Use In Transmission Systems Research Articles

Enhanced distance-based protection for high impedance faults considering dynamic load modelling

The load can be represented by different models, including static and dynamic representations; each has different responses when analysing a power system, which also impacts the protection system's performance. For instance, in the distance relay, the estimated impedance can present overreach or underreach, affecting the selectivity of the protection and causing malfunction of triggering schemes. Under fault conditions, the load modelling effect can be magnified by the fault resistance effect, where the combination of both effects has not been addressed in the revisited bibliography. The present paper analyses the effect of load modelling for non-bolted faults in the distance relay impedance estimation. Distance relays are of interest due to their wide use in transmission systems and the emerging applications in distribution systems and microgrids. The fundamental contribution of the present paper is to propose a countermeasure for the effects of four different load types and fault resistance. The results demonstrate that the distance estimation is correctly enhanced, and then a close to the real positive sequence impedance is estimated from the relay point to the fault point. The proposal can be included in distance relays without requiring additional hardware, allowing countermeasure of the load type and fault resistance effects.

Performance Analysis of DPSK Technique for Optical Transmission Systems

The long-distance high data rate transmission is accompanied by many transmission defects, which reduce the performance of optical communication systems. Therefore, due to the need to increase data capacity for the end user, signal regeneration techniques were used to mitigate these non-linear defects in the electric or optical field. Several techniques used to modify the optical signal, which is the possible solution to reduce the limit of non-linear transmission defects, especially before converting the signal from the optical field to the electric field. Since most of the techniques used to reduce the attenuation in the optical signal do not have the ability to reduce the error rate to reach a bit error rate (BER) less than 10-10 with a transmission capacity less than -10dBm. In this paper, the performance evaluation of DPSK has been validated for its adequate use in transmission systems. Nevertheless, the performance of the DPSK optical system was assessed to rely on a different coding format such as: Return to Zero (RZ) & Non-Return to Zero (NRZ-DPSK). The system is designed to withstand high data rate on long-distance optical transmission systems. The system investigated was simulated with OptiSystemTM 13.0 commercial software. The investigated system demonstrated the ability to mitigate nonlinear impairments from the noisy optical DPSK system with high bit-error rate (BER) improvement at low power transmission. Optical DPSK demonstrates the ability to send high-rate data transmission systems for use in the next generation of optical networks.

Minimizing Losses on Distribution System by PV and Compensating Capacitors

Electric power has become an essential measure of the structure of modern society with most of today’s daily activity based on the proposition that the desired electric power constantly exists. In The Electrical Distribution System (EDS), each component is essential to the process of distributing power from the site where it is generated then supplied to the customer who utilizes it. Distribution system plays an utmost role in providing the electrical energy from its generation point to the consumers’ end by the use of transmission system. Since the R/X -Where R is the Resistance and X denotes for the impedance- ratio in the distribution network is high, the losses in the distribution system is more. The DGs employed in this work is a mix of Photovoltaic panels (PVs) for active power compensation and capacitors for reactive power compensation. Location, range and type of capacitors used in the system manipulate the amount of compensation provided by the capacitors. To decide the location and size of the DGs, a load flow will be used and losses in the radial network are considered. The backward-forward sweep load flow technique is used on the IEEE 69 bus standard network. Also, the Genetic algorithm, antlion technique and Cuckoo search algorithm (CS) are used as optimization techniques. The results are tested on the IEEE 69-bus standard test network to validate the proposed algorithms. The proposed algorithms showed enhanced results compared to the genetic algorithms.

Identification of the Most Effective Point of Connection for Battery Energy Storage Systems Focusing on Power System Frequency Response Improvement

With the massive penetration of intermittent generation (wind and solar), the reduction of Electrical Power Systems’ (EPSs) inertial frequency response represents a new challenge. One alternative to deal with this scenario may be the application of a Battery Energy Storage System (BESS). However, the main constraint for the massive deployment of BESSs is the high acquisition cost of these storage systems which in some situations, can preclude their use in transmission systems. The main goal of this paper is to propose a systematic procedure to include BESSs in power system aiming to improve the power system frequency response using full linear models and geometric measures. In this work, a generic battery model is developed in a two-area test system with assumed high wind penetration and full conventional generators models. The full power system is linearized, and the geometric measures of controllability associated with of the frequency regulation mode are estimated. Then, these results are used to identify the most effective point of connection for a BESS aiming at the improvement of the power system frequency response. Nonlinear time-domain simulations are carried out to evaluate and validate the results.

Waveguide Filters and Related Technologies:Issues and Solutions for Practical Use in Transmission Systems

Passive waveguide devices have been utilized for many applications such as optical communication, optical sensing, and so forth. Owing to the intrinsic small footprint of passive waveguide devices, they can realize many functional devices in an integrated form, such as a waveguide branch, directional coupler, Mach-Zehnder interferometer, arrayed waveguide grating (AWG) filter, microring resonator filter, and so forth. Among them, the most successful application of passive waveguide devices is the wavelength filter, as typified by an AWG wavelength multi/demultiplexer. However, for the practical use of these waveguide-type wavelength filters, many issues should be solved, such as the polarization dependence, ambient temperature dependence, the tailoring of characteristics, and sometimes trimming. In this tutorial, waveguide-type wavelength filters are reviewed from the viewpoint of functionality realized by solving such issues with ingenuity, because the most widely used functions are the wavelength filter and wavelength multi/demultiplexer.

A three-phase algorithm for state estimation in power distribution feeders based on the powers summation load flow method

State estimation approaches for use in transmission systems are common in the literature, however, there are few algorithms intended for distribution systems. This occurs, mainly, due to the small amount of measurement data available in real time and topological complexity of these systems. In this context, this paper proposes a new three-phase state estimation algorithm for radial distribution feeders, which is based on adjustment of loads from a dynamic utilization and imbalance factors, in order to model pseudo-measurements of powers, and take into account the imbalance of loads, frequently presents in feeders. The method performs the estimation by section, starting from the substation toward the loads, where estimated quantities in a section are used as pseudo-measurements to estimate the subsequent section. This procedure provides a computational optimization for real-time methodology presented here. Tests were performed in distribution feeders from a Brazilian power company and the results show satisfactory performance of developed state estimator in respect to adjustment of estimated values compared with corresponding real-time measured quantities.

Wheeling Charge Reflecting the Transmission Conditions based on the Embedded Cost Method

This paper proposes a practical and devised method for designing the wheeling charge based on the embedded cost method. In setting up the wheeling charge, one of the most important items is recovering the invested cost. Because the marginal cost method has the disadvantages regarding the above point, the embedded cost method is focused in this paper. By applying the proposed method, the wheeling charge that reflects the use of transmission systems not only gives an incentive for the efficient operation of power systems but also achieve the recovery of the invested cost by electric utilities. In order to verify the proposed method, several simulations have been conducted on the IEEE 30-bus test system.

A probabilistic approach to determining generation equivalence to a transmission facility

The electricity transmission system will be planned, operated and maintained by an independent transmission administrator in the new electric industry structure. The primary objective of any electricity transmission system administrator in the new competitive environment would be to increase the market value of the services it provides with the right amount of reliability and, at the same time, lower its costs for operation, maintenance and construction of new facilities in order to provide lower rates for customers. The electricity transmission administrator will strive to achieve this objective via many different means, one of which is to defer capital transmission facility requirements in favor of a generation solution by an independent generator to meet the growing customer load demand. In this case, the transmission capital investment deferral credit received by the independent generator will be dependent on the incremental system reliability improvement rendered by the transmission solution. In other words, the size, location and the reliability of the independent generator will be based on comparable incremental reliability provided by the transmission solution under consideration. This paper presents a probabilistic technique for determining generation equivalence to a transmission facility for use in transmission system planning studies in the new competitive environment.

A Compromise Equalizer Design Incorporating Performance Invariance

We give a solution to the problem of designing a fixed compromise equalizer for use in transmission systems involving an ensemble of random channels. The signal and noise spectra, along with the second-order statistics of the channel ensemble, are used to find the equalizer characteristic that minimizes the mean-square distortion between the equalizer output and a scaled version of the transmitter output. The key departure from previous work is that the criterion better captures practical performance invariance; specifically, the cost function incorporates the insensitivity of a well-designed demodulator to any amplitude scaling or time delay introduced by a particular channel. After demonstrating that the optimum equalizer shape is related to the principal eigenfunction of a normalized channel correlation function, we consider several special cases that give further insight into the properties of the solution. We find that the equalizer amplitude is attenuated over those frequencies where the signal-to-noise or signal-to-channel-variance ratios are small. The analysis confirms the standard engineering practice of inverting the average channel in the absence of noise and when the variance of the channel characteristics is small.

Speech compression

A bandwidth of 3-4 kc/s is obviously not being exploited to the full when used for conveying information about events happening at only a few cycles per second. A means of making more economic use of transmission systems by compressing speech has taken many years to evolve. Its progress and principles are surveyed in this article.