In order to protect underground pipelines from corrosion, the cathode protection units (CPS) are installed on the pipeline route. CPS includes a DC power supply source (protective setup), an anodic earthing, a control units, wires and cables. Depending on the conditions, protection stations can be powered from AC circuit 0,4, 6 or 10kV or from independent power supply sources.

1. pipeline; 3. anodic earthing; 6. cathode protection station.

Fig.2. Connection diagram of cathode station:

1. Cathode installation;
2. Anodic earthing;
3. Protected pipeline;
4. Contacts;
5. Cable line;
6. Control measuring point;
7. Electrode of changes.

According to the connection schemes, direct current from "+" end of power supply unit 1 is applied to anodic earthing 2 and then to pipeline 3 thus performing its protective function and then returns to «-» end of the power supply unit. Bolted contacts 4 are intended for connection of cable line 5 and potential measurement 6. Electrode of changes 7 installed for definition of voltage on pipeline.

Electrochemical Protection LLC. performs construction and assembling of all types of cathode protection stations and anodic earthings.
1. The simplest and the cheapest design of anodic earthing is illustrated in Fig. 3.

Electrodes of anodic earthing 1 are installed to the trench to the depth exceeding soil freezing depth. At that, the electrode should have a bed and coke breeze dusting 4. All electrodes, by means of earth-insulated clamps 3, are connected to the main cable 3, which goes to the contact of anodic earthing.

Fig. 3. Horizontal anodic earthing is represented with a sample of a graphite-plastic electrodes of the EGT-2500 (1500) type:

1. electrode;
2. mono conductor cable in vinyl coating AVVG 1x25;
3. dividing box;
4. 4 coke breeze backfilling in a dib hole 3000x400.

In some cases it is more rationally to use a vertical anodic earthing. At that the more expensive work is required — well drilling.

Fig. 4. Vertical anodic earthing is represented with a sample of graphite-plastic electrode EGT-2500(1500):

1. electrode;
2. mono conductor cable in vinyl coating AVVG 1x25;
3. dividing box;
4. coke breeze backfilling in a hole.

More complicated anodic earthing is a deep-seated anodic earthing made from the same electrodes of the EGT type, is shown on Fig. 5.

The deep-seated anodic earthing is usually less than 100 meters and used in urban conditions or in some other cases.

Fig. 5. The deep-seated anodic earthing from electrodes of the EGT-2500 type:

1. direct head;
2. collar for string;
3. cable to "+" end of transformer;
4. steel wire PSO-4;
5. electrode EGT-2500;
6. contact connection.

Earth leads made from ER type electro conductive elastomers have been successfully used for rock and high-resistance (deep frozen, dry and desert areas) soils as well as in river and sea areas.

Such electrodes can be installed both horizontally close with pipeline and vertically as deep anodic ground. The ER type electrodes serve for tanks protection both for outer and inner surfaces