PM511V08 3BSE011180R1 Serial Communication

The PM511V08 3BSE011180R1 samples every 20 ms and saves the sampled data to the fault data area every 40 ms. When a fault occurs, the PLC records the data for 13 seconds after the fault occurs and the fault data recording process ends. When the PLC receives a transmission command from the host computer, the PLC transmits the recorded fault data to the host computer via serial communication. The host computer receives the data completely, and after data processing displays the waveform curves of the unit operation quantities U, If, P, Q, Ug (voltage given) in 7 seconds before and 13 seconds after the fault, so that the generator fault can be analysed. In this system, PLC selected SIMATIC S7-226; analogue module selection and S7-226 supporting products EM235; PLC and computer through the PC / PPI cable connection to communicate in serial mode.

PM511V08 3BSE011180R1 Define a continuous data area VW4000 to VW8998 in the PLC to save fault data. Each running volume of data occupies a 1000-byte data block with the following address assignments, U: VW4000 to VW4998 If: VW5000 to VW5998 P: VW6000 to VW6998 Q: VW7000 to VW7998 Ug: VW8000 to VW8998 When the last 13 seconds of data have been logged, the wave recording subroutine ends.

PM511V08 3BSE011180R1 sends the sampled data to the respective data block every 40 ms. A data pointer is defined for each data block, and its initial value points to the first address of the respective data block. Each time data is transmitted, the respective pointer is moved down by 2 bytes. The first 7 seconds of data (350 bytes) are recorded cyclically, i.e., if the data is full before the fault arrives, the data pointers will point to the first address of the data block again. The definition pointer index is used to record the position at which the 20 seconds of fault data begins. When the fault arrives, the data pointer points to the 13 seconds of data after the fault (the last 650 bytes), at this time the pointer index will be divided into the first 7 seconds of data before and after the two parts, the correct order is to swap the two parts before and after.