Fixed time limit protection method and device

Abstract

The invention discloses a fixed time limit protection method. The method comprises: performing AD sampling on an external signal to obtain a signal AD sampling value; calculating a signal effective value according to the signal AD sampling value; any AD sampling value in one sampling period exceedings the normal range of the sampling value; if the signal effective values of n continuous sampling periods after one sampling period exceed a preset action signal setting value, and the sum t of the continuous n + 1 sampling periods is greater than or equal to tm-t0, delaying (t0-t1) + (t0-tn) time,and sending out a protection action instruction; wherein tm is a preset action time setting value, t0 is the sampling period of AD sampling, tn is a preset value and is the time required from the sending of the protection action instruction to the completion of the protection action, t1 is the time from the first sampling point with the AD sampling value exceeding the normal range of the samplingvalue in one sampling period to the end of the sampling period, and the normal range of the sampling value is calculated by the action signal setting value. The invention further discloses a fixed time limit protection device. Compared with the prior art, the method can effectively improve the time precision of the fixed-time-limit action.

Description

technical field [0001] The invention relates to a definite time limit protection method and device, belonging to the technical field of switching appliances. Background technique [0002] With the development of smart grids, the importance of low-voltage circuit breakers is becoming more and more obvious. As the core component of circuit breakers, the functions of intelligent controllers are also becoming more and more perfect, from traditional three-stage protection plus grounding protection to voltage and power protection. , and then to the following directional protection, synchronous function, etc., the requirements for the controller are more and more stringent. However, for low-voltage circuit breakers, overcurrent protection is still the most important function, and people have higher and higher requirements for the accuracy of overcurrent delay and definite time limit action time. [0003] At present, the common overcurrent definite time limit action method is to ca...

AI Technical Summary

Problems solved by technology

In fact, there is a certain time difference t1 between the judgment of the sampling value I1 of the fault current and the judgment of the effective value I' of the fault current. It takes a period of time t n (such as figure 1 shown), due to the existence of t1 and t n, the definite time action time error is relatively large

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