Impressed current cathodic protection of underground metal structures

We have already mentioned sacrificial anode cathodic protection system. Now we will talk about impressed current cathodic protection system. The first is the test project. The test items include soil resistivity, natural potential, anode grounding resistance, power output current and voltage, pipeline protection potential, protection current direction and anode electric field potential gradient.

There are four requirements for test interval. Comprehensive test of all parameters should be conducted once a year. The protection potential of pipeline should be once a month. The working parameters of power equipment should be copied once a day. If telemetry or SCADA system is used, the parameters included in the system should be tested once a day.

And then we have to talk about the commissioning of the impressed current cathodic protection system. At the beginning, you should remember to check the effectiveness of the insulation joint first. When one side of the power is transmitted and the offset is at least 400mV, the potential of the other side should be measured. If it should be natural potential or slightly positive, it is proved that it is effective, and the resistance is measured with a megohmmeter. The second step is side anode grounding resistance, anode to pipe resistance. When this value is greater than the design value, anode should be added.

The first step is to measure the natural potential of the pipeline and the potential on adjacent structures on all test piles. Then it is put into production and debugging. First, turn on the power supply, adjust the potential at the power on point to the design allowable value, and keep it for 48h.

The second step is to test the whole line protection potential and measure the line current at the current test pile.

In the third step, the tube / ground potential was measured repeatedly after 15 days of polarization.

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