为防止气井套管的腐蚀，对气井套管实施强制电流阴极保护。在阴极保护系统投运时，套管的保护电位始终无法达到要求的保护电位。通过计算保护电流需要量和现场测试发现，由于井套管外壁没有防腐层，保护电流就会在整个井套管周围产生阴极电压锥，因此井套管周围土壤的电位降低超过远方土壤中的电位，放置在井套管附近的参比电极由于受到井套管周围阴极电压锥的影响，造成设备显示的井套管的保护电位比其实际的保护电位要正。因此，井套管阴极保护所设置的参比电极应位于阴极干扰区以外。

Well casing shall be protected by impressed current cathodic protection in order to prevent corrosion. When cathodic protection system is put into operation, protective potential cannot meet relative requirements from beginning to end. Through calculating protection current requisite amount and field testing, it is found that due to lack of anticorrosive coating on external wall of well casing and protective current may produce cathode voltage cone around the whole well casing, soil potential around the well casing will greatly reduce and even becomes less than that in distant soil, the reference electrode installed near the well casing will be affected by the cathode voltage cone around the well casing, which will make protection potential displayed in device more positive than its actual protection potential. Therefore, the reference electrode for well casing cathodic protection shall be installed outside the cathode interference area.