A sensor apparatus for measuring power parameters on a power conductor, such as a high voltage transmission line may include a corona structure, an electronics assembly and a conductor mountable device. The corona structure may define an outer boundary surrounding the electronics assembly and the conductor mountable device. The corona structure may shield the electronic assembly and conductor mountable device from a corona produceable with the power conductor. The conductor mountable device may be a power parameter measurement device, such as a current sensor assembly. The current sensor assembly may be a split-core design that includes multiple transformer cores. The electronics assembly and the conductor mountable device may powered from a line voltage suppliable on the power conductor. Data may be wirelessly transmitted and received with the sensor apparatus.

Current sensor assembly

The review makes a brief overview of traditional methods of measurement of electric current and shows in more detail relatively new types of current sensors. These include Hall sensors with field concentrators, AMR current sensors, magneto-optical and superconducting current sensors. The influence of the magnetic core properties on the error of the current transformer shows why nanocrystalline materials are so advantageous for this application. Built-in CMOS current sensors are important tools for monitoring the health of integrated circuits. Of special industrial value are current clamps which can be installed without breaking the measured conductor. Parameters of current sensors are also discussed, including geometrical selectivity. This parameter specific for current sensors means the ability to suppress the influence of currents external to the sensor (including the position of the return conductor) and also suppress the influence on the position of the measured conductor with respect to the current.

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Electric current sensors: a review

With the fast-paced changing technologies in the power industry, new references addressing new technologies are coming to the market. Based on this fact, there is an urgent need to keep track of international experiences and activities taking place in the field of modern transformer design. The complexity of transformer design demands reliable and rigorous solution methods. A survey of current research reveals the continued interest in application of advanced techniques for transformer design optimization. This paper conducts a literature survey and reveals general backgrounds of research and developments in the field of transformer design and optimization for the past 35 years, based on more than 420 published articles, 50 transformer books, and 65 standards.

Transformer Design and Optimization: A Literature Survey

An HV dielectric spectroscopy system has been developed for diagnostics of water tree deteriorated extruded medium voltage cables. The technique is based on the measurement of nonlinear dielectric response in the frequency domain. Today's commercially available systems are capable of resolving low loss and small variations of permittivity as a function of frequency and voltage. Experience from more than 200 field measurements was combined with laboratory investigations. Small samples were used in an accelerated aging test to elucidate the correlation between water tree growth and dielectric response. Furthermore, field aged cables were investigated in the laboratory. It has been shown that the dielectric response of water tree deteriorated crosslinked polyethylene (XLPE) cables can be recognized and classified into different types of responses related to the aging status and breakdown strength. The influence of termination and artifacts such as surface currents was investigated. The measurement method enables us to separate the response of the cable from the influence of accessories. Finally, two different field studies of the implementation of the diagnostic method are presented. The field studies show that the fault rate decreased significantly when replacement strategy was based on the diagnostic criteria formulated.

Dielectric spectroscopy for diagnosis of water tree deterioration in XLPE cables

An apparatus for sensing the current in a power line of a power system and systems incorporating the apparatus are disclosed. The apparatus may comprise an enclosure providing a window operable to permit the passage of the power line therethrough.

Power line sensors and systems incorporating same

The development of a computer-controlled current-comparator-based calibration system to determine the current ratio errors of high-voltage conventional and nonconventional current transformers (CTs) under actual operating conditions of high-voltage and distorted current waveforms up to 100 kV and 2000 A is described. The ratio errors of a CT are affected by the applied high voltage due to capacitive currents flowing in its winding. The errors are also affected by the phase angle of the primary currents with respect to the operating high voltage. Therefore, the new calibration system allows the phase angle of the test primary currents to be adjusted at power factors of zero lag through unity to zero lead. The uncertainty k = 2 of the new calibration system is estimated to be not more than 20 × 10-6 for both the in-phase and quadrature components of the measured ratio errors.

A Current-Comparator-Based System For Calibrating High-Voltage Current Transformers Under Actual Operating Conditions

This paper describes a high precision circuit for quadrature phase shifting in which frequency controlled signal amplification is introduced so that the amplitude of the phase shifted signal is not dependent on the frequency of the input signal. The proposed quadrature phase shifting method is aimed at high accuracy reactive power measurements in ac power systems. The implementation of the new phase shifter at the voltage input of a watt/watt hour meter allows for high accuracy var/varh measurements. A prototype of the quadrature phase shifter has been built with magnitude and phase errors within /spl plusmn/15/spl middot/10/sup -6/ and less than 40 /spl mu/rad, respectively. Its performance was further confirmed when the QPS was used for reactive power measurements.

A high performance frequency insensitive quadrature phase shifter and its application in reactive power measurements

An electronically aided multistage technique is applied to a hand-held openable-core damp-on current transformer which enables accurate low current measurements to be made over a wide dynamic and frequency range of operation, for use in conjunction with highly accurate active/reactive power and energy meters, and harmonic power analyzers The clamp on current transformer can be used to measure currents in the range from 1 A to 200 A, at frequencies between 50 Hz ad 5 kHz, with ratio errors of less than 50/spl times/10/sup -6/ in both magnitude and phase

A low-current multistage clamp-on current transformer with ratio errors below 50/spl times/10/sup -6/

An international comparison of 50/60 Hz power is described. The traveling standard was an electronic power transducer which was tested at 120 V, 5 A, 53 Hz, at five power factors (1.0, 0.5 lead, 0.5 lag, 0.0 lead, and 0.0 lag). Fifteen national metrology institutes from six metrology regions participated in the comparison.

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An international comparison of 50/60 Hz power (1996-1999)

The surface characteristic of a number of electrode materials including stainless steel, brass, brass whit various plated surfaces, aluminum, and anodized aluminum has been examined over a wide range of humidity. The measurements of surface charcteristic, expressed in microradian millimeters, have an estimated uncertainty of 0.01 ?rad · mm.

Eddy So

Papers

A Current-Comparator-Based System For Calibrating High-Voltage Current Transformers Under Actual Operating Conditions

A high performance frequency insensitive quadrature phase shifter and its application in reactive power measurements

A low-current multistage clamp-on current transformer with ratio errors below 50/spl times/10/sup -6/

An international comparison of 50/60 Hz power (1996-1999)

Losses in Electrode Surface Films in Gas Dielectric Capacitors