T line protection scheme fit for distributed electrical connection

Abstract

The invention belongs to the technical field of power system relay protection and especially relates to a T line protection scheme fit for distributed electrical connection. The T line protection scheme is characterized in that a distance protection starting element acts after the fault occurs; if the inaction condition for main criterion is not met, the trip protection is performed through zero sequence voltage amplitude difference, and if not, the distance section-II protection can be used for judging the fault direction; if section-II measuring elements at three ends are judged as positive direction fault and the acting condition of auxiliary criterion section-I protection is met, the trip protection is performed through the distance section-I protection at three ends; if the acting condition of auxiliary criterion section-I protection is not met, the section-II protection at three ends is delayed and then is tripped out; if two section-II measuring elements judge as positive direction fault and one section-II measuring element judges as negative direction fault, a locking signal is sent to section-I protection at the opposite end by the negative direction fault end and the section-I protection at three ends all shall not trip out. According to the T line protection scheme fit for distributed electrical connection, the active criterion and the auxiliary criterion are organically matched and formed into a comprehensive criterion, so that the selectivity, sensitivity and reliability of the T line protection can be ensured.

Description

technical field [0001] The invention belongs to the technical field of electric power system relay protection, and in particular relates to a T-connection line protection scheme suitable for accessing distributed power sources. Background technique [0002] With the rapid development of social economy, the user's demand for power supply has increased significantly. Due to the limitation of power supply radius and power supply corridor, etc., and in order to save equipment investment and ensure power supply, the nearest T-connected outgoing line or step-down transformer is more and more common in 35kV and 110kV systems, resulting in many three-terminal or even four-terminal line. The longest of these lines is 30km, and the shortest is several hundred meters. The emergence of multi-terminal transmission lines has brought many adverse effects to the design and operation of relay protection, which makes the traditional medium and low voltage protection configuration more diffi...

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Problems solved by technology

[0009] (2) The combination of the three-terminal line lengths of the T-connection line is complex and diverse. When the lengths of the three lines are very different, such as two lines being extremely short and one line being extremely long, the distance section I is still set according to 80% of the total length of the protection line , there will be a protection blind zone, see figure 2

[0010] (3) The ability to withstand transition resistance of the three-stage distance protection is poor, and the high-impedance grounding situation may lead to misoperation and refusal of the protection

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