scholarly journals Analysis of Internal Overvoltages in Transformer Windings during Transients in Electrical Networks

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2644 ◽  
Author(s):  
Jakub Furgał ◽  
Maciej Kuniewski ◽  
Piotr Pająk
Keyword(s):  
Power Systems ◽  
Electromagnetic Waves ◽  
Power Transformer ◽  
Electrical Power ◽  
Operating Conditions ◽  
Electromagnetic Transients ◽  
Electrical Network ◽  
Electrical Networks ◽  
Insulation Systems ◽  
The Impact

Due to the increasing requirements for the reliability of electrical power supply and associated apparatus, it is necessary to provide a detailed analysis of the overvoltage risk of power transformer insulation systems and equipment connected to their terminals. Exposure of transformer windings to overvoltages is the result of the propagation condition of electromagnetic waves in electrical networks and transformer windings. An analysis of transformer winding responses to transients in power systems is of particular importance, especially when protection against surges by typical overvoltage protection systems is applied. The analysis of internal overvoltages in transformers during a typical transient related to switching operations and selected failures is of great importance, particularly to assess the overvoltage exposure of insulation systems in operating conditions. The random nature of overvoltage phenomena in electrical networks implies the usage of computer simulations for the analysis of overvoltage exposures of electrical devices in operation. This article presents the analysis of the impact of transient phenomena in a model of a medium-voltage electrical network during switching operations and ground faults on overvoltages in the internal insulation systems of transformer windings. The basis of the analysis is simulations of overvoltages in the windings, made in the Electromagnetic Transients Program/Alternative Transients Program (EMTP/ATP) using a model with lumped parameters of transformer windings. The analysis covers the impact of the cable line length and the ground fault resistance value on internal overvoltage distributions.

scholarly journals Analysis of the influence of non-sinusoidal and unbalanced network modes on induction motors

2021 ◽  
Vol 289 ◽  
pp. 01002
Author(s):  
Ngo Van Cuong ◽  
Lidiia I. Kovernikova
Keyword(s):  
Power Systems ◽  
Power Quality ◽  
Induction Motors ◽  
Electrical Power ◽  
Electrical Energy ◽  
Operating Conditions ◽  
Premature Aging ◽  
Electrical Network ◽  
Electrical Networks ◽  
Electrical Power Systems

The parameters of electrical network modes do not correspond the requirements GOST 32144-2013 of Russian and the National technical regulation of Vietnam. In real operating conditions in electrical networks in non-sinusoidal and unbalanced modes there are harmonic components of voltages and currents as well as voltages and currents of negative sequence. They cause additional losses of active power, which leads to additional heating and causes premature aging of the insulation, and as the result, the reduction in the service life of induction motors. Currently, we see that the process of formation of intelligent electrical power systems is underway. Systems for continuous monitoring of power quality indices and parameters of electrical systems modes are being developed. These systems can be supplemented with programs for calculating characteristics that issue the warning when the unfavorable influence of the parameters of non-sinusoidal and unbalanced modes is detected on various electrical equipment of both electrical power systems and consumers of electrical energy. The paper provides an overview of the characteristics used to analyze, assess and predict the influence of poor power quality associated with non-sinusoidal and unbalanced of currents and voltages on induction motors. A computer program was developed to calculate these characteristics. The program was used to study the influence of non-sinusoidal and unbalanced modes on the induction motors of the coal sorting plant of the Vietnamese company “Cua Ong-Vinacomin”.

scholarly journals Overvoltage Impact on Internal Insulation Systems of Transformers in Electrical Networks with Vacuum Circuit Breakers

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6380
Author(s):  
Marek Florkowski ◽  
Jakub Furgał ◽  
Maciej Kuniewski ◽  
Piotr Pająk
Keyword(s):  
Power Systems ◽  
Circuit Breaker ◽  
Dielectric Strength ◽  
Electrical Network ◽  
Electrical Networks ◽  
Circuit Breakers ◽  
Zero Crossing ◽  
Vacuum Circuit Breaker ◽  
Insulation Systems ◽  
The Impact

Vacuum circuit breakers are increasingly used as switching apparatus in electric power systems. The vacuum circuit breakers (VCBs) have very good operating properties. VCBs are characterized by specific physical phenomena that affect overvoltage exposure of the insulation systems of other devices. The most important phenomena are the ability to chop the current before the natural zero crossing, the ability to switch off high-frequency currents, and the rapid increase in dielectric strength recovery. One of the devices connected directly to vacuum circuit breakers is the distribution transformer. Overvoltages generated in electrical systems during switching off the transformers are a source of internal overvoltages in the windings. The analysis of the exposure of transformers operating in electrical networks equipped with vacuum circuit breakers is of great importance because of the impact on the insulation systems of switching overvoltages (SO). These types of overvoltages can be characterized by high maximum values and atypical waveforms, depending on the phenomena in the circuit breaker chambers, system configuration, parameters of electrical devices, and overvoltage protection. Overvoltages that stress the internal insulation systems are the result of the windings response to overvoltages at transformer terminals. This article presents an analysis of overvoltages that stress the transformer insulation systems, which occur while switching off transformers in systems with vacuum circuit breakers. The analysis was based on the results of laboratory measurements of switching overvoltages at transformer terminals and inside the winding, in a model medium-voltage electrical network with a vacuum circuit breaker.

scholarly journals Integrated Risk Assessment for Robustness Evaluation and Resilience Optimisation of Power Systems after Cascading Failures

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 2028
Author(s):  
Jesus Beyza ◽  
Jose M. Yusta
Keyword(s):  
Power Systems ◽  
Circuit Breaker ◽  
Recovery Process ◽  
Daily Basis ◽  
Operating Conditions ◽  
Power Lines ◽  
Mixed Integer ◽  
Electrical Network ◽  
Overload Capacity ◽  
The Impact

Power systems face failures, attacks and natural disasters on a daily basis, making robustness and resilience an important topic. In an electrical network, robustness is a network’s ability to withstand and fully operate under the effects of failures, while resilience is the ability to rapidly recover from such disruptive events and adapt its structure to mitigate the impact of similar events in the future. This paper presents an integrated framework for jointly assessing these concepts using two complementary algorithms. The robustness model, which is based on a cascading failure algorithm, quantifies the degradation of the power network due to a cascading event, incorporating the circuit breaker protection mechanisms of the power lines. The resilience model is posed as a mixed-integer optimisation problem and uses the previous disintegration state to determine both the optimal dispatch and topology at each restoration stage. To demonstrate the applicability of the proposed framework, the IEEE 118-bus test network is used as a case study. Analyses of the impact of variations in both generation and load are provided for 10 simulation scenarios to illustrate different network operating conditions. The results indicate that a network’s recovery could be related to the overload capacity of the power lines. In other words, a power system with high overload capacity can withstand higher operational stresses, which is related to increased robustness and a faster recovery process.

scholarly journals Assessment of the Impact of the Rigidity of Nodes on the Operating Reliability of EPSs

2019 ◽  
Vol 139 ◽  
pp. 01070
Author(s):  
Nailya Chemborisova
Keyword(s):  
Power Systems ◽  
Short Circuit ◽  
Electrical Power ◽  
Operating Conditions ◽  
Electrical Power Systems ◽  
Operating Reliability ◽  
The Matrix ◽  
Active Power Losses ◽  
The Impact ◽  
Short Circuit Currents

The operating reliability of electrical power systems is mostly based on the topology and parameters of the schemes considered in this article. The preliminary (before the calculation of operating conditions) analysis of the rigidity or sensitivity of nodes, based on the matrix of node conductivity, allows for evaluating and increasing the controllability of conditions by voltages and limiting short-circuit currents, making the reduction of active power losses in the grid more efficient. A conclusion was made regarding the consistent effects of changes in the node rigidity on increasing the EPS operating reliability.

The influence of ultrasound signal parameters on sonoluminescence light intensity

2013 ◽  
Vol 62 (4) ◽  
pp. 605-612
Author(s):  
Marek Szmechta ◽  
Tomasz Boczar ◽  
Dariusz Zmarzły
Keyword(s):  
Acoustic Emission ◽  
Acoustic Waves ◽  
Power Transformer ◽  
Electrical Power ◽  
Partial Discharges ◽  
Research Project ◽  
Insulation Systems ◽  
Secondary Phenomenon ◽  
New Research ◽  
The Relationship

Abstract Topics of this article concern the study of the fundamental nature of the sonoluminescence phenomenon occurring in liquids. At the Institute of Electrical Power Engineering at Opole University of Technology the interest in that phenomenon known as secondary phenomenon of cavitation caused by ultrasound became the genesis of a research project concerning acoustic cavitation in mineral insulation oils in which a number of additional experiments performed in the laboratory aimed to determine the influence of a number of acoustic parameters on the process of the studied phenomenona. The main purpose of scientific research subject undertaken was to determine the relationship between the generation of partial discharges in high-voltage power transformer insulation systems, the issue of gas bubbles in transformer oils and the generated acoustic emission signals. It should be noted that currently in the standard approach, the phenomenon of generation of acoustic waves accompanying the occurrence of partial discharges is generally treated as a secondary phenomenon, but it can also be a source of many other related phenomena. Based on our review of the literature data on those referred subjects taken, it must be noted, that this problem has not been clearly resolved, and the description of the relationship between these phenomena is still an open question. This study doesn’t prove all in line with the objective of the study, but can be an inspiration for new research project in the future in this topic. Solution of this problem could be a step forward in the diagnostics of insulation systems for electrical power devices based on non-invasive acoustic emission method.

scholarly journals Predicting the influence of the non-sinusoidal network mode on power transformers

2019 ◽  
Vol 114 ◽  
pp. 04005
Author(s):  
Ngo Van Cuong ◽  
Lidiia I. Kovernikova
Keyword(s):  
Service Life ◽  
Electric Power ◽  
Power Quality ◽  
Electrical Equipment ◽  
Operating Conditions ◽  
Transformer Oil ◽  
Power Transformers ◽  
Electrical Network ◽  
Electrical Networks ◽  
Current Harmonics

The parameters of electrical network modes often do not meet the requirements of Russian GOST 32144-2013 and the guidelines of Vietnam. In the actual operating conditions while there is the non-sinusoidal mode in electrical networks voltage and current harmonics are present. Harmonics result in overheating and damage of power transformers since they cause additional active power losses. Additional losses lead to the additional heat release, accelerating the process of insulating paper, transformer oil and magnetic structure deterioration consequently shortening the service life of a power transformer. In this regard there arises a need to develop certain scientific methods that would help demonstrate that low power quality, for instance could lead to a decrease in the electrical equipment service life. Currently we see a development of automated systems for continuous monitoring of power quality indices and mode parameters of electrical networks. These systems could be supplemented by characteristics calculating programs that give out a warning upon detection of the adverse influence of voltage and current harmonics on various electrical equipment of both electric power providers and electric power consumers. A software program presented in the article may be used to predict the influence of voltage and current harmonics on power transformers.

scholarly journals Indices to Assess the Integration of Renewable Energy Resources on Transmission Systems

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Alexandros I. Nikolaidis ◽  
Francisco M. Gonzalez-Longatt ◽  
C. A. Charalambous
Keyword(s):  
Renewable Energy ◽  
Power Systems ◽  
Renewable Energy Sources ◽  
Ghg Emissions ◽  
Electrical Network ◽  
Transmission Network ◽  
Renewable Energy Resources ◽  
Continuous Increase ◽  
And Control ◽  
The Impact

The continuous increase on the penetration levels of Renewable Energy Sources (RESs) in power systems has led to radical changes on the design, operation, and control of the electrical network. This paper investigates the influence of these changes on the operation of a transmission network by developing a set of indices, spanning from power losses to GHG emissions reduction. These indices are attempting to quantify any impacts therefore providing a tool for assessing the RES penetration in transmission networks, mainly for isolated systems. These individual indices are assigned an analogous weight and are mingled to provide a single multiobjective index that performs a final evaluation. These indices are used to evaluate the impact of the integration of RES into the classic WSCC 3-machine, 9-bus transmission network.

Testing of Underground Power Cables

2016 ◽  
pp. 288-317
Keyword(s):  
Power Systems ◽  
Electrical Power ◽  
Current Source ◽  
Electrical Equipment ◽  
Alternating Current ◽  
Power Cables ◽  
Test Procedures ◽  
Electrical Power Systems ◽  
Insulation Systems ◽  
Underground Power Cables

Probably 80% of all testing performed in electrical power systems is related to the verification of insulation quality. This chapter briefly describes the fundamental concepts of insulation testing including – insulation behavior, types of tests, and some test procedures. Most electrical equipment in utility, industrial, and commercial power systems uses either 50 or 60 Hz alternating current. Because of this, the use of an alternating current source to test insulation would appear to be the logical choice. However, as will be described a little later, insulation systems are extremely capacitive. For this and other reasons, DC has found a large niche in the technology. Before we can really evaluate the value of one system as opposed to the other (e.g. AC vs DC), let us examine how each type of voltage affects insulation. Testing of underground power cables are reported by NS161. (2014). IEC 6038. (1979). IEC Standard 60228. (1979). IEC60229. (2007). IEC60230. (1974). IEC60233. (1981). IEC 60332 (1974). IEC 6071 (2008). IEC 60270. (2000), IEC 60287. (2002).

scholarly journals Radiation in the Optical and UHF Range Emitted by Partial Discharges

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4334 ◽  
Author(s):  
Michał Kozioł ◽  
Łukasz Nagi ◽  
Michał Kunicki ◽  
Ireneusz Urbaniec
Keyword(s):  
Electromagnetic Waves ◽  
Electrical Power ◽  
Partial Discharges ◽  
Radio Waves ◽  
Insulation Systems ◽  
Surface Discharges ◽  
High Voltage Insulation ◽  
Solid Dielectrics ◽  
Electrode Systems ◽  
Optical Spectrophotometry

This paper presents the results of analysis of a solid dielectric’s influence on the phenomena associated with the signals emitted by surface partial discharges. Three types of electrode systems were tested, in which solid dielectrics made of pressboard, Teflon, and glass were used. The emission of such signals as radio waves in the Ultra high frequency (UHF) range and optical radiation was analyzed. The measurements were carried out in the insulation systems most commonly used in electrical power equipment, i.e., mineral oil and air. UHF and optical spectrophotometry methods were used to register the emitted signals. The obtained results indicate that the type of material from which the dielectric solid is made may have a potential impact on some ranges of emitted electromagnetic waves during the surface electrical discharges. The research topic undertaken is important in issues associated with high-voltage insulation systems and in particular with surface discharges, which are often the cause of their damage.

Sign in / Sign up

Export Citation Format

Share Document