Journal of Energy - Energija

Automated Measurement System of High Accuracy for Shunt Reactors

Toni Pohovski — 2024-06-04

System for automated transformer tests (ATT) enables different measurements on power transformers, from simple to the most complex, with a high degree of automation. ATT system is now expanded with modules for measurements on shunt reactors. The measurements related to shunt reactors that are covered with the system are: measurement of losses, impedance measurement, linearity test, zero impedance measurement, winding resistance measurement, temperature rise test and measurement of mutual reactance. Besides the measurement, ATT enables data analysis and report generation, all in accordance with [1,2]. Measurement of shunt reactor losses with satisfactory accuracy is a big challenge due to power factors of the reactors as low as 0,001. A system for loss measurements with high accuracy, consisting of measuring bridge, current comparator and standard capacitor is integrated into ATT. In the paper, a comparison in terms of loss measurement accuracy on shunt reactor is given for two measurement systems – a newly integrated system for shunt reactors and standard system used for transformer measurements.

Numerical Calculation and Direct Measurement of Local Hot Spot Temperatures in Transformer Clamping Plates

Dino Kovačević — 2024-06-04

A verified multiphysics model is developed to simulate local hot spot temperatures in clamping structures. Stray field losses in clamping plates are obtained with the use of nonlinear impedance boundary condition through finite element method (FEM) while hot spot temperatures are simulated with the use of computational fluid dynamics (CFD). This multiphysics coupling is validated through direct measurements of local hot spot temperatures that were carried out with fiber optic temperature probes in real transformer. The local hot spot temperatures obtained with the simulations were in good agreement with the measured values, thus verifying overall approach and indirectly the calculation of local stray field losses.

Regression Learner Application Model-Based Short-Term Load Forecasting for Mascouche (Quebec, Canada)

Mouctar Tchakala — 2024-06-04

Load forecasting is crucial for power systems optimal operation and allows power utilities to overcome technical and economic issues. Some forecasting techniques are currently being deployed on a large scale to meet the requirements of increased energy demand while balancing it with the production to achieve socio-economic benefits for sustainable development. In this paper, we are diving into the forecasting using the regression method. We are focusing on short-term load forecasting and how it can give businesses valuable insights into future sales, labor needs, and more. Power utilities use short-term load forecasting technology to make reasonable power systems. A forecasting model with low prediction errors helps reduce operating costs and risks for the operators leading to models’ optimization. To make things real, we are using actual load and weather data from the Hydro-Quebec database. We will be exploring the capabilities, advantages, and limitations of this method, all while keeping an eye on the changing landscape of electricity supply and demand. Our study is centered around the Mascouche region in Quebec, Canada, where the load fluctuates between 60 to 140 megawatts.

Proposal of Testing Procedure for Resonance and Ferroresonance Inception Possibility in Instrument Transformers

Bruno Jurisic — 2024-06-04

This paper deals with the possibility of ferroresonance occurence in the interaction between circuit breakers and inductive instrument transformers. Existing standards lack guidance on testing for ferroresonant behaviour. The paper proposes a standardized testing procedure and presents measurements on a full-scale system. EMTP simulations complement the measurements for a broader network topology analysis, i.e. circuit breaker capacitance combinations. EMTP simulations are validated for a 170 kV voltage transformer and a combined instrument transformer, showing accuracy within 10%. The paper also extends the EMTP modelling application to a 420 kV voltage power transformer during design phase, ensuring it doesn't experience ferroresonance. This study offers a practical approach for testing and simulating ferroresonance in inductive instrument transformers, contributing to the safe operation of power networks.

Several Aspects of Human Exposure to Low Frequency Fields; Incident and Internal Field Dosimetry Procedures and Related Legal issues

Dragan Poljak — 2024-06-04

The paper deals with simple and efficient dosimetry procedures for human exposure to low frequency (LF) electric and magnetic fields at single and multiple frequencies, respectively. The electromagnetic interference (EMI) sources of interest are overhead power lines and transmission substations. Electric and magnetic fields due to EMI sources are either calculated or measured. Theoretical dosimetry is based on scalar potential integral equation (SPIE) for the case of the electric field assessment while the magnetic fields are computed by means of the Biot-Savart law. The internal fields in the human body are determined by using the canonical body models (disk model and cylindrical model). The obtained results are compared to exposure limits proposed by national and international legislation, respectively (National Gazette No 146/2014, 31/2019, 59/2016) and ICNIRP International Commission on Nonionizing Radiation protection). Finally, legal issues pertaining to human exposure to LF fields are addressed.