Failures in power transformers are one of the most serious occurrences in a power system. Thus, the monitoring of transformers and their ancillary equipment, such as bushings, is of great importance to improving the operational efficiency of these assets. In this context, this paper presents the development of a monitoring system for the measurement of partial discharges (PDs), which are a key parameter in the analysis of insulation condition. PD measurements were performed using the electrical method. For this purpose, a capacitive coupling device was developed for bushings that works as a sensor for high-frequency signals and also as a protection apparatus to guarantee the integrity of the bushings in cases of extreme events, such as lightning surges. In addition, a computational routine is presented that applies a digital filtering process followed by a proposed step for differentiating PDs from noises. For validation, the proposed system was subjected to laboratory tests and field applications, from which the viability of the project and the efficiency in detecting PDs were verified.

The performance of salient-pole synchronous generators protection is of great importance for the stability of power systems, as they are present in large hydropower plants, subject to various abnormal operating conditions such as three-phase or two-phase faults, electromechanical disturbances and loss-of-excitation. In this context, this work proposes a testing philosophy of salient-pole synchronous generators, in order to define more accurately the setting of the protections and controls of this asset. Thus, in the developed methodology, the admittance plan (G-B) proves applicable to analyze the coordination between the loss-of-excitation protection and the underexcitation limiter, as an alternative to the power (P-Q) and impedance (R-X) planes, normally employed in literature. In modeling the problem, real data for both the hydrogenerators and the electrical network are used. The simulations were performed in a hardware-in-the loop scheme integrated by a Real Time Digital Simulator and a physical relay. Thus, analyzes are made for situations of stable power swing and partial and total loss-of-excitation. The results are useful to prove, through the monitoring of relevant variables of the hydrogenerators, the feasibility and accuracy of the G-B plane in the coordination between the protection and the control of the synchronous machine.

Synchronous generators have automatic voltage regulators with limiters that are used to prevent high or low flux in the generator by controlling the Volts/Hertz ratio. Within the operating range of this limiter, it is not necessary to activate the protection functions associated with voltage and frequency. For that, it is necessary to coordinate these limiters with such protection functions. So, this paper increases the scope of [11] and [12] by including the coordination studies between Volts/Hertz limiter with overexcitation, overvoltage and underfrequency protections of synchronous generators. A hardware-in-the-loop simulation is implemented in laboratory to test and evaluate this coordination, and the best settings for it are proposed. An actual power system was modelled in a Real Time Digital Simulator. A great quantity of tests was applied to a synchronous machine (including all its electrical protections and controls) by separately applying frequency steps and voltage steps. The hardware-in-the-loop simulator was prepared to observe an actual digital relays dynamic responses to these steps. A Volts/Hz limiter, associated with the generator under analysis, is added to the RTDS library. In addition, by analyzing the above-mentioned protections and their interaction with the Volts/Hertz limiter of the synchronous machines excitation system, it is demonstrated that the protections and the limiter should always be jointly investigated.

A novel application of the meta-heuristic “Particle Swarm Optimization” is implemented in this work to solve the problem of reconfiguration of power distribution systems in the presence of non-linear loads with the objective of minimizing the total harmonic distortion. The proposed methodology is based on the behavior of a flock of birds when flying in search of food. In order to guarantee the convergence when the distribution power network is radial and large, a heuristic rule is deployed to improve the methodology efficiency. The developed algorithm was applied to the IEEE 33-bus radial system. The results demonstrate the efficiency of the proposed method to find the optimal topology of the distribution system to reduce harmonic distortion.

This paper illustrates a method for solving the capacitor allocation problem with the purpose of reducing the active losses in an electricity network, which should operate with a voltage profile complying with the corresponding regulation. Allocation means determining the types, sizes, locations and control type of the capacitors to be installed in the power network. In this work, the optimization technique used to solve the capacitor allocation problem is the Clonal Algorithm, inspired by the behavior of the mammalian immune system. The algorithm starts with a high number of capacitors. Subsequently, such a quantity gradually decreases until a configuration with a minimum number of capacitors is found, as well as the indication of where each capacitor should be installed is determined. The objective is to ensure that the network operates with minimal losses and voltages within a pre-defined range. In order to validate the proposed methodology, the algorithm is applied to the IEEE 33-bus system. The results demonstrate the feasibility of the application of the technique.

This work presents a network reconfiguration method aimed at improving, simultaneously, stability voltage and harmonic distortion in a distribution system where non-linear loads are present. In such reconfiguration process, the meta-heuristic Particle Swarm Optimization, which uses a local search, is deployed to evaluate the stability voltage and harmonic distortion using the maximum loading supported by the network and the Total Harmonic Distortion (THD) in a multi-objective cost function. The methodology is applied to the IEEE 33-bus distribution network. The results prove the efficiency of the developed method to find the best topologies of the electrical network in relation to the maximum loading supported by the network and the level of harmonic distortion.