A system and method for suppressing transmission line fault load shedding overvoltage
A transmission line and load shedding technology, which is applied in the field of single-phase grounding fault of ultra/ultra-high voltage transmission line, suppressing the field of transmission line fault load shedding and overvoltage, can solve the problems of resonance risk and increased reactive power demand, and achieves design and manufacturing The effect is not difficult, the principle is clear, and the structure is simple
Active Publication Date: 2016-05-25
STATE GRID CORP OF CHINA +1
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Problems solved by technology
[0004] Using a high-capacity high-resistance can reduce power frequency overvoltage, but there are two disadvantages if the high-resistance capacity is too large: (1) The reactive power demand increases correspondingly when the line is heavy-loaded; (2) When the high-resistance compensation degree is close to At 100%, there is a risk of resonance
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[0042] The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.
[0043] The main idea of this embodiment is:
[0044] Power frequency overvoltage mainly focuses on the two scenarios of single-phase grounded three-phase load shedding and ungrounded three-phase load shedding. The main factors affecting power frequency overvoltage are as follows: (1) Capacitance effect and system impedance of long no-load lines (2) Line load shedding effect; (3) Asymmetric effect of line single-phase ground fault.
[0045] Asymmetrical short-circuit is the most common fault mode of transmission lines. The zero-sequence component of the short-circuit current will increase the power frequency voltage of the sound phase, which is often called the asymmetric effect. Asymmetrical short-circuit faults in the system are most common with single-phase ground faults. When one end of the line trips and dumps loa...
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The invention provides a system and a method for retraining fault load shedding overvoltage of an electric transmission line. High-voltage parallel reactance devices are respectively arranged at two ends of the electric transmission line, one end of the electric transmission line is connected with a power supply through a line breaker, and the other end of the electric transmission line is connected with a user side system through another line breaker. Each high-voltage parallel reactance device comprises a three-phase electric reactor and a small neutral point electric reactor. According to the system and the method, the three-phase electric reactors are additionally provided with secondary side windings which are connected in a triangular connection mode, by-pass switches are connected with two ends of each small neutral point electric reactor in parallel, the by-pass switches are connected with a relaying protection system of the electric transmission line through a small reactance by-pass control system, and the small reactance by-pass control system controls switching-on and switching-off of the by-pass switches according to commands of the relaying protection system. The system and the method can limit the one-phase grounding load shedding power-frequency overvoltage within a standard permissible range under a relatively low high resistance compensation degree.
Description
technical field [0001] The invention belongs to the field of power systems, and in particular relates to a system and method for suppressing fault load shedding and overvoltage of transmission lines, and is especially suitable for single-phase grounding faults of super / ultra-high voltage transmission lines. Background technique [0002] For long EHV / UHV transmission lines, in the event of line fault load shedding, overvoltage may occur at the end of the line, which may cause line flashover or even cause equipment insulation damage in severe cases. Installing high-voltage shunt reactors on the line is a An effective overvoltage limiting means. In order to effectively limit the overvoltage, high resistance is required to have sufficient capacity. [0003] The following calculation example is used to illustrate: A and B UHV substations are connected by a transmission line with a length of 500km, the short-circuit current level of the substation is about 15kA, the operating vol...
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IPC IPC(8): H02H9/04H02H9/08
Inventor 项祖涛班连庚宋瑞华郑彬韩彬张媛媛王晓彤韩亚楠
Owner STATE GRID CORP OF CHINA