Phase Displacement Errors Research Articles

Testing Rogowski Coils with Merging Units for Smart Grids

As smart grids incorporate renewable energy sources and advanced power electronics, ensuring accurate measurement systems becomes paramount due to the increased complexity and potential sources of disturbances. This article focuses on the laboratory calibration of Rogowski coils (RCs) and merging units (MUs), which are fundamental for measuring, controlling, and monitoring digital power systems. A comprehensive digital calibration system is introduced, utilizing precise, commercially available components such as a fluxgate current transducer and a National Instrument. The system assesses magnitude and phase displacement errors under various operating conditions, including abnormal scenarios. Additionally, the impact of uncertainty sources on the measurement chain analysis is discussed, with test results conforming to established standards. This research contributes to enhancing the accuracy and reliability of measurement systems in the context of evolving smart grids.

Real time live line high voltage measurement of instrument transformer's ratio and phase displacement errors

Real time live line high voltage measurement of instrument transformer's ratio and phase displacement errors

Topological error correction with a Gaussian cluster state

Topological error correction provides an effective method to correct errors in quantum computation. It allows quantum computation to be implemented with higher error threshold and high tolerating loss rates. We present a topological a error correction scheme with continuous variables based on an eight-partite Gaussian cluster state. We show that topological quantum correlation between two modes can be protected against a single quadrature phase displacement error occurring on any mode and some of two errors occurring on two modes. More interestingly, some cases of errors occurring on three modes can also be recognised and corrected, which is different from the topological error correction with discrete variables. We show that the final error rate after correction can be further reduced if the modes are subjected to identical errors occurring on all modes with equal probability. The presented results provide a feasible scheme for topological error correction with continuous variables and it can be experimentally demonstrated with a Gaussian cluster state.

The impact of current, voltage and phase displacement errors on the cross-border energy exchange

Cross-border energy exchange in the electricity market environment requires high quality measurement and accounting procedure considering the fairness in technical and economic sense. In order to fulfill these requirements, the necessary step is to clarify all uncertainty contributions at the metering point and to correct the exchanged energy for corresponding systematic errors. This approach resulted by a mathematical model for energy correction. The model is briefly presented and the sensitivity analysis of the model is performed: the impact of the current, voltage and phase displacement of the measuring transformers, error of the energy meter and voltage drop in voltage measurement circuits to the corrected energy. The presented procedure shows that the voltage drop has the highest impact to the corrected energy.

The Design and Characterization of a Prototype Wideband Voltage Sensor Based on a Resistive Divider.

The most important advantage of voltage dividers over traditional voltage transformers is that voltage dividers do not have an iron core with non-linear hysteresis characteristics. The voltage dividers have a linear behavior with respect to over-voltages and a flat frequency response larger frequency range. The weak point of a voltage divider is the influence of external high-voltage (HV) and earth parts in its vicinity. Electrical fields arising from high voltages in neighboring phases and from ground conductors and structures are one of their main sources for systematic measurement errors. This paper describes a shielding voltage divider for a 24 kV medium voltage network insulated in SF6 composed of two resistive-capacitive dividers, one integrated within the other, achieving a flat frequency response up to 10 kHz for ratio error and up to 5 kHz for phase displacement error. The metal shielding improves its immunity against electric and magnetic fields. The characterization performed on the built-in voltage sensor shows an accuracy class of 0.2 for a frequency range from 20 Hz to 5 kHz and a class of 0.5 for 1 Hz up to 20 Hz. A low temperature effect is also achieved for operation conditions of MV power grids.

Testing Methods for Measuring the Effects of Stray Capacitances on High-Voltage Current Transformers

This paper evaluates different measuring systems to estimate the effect of stray capacitances between primary and secondary windings on current transformers (CTs) used in high-voltage power networks. All windings are at nearly ground potential during laboratory calibration because this is the typical configuration for almost all CT’s calibration systems. However, in service, the primary winding is at high potential, so that additional currents flow through the load due to stray capacitances between primary and secondary windings, even if the CT has an electrostatic shield for reducing these capacitances. This effect changes the CT errors determined at no potential. Experimental determination of the variation of ratio and phase displacement errors between both working conditions is evaluated for a set of different CTs using different measuring systems. These systems include from the simplest low-voltage bridge capacitance measurement to the most complex one that simultaneously applies current and voltage.

Influence of the objective function in the process of optimal design of an electromagnetic measurement system

In the paper an analysis of the influence of the objective function during the process of metrological optimal design of an electromagnetic measurement system is made. The case study is a combined measurement transformer. The optimal design of the transformer is made by using an original program based on the genetic algorithm. Four different objective functions comprising the main metrological parameters of the transformer (voltage and phase displacement error of the voltage measurement core and current and phase displacement error of the current measurement core) are posed for the optimal design. Twometrological approaches areembedded intheobjective functions: 1) theconservative (withcertainmeasurement errors) and 2) the Guide EA-4/02 Expression of the Uncertainty of Measurements inCalibration (GUM) statisticalapproach. The optimal design solutions derived for the different objective functions are compared and discussed.

Genetic algorithm coupled with FEM‐3D for metrological optimal design of combined current‐voltage instrument transformer

The combined current‐voltage instrument transformer (CCVIT) is a complex non‐linear electromagnetic system with increased voltage, current and phase displacement errors. Genetic algorithm (GA) coupled with finite element method (FEM‐3D) is applied for CCVIT optimal design. The optimal design objective function is the metrological parameters minimum. The magnetic field analysis made by FEM‐3D enables exact estimation of the four CCVIT windings leakage reactances. The initial CCVIT design is made according to analytical transformer theory. The FEM‐3D results are a basis for the further GA optimal design. Compares the initial and GA optimal output CCVIT parameters. The GA coupled with FEM‐3D derives metrologically positive design results, which leads to higher CCVIT accuracy class.

Electronic error reduction system for clamp-on probes and measuring current transformers

An original electronic device for compensating ratio and phase-displacement errors, of measuring current transformers and clamp-on probes, is proposed. It is intended for low-frequency applications (power frequency and its harmonic components), where the magnetizing current is the main cause of measuring errors. This system reduces the magnetic flux in the transformer core, reducing in this way the magnetizing current. The proposed system even reduces the influence of the error produced by the variation of the burden connected to the secondary winding. Large values of burden can be used without effects on the transformer measuring errors. This device can be directly applied to conventional current transformers, connecting the device to the secondary terminals. It is not necessary to use any auxiliary winding or auxiliary core, or any modification of those transformers.

INTEGRATION OF THE NONDIVERGENT BAROTROPIC VORTICITY EQUATION WITH AN ICOSAHEDRAL-HEXAGONAL GRID FOR THE SPHERE1

Abstract A finite difference scheme is developed for numerical integration of the nondivergent barotropic vorticity equation with an icosahedral-hexagonal grid covering the sphere. The grid is made by dividing the 20 triangular faces of an icosahedron into smaller triangles, the vertices of which are the grid points. Each grid point is surrounded by six neighboring points, except the 12 vertices of the icosahedron which are surrounded by five points. The difference scheme for the advection of vorticity exactly conserves total vorticity, total square vorticity, and total kinetic energy. A numerical test is made, with a stationary Neamtan wave as the initial condition, by integrating over 8 days with 1-hr. time steps and a grid of 1002 points for the sphere. There is practically no distortion of the waves over the 8 days, but there is a phase displacement error of about 1° of long. per day toward the west.