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This paper presents a new method for islanding detection in distributed generations. In the proposed method, the current transient signal at the utility side of the circuit breaker is processed using wavelet transform. Also the maximum value of wavelet transform distinguishes islanding conditions from non-islanding ones. This technique is very effective in the islanding detection at different target...
Microgrids can provide economic and environmental benefits, but their performance poses great technical challenges in control, protection and energy management. Microgrids can be operated either grid-connected or islanded mode. Such dual configuration capability produces challenges on the design of the protection system. Fault current magnitudes will change depending on the microgrid operating mode...
Capacitive voltage transformer (CVT) is widely used to convert high voltage signals to low voltage ones for measurement, protection and control. It has poor dynamics which can lead to maloperation of protective relays. Moreover, CVT has a non-smooth frequency response and limited band width which make it inappropriate for system harmonic measurements. This paper proposes a new method for decreasing...
PMUs play an essential rule in monitoring and control of power network. However, it is not possible to install PMUs at all buses of network, due to economical and technical constrains. Therefore, optimal PMU placement (OPP) is done to obtain full observability of network with minimum number of PMUs and maximum redundancy. On the other hand, presence of HVDC links in power network and operating in...
Power transformers as an important and expensive apparatus in the power system must be protected against the faults and should be monitored permanently to increase power system reliability and to decrease maintenance costs. Internal Turn-Turn faults (TTF) are the most common failures in power transformers, which could seriously reduce the useful long life of these equipment. Although the common protection...
In this paper, a new approach for controlling the Static Synchronous Series Compensator (SSSC) during the fault condition is proposed. To limit the flow of large line currents, and therefore protect the SSSC and other system components, a fault limiting function is exploited in the SSSC operation.
In this paper, a novel method is presented to detect and classify turn-turn faults (TTF) in stator winding of the synchronous generators on the basis of resulting harmonics contents in the terminal voltage waveforms. Analytical results by using Decision Tree (DT) show that this algorithm is practicable using only the first harmonic of residual voltage and only two harmonic component values. Simulations...
During the incidence of major disturbances in a large interconnected power network, frequency deviates from its nominal value. This deviation affects the estimated parameters of the phasor. This is especially very important during fault in transmission lines and generator terminals, because under fault conditions, the exponentially decaying dc component appears in current and voltage signals. An innovative...
In this paper, a novel static external network reduction appropriate for fault studies and relay coordination in transmission system is proposed. By applying the proposed method to IEEE 14-bus network and Hormozgan Transmission Network, its major advantages, simplicity and accuracy (less than 5% error) have been confirmed in comparison with accurate classic and approximate engineering methods. Conforming...
In this paper, a novel analysis is performed to determine the bias of Weighted Least Squares (WLS) power system state estimator to find out how much different placements of Phasor Measurement Unit (PMU) will affect the state estimator's bias behavior whereas the network parameters are subjected to different quantities of uncertainties for a given measurement uncertainty. The lack of unbiasedness is...
In electric railways, thyristor rectifiers are used in order to control the speed. As a consequence in addition to substantial input lead current, an enormous amount of harmonics is injected into the grid. To avoid such harmonics as well as reactive power compensation, reactive power hybrid filters consisting of active and passive filters are utilized. Hybrid filters have several different structures...
A high speed cumulative determinant-based fault detection algorithm is presented in this paper. The proposed algorithm is proven to be faster and more reliable than other conventional sample-based methods such as sample to sample, cycle to cycle and cumulative sum based algorithms especially for high impedance faults. In the developed methodology, the impact of important parameters such as noise,...
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