Phase-sensitive protection method and protection system for low-voltage power distribution protectors in coal mines

Abstract

The invention discloses a phase sensitive protection method for a coal mine low-voltage power distribution protector, which comprises steps: multi-channel synchronous sampling is carried out on three-phase voltage and three-phase current of a coal mine power grid; sampling signal values of the three-phase voltage and the three-phase current are calculated through DFT algorithm, and a real part and an imaginary part of sampling data of each channel are obtained; the maximal current phase is selected, the real part of the phase current I is Ir, the imaginary part is Ii, the real part of the corresponding phase voltage U is Ur and the imaginary part is Ui; the phase current I is rotated at a preset angle phi in a clockwise mode, the real part and the imaginary part of the phase current I after rotation are calculated, wherein the preset angle phi is 48 DEG to 59 DEG; active power P1 of the phase current I after rotation is calculated, action judgment is carried out, and if the active power P1>0 and the maximal current amplitude value is greater than the current fixed value, the phase sensitive protection action is executed. Thus, calculation complexity is small, the calculation efficiency is high, and quickness and reliability of phase sensitive protection are improved; selectivity of a short circuit protection action is improved; and protection sensitivity is improved.

Description

technical field [0001] The invention belongs to the technical field of low-voltage power distribution protectors in coal mines, and in particular relates to a phase-sensitive protection method and a protection system for low-voltage power distribution protectors in coal mines. Background technique [0002] Coal mine power supply system has short power supply lines, harsh power supply environment, long-term moisture in the equipment leading to gradual decline in insulation performance, mechanical damage, and human misoperation, etc., which can easily cause short-circuit faults in coal mine power supply equipment. If the fault is not removed in time and quickly, the power supply line will And equipment damage, serious gas explosion will occur to threaten the personal safety of underground workers. Therefore, it is very important for the safe and automatic production of coal mines to quickly and reliably remove the short-circuit fault of mine power supply equipment. [0003] A...

AI Technical Summary

Problems solved by technology

The first method requires calculating the active power and reactive power through the multiplication and accumulation of three-phase voltage and three-phase current, then calculating the apparent power, and finally dividing the active power by the apparent power to obtain the power factor. This method involves three The calculation of phase power requires a lot of calculation. If the calculation uses the multiplication and division of floating point numbers, especially the division of floating point numbers, the calculation will take more time and reduce the quickness of the protection action. For general single-chip microcomputers, the efficiency is very high. Low, if floating-point calculation is not used, the error will be relatively large, which reduces the reliability of protection

The second method involves finding the area between the sine function and the X-axis area, and involves integral calculation. This calculation accuracy is related to the number of sampling points of the ADC in one cycle. The more sampling points, the higher the calculation accuracy, and the burden on the processor. The greater the value, the lower the sensitivity of the protection, and this algorithm also needs to calculate the moment when the inductive load current sinusoidal function and the grid current sinusoidal function cross zero in the 0-π interval, which increases the computational complexity

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