The traditional relay protection device directly compares and calculates the analog signals of input current and voltage, and determines whether to trip by comparing and calculating the analog signals with a given mechanical quantity (such as spring torque) or electrical quantity (such as threshold voltage).
The computer system can only perform digital operation or logical operation, so the working process of microcomputer protection is roughly as follows: when the power system fails, the faulty power supply is converted into digital quantity through the analog input system, and then enters the central processing unit (CPU) of the computer. The protection fault information is calculated according to the corresponding algorithm and program, and compared with the calculation result, and set as a given value at any time to judge whether the fault occurs.
Once the fault in this area is confirmed, the trip relay is input according to the current state and switch value of the circuit breaker, and the switch value output system sends out a trip signal and displays and prints the fault information.
Extended data:
The microcomputer protection device adopts the latest hardware chip, which improves the technical maturity. It adopts 80c 196kbCPU, measures 14A/D conversion, and has up to 24 analog input circuits. It uses signal processing chip DSP to process and collect data, and uses fast Fourier transform to get the eighth fundamental wave. Special software automatically corrects to ensure high measurement accuracy.
Dual-port RAM and CPU are used for data conversion to form a multi-CPU system, and CAN bus is used for communication. It has the characteristics of high communication speed (up to 100MHZ, running at 80 or 60MHZ) and strong anti-interference ability. Through the keyboard and liquid crystal display unit, field observation and various protection methods and parameters can be carried out conveniently.
Copy (or data acquisition system) CPU main system on/off (or digital) input/output system analog input system, mainly to correctly convert analog quantity into required digital quantity. The main system of CPU mainly analyzes and processes the original data of analog input system to complete various relay protection functions.
On-off (or digital) input/output system, to complete all kinds of protection export tripping. Signal alarm. External contact input and man-machine dialogue.