti substrate surface was changed to TiN by nitrogen PSII treatment.

Substrate and coating damage by arcing during sputtering

Arcing during PVD processes using d.c. glow discharges and the defects formed at the substrate are a major drawback in the application of hard wear- and corrosion-resistant coatings. This work focuses on a more complete understanding of the inter-relationships between substrate arcing and surface quality of the coating. Intense substrate arcing and the surface defect density were characterized using a current-voltage transformer and a quantitative image analysing system connected to an optical microscope. The major defects formed during the etching process are craters and canyons resulting from arcs ignited between the substrate and the anode. During deposition the surface quality of the coating is mainly determined by droplets ejected from the target due to arcing between target and anode. Optimization of the deposition parameter of argon pressure seems to be suitable to minimize the density of these defects.

Power system harmonics. Part 2: Measurements and calculations

The second part of this series of tutorials deals with the measurement and calculation of distortion in power systems. The measurement of harmonic distortion in power systems is almost always a compromise between the desirable and the possible. In an ideal world it would be possible to use calibrated voltage dividers with a well established frequency response connected to the higher voltage system busbars and current transformers with good response in each of the three phases. The reality, however, is different, as the only access given will be to existing voltage transformers and current transformers. The choice of how to calculate harmonics in a power system is also often a compromise which depends on the system information available to the designer and also the purpose for which the calculations are being made. The author discusses the voltage transducers and measurement instruments for harmonics measurement. Calculations in the frequency domain and the time domain are discussed.

Transmission level instrument transformers and transient event recorders characterization for harmonic measurements

A technique for laboratory characterization of instrument transformers designed for transmission level voltage and current measurements is presented. The technique is also extended to transient event recorders (TERs). The objective of the method is to determine the suitability of existing substation instrument transformers for harmonic measurements, particularly in the frequency range of 60 to 1500 Hz covering the first 25 harmonics. Specifically, the following characteristics are of interest: transfer function magnitude and phase, linearity, and sensitivity of the frequency response to burdens. The measurement technique is based on exciting the instrument transformer primary with an impulsive waveform. Both input and output waveforms are recorded using laboratory grade probes and digitizers. Digital signal processing techniques are used to compute the instrument transformer frequency response. Several voltage transformers and current transformers in the 230 kV-765 kV voltage range were tested. The results are described. >

A new power standard for audio-frequency measurements

A thermal power comparator for audio-frequency measurements is presented. It is essentially a double-bridge-type multiplier that consists of two multijunction thermal converters that contain two heaters. Together with a precision inductive voltage divider and current transformer for extending the voltage and current range, the comparator ensured a high-precision power standard with an AC/DC transfer error of less than 15 p.p.m. in the audio-frequency range. >

Seismic Behaviour of Very High Voltage Current Transformers

With the introduction of the "inverted type" current transformers (CTs) into the electrical industry, a reasonable question to ask is : "How does the relatively high center of gravity affect the transformer during an earthquake ? This paper shows through detailed calculations the response of the "transformer system" and then verifies the calculation through five important tests : 1. Release test 2. Static test 3. Frequency scan 4. Sinus beat 5. Final check.

Seismic Behavior of Very High Voltage Current Transformers

Seismic Behavior of Very High Voltage Current Transformers

Instrumentation for EM launcher systems

This paper reviews the techniques found successful for the measurement of current, voltage and velocity in electromagnetic (EM) launcher experiments at the Center for Electromechanics at The University of Texas at Austin (CEM-UT). Current measurement methods using shunts, current transformers, and Rogowski coils are presented and discussed. Special attention is given to the construction and calibration of Rogowski coils and their integrators. Voltage measurements by means of high impedance voltage dividers and current transformers are reviewed. Finally, velocity measurements are presented, with attention to obtaining reliable measurements from time-of-flight velocimeters and ballistic sleds.

Discussion on “Voltage transformers and current transformers associated with switchgear” before the South-East Scotland Sub-Centre at Edinburgh, 15th December, 1953, and the North Midland Centre at Leeds, 5th January, 1954

Discussion on “Voltage transformers and current transformers associated with switchgear” before the South-East Scotland Sub-Centre at Edinburgh, 15th December, 1953, and the North Midland Centre at Leeds, 5th January, 1954

Discussion on “Voltage transformers and current transformers associated with switchgear” before the Mersey and North Wales Centre, at Liverpool, 19th January, 1953

Discussion on “Voltage transformers and current transformers associated with switchgear” before the Mersey and North Wales Centre, at Liverpool, 19th January, 1953

Discussion on “Voltage transformers and current transformers associated with switchgear” before the Measurements and Supply Sections, 9th December, 1952

Discussion on “Voltage transformers and current transformers associated with switchgear” before the Measurements and Supply Sections, 9th December, 1952

The authors' reply to the discussions on “Voltage transformers and current transformers associated with switchgear”

The authors' reply to the discussions on “Voltage transformers and current transformers associated with switchgear”

Discussion on “Voltage transformers and current transformers associated with switchgear” before the North-Eastern Centre, at Newcastle, 10th November, 1952

Discussion on “Voltage transformers and current transformers associated with switchgear” before the North-Eastern Centre, at Newcastle, 10th November, 1952

Discussion on “Voltage transformers and current transformers associated with switchgear” before the North-Western Measurements Group, at Manchester, 25th November, 1952

Discussion on “Voltage transformers and current transformers associated with switchgear” before the North-Western Measurements Group, at Manchester, 25th November, 1952