Main transformer low voltage backup protective device with break variable startup

Abstract

The invention discloses a main transformer low voltage backup protective device with break variable startup, relating to the power system and relay protection and setting calculation field. The main transformer low voltage backup protective device has a cabinet, in which the strong electricity and the weak electricity are separated; the cabinet is provided with an input button and an input interface; the input interface is installed in a displayer; the cabinet is internally provided with an insert and a CPU main board; the insert is plugged onto the CPU main board from the back side of the cabinet; the CPU main board is provided with a CPU; the CPU is connected to the displayer and the input button; the information is transmitted to the CPU through the input button and the input module in the displayer; the insert comprises two BO outlet inserts, a PWR power supply insert and an AI AC input insert; the two BO outlet inserts provide 7 groups of protection tripping output connection points and 3 groups of remote control output connection points and 8 kinds of signal output connection points; the insert is also provided with functions of 18 paths of remote signaling input, device time synchronization and communication; the AI AC input insert is connected to the input of the external current and voltage which are transmitted to the CPU after conversion by an insulation mutual inductor.

Description

technical field [0001] The invention relates to a main transformer low backup protection device with abrupt start and relates to the field of power system relay protection and setting calculation. Background technique [0002] The setting principle of compound voltage blocking overcurrent protection in the existing main transformer low backup protection is as follows: [0003] (1) Sufficient sensitivity when the 10kV busbar fails. [0004] (2) Avoid the rated current of the 10kV side of the main transformer, and the reliability factor is 1.2. [0005] (3) Cooperate with 220kV side compound voltage blocking (direction) overcurrent protection. [0006] ⑷ Cooperate with 10kV outgoing line overcurrent protection. [0007] However, to meet the second principle, the overcurrent setting must be greater than 1.2 times the rated current of the main transformer (assumed to be 3500A). In order to meet the fourth principle, the overcurrent setting value needs to be less than a curre...

AI Technical Summary

Problems solved by technology

However, the existing power grid is currently relatively weak. The average length of a 10kV line is about 18 kilometers. When a fault occurs at the end of the line, if the switch refuses to operate, the fault current is relatively small (assumed to be 2000A), and the configured main transformer is low-backup. The protection (assumed to be 3500A, because the fault current 2000<3500, did not reach the operating value) cannot operate, and the fault continues and expands, causing more serious equipment accidents

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