Voltage Transformer Research Articles

Analisis Penggunaan Transformator Sisipan Untuk Mengatasi Rugi Tegangan dan Pembebanan Lebih

On the JD267 distribution transformer with a capacity of 100 kVA at the Kalibaru feeder on the PT PLN (Persero) ULP Genteng experienced overloading at WBP (88.03%) and high voltage losses. The magnitude of the load exceeds 80% of the standard transformer capacity and is in the bad category (load >= 80%) according to Table I. SE No. 0017.E/DIR/2014, related to transformer loading percentage. Meanwhile, the voltage loss of the JD267 transformer when the WBP is in Phase R is 19.05%, Phase S is 17.08%, and Phase T is 18.33%. This exceeds the voltage tolerance limit in SPLN 1:1995 that the voltage is not allowed to exceed +5% and -10% of the PLN standard voltage, namely 220 V. To handle this problem, PT. PLN (Persero) ULP Genteng carried out the installation of insert transformers by estimating load growth in the next 5 years using the Least Square method. After the addition of the insert transformer, the loading on the JD267 distribution transformer fell to 58.93% on WBP. Meanwhile, the magnitude of the JD267 transformer voltage loss when the WBP after insertion in the R Phase decreases to 0.84%, the S Phase is 1.04%, and the T Phase is 1.63%, and when the LWBP after insertion in the R Phase decreases to 0 .76%, S Phase 0.30%, and T Phase 0.6%. Based on the data above, adding an insert transformer can improve the loading percentage on the transformer and reduce voltage losses that occur at the end voltage of the transformer.

A series inductance based three-port isolated hybrid DC–DC converter for microgrid applications

The paper proposes a series inductance based three-port isolated hybrid converter (3PIHC) for wide change in voltage transformation ratio (VTR) which supports DC microgrid applications. Three-ports in the proposed converter is integrated by means of a three-winding high frequency transformer (HFT). The leakage inductance of three-winding HFT acts as an energy transfer element between the ports. The factors which need to be considered for designing the leakage inductance are power transfer flexibility and limits of current transfer at wide change in VTR. In a feasible scenario, the intricate aspects such as inconsistency of leakage inductance, requirements of power flow variability and current restrictions necessitates auxiliary inductors in series with the three-winding HFT. This paper focuses on selecting appropriate value of series inductance for 3PIHC based on the application demand and minimized converter losses. Study and analysis are carried out to evaluate the converter performance at certain values of series inductance which is the sum of leakage inductance of HFT and auxiliary inductance. A hybrid configuration is adopted in the proposed converter where the primary port holds multi-level half bridge structure which reduces the voltage stress across the transformer primary winding and semiconductor switches. The secondary and tertiary port occupies H-bridge circuit topology. Converter analysis is presented for both conventional phase-shift modulation (CPM) and dual phase shift modulation (DPM). A simple computational method for obtaining the phase-shift variables at minimum value of current stress is developed. Evaluated the converter current stress for various values of series inductance and at wide change in VTR. A prototype of the proposed converter is implemented and examined. The experimental results demonstrated authenticates the accuracy of theoretical analysis.

Dielectric response of vegetable oil-based nanofluid and impregnated Kraft paper for high voltage transformer insulation

Methyl ester from vegetable oil has been considered a potential replacement for mineral oil used for power transformer cooling and insulating applications. However, some pertinent properties in making this liquid a better transformer oil based on the laydown standards need to be enhanced to maximize the use of this insulating liquid. Technology involving nano-modification can enhance the properties of these ester liquids placing them in a better position as a good alternative. In this study, we aim to investigate the performance of methyl ester liquid from neem seed oil, a non-food grade oil, when modified with SiO2 insulating nanoparticles at several concentrations. Furthermore, Kraft paper compatibility has also been analyzed to observe their compatibility after impregnation. The breakdown strength, temperature-dependent dissipation loss factor, dielectric constant, and viscosity of both pure and nanofluid samples of neem ester liquid have been measured per standard methods. The nanofluid's dielectric performance has been significantly enhanced by the presence of SiO2 nanoparticles according to results obtained from the experiment. For instance, the dielectric dissipation factor at an operating frequency of 60 Hz has been improved by 96%, 89%, and 79% at 30 °C, 50 °C, and 70 °C respectively relative to the base neem liquid. This remarkable improvement has been attributed to the SiO2 nanoparticle's ability to polarize, trap, and de-trap mobile electrons develop in nanofluid when an electric field is applied.

Implementation of a Real-Time IoT Based Energy Management System

Energy Management System has received a lot of attention from both academia and industries due to the rate of energy consumed by electrical appliances. These industries are faced with inflation in the cost of electrical bills. Therefore, this study presents the design and implementation of a real-time IoT based Energy Management System (EMS) to reduce the inflation in the cost of these electrical bills. The system comprises four (4) basic units namely; the sensing unit, control unit, display unit and switching unit. The sensing unit comprises of two sensors namely; Current Transformer (CT) sensor and voltage sensor which senses and measures the parameters (voltage and current) and sends the parameters to the control unit. This control unit comprises two (2) microcontrollers namely; Arduino Nano and ESP32. The Arduino Nano processes the received data from the sensing unit and sends the processed data to the display unit and ESP32 microcontroller for real-time monitoring. In addition, the ESP32 microcontroller sends the processed data to the cloud. Furthermore, the web-based application receives the measured parameters from the cloud and thus, allowing the user to monitor as well as control the rate of energy consumption of electrical appliances. The experimental results obtained showed that the developed system efficiently monitors and control the rate of energy consumption of the three applied loads (Edison 2.7 bulb, standing fan and phone charger). Hence, reduces the cost of electrical bills consumed by these appliances.

Metrological support of digital electronic voltage transformers and low-power voltage transformers

Metrological support of digital electronic voltage transformers and low-power voltage transformers (sensors) is represented. The methods and reference measuring instruments of the State primary special standard of units of the ratio error and the phase displacement of AC electric voltage of power frequency in the range from to and units of electric capacitance and tangent of loss dissipation factor at AC voltage of power frequency in the range from 1 to 500 kV – GET 175-2023, used for metrological support of the measuring instruments mentioned above. The results of research of GET 175-2023 are presented. The expanded uncertainties of GET 175-2023 when reproducing the units of the ratio error and the phase displacement of AC electric voltage of power frequency for metrological support of analog low-power voltage transformers (sensors) include the budget of the uncertainties of the current comparator, low-voltage (reference) and high-voltage measuring measures, the high-voltage MVE-01 bridge (SA7400MA1 amplifi er) and are respectively 9.62·10–5 and The expanded uncertainties of GET 175-2023 when reproducing the units of the ratio error and the phase displacement of AC electric voltage of power frequency for metrological support of electronic digital voltage transformers and digital low-power voltage transformers (sensors) include the budget of uncertainties of the converter «high voltage – current», converter «current – low voltage», converter «low voltage – a digital copy of voltage», a digital comparison device and constitutes 10.8·10–5 and respectively. GET 175-2023 allows solving the problems of metrological support of electronic digital voltage transformers and digital low-power voltage transformers (sensors).

Evaluation of hosting capacity of the power grid for electric vehicles – A case study in a Swedish residential area

The deployment of electric vehicles (EVs) is growing significantly in recent years. The increasing EV charging loads pose great stress on power grids in Sweden, as many existing power grids are not designed to host such large shares of new electric loads. Hence, studies investigating the impact of EV charging are needed. This study conducts a case study based on an existing Swedish residential power grid using real-life EV charging data to estimate the local grid hosting capacity (HC) for EVs. A combined time-series and stochastic HC assessment method is used with voltage deviation, cable loading and transformer loading as the performance indices. Uncertainty in EV charging locations and individual charging behaviour have been considered via Monte Carlo simulations. The power grid HC is analysed and compared under three charging strategies and four EV penetration levels. Study results show that a charging strategy based on low electricity prices gave lower HC due to simultaneous EV loads compared to the other two strategies: charging directly after plugging in the EV and an even charging load through the plug-in session. This implies the need for coordinated charging controls of EV fleets or diversified power tariffs to balance power on a large scale.

Medium‐term forecasting of daily aggregated peak loads from heat pumps using clustering‐based load duration curves to calculate the annual impact on medium to low voltage transformers

AbstractThe energy transition drives the adoption of heat pumps (HPs). Their peak loads have a large impact on distribution networks. Therefore, the proposed methodology calculates the annual impact on medium to low voltage (MV/LV) transformers based on a medium‐term forecast of daily aggregated peak loads from HPs using the number, their rated power, a normalised load duration curve, and the daily average ambient temperature. The forecast differentiates between daily aggregated peak loads of HPs with different heating demands and the varying impact due to seasonal weather differences. First, 221 measured residential HPs over two years were randomly selected and clustered to identify different heating demands. These clusters were used to calculate four representation functions. Second, 108 other measured HPs were clustered and used to forecast the aggregated peak load with the calculated four representation functions. These forecasts were used to calculate the annual impact on an MV/LV transformer with a daily time resolution. These results indicate the periods over a year that the MV/LV transformer is at risk of congestion and it indicates the potential to mitigate congestion through demand‐side management.

Design a microwave transmitter using magnetron and two layers waveguides

A magnetron is a power oscillator device used in several radar transmitters for generating the electromagnetic wave (EMW) with a constructive and fixed frequency. In this work, a radar transmitter has been carried out using magnetron operates at 2,458 MHz and two conducting layers waveguides to achieve minimum loss of the signal due to the increased temperature. The magnetron is connected with the high voltage capacitor (1.0 μF) in order to store the alternating current (AC) signal delivered from the high voltage transformer. A waveguide parts have been used as transmission lines in view of connecting the magnetron to the antenna. These parts include two metal layers, the upper layer (outer) is advanced audio coding (AAC) 1350 aluminum conductor and the lower (inner) is copper. The waveguide dimension should be suitable to flow frequency from 2.2 GHz to 3.3 GHz. To measure the operating frequency, a waveguide adapter and a coaxial cable which combined with n-female connector have been connected to magnetron. The wave is delivering to the frequency counter by Bayonet Neill–Concelman (BNC) to n-female connectors. The promising results of the proposed work have been achieved with a maximum power, efficient return loss, acceptable voltage standing wave ratio (VSWR) and low-cost manufacturing.

Error Evaluation Method of Capacitive Voltage Transformer Based on Improved Principal Component Analysis

The capacitive voltage transformer is an important data source for electricity trading and is easily influenced by environmental factors during operation, resulting in decreased metering accuracy. Because the voltage data does not satisfy the Gaussian distribution, the accuracy of the traditional principal component analysis method is poor when evaluating the error of capacitive voltage transformers. This paper proposes an improved principal component analysis method based on the local outlier factor. First, principal component analysis is utilized to separate the primary voltage fluctuation and error change. Then, a new statistic is established by using the local outlier factor instead of the traditional statistic as an evaluation standard, which reduces the missed diagnosis and misdiagnosis caused by the data distribution characteristics. The experimental results show that the improved method is better than the traditional method in terms of the detection rate of transformer anomaly detection, can effectively detect the abnormal change of transformer error and is more suitable for capacitive voltage transformers in operation.

Detection of Interturn Short-Circuit Faults in Dry-Type Voltage Transformers Using the Pulse Voltage Method

This article investigates the application of the pulse voltage method for detecting interturn short-circuit faults in the high-voltage windings of dry-type voltage transformers. We determined the characterization parameters of the high-voltage windings of dry-type voltage transformers and trends in the variation of the characterization parameters with frequency in the presence and absence of faults. The viability of using the pulse voltage method for the detection of interturn short-circuit faults in dry-type voltage transformers was analyzed. A pulse voltage test platform was designed to analyze the response voltage waveforms using pulse-oscillating voltage experiments on transformers with various short-circuit faults. The results demonstrate that during a turn-to-turn short circuit, the equivalent resistance and inductance of a high-voltage winding are significantly lowered. When employing the pulse voltage method to investigate interturn short-circuit faults, tiny inductors are connected in parallel to produce an oscillating voltage waveform that is more uniform. Upon incurring a short circuit between turns, the pulse’s oscillating voltage frequency increases. The greater the number of turns in the short-circuit fault is, the more significant the effect of the test.

Heat recovery opportunities from electrical substation transformers

The transformation of voltages in electrical substations leads to energy losses in the form of waste heat; the quantity of which depends on transformer size and electrical loading. This paper investigates how a novel waste heat source, namely transformer waste heat could be harvested and distributed via district heating networks. Firstly, the investigation considered nameplate heat loss factors to quantify the theoretical waste heat potential from electrical substation transformers in England, Wales and Northern Ireland, which varied from 3.0 to 5.4 TWh a−1, equivalent to between 0.7 and 1.25% of annual heat demand for these countries, depending on loading assumptions. A number of heat recovery approaches which could be integrated with existing transformer cooling systems were then proposed. A spreadsheet model was then developed to simulate heat recovery from a transformer, together with the upgrade of the recovered heat using a heat pump prior to delivery via district heating. The model was used to evaluate the merits of capturing transformer waste heat losses, estimated using industry supplied electrical loading data, to meet different heat network demands based on an existing network, compared to conventional heating technologies. Findings suggest that the system proposed can achieve levelised costs that are up to 17% lower than the running costs of air-source heat pumps, whilst reducing emissions by almost 80% when displacing gas boilers. The methodology hereby described can also be used to evaluate the feasibility of recovering transformer waste heat in other countries.

A three-port isolated hybrid converter with wide range of voltage transformation ratio for DC microgrid

A three-port isolated hybrid converter with wide range of voltage transformation ratio for DC microgrid

Research on protection and control technology of power electronic transformers

As the key equipment in the modern power system, the power electronic transformer's performance and reliability play a vital role in the stable operation of the power system. This paper studies the soft switching technology, control technology and fault protection method of power electronic transformer. First, the soft switching technology of power electronic transformers is introduced, including zero voltage switching, zero current switching and so on. These soft switching technologies can effectively reduce the switching loss of the transformer, improve efficiency, and reduce electromagnetic interference and harmonic generation. Secondly, the control technology of power electronic transformer is introduced, including traditional proportional, integral, and derivative control (PID) control, model predictive control and direct power control. These control technologies can realize the precise control of the output voltage and current of the power electronic transformer, to meet the requirements of the power system for power quality and stability. In addition, this paper also introduces the fault protection methods of power electronic transformers, including short-circuit protection, over-voltage protection and over-medium current protection. These fault protection methods can effectively protect power electronic transformers from various faults and ensure their normal operation and safety.

Retracted: High Efficiency Compound Vacuum Oil Gas Separation Technology Based on Integrated Oil Filter of Ultra-High Voltage Transformer

Retracted: High Efficiency Compound Vacuum Oil Gas Separation Technology Based on Integrated Oil Filter of Ultra-High Voltage Transformer

FAULT DETECTION AND LOCATION BASED SVM FOR THREE PHASE TRANSMISSION LINES APPLYING POSITIVE SEQUENCE FAULT COMPONENTS

Transmission lines are an imperative element of the modern power systems. Any faults in them can cause an undesirable interruption in power supply. Precise analysis of these faults is important in-order to ensure an incessant supply of power. For this purpose, fault detection and classification are needed to clear any such faults and re-establish the system to maintain its normal operation. In this paper, a novel integrated approach of protective relaying with enhanced support vector machine algorithm has been adopted for detecting faults and its location estimation in long transmission line. The proposed scheme is successfully able to detect and classify different symmetrical and unsymmetrical faults along with some peculiar cases related to High Impedance Faults (HIF) and evolving faults, current transformer (CT) saturation/ capacitive voltage transformer (CVT) transient, close-in faults, swing condition, source strength variation, etc. The comparative analysis with recent proposed techniques declared the potentiality and robustness of the scheme

Multiple distribution networks hosting capacity assessment using a stochastic approach

The stochastic approach is applied to an entire concession area with 1264-LV distribution networks to estimate the hosting capacity. About 15 000-customers are connected to the individual secondary distribution networks supplied through 48-medium voltage 10 kV radial feeders.The hosting capacity assessment uses the end-customer voltage magnitude rise and transformer thermal overload. The hosting capacity is estimated by applying the “stochastic mixed aleatory-epistemic method” to determine the voltage magnitude rise and load flow with solar PV. The minimum power consumption is compared with the solar PV power infeed through the individual transformers.The hosting capacity estimation is done for three-phase connected solar PV sizes from 3 to 18 kW. At moderate PV penetration (25%–50%), the results showed that overvoltage would limit the hosting capacity more often than overload, but it becomes an issue only for LV networks studied with more than 8-customers. Considering all LV networks, most of the customers could install 6 kWp. Even when installing PV systems of 18 kWp (about twice the average size today and about the maximum area of a typical residential roof), two-thirds of houses would not need an upgrade to withstand SS-EN 50160 voltage limits. The latter customers can connect solar PV units with 18 kWp size without overvoltage or overload issues.

Characterization of Instrument Transformers under Realistic Conditions: Impact of Single and Combined Influence Quantities on Their Wideband Behavior.

Instrument transformers (ITs) play a key role in electrical power systems, facilitating the accurate monitoring and measurement of electrical quantities. They are essential for measurement, protection, and metering in transmission and distribution grids and accurately reducing the grid voltage and current for low-voltage input instrumentation. With the increase in renewable energy sources, electronic converters, and electric vehicles connected to power grids, ITs now face challenging distorted conditions that differ from the nominal ones. The study presented in this paper is a collaborative work between national metrology institutes and universities that analyzes IT performance in measuring distorted voltages and currents in medium-voltage grids under realistic conditions. Both current and voltage measuring transformers are examined, considering influence quantities like the temperature, mechanical vibration, burden, adjacent phases, and proximity effects. The study provides detailed insights into measurement setups and procedures, and it quantifies potential errors arising from IT behavior in measuring distorted signals in the presence of the various considered influence quantities and their combinations. The main findings reveal that the temperature has the most evident impact on the inductive voltage transformer performance, as well as the burden, causing significant changes in ratio error and phase displacement at the lower temperatures. As for low-power ITs, establishing a priori the effects of adjacent phases and proximity on the frequency responses of low-power ITs is a complex matter, because of their different characteristics and construction solutions.

Analyses on an electronic voltage transformer's failure by its resonance with very fast transient overvoltage and suppression

AbstractAs voltage measuring devices are widely used in the high voltage power system with a primary‐secondary‐fusion structure, electronic voltage transformers are directly connected to the primary conductor and would face much more serious electromagnetic environments than general secondary equipment. As a result, they would still experience failures even when general protection measures are adopted to suppress overvoltages' amplitudes. To address this issue, an innovative method is proposed after analyses are conducted on the resonance between a transformer and an overvoltage. Within this method, an air‐cored coil is installed in a transformer to artificially shift its natural frequency and to dodge the high‐frequency dominant component of a transient overvoltage, avoiding the aforementioned resonance and suppressing the secondary overvoltage. In addition, simulations and laboratory tests are conducted to prove this method's validity.

Sensorless Control Design of High-Speed Electric Drives in Discrete-Time Domain for Mild-Hybrid Turboprop Aircraft Applications

High-speed Permanent Magnet Synchronous Machine (PMSM) sensorless control design is not without challenges, especially when the ratio of power electronic modulation frequency to electrical fundamental frequency (M-F ratio) is relatively low. The Model Reference Adaptive System (MRAS) is a mature sensorless control method and has been widely used in industrial drives. There, an observer is commonly used to estimate rotor speed and angle using machine voltages and currents. The estimated angle is then further implemented for voltage and current frame transformations. Thus, the MRAS sensorless control is indeed a strong-coupled, multi-variable and nonlinear system. This paper proposes a detailed MRAS sensorless control system design method in discrete-time domain for high speed drives with relatively low M-F ratio with good system stability confidence. A detailed discrete local-linearized small-signal model is developed and state-space evolution matrix of current closed-loop system has been derived. The system stability can be defined and analysed with its maximum eigenvalue and the controller design is to make sure that the maximum eigenvalue is falling within the stable region. This proposed design method has been validated on a dual three-phase PMSM by simulation and experiment results with selected stable design point.

Distributed Photovoltaic Optimization Configuration Based on Marine Predators Algorithm in Low Voltage Transformer Area

This article proposes a method for determining the scale and location of Distributed Photovoltaic (DPV)under the operational constraints of low-voltage transformer areas. Firstly, a low-voltage transformer areas operation model and a DPV output model were established. Determine the access nodes and rated capacity of the DPV using the indicators of minimizing voltage fluctuations and minimizing line loss rate in the optimized configuration model; Then, the maximum capacity of DPV that can be installed in the transformer area is determined with the goal of maximizing the photovoltaic penetration rate in DPV accessible nodes; Use Marine Predators Algorithm(MPA) to solve nonlinear problems in the model. Finally, simulation analysis was conducted using an actual low-voltage transformer area as an example to demonstrate the effectiveness of the proposed model and method, ensuring the safe and stable operation of the low-voltage transformer area when connected to a high proportion of photovoltaic energy.