Power Frequency Variation Research Articles

Power Quality Improvement of Micro Grid by Using DVR

Power quality is defined as the degree of voltage, current, frequency and waveform of power system under designed specification of the system. While transmitting the power from one end (generation) to another (load) utility has to face some power quality issues such as voltage sag, voltage swell, harmonics, inter-harmonics, voltage imbalance, voltage fluctuation, short duration voltage variation, long duration voltage variation, transient, power frequency variation, waveform distortion etc. These power quality issues directly effect on the efficiency of the power system and performance of the load equipment’s. Problems like voltage sag, voltage swell occurs due to sudden removal of large load from the system, energization of large capacitor bank or system fault like single-line-to-ground fault. These types of problems directly effect on equipment performance and accuracy, especially on sensitive equipment’s as computer, medical instruments, some electronic devices etc. To mitigate voltage sag, voltage swell problem in power system various devices are used such as DVR (dynamic voltage restorer) Key Words: Voltage sag, Voltage swell, Power quality, MATLAB simulation, Single-phase AC system, Single-phase AC load.

Fault Detection and Diagnosis of a 3-Phase Induction Motor Using Kohonen Self-Organising Map

This paper uses the Kohonen Self-Organising Map (KSOM) to detect, diagnose, and classify induction motor faults. A series of simulations using models of the 3-phase induction motor based on real industrial motor parameters were performed using MATLAB/Simulink under fault conditions such as inter-turn, power frequency variation, over-voltage and unbalance in supply voltage. The model was trained using the input signals of the various fault conditions. Various faults from an unseen induction motor were fed to the model to test the model’s ability to detect and classify induction motor faults. The KSOM adapted to the conditions of the unseen motor, detected, diagnosed and classified these faults with an accuracy of 94.12%.

Sequence component direction element based on power frequency variation

Unlike the relatively stable network structure of the transmission and distribution network, under the new distribution network, resulting in errors in the impedance tuning of the fault directional element, misjudgment of the fault directional element, and a decrease in sensitivity. For this reason, this paper proposes a sequence component adaptive fault directional element based on power frequency variation. The sequence impedance amplitude is calculated through the measured values of the voltage sequence component and the current sequence component of the relay location. Then the phase angle of the setting impedance is determined according to various sequence components in the system. It improves the problem that the setting impedance of power frequency distance directional element is greatly affected by the amplitude and phase angle fluctuation of distribution system impedance and line impedance. The reliability and stability of the sequence component adaptive fault directional element based on the power fresquency variation are verified by Matlab simulation.

Starting Pulse Vibration Torque Analysis of Aviation Variable Frequency Asynchronous Motor Based on Low-Frequency Step-Down Starting Methods

The more electric aircraft provides 115 V/360~800 Hz variable frequency power supply for the variable frequency asynchronous motor, and the motor operation characteristics change with the power frequency variation. It causes the starting pulse vibration torque with the low-frequency power supply (360 Hz) to increase greatly and the mechanical shock and fatigue damage. Therefore, this paper proposes step-down starting method with the low-frequency power supply. Based on the electromagnetic principles generated by the starting pulse vibration torque, this paper uses a novel method of simulation data fitting to establish an approximate model of the starting pulse vibration torque. The parameter design formulas of the low-frequency step-down starting methods, including the reducing voltage, the series resistance, and the series inductance are proposed. The effectiveness of the different methods are verified, and the performance is compared through the simulation. The experimental verification of a small power asynchronous motor is completed. The simulation and experiment results show that the low-frequency step-down starting methods effectively reduce the starting peak torque, and also suppress the shock impact of starting current on the power supply.

A Novel Power-frequency Variation Protection Strategy Based on System Setting Impedance

By analyzing the protection principle of power-frequency variation and the influence of the current transformer saturation, this paper proposes a novel protection strategy based on power-frequency variation of the maximum and minimum setting impedance of the system to cope with the transformer saturation. Typical saturation cases of transmission line are analyzed and the simulation results based on PSCAD indicate that the proposed strategy could guarantee the correct operation of protection, which maintains the original operation characteristics of power-frequency variation protection.

Fast Distance Protection for Proximal Fault of EHV Transmission Line

As the full length is considered in the traditional EHV line protection, proximal circuit fault can’t be moved in an ideal short time. A fast distance protection algorithm for proximal fault of EHV transmission line is proposed in the paper. Based on differential equation model and power frequency variation principle, the method has fast response speed and small workload. And the protection for proximal fault of long distance EHV transmission lines can be correctly implemented in a very short time. The method is realized with a low pass prefilter and without digital filter. Finally, through the RTDS simulation platform, a variety of fault modes of 500kV transmission lines is realized, and the accuracy and rapidity of the algorithm is verified by the simulation result. DOI: http://dx.doi.org/10.11591/telkomnika.v11i2.1984

Agent-Based Multi-Source Wide-Area Current Protection for Systems With Distributed Generators

With the introduction of distribution generation, the distribution network changes from radial network into multi-source network, so the traditional inverse-time over-current protection based on radial network is not applicable. The demand for the research of a new type of protection strategy is urgent. This paper introduces the application of intelligent agents to the protection of the distribution system with distributed generators (DGs). The method of fault location is accomplished in two steps. First, find out the node with a T-type branch formed by the DG connection, through comparing amplitude of power frequency variation of each branch to lock the fault branch and to narrow down the fault area between two T-type nodes. So as to find out the specific fault area B, namely the smallest power-cut scope, in the sketchy fault area, amplitude comparison of fault current and PFVC at the line section’s two ends is used to discriminate whether fault occurs in this section. Once this method fails the phase relation between PFVC and load current after the shifted phase would be applied, so that fault area B is located. The scheme of protection is applicable in fault area location for complicated networks with distributed generation and the proposed intelligent multi-agent-based architecture is illustrated.