Evaluation of the reliability of an automated filtration device in the upgraded microprocessor relay protection of contact network feeders

The article presents the results of scientific research in the field of assessing the reliability and safety of the patented automated device for filtering and isolating the first harmonic based on the PLL scheme integrated into a typical microprocessor system for relay protection of AC contact network feeders in order to meet the reliability and safety indicators during its operation. The operation of the device is based on pre-filtering the signal using a low-pass filter tuned to the cutoff frequency of the third harmonic, fixing zero timestamps, forming control pulses, rectification of the signal and subsequent inverting to obtain a pure output sinusoidal signal in frequency, phase and amplitude coinciding with the measured signal representing its first harmonic. To assess the reliability of the proposed filtering device and the allocation of the first harmonic, a model of the reliability of the device is compiled based on its basic electrical circuit. The values of the basic and operational failure rates of all elements included in the schematic diagram of the device are found, taking into account the correction coefficients of operation, acceptance, electrical load, etc. The probability of trouble-free operation of the entire device for the normalized period of operation of 20 years is determined, including, taking into account the most unfavorable case - the serial connection of all elements included in the calculated reliability model. The level of safety of operation of the device for filtering and allocating the first harmonic based on the PLL scheme is determined, options for increasing this indicator are proposed by introducing additional circuit control into the scheme and implementing the power supply subsystem of the device based on the safe decoder scheme. The results of the conducted studies confirmed the compliance of the developed device with the reliability and safety requirements for railway microprocessor relay protection devices, and the safety of the proposed device as part of the relay protection terminal is provided with appropriate circuit solutions.