Power-frequency overcurrent judgment method and power-frequency overcurrent protection device

Abstract

The invention discloses a power-frequency overcurrent judgment method and device. According to the overcurrent judgment method, by adopting a time start module, a time stop module and a time data application module of the time query / comparison type to form two novel overcurrent protection devices which, with new and different structures, have the same formula, time and data method for overcurrent judgment application but different data application methods, it is possible to make quick judgment in accordance with the tested sinusoidal current sample obtaining time t, so as to get the current magnitude and carry out precise time delay control at multiple periods of time. Especially when the tested overcurrent exceeds a setting value for more than 10 times, it takes only less than 1 ms to make a judgment and output protection signals, so that current-protection dead zones are effectively eliminated. The invention can be effectively applied in occasions with short power supply lines, multiple series, small current-protection series difference and poor guarantee of protection selectivity, and achieves flexible application, easy adjustment, reliable protection, multi delay 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

Images