對于重要的控制回路,可以采用手動后備的方法來提高可靠性。一旦自動控制失靈,用手動操作站直接進行操作,在這種情況下,手動操作站直接輸出4~20mA或1~5V的模擬量信號去控制執(zhí)行機構或直接接地進行設備的操作,可以手動控制生產(chǎn)過程。
② 自動后備
自動后備是采用冗余的方式設置另外一套或幾套備用控制裝置。當處于運行狀態(tài)的自動控制裝置發(fā)生故障時,備用控制裝置自動投入,維持系統(tǒng)的自動控制。自動后備是冗余系統(tǒng)的一種形式,冗余有主控單元冗余、電源系統(tǒng)冗余、網(wǎng)絡冗余、I/O模塊冗余、操作員站冗余、服務器冗余等。運行設備出現(xiàn)
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