High Voltage Instrument Transformers Research Articles

Interpretation of IS/IEC and IEEE Standards for Dielectric Type Testing of Instrument Transformers

The requirements of Instrument Transformers are given in standards IS16227-1, IEC 61869-1 and IEEE Std. C57.13.5. Indian Standard IS 16227-1 is in line with IEC 61869-1. Most of the utilities in India are the following IS: 16227-1/IEC 61869- 1. Many failures of the high voltage instrument transformers are being reported by the utilities. In this connection, a review of the requirements/test procedure and acceptance criteria specified by IEC 61869-1 and IEEE Std C57-13.5 for dielectric-type tests are reviewed in this paper which may help decision-making for adopting a particular standard for dielectric-type tests on instrument transformers considering Indian climatic conditions.

Failure causes and operational life of measuring transformers intalled in 150Kv transmission network

Electric power infrastructures are the most critical. The required monitoring of electricity networks is achieved using instrument transformers. The instrument transformers' operating conditions must be kept steady and within safe limits. However, this entails the comprehension of the several reasons that lead toto failure. These reasons can introduce condition assessment monitoring techniques aiming to protect this type of electrical equipment and maybe contribute to their predictive maintenance. This paper describes the probable failures in high voltage instrument transformers with an operating voltage of 150kV, the rate and trend of failures as well as the basic sources for these failures. More specifically, this research has been applied to the 150kV instrument transformers that are installed at the Hellenic Electricity Transmission Network.

Algorithms for automatic of metrological characteristics of transducers

The algorithms for automatic correction of metrological characteristics of high-voltage instrument transformers in the absence of benchmark measurement signals at the source input are proposed. The investigated algorithm can be applied for automatic correction of metrological characteristics of measuring channels in the case of multiplicative distortions caused by the nonlinear dependence of the transmission coefficient on the input value.

Estimation peculiarities of external polymer insulation reliability of gas-filled instrument transformers

In the article, the authors propose a method for estimating the parameters of theoretical distributions for calculating the indicators of operational reliability. In the article, the authors propose a method for estimating the parameters of theoretical distributions for calculating the indicators of the operational reliability of a solid insulating structure of high-voltage devices, which is a supporting insulating cover for high voltage instrument transformers filled with gas as an insulating liquid. This technique makes it possible to estimate the parameters of a new distribution law, which is chosen on the condition that it does not contradict the existing distribution law with its known parameters. The developed technique makes it possible to obtain the values of the indicators of the operational reliability of high-voltage equipment by determining the parameters of theoretical distributions, if the developer is the data of experimental studies or statistical information as a result of monitoring the operation of insulating structures, taking into account the actual operating conditions of such high-voltage devices. This makes it possible to take into account the influence of external factors and performance characteristics inherent in instrument transformers, both current and voltage. In the proposed methodology, as an example, a supporting insulating casing is considered, which is during operation in the most unfavorable conditions, such as external pollution, humidification, overvoltage, etc. The theoretical conclusions are confirmed by the results of calculations using the example of the design of a current transformer of the ТОГ-362 series. A more accurate determination of the effectiveness of the proposed method for predicting the parameters of theoretical distribution laws can be achieved by performing an additional series of calculations and experimental tests of specific insulating structures. Thus, it was concluded that it is possible to use the results obtained to assess the operational reliability of both gas-filled instrument transformers and similar high-voltage equipment.

Machine Learning Approach Application for High-voltage Instrument Transformers Technical State Assessment

This paper describes the possibilities of machine learning application in the tasks of technical state assessment of high-voltage instrument transformers. An analytical review of modern systems for technical state assessment of high-voltage equipment is presented, their advantages and disadvantages are described. A mathematical model of an automated system for assessing the high-voltage instrument current and voltage transformers based on gradient boosting over decision trees has been developed. The efficiency of the developed solution is proved using the example of analysis of a real distribution zone, which allows identifying the state of instrument transformers with an accuracy of 84%.

Electric field at sharp edge as a criterion for dimensioning condenser-type insulation systems

Inside the oil-paper insulation of high voltage condenser-type bushings and instrument transformers, conducting surfaces or capacitive shields have been in use for many years to control electric field distribution. Traditional insulation design methods take into consideration dielectric stresses in axial and radial directions, but experience shows that partial discharges occur in the vicinity of capacitive shield edges and can severely affect the expected life of oil-paper insulation. In this paper, a criterion for dimensioning condenser-type insulation systems is presented, based on maximum electric field at sharp edge of capacitive shield. Maximum permitted value of the electric field at the shield’s edge was obtained through numerous experimental tests and numerical field calculations based on the finite element method (FEM).

Determining Insulation Condition of 110kV Instrument Transformers Using Gas Chromatography

The paper dwells on determining insulation condition of high voltage instrument transformers and contains both theoretical contributions and measurements (performed on electrical equipment in 110/20kV substations in Sibiu county, Romania) regarding, namely, the partial discharge phenomena, highlighted using gas chromatography. Measurements have shown the negative effects of these internal possible mechanisms, such as arcing, corona discharges, spark discharges (local penetrations of insulation, possessing a high density of ionization or appearance of low energy arcing, sometimes described – not as an absolute rule – as partial discharge), on the solid insulation of high voltage instrument transformers. These conditions occurring singly or as several simultaneous events can result in decomposition of the insulating materials and the formation of various combustible and noncombustible gases. The technique used by the authors proved itself to be up to date, extremely advantageous, with extraordinary precision, speed and handling flexibility. Very reproductive results recommend the use of gas chromatography.

Labview based testing system for the aim of construction of energy efficient magnetic cores

There is increasing demand for more and more energy efficient magnetic cores to be used in modern electrical devices like inverters or smart grid instrumentation (high and medium voltage instrument transformers). The most important magnetic parameters are as high as possible magnetization characteristics (B m = f(H m ) curve) associated with lowest specific total core losses. As magnetic properties of magnetic cores become worse during production processes it is extremely important to test them in order to improve the production process. In the case of large magnetic cores they cannot be tested in generally used computer systems. Therefore, there is a need for quality testing system for cores of large mass, in the order of several hundred kilogramms.The paper presents an example of an application for testing the system based on Labview platform for quality checking of large magnetic cores in the order of 1000 kg. Example of testing data for one and three phase core are presented.

Research on the Metrological Characteristics and Voltage Transformer with Open Core Antiresonance Properties

This work presents research results of open core high-voltage instrument transformers. The authors proposed different transformer constructions (designs) and implemented mathematical modeling on the basis of specially developed computer models carrying out field and circuit calculations simultaneously. According to the calculation results, the investigated voltage transformer amplitude and phase errors are defined. Also, research results of the investigated transformer antiresonance properties on the basis of symbolic models are given.

Condition Assessment of High Voltage Instrument Transformer Using Partial Discharge Analysis

Determining the incipient faults in high voltage apparatus is important because failure without warning can result in damage to adjacent equipment, personnel injures, customer dissatisfaction and disruption to economic activity. The failure of several high voltage instrument transformers during in-service prompted Tenaga Nasional Berhad (TNB) to identify more effective diagnostic tool to predict insulation breakdowns. The viability of partial discharge (PD) measurements in the field on instrument transformers is investigated. This paper presents the results of partial discharge tests that have been carried out under laboratory experiments and field measurement on high voltage instrument transformers.

Mixed D-Core With a Distributed Air Gap as an Alternative for Medium Voltage Instrument Transformers

This paper propounds a practice of using cut cores with a distributed air gap in the production of magnetic circuits for high quality medium voltage instrument transformers. It discusses utilization, for this purpose, of both grain-oriented and non-oriented electrical steel sheets of different grades, hence of considerably different characteristics and cost. The magnetic properties of the transformers were enhanced, and substantial technical and economical benefits in the manufacture of the end product were realized.

The Application of a New Nontracking Butyl to High-Voltage Instrument Transformers [includes discussion

A new nontracking butyl insulation which will not carbonize even under severe surface contamination has been applied to 15,000-volt outdoor instrument current transformers, and makes practical still higher voltage outdoor butyl designs. The discovery of a novel principle 1 to overcome the susceptibility of organic materials to carbonization and tracking and the application of this principle to butyl rubber have enabled this major advance to be made.

Improvements in Transformer-Loss Compensators for Walt-hour and Var-hour Meters

Transformer-loss compensators provide an economical means for metering the loads of utility company customers supplied at transmission voltages on the low-voltage side of the power transformer bank by compensating the watt-hour meter to include the transformer losses in its registration. Improvements have been made in the basic compensator <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> by neutralizing the effect of the flow of meter potential circuit current through the copper-loss compensator. This improves the performance of the compensator, particularly on inductive loads, and makes possible its correct adjustment also for the higher values of losses incurred with var compensation. The burdens imposed by the compensator are sufficiently small to be acceptable in watt-hour metering practice, and for connection to the output side of standard var autotransformers. Under present-day conditions the use of transformer-loss compensators results not only in economies, but also in the conservation of critical materials that would be required for high-voltage instrument transformers on metering installations.