Standard Voltage Transformer Research Articles

Modeling and Simulation of Wide-Frequency Characteristics of Electromagnetic Standard Voltage Transformer

To achieve the broadband applicability of standard voltage transformers in “dual high” power systems, an equivalent circuit model of the standard voltage transformer is first established. Using the complex magnetic permeability method and utilizing existing core parameters, the excitation impedance values are obtained. Next, based on the equivalent circuit model, the no-load error function of the standard voltage transformer is analyzed, and through simulation, the no-load error response curve of the standard voltage transformer in the frequency range of 20 Hz to 3000 Hz is derived. The simulation results indicate that within the 20 Hz to 700 Hz range, both the no-load ratio error and the no-load angular error meet the accuracy requirements, with the ratio error within ±0.05% and the angular error within 2′. Additionally, the derivation of the error transfer function demonstrates the correlation between the no-load error values and the number of turns and cross-sectional area of the standard voltage transformer. Simulation results, obtained by increasing and decreasing the number of turns and cross-sectional area by 10%, provide valuable insights for the error compensation and structural design of standard voltage transformers.

Research on the traceability method based on half symmetric superposition

In order to achieve high-accuracy self-calibration and traceability of electromagnetic standard voltage transformers, a measurement method that can be used for voltage ratio standard error voltage coefficients is proposed. Using two auxiliary standard voltage transformers, the error variation of the voltage transformer under different voltages can be obtained through three-step measurement. Compared with the traditional error voltage coefficient measurement method and international comparison, the feasibility of the method and the rationality of the uncertainty evaluation of the measurement results are verified. The self-calibration ratio difference measurement uncertainty of the 110 kV standard voltage transformer is better than 5 × 10−6, and the angular difference measurement uncertainty is better than 5 µrad. The method can be used to trace the source of standard devices up to 1000 kV power frequency voltage ratio, which have characteristics such as high accuracy and good stability.

Self-Detecting the Measurement Error of Electronic Voltage Transformer Based on Principal Component Analysis-Wavelet Packet Decomposition

The poor long-term stability of measurement error is the main problem in the operation of an electronic voltage transformer (EVT). Prevalent methods of error detection involve calibrating it regularly with a standard voltage transformer, but this is not conducive to the timely detection of the degradation in the error of the EVT. In light of this, this paper proposes a method to self-detect error based on principal component-wavelet packet decomposition. A standard of comparison for error detection is first established based on the characteristics of three-phase symmetrical operation. Principal component analysis is then applied to the measurement data of the three-phase EVTs, and their error is mapped to the online process monitoring of squared prediction error (SPE) statistics. Furthermore, the SPE statistics are decomposed by a three-level wavelet packet to eliminate the influence of the time-varying characteristics of node imbalance on the results of detection. The results of experiments show that the proposed method can detect the measurement error with an accuracy of 0.2 class without a standard.

Design and Research of 10KV Electronic Transformer Live Performance Evaluation Platform

Design and research a test platform suitable for 10KV electronic voltage transformer and 10KV electronic current transformer for long-term charging performance evaluation. The 10KV electronic transformer live test platform includes a primary boost device, a primary current boost device, a reference voltage transformer, a reference current transformer, a standard voltage transformer and a standard current transformer. The test circuit is designed to be three-phase. Under the condition that the system input voltage is 380V / 220V and the total input capacity is not greater than 100KVA, the auxiliary transformer and other auxiliary equipment are used to achieve long-term live operation and performance evaluation of the 10KV electronic transformer.

The Research on Additional Errors of Voltage Transformer Connected in Series

The series summation method is an important method in the calibration of the voltage coefficient (VC) of the standard voltage transformers (VTs), in which the key step is connecting a fullyinsulated VT and a semi-insulated VT in series, and comparing them with the third VT under test. Caused by the imperfect electrical shielding of the serially-wound VTs, additional errors are introduced in the calibration. By analyzing the cause of the additional errors in the serial connection of the VTs, two methods were designed in this paper to measure the additional errors. The proposed methods were harnessed to measure the additional errors for a serial connection of a 35 kV fully-insulated two-stage voltage transformer (TSVT) and a 35 kV semi-insulated TSVT. The results show that the two methods give a consistency of better than 1.0 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> in ratio error and 2.0 μrad in phase displacement, respectively. The accurate measurement of the series additional errors and the correction of them significantly improve the accuracy of the VC measurement of a 110/√3 kV TSVT based on the series summation method. Furthermore, the VC measurement result is verified by the consistency of the series summation method with the series additional errors corrected and the high-voltage standard capacitor method.

The development and application of voltage summation method with voltage transformers for determining ratio errors in power frequency

The ratio error of a standard voltage transformer must be determined by metrological method. This article introduces and illustrates the principles of series-parallel summation method in 1954, and the bilateral series summation method in 1988 along with the bilateral series summation method with series type voltage transformers in 2006 and 2008. Benefited from the improvement of voltage summation circuits and facilities the errors of voltage ratios at 1000 kV/√3 and below have been derived in this way. The uncertainties of all ratios at and below 1000 kV/√3 are less than 4×10−5 (P=95%). For eliminating the errors caused by imperfect shielding and proximity effect, the theory of response superposition with a three ports network was presented and realized in 2012 on voltage summation operation. The results obtained by response superposition method were satisfactory. For instance, the uncertainty at ratio 500kV/√3 over 100V/√3 decreased from 15×10−6 to 7×10−6 (P=95%).

A Fundamental Step-Up Method for Standard Voltage Transformers Based on an Active Capacitive High-Voltage Divider

This paper presents the new fundamental step-up method for standard voltage transformers (VTs) at the Physikalisch-Technische Bundesanstalt, as well as the setup of the required components. A main component is an active low-voltage capacitor, designed to realize capacitive voltage dividers by means of compressed gas, high-voltage capacitors for rated primary voltages between 5 kV and 800 kV/ $\surd 3$ . This divider has a negligible voltage dependence and low phase errors at 50/60 Hz. Using the other components, mainly a two-stage VT with integrated inductive voltage divider and a sampling-based voltage comparator, a transfer uncertainty for one build-up step of below $1\cdot 10^{-6}$ ( $k = 2$ ) has been reached.

Development of ultrahigh‐voltage standard voltage transformer based on series voltage transformer structure

An ultrahigh-voltage standard voltage transformer (VT) based on series voltage transformer (SVT) structure is described. A precise isolation VT is designed to realise the connection between the VTs of an SVT. Moreover, the ratio and errors of the SVT are discussed and calculated to reduce the magnetic error of the isolation VT, and capacitor compensation is proposed. Two calibration methods for the SVT are compared. The results are very approaching, and the largest differences between the two methods are <;0.08 × 10 -4 and 0.08 min. The results indicate that the errors of an SVT can be obtained by testing at only half the voltage of the SVT.

Monitoring the metering performance of an electronic voltage transformer on-line based on cyber-physics correlation analysis

Metering performance is the key parameter of an electronic voltage transformer (EVT), and it requires high accuracy. The conventional off-line calibration method using a standard voltage transformer is not suitable for the key equipment in a smart substation, which needs on-line monitoring. In this article, we propose a method for monitoring the metering performance of an EVT on-line based on cyber-physics correlation analysis. By the electrical and physical properties of a substation running in three-phase symmetry, the principal component analysis method is used to separate the metering deviation caused by the primary fluctuation and the EVT anomaly. The characteristic statistics of the measured data during operation are extracted, and the metering performance of the EVT is evaluated by analyzing the change in statistics. The experimental results show that the method successfully monitors the metering deviation of a Class 0.2 EVT accurately. The method demonstrates the accurate evaluation of on-line monitoring of the metering performance on an EVT without a standard voltage transformer.

An Online Calibration Method for Electronic Voltage Transformers Based on IEC 61850-9-2

Since electronic voltage transformers (EVTs) based on IEC 61850-9-2 are widely used in the substations, especially in the automating substations, their calibration becomes very important. Generally, the calibration of EVTs needs for the power to be interrupted and causes power outage, and also the faults of the running transformers cannot be found in time. For this reason, an online calibration system is proposed in this paper. By employing a specially designed remote-controlled hoisting unit and standard voltage transformer, the proposed system can calibrate EVTs without interrupting the power service and the power outage can be avoided. A two-order Hanning self-convolution window algorithm is adopted to suppress the influence of spectrum leakage caused by frequency fluctuation and harmonic interference. Tests have been performed in the China Electric Power Research Institute. The results show that the proposed system has good performance and it can reach the accuracy class of 0.05 in complicated electromagnetic fields.

Measure Characteristic of UHV Power Frequency Voltage Ratio Standard

In order to meet the urgent needs of voltage measurement traceability and transfer in the construction of ultra-high voltage power grid, 1000kV series standard voltage transformer is developed as the standard instrument, and then its measurement characteristics is tested. According to the theory and construction of the series power frequency voltage ratio standard, semi-insulating transformer voltage summation is proposed to make the voltage ratio measurement of SSTV whose accuracy can reach the 0.02 level trace to the source of national power frequency ratio standard of 500kV successfully. The compatibility is better than compared to traditional voltage coefficient measuring method.

International comparison of a standard voltage transformer between Ukraine and Germany

Results are provided for international comparisons of a standard voltage transformer performed in Ukraine and Germany. Algorithms are given for the equivalence of national standards taking account of expanded uncertainty.

Electronic compensation of inductive voltage dividers and standard voltage transformers

A new compensating system is proposed to reduce the ratio error and the phase error of inductive voltage dividers and standard voltage transformers, operating at no load. An electronic amplifier reduces the input current, which is the main cause of error in low-frequency applications, while at the same time the input impedance is greatly increased.

Determination of Voltage Transformer Errors by Means of a Parallel-Series Step-Up Method

Improvements in the accuracy of determining standard voltage transformer errors by the utilization of specially developed amplifiers are described. Results of recently evaluated measurements in the fundamental parallel-series step-up method of the Physikalisch-Technische Bundesanstalt (PTB) are reported. The overall limit of uncertainty in the calibration of high voltage ratios has been improved by a factor of ten as compared with previous results at power frequencies.