A power frequency overcurrent judging method and protection device

Abstract

The invention discloses a power frequency overcurrent judging method and its device. Based on the overcurrent judging method, the invention uses a time start module, a time cutoff module and a time data application module in a time query mode and a time comparison mode to form two kinds of overcurrent The formula, time, and data method for judging the application are the same, but the data is used in a different way, and the new overcurrent protection device with a different structure can quickly judge according to the time t obtained by sampling the measured sinusoidal current, so as to know the overcurrent The size and the implementation of multi-period precise time delay control, especially when a measured overcurrent exceeds 10 times the set value, the time for judging and protecting the signal output is less than 1ms, which can effectively eliminate the current protection The dead zone is effectively used in the occasions where the power supply line is short, the number of stages is large, the current protection level difference cannot be opened, and the protection selectivity is difficult to guarantee. It has flexible application, simple adjustment, reliable protection, multiple delays, and high precision.

Description

technical field [0001] The invention relates to a power frequency overcurrent judging method and a protection device applied to relay protection. Background technique [0002] Quickly and accurately obtain the current value exceeding the rated value or setting value in the protected power and electrical equipment, and make accurate judgments on it in order to take corresponding measures in time to prevent the occurrence of the fault and stop the expansion of the fault in time after the fault occurs. The primary task of the relay protection device is to meet the prerequisites for the four basic requirements of selectivity, quick action, sensitivity and reliability of the protection device. [0003] In order to obtain the over-limit current amplitude in the protected power electrical equipment and judge whether it is a short-term overload current or a fault current, and whether a fault has occurred or is about to occur, most of the previous methods and devices use current tran...

AI Technical Summary

Problems solved by technology

These existing technologies have complex methods for fault current judgment and low judgment accuracy, and cannot realize multi-period and time-accurate control of fault current, and cannot cover the low overload area of ​​load current. There is a "dead zone" for protection, which cannot meet Extensive needs in today's power protection market

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