Study On The Testing Method And Testing Device Of Analog-input Merging Unit

Analog-input merging unit is widely used in intelligent substation,whose accuracy and reliability of sampling data is the precondition for measuring and protecting equipment's regular operation.In order to avoid the problem caused by poor performance of analog-input merging unit,it's of great significance to use reasonable and reliable testing method and device to verify its function and accuracy.The current research mostly focuses on the influence of merging unit on the reliability of intelligent substation protection system and doesn't fully consider the performance of analog-input merging unit.The time performance testing method using computer for timing control can only be accurate to millisecond,whose accuracy can't meet the requirement of time performance testing.The steady-state performance testing research using analog-to-digital conversion instrument with high precision requires a variety of ancillary equipment,which is not convenient for interface matching and data processing.Referring to the technical requirements of field testing items in Testing Specification for Merging Unit with Analogue Input,this paper carries out research on the time performance,communication performance and steady-state performance testing items of analog-input merging unit.The time performance,communication performance testing is realized by the high speed parallel hardware circuit based on FPGA,which improves the time resolution and accuracy.The high-precision analog signal source and standard data acquisition module are developed,which satisfy the requirement of steady-state performance testing based on standard meter method.Aiming at the time performance testing,this paper analyzes two kinds of synchronization modes of analog-input merging unit,makes sure the meaning and influencing factors of different time performance parameters,and carries out the testing method design of time performance parameters based on TDC.Aiming at the communication performance testing,according to the communication mode of analog-input merging unit,this paper carries out the testing method design of sampling value message integrity based on parsing IEC 61850-9-2(LE).Aiming at the steady-state performance testing,this paper analyzes the sampling principle of analog-input merging unit,and carries out testing method design of amplitude error,phase error based on standard meter method.Then,the overall scheme and parameter design of analog-input merging unit testing device are carried out,and the hardware circuit and hardware program of the multi-channel signal source based on 16-bit D/A circuit,the high-speed parallel timing processing and message parsing module based on FPGA,the 24-bit high-precision standard data acquisition module are developed respectively.In the end,this paper verifies the function and accuracy of testing device in the aspects of time performance,communication performance and steady-state performance.Results show that the stability of multi-channel analog signal source is better than that of ±0.1%;the timing processing and message parsing module function normally,whose output fluctuates less than 200 ns,whose time measurement accuracy based TDC is better than 300ns;the standard data acquisition module satisfies the 0.05 class of accuracy.