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In order to do protection settings and performance analysis for doubly-fed induction generator (DFIG) wind power system, the equivalent circuit of DFIG is proposed in this paper. It has been discovered that there exists a lot of rotor speed frequency component in DFIG short-circuit current, but no equivalent circuit of DFIG has been able to represent that component distinguished from the synchronous...
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This paper describes a new, high-speed protection for EHV transmission lines. The presented scheme also performs well on series compensated lines. The High speed distance protection (ZMFPDIS) function is a six zone full scheme protection with three fault loops for phase-to-phase faults and three fault loops for phase-to-earth faults for each of the independent zones, which makes the function suitable...
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In recent years, electric power systems, in order to improve their efficiency, are increasingly using the latest innovations in the field of information and communication technologies (ICT). The combination of those systems, year by year, used of more and more sophisticated communication algorithms leading to automatic management of energy distribution process. The use of ICT communication equipment...
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In this paper the problem of wrong actions of relay protection (RP) and emergency automation (EA), including the transformer differential protection (TDP), is considered. It was found that this problem is caused by the discrepancy of TDP settings from the real operation conditions, associated mainly with the use of several gross simplifications in existing method of TDP settings calculation. Based...
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Normally the protection relay tracks the power system frequency in real time. It shall provide precise frequency measurement and adjust its sampling frequency according to the system frequency to ensure the accuracy of protection functions. So the frequency estimation is a fundamental function for the protection relay. This paper analyzes the basic principle and the performance of the conventional...
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The paper concerns reactive power compensation of nonlinear load. At the beginning power definitions and problems related to calculation of reactive power are presented. Based on the definitions, simplified distortion factor is determined. Two possibilities of reactive power compensation are analyzed. The first is equality between apparent and active power for fundamental component. The second, when...
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Traditionally, differential protections are used in a substation to protect important plants such as busbars and transformers. They are unit protection schemes which provide good selectivity and fast operating times, but do not provide backup capability. Backup protections are usually provided by overcurrent, under impedance or distance zone 2/zone 3 schemes. They are less discriminative, and because...
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This paper presents the development of an algorithm for identifying the saturation and locating the fault in relation to the protected object (internal or external fault). The methodology applied was based on the ability of detecting sudden changes of the signal through the Discrete Wavelet Transform and on the learning capacity of the Artificial Neural Network. In the localization stage, a decision...
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This paper proposes a novel implementation of a differential protection scheme using magneto-optic current sensors. The proposed all-Optical Differential Protection (ODP) scheme utilizes inherent properties of magneto-optic sensors connected in series to perform differential protection functionality. In order to demonstrate the validity of the proposed scheme, all constituent components such as optical...
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In the hybrid HVDC system, the rectifier station adopts the line commutated converter (LCC) and the inverter station adopts the voltage source converter (VSC). Since the converter structures and the control strategies at two ends of the line are different, the fault characteristics at rectifier side and inverter side are different. In order to enhance the protection sensitivity, this paper proposes...
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This paper presents a study on differential protection for transmission lines and the effect of charging currents in it. It presents a characteristics analysis of the percentage differential protection and its representation in the alpha plane, the benefits imposed are analyzed. Trajectories for CT saturation in the alpha plane are presented. A hardware-in-the-loop was assembled in laboratory, where...
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With the growth in the number of PMUs in the electrical system, the discussion and understanding of performance requirements required in IEEE standard C37.118.1-2011 and its addendum IEEE C37.118.1a-2014 is of fundamental importance for the future specification, operation and maintenance of future interconnected power grids. This paper presents an analysis of two different algorithms for calculating...
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Rotating machines are one of the most expensive and complex components in any electrical power systems. Disruptions caused by tripped motors or generators could be expensive and very time consuming to repair and return to service. Therefore, rotating machines require special attention and consideration when it comes to protection. Things become even more complicated for protection engineers when rotating...
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The DC-side line faults in high-voltage direct-current (HVDC) systems utilising voltage-source converters (VSCs) are a major concern for multi-terminal HVDC systems in which complete isolation of the faulted system is not a viable option. A number of challenges are posed by both pole-to-pole and pole-to-ground faults including the presence of very fast and high amplitude discharge current from the...
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The ongoing expansion of distributed generation connected to distribution networks may increase the possibility of unintentional islanding incidents. Traditionally, islanding, due to loss of mains condition, has been detected with active or passive methods based on local grid parameters. However, an inevitable drawback of them is a non-detection zone where the protection does not detect the islanding...
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Overheating is the single biggest cause of failure in switchgear. Modern circuit protection is provided by digital overcurrent relays which are operated by current, not heat so abnormal heating caused by loose connection bolts, ventilation failure or worn contacts is usually left undetected by conventional circuit breakers. This can lead to pre-mature failure of switchgear and also constitutes a potential...
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As Distributed Generation (DG) is increasingly integrated into the networks, intermittency issues of some types of DG (such as wind energy) will potentially increase network operating costs or decrease network security. Concern regarding these effects has grown among Network Operators and in order to avoid them, new or updated wind parks are required to provide ancillary services to the network. These...
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Rapid growth of renewable generation in Scotland has triggered a major programme of capital works to upgrade and reinforce the Transmission system in the south of the country and the interconnection with the England and Wales system. The measures taken have included voltage uprating, the installation of shunt reactive compensation, series compensation of the 400kV interconnection to England &...
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Current differential protection has stringent real-time communications requirements and it is critical that protection traffic is transmitted securely, i.e., by using appropriate data authentication and encryption methods. This paper demonstrates that real-time encryption of protection traffic in IP/MPLS-based communications networks is possible with negligible impact on performance and system operation...
