Daniel S. Gazzana

The Transmission Line Modeling Method to Represent the Soil Ionization Phenomenon in Grounding Systems

This paper presents an extended methodology based on the transmission line modeling method (TLM) aiming at a soil ionization representation for the simulation of grounding systems. This natural phenomenon can be represented by considering the variation of the conductive components present in the TLM circuit. The proposed analytical formulation is introduced with a focus on the computational implementation of the TLM method in one dimension. The method is not subject to divergent solutions, being numerically stable and the methodology can be incorporated into a general algorithm irrespective of the soil properties or characteristics of the grounding electrode and lightning surge.

A unified impedance-based fault location method for generalized distribution systems

This paper proposes an extended and unified impedance-based fault location method which accounts for the inherent characteristics of distribution systems (unbalanced operation, presence of intermediate loads, laterals, and time-varying load profile). The technique is developed using phase-component analysis, and uses only local voltages and currents as input data. The time-varying load profile of distributions systems is considered by using an iterative procedure to update the load data used in the fault location algorithm. The procedure is based on matching both magnitude and angle of the prefault load impedance at the local terminal and the load impedance estimated through a power-flow analysis. In determining the equivalent power flow paths of branched distribution feeders a power-flow-based analysis is performed, enabling the technique to be applied in large distribution systems. Aiming to extend the application of the proposed method to underground in addition to overhead distribution systems, a set of generalized fault location equations which consider the shunt admittance of the lines was used. Test results show the accuracy and robustness of the fault location algorithm to different fault types, distances and resistances, considering systems load profile variations up to ± 50%.

Improved distribution feeder topology against lightning

Energy supply is a significant resource for economic and social development. Power systems statistics shows that the lightning phenomenon is one of the most important causes of power systems outage. In this context, the paper present a study of the performance of a 23kV distribution line related to the occurrence of direct lightning in a particular point of the system, with focus in a comparative analysis of different feeders and poles configurations. The analysis is based on the calculation of flashover and backflashover using ATP-Draw version of the EMTP. The differences of the performance between the horizontal and the vertical feeder configurations with grounding system are demonstrated through the comparison of the maximum lightning current withstand by the feeder. Non-linear grounding resistance and variability of the resistivity of the soil were considered. Simulation results show that the configuration with guard-wire can improve the immunity up to 100% related to the maximum lightning current that the feeder withstand.

Improvement of an overhead distribution feeder performance against lightning considering the wire-guard protection

This paper presents a study about the influence of the wire-guard as a protection system in overhead distribution line in comparison with unprotected topology against lightning. A real feeder was considered as a case study using ATP-EMTP software. Practical aspects related to the modeling of a distribution line are presented. Simulation results show that the shielding configuration ensures a protection significantly better than the actual topology, around 10 times in terms of lightning peak current. Thus, the wire-guard can improve the immunity of distribution system against atmospheric discharges.

Transient response of grounding electrode with emphasis on the Transmission Line Modeling Method (TLM)

This paper presents practical aspects of a computational implementation based on the Transmission Line Modeling Method in one dimension (TLM-1D) for the transient analysis of grounding electrodes. Initially, an introduction on the subject with a brief revision of the state-of-the-art methodologies currently used for impulsive grounding transient evaluation is made, emphasizing TLM. In the following, aspects related to the representation of the grounding conductors are reported considering the soil ionization phenomenon in the transitory analysis. Finally, simulation results are presented and discussed.

A system for incipient fault detection and fault diagnosis based on MCSA

The paper describes a system for automated detection of incipient faults in induction machines. The system has been based on the Motor Current Signature Analysis method (MCSA) and aimed to be applied in a thermal electric power plant in south Brazil. First, the mechanism of fault evolution is introduced and clarified regarding the most common induction motor faults: stator winding short-circuits, broken and cracked rotor bars and eccentricity faults. The influence of the load condition on the fault indicator is discussed based on practical cases, obtained through fault simulations using a prototype. The main theoretical and conceptual aspects of the developed system are presented, including the signal acquisition and conditioning as well the database which stores the motor signals acquired over a time period. Some results from the practical use of the system are shown to illustrate the system capabilities.

Impedance-based fault location for overhead and underground distribution systems

This paper presents an extended formulation for fault location on electric distribution systems based on one-terminal measurement of apparent impedance. The method is developed using phase-components analysis to account for the inherent unbalanced operation of distribution feeders. Since distribution loads present a stochastic variation through time, a technique for compensation of load variation in both magnitude and angle is also presented. The proposed developments include two general fault location equations that account for any fault type. An iterative algorithm to compensate the line capacitive current component is also provided, thus enabling the application of the technique to long rural and underground systems, in addition to overhead distribution systems. Test results show the accuracy and robustness of the fault location algorithm to different fault types, distances and resistances, considering systems load profile variations up to ± 50%.

Non-technical losses identification using Optimum-Path Forest and state estimation

This work proposes a new method to identify non-technical losses in typical Electrical Power Distribution Systems (EPDS). Aiming to improve the efficiency of on-site inspection for fraudulent clients, the consumers are classified in suspects and non-suspects using the Optimum-Path Forest (OPF) classifier. The authors propose an improvement to this method using results of a Distribution State Estimator (DSE) and geographic information. The method is tested in the IEEE 123 Bus Test Feeder considering a group of consumers for each load. The consumers are based on typical Brazilian residential consumers. The results indicate that the proposed method improves the performance of previously developed techniques and is suitable for both typical and smart EPDS. The best results are obtained when the DSE and OPF are associated using normalized data as the input for this hybrid approach, with expected success rate of up to 72.43% for on-site inspections in the EPDS test system.

An Improved Soil Ionization Representation to Numerical Simulation of Impulsive Grounding Systems

This paper presents a hybrid method based on the transmission line modeling method (TLM) aiming to represent the soil ionization effect for grounding systems simulation. This natural phenomenon can be better represented by taking into account the variation of the conductive components present in the TLM circuit and considering the residual resistivity remaining in the soil. The proposed analytical formulation is developed with a focus on the computational implementation of the method. The model is validated by comparing synthetized test results with measured data and other numerical models (residual resistivity, TLM, and analytical model). High precision together with an easy to implement formulation indicates that the methodology presents potential for real-life applications.

Effect of shielding and grounding on lightning performance of 23kV distribution feeders

This paper presents a study of the behavior of distribution feeders against lightning, where the magnitude of the surge caused by this phenomenon is calculated. The feeder model and the lightning phenomena have been implemented in the electromagnetic transients program ATP-Draw. The magnitudes of the surges are obtained by numerical simulations in this program. Simulations were performed for cases where the lightning impacts the wire-guard or the phase conductor. A sensitivity study to establish the parameters that influence the maximum values of the surge is also performed. The model is applied to a rural distribution line in southern Brazil, where very often lightning causes insulation failure and power cuts. The results show how to improve the feeder protection in order to enhance the level of system reliability.