The occurrence of a current in a conductor is due to the potential difference at its ends. Stray currents occur when earth becomes a conductive medium. This phenomenon has a destructive effect on metal objects that are in the ground or have points of contact with it.
Content
- Leakage reasons
- Protection against electrocorrosion
- Stray currents at gas stations
Leakage reasons
The appearance of stray currents occurs due to poor insulation in electrical wiring systems, wire breaks in power lines, insufficient insulation of tramway and railroad rails. Stray currents in water pipes cause electrochemical corrosion and accelerate their destruction. Are exposed to corrosion and laid in the ground metal structures and cables.
In apartment buildings, stray currents appear due to leaks in the power supply systems. This accelerates pipe corrosion several times. compared to the design. The nature of stray currents is that the potentials of grounded structures are different. The reasons for the appearance of leakage currents can be:
- Improper operation of electrical networks, the use of water and heating pipes instead of a neutral conductor.
- Connection of household appliances that does not meet safety requirements: sterilizers, washing machines, dishwashers, in which the power supply system of the house is connected to the water supply pipes and heating.
- Damage to the insulation of conductors during operation.
Incorrect connections in 3-wire circuits, where, in addition to the phase and neutral working conductors, there is also a zero protective conductor, leads to current spreading over the metal structures. Connection errors should be avoided. Do not connect the zero working and zero protective conductors in one place, do not use the protective one instead of the working one. In addition to corrosion, it can cause electrical injuries to people.
The occurrence of stray currents can be caused by replacing metal pipes with plastic ones. The plastic pipes themselves are not susceptible to corrosion, but metal fittings in apartments, such as heated towel rails and faucets, can rust. This is explained by the fact that when all the pipes were metal, they were grounded in the basements with special circuits.
Plastic pipes violate the integrity of the grounded circuit, and water, which is a conductor, conducts current through the pipes. A fairly high voltage is created inside the pipes, and this is dangerous. There have been cases of electric shock in the bathroom, even with a voltage of only 4 V. The current is dangerous, not the voltage.
Protection against electrocorrosion
The most common method of protection against stray currents is to ground all electrical appliances, gas and water pipes in the house. The potential difference causes the appearance of a current flowing from areas of high potential to areas of low potential. The grounding equipotentializes, and possibility of leaks excluded.
A large number of pipelines and cables pass underground, which need anti-corrosion protection. The following methods are used to protect main pipelines:
- Cathodic protection method. It is based on the formation of potentials with the help of cathode stations on underground structures that increase the resistance to stray current.
- Creation of dielectric insulation.
- It is possible to increase the longitudinal resistance of pipelines by using a tie-in of insulating sleeves.
- Replacement of metal pipes with plastic ones.
Stray currents at gas stations
At gas stations, the appearance of stray currents is most dangerous. There, the slightest possibility of sparking should be prevented. For protection, a ground loop and careful grounding of all metal parts are used. You should also beware of static electricity from the driver. Wandering currents on the body can form by friction o synthetic coatings inside the car. This is sometimes enough to ignite a pistol. When leaving the car, it is necessary to equalize the potentials by grasping the car with one hand and the gas station with the other.
Static electricity builds up not only on clothes. A mobile phone and a running engine can be dangerous. It is not recommended to keep fuel in plastic containers. Gasoline rubbing against the plastic surface also creates static electricity. This can cause a spark when trying to fill the gas tank with gasoline. Best used to transport gasoline iron cans.
Stray currents are dangerous. They cause corrosion and failure of underground utilities. In apartment buildings, they disable engineering equipment ahead of schedule, destroy water pipes and heating systems. In some cases, they even pose a threat to human life. It is necessary to combat this phenomenon, do not violate safety rules during any electrical work and make sure that all devices are correctly connected and grounded.
