The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In this thesis, existing instability criterion and its stability indicator τ for autonomous single machine infinite-bus system (SMIB) are firstly given, which reflect convex-concave characteristics of the trajectory inΔω-δ phase-plane. On this basis, it is discussed that there are some problems when the instability criterion of autonomous SMIB system is used in non-autonomous SMIB system. Proceeding...
This paper presents a new relay for the protection of power transmission systems by using the global positioning system (GPS) and the transient polarity comparison techniques, the positional polarity comparison relay. A specially designed protection relay detects the fault generated high frequency current transient signals and records the polarity of the transient signal and the time instant corresponding...
This paper presents a new protection scheme for high-speed protection of transmission lines, the Integrated Positional Protection scheme. The concept of integrated protection is firstly introduced, in which a centralized protection relay provides the protection for multiple transmission lines. The proposed scheme is based on a specially integrated relay unit, which is installed at each substation...
The conventional dynamic phasor models of HVDC systems based on Damping Trapezoidal Integration technique are liable to numerical oscillations occurred when the network architecture changes. In order to solve this problem, this paper firstly conducts theoretical analysis on the causes of numerical oscillations resulted from the use of the conventional dynamic phasor models of HVDC systems. Secondly,...
The fast development in both microprocessor and transducer technologies has enabled fault detection techniques to be considered which were impractical in the past and encouraged interest in the utilization of fault generated transients for protection. This paper presents an integrated approach for high-speed protection of transmission lines. The technique uses a fault transient detector unit at the...
The paper presents extensive simulation studies with respect to a typical EHV transmission line systems, the proposed protection technique is able to give correct responses for various system and fault condition. Furthermore, the protection scheme offers not only fast protection for individual line section, but also integrated protection for all lines connected to the substation, therefore it could...
This paper presents a new scheme for power line autoreclosure technology, the integrated adaptive optimal reclosure. The background of the development is firstly outlined and the basic principles of these new techniques are described. These include the adaptive reclosure and the optimal reclosure techniques. The new scheme proposed is based on the latest development in digital substation, in which...
Arc grounding over-voltage is one of the worst over-voltages in the neutral isolated system. It is an important factor to be considered when selecting neutral ground mode. At present, system simulation is the main method for the study of the arc grounding over-voltage. Arc extinguish and re-ignition is simulated by controlling the switch on or off. However, the switch opening or closing need to be...
This paper presents a novel relay for power transmission line systems, which is based on a combination of positional and boundary protection principle. The relay installed at a substation is responsible for the protection of the transmission lines associated with the substation. The relay is able to offer fast trip for any fault on its protected line sections without the need for communication link...
It is difficult for existing HVDC line protections to distinguish internal fault from external fault rapidly and accurately, and the protective setting work encounters problems and difficulties. As a result, these protections have a low correct action rate. According to the feature of HVDC transmission system, this paper studies the characteristics of the natural boundary composed of the smoothing...
Based on the transient energy function (TEF) theory with classical models considered, the optimal re-closing time (ORT) can be calculated accurately. This paper mainly focuses attention on the validity and practicability analyzing of ORT obtained from this method. Firstly, the characteristics and influencing factors of the ORT are put forward and analyzed, and also the setting strategy of re-closing...
In order to study phase-frequency characteristic of zero sequence current after single-phase earth fault in neutral indirectly grounded power system, this paper starts with the line model of distribution network, and analyzes phase-frequency character of zero sequence impedance for distributed parameter line model. By simulation analyzing, for a single feeder, the factors such as transmission line...
In this paper, a method is proposed for fast and accurate online detection of transient instability based on real-time measurement. The cluster of critical machines is determined and refreshed at each time. Determination of the irrevocable loss of synchronism is made based on the geometric characteristic of critical machines trajectory. Unlike the previous extended equal-area criterion method, it...
This paper presents a novel integrated protection scheme for distribution lines based on Transient Polarity Comparison technique. In the proposed scheme, the specially designed interface units are installed at each substation and connected to the CTs on every line associated to the busbar. The unit converts the measured signals to optical format and sends to the central protection relay through a...
The re-closing time of a transmission line has a distinct influence on power system transient stability. There is an optimal re-closing time (ORT) for all transmission line faults, no matter the instantaneous fault or permanent one. Based on the transient energy function (TEF) theory with classical models considered, the ORT can be calculated accurately. This paper mainly focuses attention on the...
In this paper, a method, which is essential in initiating emergency control measures, is proposed for fast and accurate online detection of transient instability based on real-time measurement. Under a certain disturbance, the candidate critical cluster of power system is predicted and refreshed at each sampling step. The method identifies the loss of synchronism at each time step by observing the...
This paper presents a new technique for the protection of power transmission systems by using the global positioning system (GPS) and fault generated transients, the integrated positional protection technique. The technique is based on the detection and processing of fault generated high frequency transient signals, in which a centralized protection relay provides the protection of multiple transmission...
The key issue of current differential protection is the correct reorganization inrush current and the internal fault current. The algorithm based on equivalent instantaneous inductance can correctly discriminate inrush current from the internal fault current since it makes full use of the measured voltage information. For the Y-Delta connected three-phase transformer, the phase current of the delta...
On the basis of effective extraction and utilization of transient fault information, this paper presents a whole scheme of ultra- high-speed transient based protection for EHV/UHV transmission lines, which consists of the main protection, the auxiliary protection and related protection elements. All protection elements are introduced, including starting element, directional element, boundary element,...
Autoreclosure schemes have been widely used in power system and an effective way to improve greatly the dependability and stability of power systems. However, most of these schemes adopt a presetting time to reclose breaker after a tripping operation. There are many problems due to the conventional reclosure schemes. In this paper, a self-adaptive auto-reclosure criterion using dual-window transient...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.