大型地網接地電阻測試儀結構與原理
本儀器主(zhu)要由提供測試電(dian)流的(de)異頻電(dian)源(yuan)、電(dian)流和電(dian)壓測量電(dian)路以及微電(dian)腦測控系統組成。儀器通(tong)過測量接地(di)(di)裝(zhuang)置(zhi)的(de)電(dian)位升高與流入接地(di)(di)裝(zhuang)置(zhi)的(de)電(dian)流之比來測量接地(di)(di)阻(zu)抗。
大型地網接地電阻測試儀結構與原理
異頻恒流電源可輸出頻率為45Hz或55Hz的正弦波測試電流，輸出頻率受微電腦系統控制。其輸出經過隔離后通過儀器面板上的C1、C2兩個端子輸出。電壓放大器為一個高輸入阻抗放大器，它將P1、P2兩端的電壓放大后送給濾波器。電流放大器將從電流互感器取得的電流信號進行放大后送給濾波器。濾波器用于濾除干擾信號，只允許45Hz和55Hz信號通過。A/D轉換器用于將電壓和電流信號轉換為數字信號以便微電腦系統進行分析處理。 大型地網接地電阻測試儀用戶啟動接地阻抗(kang)(kang)(kang)測量后(hou)(hou)，儀器(qi)首先開啟異(yi)頻電(dian)(dian)(dian)源使之(zhi)輸(shu)出(chu)(chu)(chu)頻率為45Hz的(de)電(dian)(dian)(dian)流，待電(dian)(dian)(dian)流穩(wen)定之(zhi)后(hou)(hou)，微(wei)電(dian)(dian)(dian)腦(nao)系統通過A/D轉換器(qi)取(qu)得電(dian)(dian)(dian)壓和電(dian)(dian)(dian)流波形數(shu)據，進行數(shu)字濾波后(hou)(hou)計算出(chu)(chu)(chu)電(dian)(dian)(dian)壓V45和電(dian)(dian)(dian)流I45及(ji)其(qi)相位差,再進一步計算出(chu)(chu)(chu)阻抗(kang)(kang)(kang)Z45、電(dian)(dian)(dian)阻分(fen)(fen)量R45和電(dian)(dian)(dian)抗(kang)(kang)(kang)分(fen)(fen)量X45。然后(hou)(hou)，切(qie)換異(yi)頻電(dian)(dian)(dian)源的(de)輸(shu)出(chu)(chu)(chu)頻率為55Hz，經過同樣的(de)步驟后(hou)(hou)可計算出(chu)(chu)(chu)阻抗(kang)(kang)(kang)Z55、電(dian)(dian)(dian)阻分(fen)(fen)量R55和電(dian)(dian)(dian)抗(kang)(kang)(kang)分(fen)(fen)量X55。取(qu)Z45 和Z55的(de)平均值作為工頻接地阻抗(kang)(kang)(kang)Z50。后(hou)(hou)，關閉異(yi)頻電(dian)(dian)(dian)源，通過液(ye)晶屏顯示測量結果(guo)。因此阻抗(kang)(kang)(kang)測量時(shi)，儀器(qi)測量的(de)是兩電(dian)(dian)(dian)壓輸(shu)入端P1、P2之(zhi)間的(de)電(dian)(dian)(dian)壓與電(dian)(dian)(dian)源輸(shu)出(chu)(chu)(chu)電(dian)(dian)(dian)流之(zhi)比。
