Research On Condition Monitoring System Of Speaker In Nuclear Power Area

With the rapid development of nuclear power industry,more and more attention has been paid to the safety of nuclear power.The public broadcasting system is an essential electronic system in the field of nuclear power which provides emergency broadcasting and other security functions.The harsh environment in the nuclear power plant area will accelerate the aging and damage of speakers and transmission lines.In order to provide early warning and rapid response to emergencies and timely evacuation of related personnel,a speaker condition monitoring system is urgently needed to ensure the reliability of the public broadcasting system.Based on the actual requirements of CGNPC(China General Nuclear Power Group),focusing on the three application limitations of existing speaker condition monitoring systems,the inability to independently construct and operate,the inability to monitor the speaker itself,the need for additional cabling,this paper proposes and implements a kind of speaker conditions monitoring system for nuclear power applications.The main task and innovations are as follows:Firstly,aiming at the problem of detection error caused by random phase-shifting in three conventional weak signal detection methods,single-channel correlation detection,orthogonal vector dual-phase lock detection and multi-level correlation lock detection,this paper proposes a digital phase-shifting phase-locked detection method.This method uses a microcontroller unit to generate 16 times successively phase-shifted reference signal whose phase of every cycle leads ?8 to the former one,which avoids the detection error caused by random phase-shifting of the conventional phase-locked detection method.After theoretical analysis and actual test verification,the detection accuracy of this method can reach 98.1%,and the minimum detectable SNR(Signal to Noise Ratio)can reach-40 dB,which meets the application requirements of weak signal detection of this system.Secondly,this paper analyzes and compares frequency-shift keying,quadrature phaseshift keying,direct sequence spread spectrum and orthogonal frequency division multiplexing four kinds of PLC modulation technology,proposes a kind of PLC audio line bidirectional data communication scheme based on orthogonal frequency division multiplexing technology.Through the simulations of the buffer,power amplifier,power line coupling,this paper complete the design and test verification of the audio line bidirectional data communication module.This module achieves up to 1km distance PLC communication to complete the speaker detection data returning and slave controling.Then,aiming at the problem of system terminal's power supply,a system slave power supply which is powered by the main digital power amplifier and audio transmission line of the broadcasting system is designed and implemented.The power supply continuously provided operating voltages and maximum 1W output power for the slave detection module and the PLC communication module without any addition power lines.Finally,the system's architecture design and system integration are completed,and a prototype system containing one host and five slaves is set up to perform the joint debugging test under 90 dB simulated noise conditions.In 50 repeated tests,the success rate of PLC network accessing and correct rate of speaker state judgment both reached 100%,which verifies the reliability of the system.In summary,this system enables the speaker condition monitoring,data communication,power supply to be performed "collinear" so that it avoids additional communication and power supply lines,and can be constructed and operated independently of the public broadcasting system,and directly monitors the speaker itself.The system studied in this paper can finally achieve the stable monitoring of speaker state with high accuracy under up to 90 dB environment noise in nuclear power area.