To realize the online monitoring and condition assessment of transformers in a substation, synchronous acquisition of the secondary signals from multiple interval transformers across the entire station is required. A signal acquisition system has been designed, consisting of a time synchronization unit, a signal conditioning unit, a data acquisition unit, and a host computer. The time synchronization unit synchronizes the secondary signals from multiple interval transformers. The signal conditioning unit converts the output signals from the transformers into low-voltage signals. The data acquisition unit controls the sampling timing of the analog-to-digital converter (ADC) using FPGA and reduces phase errors through a time-digital-converter-based ADC sampling delay compensation method. The host computer employs the FFT algorithm with a fourth-order Blackman-Harris window to calculate the amplitude and initial phase of the secondary signals. The test results demonstrate that the system's error meets the requirement of a 0.05-class accuracy. The measurement errors between different channels and different data acquisition units are all less than 0.05%
|