基於制水閥區可靠度之自來水管網換管規劃模式

Abstract

自來水管網傳送民生用水，必須進行有計畫的換管工作，以維持供水系統的可靠度。一般在進行換管規劃或是管網可靠性分析的時候，多以管線為單位進行影響分析，但由於管線修復必須關閉周圍的制水閥才能進行，故不只影響管線本身，亦會影響管線周圍制水閥關閉所截斷的分區。若只考量損壞管線本身的影響範圍，可能會導致低估管線損壞所造成的缺水量及影響範圍，並誤導換管規劃的最終決策。為了改善上述只考量管線本身影響的缺失，本研究發展一考量制水閥分區損壞影響之換管優選模式，以期得到更合理的決策依據。 本研究首先發展出一個演算程序以決定制水閥截斷分區，並將原始管網轉換為以分區為單位之網路來呈現分區間的關係。若分區損壞會造成其他管網區域無法供水則稱之為關鍵分區，本研究利用深先搜尋(depth-first search)之衍生演算程序進行關鍵分區之判識，並推估所可能影響之缺水量。至於其他種分區的損壞，雖不至於造成其他區域完全無法供水，但或多或少也會對其他分區造成影響，此部分利用EPANET2 進行模擬，以推估所損壞影響缺水量。本研究以各分區損壞所影響之缺水量以及各分區之整體失敗率評量自來水管網系統之可靠度，並據以發展一考量制水閥分區影響之換管優選模式。並與只考量管線本身影響之換管優選模式進行比較，由案例分析結果可發現，考量制水閥分區影響的優選模式，可以在較經濟有效的花費成本下，得到更高的缺水可靠度改善量，使得管網系統更為可靠。 關鍵詞：自來水管網、可靠度、換管規劃、制水閥分區

Proper pipe replacement is necessary for a water distribution network to assure its reliability for water supply. Previous studies for pipe replacement planning generally regarded each pipe as an independent unit during analysis. However, closing all peripheral valves is required prior to performing maintenance on a failed pipe, and the actual influence includes the network segment closed off and adjacent segments. Regarding each pipe as an independent unit may underestimate total shortage or influenced area and thus result in an inappropriate decision. This study therefore views valve-enclosed segments as units for determining the impact of damage to pipes and establishing an optimization model to facilitate decision-making analyses. In this study, an algorithm is proposed to identify valve-enclosed segments in a water distribution network and a conceptual segment network can thus be created for further analyses. A computer program based on a depth-first search algorithm is developed to determine critical segments. The EPANET2 model is used to estimate demand shortage impact from damage to segments. A segment-based pipe replacement optimization model with the objective to maximize improvement in shortage reliability after replacement is developed. A case study is implemented under various cost limitations for comparing the proposed model with the conventional pipe-based model. Results show that the proposed model is effective in making an appropriate replacement decision for improving overall shortage reliability. Keywords: optimization, water distribution network,reliability, pipe replacement, valve-enclosed segment, environmental systems analysis.