J. H. Estrada

Magnetic Flux Entropy as a Tool to Predict Transformer's Failures

This paper proposes magnetic flux entropy as another technique to assess electric transformer failures. The obtained tool based on entropy may reveal some irregularities, distortions, aging, overloading, and harmonics, all of them reflected over the electrical sine wave that supplies power to dwelling and industry. Some entropy concepts are reviewed and the basic equations are applied to data obtained from magnetic and infrared waves radiated by the (18 watts 110-20 V) prototype. Several experiments were made through non-invasive and indirect measurements of magnetic and thermal fluxes. Entropy, as an accepted indicator of physical complexity, is proportional to the logarithm of the number of states in a thermodynamic system. Failure prediction based on entropy of radiated magnetic waves could be easier, faster, and cheaper.

Harmonics detection in transformers by entropy of electromagnetic signals radiated

This paper presents another way to assess power quality delivered by transformers. The electro-magnetic signal entropy reveals the presence of harmonics in the industrial and domestic electric power supply. It will show some electromagnetic radiated wave measurements taken below 115 kV electric transformers circuits of Manizales city (Colombia) through a non-invasive and indirect measurement (using wireless sensors) of the power complexity transported by the supply. The electric users are concerned over the electric power quality, since poor quality causes many damages and malfunction for different kind of loads. Some industries are very sensitive and many losses occur by instabilities, harmonic distortion, shorts, line disturbances, impulses, notches, glitches, interruptions, over voltages, under voltages, wave faults, computer lockups, flicker, equipment damage (at partial load),data processing equipment PFC instability, overloading problems when switching heavy loads, overheated neutral, problems with long lines, nuisance tripping, utility metering claims, and others.

Optimal process in electric arc furnaces

Recorders provide information related to the “tap to tap” Arc Furnaces operation time. In this article, a heuristic analysis is performed for electric arc furnace operation. At a later stage of the investigation, an optimization of the operation is performed. Each step of the process is analyzed or put into operation according to the conditions of an expert. Under the specified operating conditions, furnace behavior is characterized, and the relationship between voltage levels in the secondary arc and the melting process is identified. Further, a search is carried out in the furnace s feeder, and the specific mechanics in the furnace for “Tap to Tap” decrease are identified. This analysis enables the proposal of a new optimization model, which considers dynamic programming. Part of the proposal is implemented in a 17-ton furnace, used for melting and refining.

Hybrid Simulation of Power Quality Assessment: An Application for Power Ground Grid in Arc Furnace Systems

Transient behavior in grounding systems related to electric arc furnaces might be studied using an approach to Krons circuit model to solve Maxwells differential equations in electromagnetic field theory. This paper presents a circuit model designed using Krons approach implemented in ATP. The model is suitable to describe accurately the behavior of real complex grounding systems dealing with continuous operation of an electric arc furnace. Some ideas about the behavior of the power quality are evaluated by simulation of the grounding system in ATP.

Increasing Copper Production in Electrochemical Plants Using New Small Transformer–Rectifiers in Parallel With Existing Power Rectifiers

The production of copper in electrochemical plants requires a large amount of DC current to obtain the desired copper product output. The DC current is supplied by high current thyristor-based controlled rectifiers. Many copper plants use rectifier systems designed with two or more similar transformer-rectifiers connected in parallel to obtain the desired DC current output. Parallel rectifier systems may use 12- or 24-pulses depending on rated values of DC current [1]. To maximize copper production when higher quality mineral is being processed, the DC current needs to be increased to values that exceed the designed rated output value of the transformer-rectifier. To solve this problem a smaller, supplementary low-current rectifier can be connected in parallel with the existing rectifiers to achieve the desired DC current output. This solution proves to be economical compared to other alternatives such as increasing the number of cells in the process or replacing the existing transformer-rectifiers with larger ones. This solution has been implemented in several copper plants with satisfactory results. As an example a 2 × 25 kA, 12- pulse rectifier installation was modified to a 60 kA, 18-pulse rectifier installation by adding a 10 kA auxiliary transformer-rectifier in parallel with the existing rectifiers. This modified design has operated continuously and successfully for the past 5 years. This paper will describe the requirements for determining if an auxiliary transformer-rectifier is the best solution for increasing the total DC current capacity.

Power quality assessment by entropy

This paper presents another way to assess power quality delivered by transformers. It has been shown that is possible to measure the wave form irregularity of electrical signals radiated by electrical systems by means of the sample entropy algorithm. The electro-magnetic signal entropy reveals the presence of harmonics in the industrial and domestic electric power supply. It will show magnetic radiated wave measurements taken in the closest point to the transformer PCC, through a non-invasive and indirect measurement (using wireless magnetic sensor).