Capacity Of Power Transformers Research Articles

An individualized adaptive distributed approach for fast energy-carbon coordination in transactive multi-community integrated energy systems considering power transformer loading capacity

The optimization of multi-community integrated energy systems (MCIES), as a proficient means of integrating distributed energy resources and diverse loads, poses a compelling challenge. This challenge revolves around strategically harnessing the energy-carbon synergy advantages within these systems, while factoring in the heterogeneity among different communities and the constraints imposed by electrical connectivity devices. Facing the challenge, this paper proposes an individualized adaptive distributed approach for energy-carbon coordination in MCIES with power transformers (PT-MCIES). Firstly, a feasible region is constructed based on current and temperature limits to assess the loading capacity of power transformers. Based on this, a transactive energy (TE) based co-optimization model for PT-MCIES considering energy sharing and carbon trading is developed, where rolling horizon optimization is adopted to cope with the randomness from renewable energy and loads. For the TE problem, the alternating direction method of multipliers (ADMM) algorithm is employed to achieve distributed optimization. Uncertain renewable energy and loads, along with variable rolling horizons, make it difficult for the traditional ADMM to ensure convergence speed in the co-optimization of PT-MCIES. Accordingly, an individualized adaptive ADMM (IAADMM) embedded a spectral penalty parameter selection rule is adopted. Simulation results show that the proposed scheduling model can effectively guarantee the safe operation of power transformers with the suggestion of a feasible region, and achieve higher economic and environmental benefits than the reference one that ignores energy-carbon coordination. Furthermore, the proposed IAADMM exhibits superior performance in terms of convergence speed and robustness to the initial penalty parameter when compared to ADMM and its various variants.

THE RELIABILITY ASSESSMENT OF POWER TRANSFORMERS

This research investigated the assessment of power transformer reliability with emphasis on the transmission network within Rivers State in Nigeria, focusing on the perspectives of electricity consumers, organizational personnel, and business operators using descriptive survey. The study encompassed the entire population of 725,372 electricity consumers in the Port Harcourt Electricity Distribution Company (PEDC) in Rivers State, which included both households and business owners. To select a representative sample, the Convenience Sampling Technique was employed, resulting in the inclusion of 390 electricity consumers in Rivers State. Data collection utilized the Consumers Perception of Electricity Power Transformer Reliability (COPEPT) questionnaire and Structured Interview, with the instrument's reliability established through the test-retest technique, yielding a reliability coefficient for each investigation. Research questions were addressed through the weighted mean score (WMS) analysis. Key findings indicated dissatisfaction among electricity consumers in Rivers State, primarily attributed to factors such as transformer age, overall condition, uncontrolled overloading, adverse weather conditions, and inadequate transformer capacity to meet increasing demand. Addressing these issues, different approaches including upgrading or replacing outdated transformers, implementing limits on transformer loading, introducing robust earthing systems, and increasing transformer capacity, were recommended to enhance consumer satisfaction and overall reliability. The study further revealed that persistent power transformer failures resulted in power outages, adversely impacting businesses, households, communication, and contributing to reduced production and national income. Based on these findings, recommendations in the form of strategies were provided, emphasizing a comprehensive analysis of power surge control during adverse weather conditions, a plan for upgrading or replacing outdated transformers, an assessment of power transformer capacity needs, and collaboration with relevant stakeholders to develop strategies mitigating the negative economic impact and enhancing communication with consumers.
 Keywords: Reliability Assessment, Power Transformers, Rivers State and Transmission Network.

Variasi Nilai Tegangan Percik Arrester Akibat Pengaruh Kapasitas Trafo Daya dan Jarak Arrester

The ability of each substation to withstand lightning and overvoltage affects the power distribution of the power system. In order to make the best operation of the substations, it is necessary to install Arresters which are used to protect the transformers in each substation from overvoltage caused by lightning surges. In this study, the effect of capacity on the placement distance of the arrester is discussed with 30 MVA and 60 MVA transformers. The purpose of this study was to determine the effect of the power transformer capacity of the four substations on the value of the arrester spark voltage and to obtain the optimal arrester installation technique at each substation using the Lagrange optimization method. Lagrange optimization method is used to determine the optimal distance between the arrester and the power transformer. The calculation results show that in a transformer with a capacity of 60 MVA, the Arrester spark voltage occurs at t = 20 microseconds with a voltage drop of 390.49 kV. Meanwhile, in a transformer with a capacity of 30 MVA, the Arrester spark time is at t = 13.9 microseconds with a voltage drop of 266.3 kV. This shows the capacity of the transformer that affects the magnitude of the Arrester's spark voltage and the spark time. Thus, the smaller the transformer capacity, the smaller the arrester spark time with the large voltage drop

Karakterizacija izolacionih papira primenom FTIR-ATR spektroskopije

The need to increase the productivity and capacity of power transformers has conditioned the production of insulating papers of a higher thermal class. For this purpose, various techniques of solid insulation modification were applied, which enable the increase in thermal and chemical stability of the insulating paper during the operation of the transformer. The applied additives, primarily dicyandiamide (DICY) and polyacrylamide (PAM), are one form of cellulose modification in the final stages of paper production. A significant difference between the papers is the nitrogen content in the paper, which is characterized by the addition of amine compounds (additives). The paper presents the application of infrared spectroscopy with totally attenuated reflection (FTIR-ATR) in the characterization of paper samples. The aim is to observe the difference between regularly kraft and thermally upgraded paper reflected in the presence or absence of characteristic functional groups for additives. The strip identification at 2194-2154 cm-1 confirmed the presence of dicyandiamide additives (DICY) in the spectrum of the sample of thermally upgraded paper, which is different compared with the spectrum of regular kraft paper.

Monitoring and updating of specific electric loads of residential and public buildings

Design organizations use standard specific load values to calculate the power consumed by residential and public buildings. The practice of operating power supply systems has shown that in most cases the actual load is 1.5 – 2.5 times less than the calculated load. The constructed cable networks and transformer substations of 0.4 / 10 kV are actually underloaded. The Association “Roselektromontazh” conducted research of TS loading of 0.4/10 kV in several cities of the Russian Federation, the results of which determined that about 80% of TS work with a maximum load of less than 30% during the year. The capacity of power transformers is selected according to account 70% of the total maximum load in the rated mode. Low load of power transformers leads to an increase in losses in them by comparing those working with a load of 70%; an inefficient use of investments. To solve this situation, it is proposed to monitor electric loads with subsequent updating of standard documents in terms of calculated specific electric loads, which will bring the calculated values closer to the actual ones to increase economic efficiency in the construction and operation of the power grid complex.

Risk‐based approach for power transformer replacement considering temperature, apparent age, and expected capacity

Due to the limited availability of end-of-life failure data of power transformers by electric utilities, planning the replacement of power transformers is a challenging task for utility engineers. Transformers can be replaced based on their health indices, but they do not allow utility engineers to quantify risks posed by transformer failures. In that context, the study proposes a novel risk-based approach to plan the replacement of aged power transformers considering their temperature, apparent age, and expected capacity. The approach comprises a methodology that incorporates power transformers' winding hottest-spot temperature and apparent age into the conventional end-of-life failure model, a methodology that calculates the expected capacity of power transformers, a novel transformer ranking index, and a methodology that calculates the optimum year of replacement. Subtransmission and distribution substations were included in the IEEE Reliability Test System to evaluate the performance of the approach. The results show that incorporating the winding hottest-spot temperature and the apparent age into the end-of-life failure model can make a significant improvement on transformer replacement decisions in the event of limited availability of failure data. Results further suggest that end-of-life failures of fans and oil pumps can have an impact on the prioritisation of transformer replacement.

Issues on optimization of operating modes of power transformers

The article presents measure to optimize the operating modes of power transformers in order to minimize losses of electrical energy. The influence of actual voltage and service life of power transformers on electric power losses is shown. It was proposed to determine the economic capacity of power transformers taking into account the indicated factors, as well as taking into account the time of transformer switching on into the electric network and the form of the load schedule.

Integration of Electric Vehicles into the Power Distribution Network with a Modified Capacity Allocation Mechanism

The growing penetration of electric vehicles (EVs) represents an operational challenge to system operators, mainly at the distribution level by introducing congestion and voltage drop problems. To solve these potential problems, a two-level coordination approach is proposed in this study. An aggregation entity, i.e., an EV virtual power plant (EV-VPP), is used to facilitate the interaction between the distribution system operator (DSO) and EV owners considering the decentralized electricity market structure. In level I, to prevent the line congestion and voltage drop problems, the EV-VPP internally respects the line and voltage constraints when making optimal charging schedules. In level II, to avoid power transformer congestion problems, this paper investigates three different coordination mechanisms, or power transformer capacity allocation mechanisms, between the DSO and the EV-VPPs, considering the case of EVs charging and discharging. The three mechanisms include: (1) a market-based approach; (2) a pro-rata approach; and (3) a newly-proposed constrained market-based approach. A case study considering a 37-bus distribution network and high penetration of electric vehicles is presented to demonstrate the effectiveness of the proposed coordination mechanism, comparing with the existing ones.

Power Transformer Loading Analysis in Order to Improve the Reliability of a Substation

This paper presents the power transformer loading analysis in order to improve the reliability of a substation. The substation that was the location of the study was the 150/20 KV Kentungan Substation, Sleman, Yogyakarta Special Region. Power transformers are the most important electrical equipment in a substation. The power transformer functions as a provider of electrical energy that has been transmitted from the power plant to then be channeled to electricity loads. In its operational it is very important to know the capacity and capacity of power transformers in serving electric loads for decades to come, with the aim that the electric power service can take place well. Therefore, the forecasting of the power transformer is important to know in the framework of the operational planning of a good substation. The results of the study indicate that the peak load of power transformers in the period 2014 to 2016 is still in a safe level, where the maximum peak load is 93% of the total capacity of the transformer. However, it is recommended that the power transformer capacity be planned to begin to anticipate the growth of loads in the coming years.

Reliability Analysis and Overload Capability Assessment of Oil-Immersed Power Transformers

Smart grids have been constructed so as to guarantee the security and stability of the power grid in recent years. Power transformers are a most vital component in the complicated smart grid network. Any transformer failure can cause damage of the whole power system, within which the failures caused by overloading cannot be ignored. This research gives a new insight into overload capability assessment of transformers. The hot-spot temperature of the winding is the most critical factor in measuring the overload capacity of power transformers. Thus, the hot-spot temperature is calculated to obtain the duration running time of the power transformers under overloading conditions. Then the overloading probability is fitted with the mature and widely accepted Weibull probability density function. To guarantee the accuracy of this fitting, a new objective function is proposed to obtain the desired parameters in the Weibull distributions. In addition, ten different mutation scenarios are adopted in the differential evolutionary algorithm to optimize the parameter in the Weibull distribution. The final comprehensive overload capability of the power transformer is assessed by the duration running time as well as the overloading probability. Compared with the previous studies that take no account of the overloading probability, the assessment results obtained in this research are much more reliable.

The effect of geomagnetically induced currents on the thermal conditions of power transformers

Methods to calculate the thermal processes and temperature of the most heated points of the tank and windings of a power transformer in conditions of flow of geomagnetically induced currents in grounded windings are developed. Dependences of additional loss in the tank and windings are obtained for a TRDN-63000/115/6.3/6.3 power transformer. It is shown that additional losses in power transformer windings are caused by the geomagnetically induced currents and depend on the first and nth harmonic components of magnetizing current, as well as on the load factor of a power transformer. The dependences of excess temperature of the most heated points of windings over ambient temperature on the geomagnetically induced current and load factor are determined. It is found that the excess temperature of the most heated point of winding over ambient temperature is also affected by the total additional loss of active power in the tank caused by the eddy currents at a geomagnetic storm. The acceptable load capacity of power transformers in geomagnetic storms with different intensities is determined in dependence on the ambient temperature. An increase in the load capacity of power transformers above set values in geomagnetic storms can lead to overheating of transformer windings and triggering of transformer gas protection, which will cause an electric power system to malfunction.

공동주택에서의 전기자동차 충전기 수용률 설정과 그 제어방법

In this paper, we have analyzed the power consumption property of EVs(Electric Vehicles) chargers established in a public place, proposed reasonable demand factors by the number of established EV chargers and its control method in apartments. The optimization of power system and the suppression of the peak load can be controlled through the proposed demand factors and charging scheduling control algorithm. In this paper, electrical design and an case analysis were carried out on a sample apartment complex to prove the effectiveness of the power system. As a result, emergency power transformer capacity has been reduced by approximately 25%, and we have confirmed that the electric rates saving and the control of peak load value is possible.

Analysis and Research on Influence of Seam on Power Transformer's Capacity on Restraining DC Bias

Transformer is irreplaceable to make sure power system running stably. It's showed in research that magnetic resistance is relevant to capacity on restraining DC bias both in three-phase three-column transformer and three-phase five-column transformer. Magnetic resistance can be changed by changing the seam size of transformer. 3D field-circuit coupling models of single-phase four-column power transformer with two kinds of seam were created by FEA in this paper. Models were simulated with different DC bias current. The analysis result of influence of seam size on power transformer's capacity on restraining DC bias was obtained by DC bias current efficient extraction and comparison of models with different seam size, which is the theoretical basis of developing new transformer with more capacity on restraining DC bias.