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This paper describes two concepts of automatic systems for accuracy testing of current transformers. Advantages and disadvantages of both concepts are discussed. The concept of multi channel testing is used for developing of the measuring device for current transformer accuracy testing for factory FMT Zajecar. The short description of the device is presented as well as the results of its testing.
In order to meet the current requirement of low voltage apparatus protection function test, a design of three phase high current generator based on virtual instrument technology is proposed. The coarse-fine tuning voltage regulator with the compensation transformer structure is used in the main circuit of the current generator, which not only could extend the range of current regulation, improve current...
A simulation system of distribution network design and development based on similarity principle is introduced. This simulation system includes primary simulation system and secondary control system, the primary system simulates a 10kV neutral indirectly earth distribution system, which includes a bus, four feeders with different types and different length. System structure and parameter calculation...
A system for evaluating instrument current transformer errors using a lock-in amplifier is described in the paper. The difference between the standard and the transformer under test is evaluated as the ratio error and the phase displacement. The attention is focused to measurement of errors at the range of primary currents less than 20% of the nominal value. The measurement accuracy of current and...
Recent developments of variable frequency applications have accelerated the demand to look at the measurement technology on variable frequency signals. Most low voltage (LV) circuit breakers are designed to operate at a fixed frequency. Therefore, it is necessary to propose a variable-frequency measuring concept for LV protection devices. In this paper, we propose a novel combined alternate current...
Results of research on the influence of different load on current transformers' transformation errors when cores consist of two different magnetic materials are presented in this paper. Analyses of the electromagnetic field distribution for different cases of load of the secondary winding were performed (magnetic field distributions of current transformers, current error and phase displacement diagrams)...
Assessing compliance with harmonic emission limits for utility-scale photovoltaic plants requires accurate measurements of harmonic voltages and currents at the point of connection. This paper evaluates the accuracy, reliability and temporal characteristics of harmonic measurement data obtained from a utility-size photovoltaic plant located in the Northern Cape province of South Africa. Measured harmonic...
Renewable energy resources have become an integral part of the power and energy industry in the world today. Photovoltaic (PV) systems are one of the most common and established forms of renewable energy technologies. With the increased installation of PV systems both on a small and large scale, it is critical that the impacts and operations of PV systems are accurately modeled, simulated and studied...
This article presents a kit to collect data of electric loads using a device that measures single-phase data and and second device that measures the input of three-phase main power supply of a house. To collect the data, we used current sensors based on an open magnetic core to measure the electromagnetic field induced by the current in the electric conducting wire in a non intrusive way. In particular,...
The traditional metering device has some problems in system reliability, electricity-stealing prevention and accuracy. In order to solve the above problems, a new type of integrated high-voltage energy metering device is designed in this paper. The equal potential of the measuring integrated circuit is suspended on the high-voltage side. The AD7753 is used as the core of the electric energy measurement...
In recent years, automatic technologies have been gradually applied in the batch testing process of energy measuring devices. Different from energy meters and acquisition terminals, the metering current transformers have more than ten specifications (various in size, transformation ratio, etc), and the demands for testing are more dispersed. This leads to a large number of scattered work tasks on...
State estimation (SE) is a widely used tool in power system control centers. It improves accuracy of remote measurements enabling direct power system state monitoring. In the article, the usage of median filtering (MF) in SE algorithms is proposed. Modeling of SE by MF and weighted least square method (WLS) was performed under conditions of the most challenging situations for SE, such as communication...
When using a variable-frequency drive at low and extra-low frequencies, it is difficult to control the current value. Standard current transformers are often used. This paper analyzes the transformer performance at frequencies below the industrial one. The objective is to study operation of the process transformer connected to an adjustable current source experimentally. The paper proves that frequency...
This paper dwells upon the project of autonomous wireless current sensors for an automated information-measuring system of non-commercial energy metering. This sensors are designed in the concept of the Internet of Things. Small dimensions and energy autonomy of such sensors, unlike the conventional solutions, ensure their convenient application to power supply systems. Proposed autonomous wireless...
AC current sensors are key components in the monitoring systems of electric power systems and are generally based on detecting the magnetic field induced around electric wires to measure the current into it. The most used current sensors are those based on Current Transformer (CT) that, in general, uses a ferromagnetic core and a coil around it in order to measure the primary-coil current by the secondary-coil...
Considering the growth of distributed energy generation systems in distribution networks, quick and precise protection and at the same time low cost is very perceptible. This protection includes directional relays beside overcurrent relays. The directional relays in the network require voltage and current relays; therefore, the cost of using this type of protection in the distribution network is very...
Microprocessor-based transformer differential relays offer fast and dependable protection for transformer faults while remaining secure for through faults. Differential elements in microprocessor-based relays compensate for the transformer winding connections internally based on the compensation settings provided by the user. Transformer differential settings are often misunderstood, and incorrect...
In this paper Wireless Sensor Home Area Network (WSHAN) with ZigBee interfaced smart meter is designed and implemented. Because of the increasing demands on electricity, traditional electric grid needs to be replaced with intelligent, robust, reliable and costly effective smart grid applications. Wireless Sensor Networks (WSN) has a critical role to set up a reliable and costly effective smart electric...
The application of digital measuring devices in the new generation of smart substation has increased greatly year by year. Electronic transformers export the samples in format of IEC61850-9-1 signal frame. And smart electricity meters measure electricity via this signal frame. The principle and interface of electricity measuring have changed fundamentally. Therefore, traditional field calibration...
This paper proposes a fault localization, isolation and restoration method for microgrids based on multiagent system (MAS) utilizing a communication network. The agents are located in the middle and the two ends of each section. The fault is detected through phase angle comparison of current signals at both sides of the distribution line and sends the trip signal to circuit breakers. This technique...
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