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This article proposes a new adaptive commissioning methodology for arc flash mitigation in steel manufacturer users considering the Tap-to-Tap varying current consumption. This process is achieved through adaptative protection settings computed to reduce the total clearing time of relays adding the restriction of the incident energy. The proposed methodology carries out the detection of abrupt changes in current consumption to detect Tap-to-Tap change in operation stages of electric arc furnaces. The application of this methodology is performed on a steel manufacturer user and shows the reduction of the incident energy values according to Tap-to-Tap operation cycle. [ABSTRACT FROM AUTHOR]

The emergence of applications which require high-voltage switches has created a tendency to use semiconductor device series stacks. These series stacks permit operation at blocking voltages above semiconductor elements’ nominal voltage. Insulated-gate bipolar transistors (IGBT) are currently utilized for controllability and switching speed, when these topologies are employed. The main challenge therewith is guaranteeing voltage balance between IGBTs, both when blocked and when switching transistors. Most of the methods which have been proposed to mitigate static and dynamic voltage unbalances increase transistor losses. The series stack loss-less high voltage switch (LHVS) which mitigates voltage unbalances, thus reducing switching losses, is presented in this paper. LHVS consists of a circuit, which ensures soft IGBT switching, an energy recovery circuit, and a gate delay compensation circuit. Additionally, the insulation voltage level is guaranteed to be equal between control circuit and high-voltage side of each IGBT. The operating principle of the LHVS is detailed in this paper, as is experimental validation which has been performed for three series stack modules. Static unbalances are reduced to 1%, while the differences between collector–emitter voltage curves in switching “on” do not surpass 8 ns, and switching losses are reduced by 41%, as compared to the hard-switching topology. [ABSTRACT FROM AUTHOR]

This article proposes a new adaptive protection setting methodology for steel manufacturers, aiming to reduce miscoordination between main feeders and current consumptions due to fault clearance or high load disconnection. By detecting abrupt changes in current consumption, the computation of different protection settings may be achieved. The application of this methodology is performed through the assessment of a steel manufacturer who sustained an arc blast of one of their protection cells, and a description of the way in which the proposal permits avoidance of such catastrophic conditions. [ABSTRACT FROM AUTHOR]

The use of a unified power flow controller (UPFC) to improve the power transfer in an EAF is investigated. The implemented equipment used techniques of hardware-in-the-loop to determine the required specific characteristics of the UPFC to improve the stability of the arc. The arc is mainly responsible for the conversion of electromagnetic power into thermal power and heat transfer. The stability studies of power networks help in improving the stability of the arc. These are the topics covered in this paper. This research also shows how it is possible to achieve an increment of the stability of the arc with the enhancement of the power quality between the main transformer and the distribution system through the decrease of the THDI, unbalance, and flicker. [ABSTRACT FROM AUTHOR]

The emergence of high voltage conversion applications has resulted in a trend of using semiconductor device series associations. Series associations allow for operation at blocking voltages, which are higher than the nominal voltage for each of the semiconductor devices. The main challenge with these topologies is finding a way to guarantee the voltage balance between devices in both blocking and switching transients. Most of the methods that have been proposed to mitigate static and dynamic voltage unbalances result in increased losses within the device. This paper introduces a new series stack topology, where the voltage unbalances are reduced. This in turn, mitigates the switching losses. The proposed topology consists of a circuit that ensures the soft switching of each device, and one auxiliary circuit that allows for switching energy recovery. The principle for the topology operation is presented and experimental tests are performed for two modules. The topology performs excellently for switching transients on each of the devices. The voltage static unbalances were limited to 10%, while the activation/deactivation delay introduced by the lower module IGBT driver takes place in the dynamic unbalances. Thus, the switching losses are reduced by 40%, when compared to hard switching configurations. [ABSTRACT FROM AUTHOR]

The objective of this paper is to analyze the decrease of the “tap to tap,” or operating time, of arc furnaces. A study that includes dynamic programming is carried out in the programming of operation of electric arc furnaces. Optimization of the operation is performed at a later phase of the research. Each step of the process is analyzed or put into operation following the direction of an expert. Following specific operating conditions, the behavior of the furnace is characterized and the relationship between voltage levels in the secondary arc is identified using a circular diagram in order to find the feasible region for the optimal solution. The search is carried out in the furnace feeder, and the furnace specific mechanisms are identified in order to decrease the “tap to tap.” This analysis allows the proposal of a new optimization model that considers dynamic. [ABSTRACT FROM AUTHOR]

This paper presents a new technique to characterize electrical arc furnaces through the measurement of electric power, stationary and transient states, and the imbalance of these systems. The nonstationary behavior of the voltage and current signals in electric arc furnaces is considered, and analysis techniques of power quality in the time domain are used. ATPDraw (Electromagnetic Transient Program) was used to validate the characterization of the electric arc furnace, and the simulation results were compared with the measurements taken in a local steel manufacturing facility. [ABSTRACT FROM PUBLISHER]

Practical applications, such as the incorporation of the a new theoretical approach in the definition of the instantaneous and average compensation objectives for active power filters (APFs) in multiphase systems and the description of a global indicator for the evaluation of the power quality are introduced in this paper. In order to obtain these applications, a generalized theory of instantaneous power for nonsinusoidal unbalanced multiphase systems is proposed. The instantaneous power tensor is defined based on the tensor product between vectors of voltage and current. In addition, the simulated results are included. [ABSTRACT FROM AUTHOR]

Electric arc furnace transformers are very important in the steel production industry. Currently, it is very common for companies to buy used transformers considering the huge investment that represents the acquisition of a new transformer and also the delay in the purchase transaction. Before accepting a commercial agreement and putting the transformer into operation, it is necessary to evaluate the level of wear out due to the electrical and magnetic stresses to which the transformer is subjected. Electrical, mechanical, and insulation tests, that follow procedures stipulated in guides and standards, are performed on used transformers during the purchase process in order to identify incipient faults and to determine their general condition. A methodology is proposed to carry out these tests. In addition, a new model based on fuzzy logic is implemented to assess the level of wear of the transformer, its remaining life, and its feasibility of reuse. The fuzzy input variables of this new model are the results of the tests performed on each element of the transformer. [ABSTRACT FROM AUTHOR]

Transient behavior in grounding systems related to electric arc furnaces (EAF) might be studied using an approach to Kron’s circuit model to solve Maxwell’s differential equations in electromagnetic field theory. This paper presents a circuit model designed using Kron’s approach implemented in alternative transient program (ATP). The model is suitable to describe accurately the behavior of real complex grounding systems dealing with continuous operation of an EAF. Some ideas about the behavior of the power quality are evaluated by simulation of the grounding system in ATP. [ABSTRACT FROM AUTHOR]