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This paper presents a new impedance based fault location method in the case of single phase to earth faults. This method utilized the measured impedance by distance relay and super imposed current factor, which is the ratio of post-fault current to super imposed current, to discriminate the fault position on the line. This method is robust against the fault resistance. The presented method only uses...
Different from traditional utility grid, a microgrid contains a lot of VSC (voltage source converter) interfaced distributed generators which has more controlled variables than the common used synchronous generator. VSC can be operated in active power - reactive power (PQ) mode, active power - voltage (PV) mode, voltage - frequency mode (Vf), etc. The control strategy selection has large impact on...
This paper explores the potential future need for fault current limitation in the UK's power system, and some of the technical implications of this change. It is estimated that approximately 300–400 distribution substations will require fault current limitation, based on the statistical analysis of the projected fault level “headroom” (or violation). The analysis uses a UK electrical system scenario...
This work is about the negative effects of protection devices during current transformer (CT) saturation because the performance of the protection devices such as differential and impedance relays is mainly based on the operating condition of the CTs. Distorted secondary currents due to CT saturation depending on the magnitude of the fault current and a remnant flux in the iron core can cause misoperation...
The paper describes the abstract concept of Process Bus defined in IEC 61850 9-2 and then focuses on the implementation agreement that ensures the interoperability between merging units and protection devices from different manufacturers. The components of the Merging Unit, the requirements for its performance and time synchronization are described. Protection and recording applications based on the...
This paper outlines the importance of the engineered cable cleat when considering power system protection and installation design. Particular focus is placed on the correct specification of the cable cleat in relation to the peak prospective fault current on any given installation.
A scalable and pervasive communication infrastructure represents a crucial issue in both structuring and operating modern power systems. In addressing this problem, this paper evaluates the potential role of cooperative wireless sensor networks. In order to establish their suitability for a typical set of monitoring and supervision functionalities required by Wide Area Monitoring Systems, the performance...
The installation of Distributed Generation (DG) imposes many challenges in the design of distribution systems; one of which is protection coordination. Distributed generation can affect the re-closer-fuse coordination which could lead to nuisance tripping and loss of power. In this paper, the re-closer fuse coordination problem is investigated and it is proposed to use a fault current limiter to mitigate...
Unit protection schemes for auto-transformers can be either based on autotransformer ampere-turn balance or based on first Kirchhoff low between galvanically interconnected parts. The most commonly used auto-transformer unit protection schemes will be described in this document. Advantages and disadvantages of the schemes will be discussed. Finally captured disturbance recordings in existing auto-transformer...
A novel busbar protection scheme based on wavelet transform is proposed in this paper. This busbar protection scheme utilizes the characteristic of multi-resolution signal decomposition of wavelet transform to decompose the fault current signals into different frequency bands. The differential current signals are computed from the decomposed current signals. This busbar protection scheme utilizes...
Positive feedback anti-islanding controls are designed within the inverter controllers to facilitate the islanding detection for the inverter-based distributed generation (DG). These anti-islanding controls, however, can have influence on the dynamics of DG systems. This paper investigates the impact of the positive feedback anti-islanding controls on the small-signal stability of the grid-connected...
For a long UHV line with large distributed capacitance, the lumped parameter model of SC line is no longer valid. The apparent impedances of distance relay on series compensated line are derived and analyzed in details based on the distributed parameter model. Results show that the apparent impedances are influenced by the location of series capacitors. The sensitivity of relays is reduced largely...
The power systems blackouts regularly occur around the world evidencing that the structure of protection of power system need to be improved. The already available protections in the case of disturbance, does not always allow localize emergency with following self-restoration of the normal operation conditions without personal participation. Taking into account the above considerations the research...
This paper reports on the importance of automation of power systems in reducing power downtime after faults. Traditionally power utilities used fault calls from customers to detect power outages. Following this maintenance team would be dispatched to the scene, to first identify the location of fault and then isolate the fault area through switching activities, effect repairs and then restore power...
This paper proposes a method of the relay settings of protective relay coordination for Micro-grid using modified particle swarm optimization algorithm. The key issue in selecting the relay settings is to achieve the minimum possible operating times while maintaining coordination among all relays. The relay coordination problem is solved by improving the initialization and weight of PSO algorithm...
In this paper the performance of a new fault component impedance distance relay based on voltage amplitude comparison is evaluated and its capability to mitigate the impact of UPFC on the apparent impedance measured by the relay is analyzed. As the impact of shunt branch of UPFC on the apparent impedance is mainly due to the fault resistance; thereby the proposed relay can perform better than the...
This paper presents a transient probabilistic-based technique for earth-fault detection in isolated and compensated neutral medium voltage networks. In these networks, the magnitudes of the fault currents are very small and the straight comparison of magnitudes may lead to risk of malfunction, especially at high fault resistance. The proposed technique is based on Bayesian theorem for selecting the...
This paper utilizes a significantly improved phase domain synchronous machine model [3] to test a multi-function relay model created for a real time digital simulator. One of the features of the machine model is its capability of simulating stator internal faults. Third harmonic voltage on the neutral and terminals of the machine and its variation with load and stator-ground faults is accurately represented...
This paper presents an accurate algorithm for locating faults on a series-compensated line. It applies two-end currents and one-end voltage and thus can be applied with current differential protective relays. The algorithm applies two subroutines and the procedure for selecting the valid subroutine. The algorithm has been evaluated using the fault data of ATP-EMTP versatile simulations of faults on...
The non-linear behaviour of silicon carbide varistors can be used to prevent high voltages from damaging protection systems, used in electricity T&D networks. Such ‘overvoltages’ may be created when high current transients are incident on high impedances within the protection systems. These may be due to the type of protection system used or created when current transformers are left in open circuited...
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