If the load is exceeded in a closed circuit, current leakage sometimes occurs. Various conductive objects become a load - the human body, batteries, bathtub, electrical appliances. Excessively high leakage current poses a danger to life, has risks of damage to household appliances. For this reason, it is worthwhile to figure out how to detect and protect yourself from the phenomenon.
What is current leakage?
In GOST 61140-2012 and 30331.1-2013 a definition of the concept is given. Current leakage is the flow of electric current into the ground, to open, conductive, third-party objects or protective conductors in normal operating conditions.
Current is directed from phase to earth along a route not intended for this purpose:
- housing equipment - washing or dishwashers, boilers, electric stoves;
- metal pipes of a water or gas main;
- raw plaster layer of an apartment or house;
- other conductive paths.
The phenomenon occurs in conditions of insulation damage during aging, overloading of home equipment or mechanical damage to the wiring.
Leakage current direction
The direction of the currents depends on the type of grounding:
- Insulated neutral IT - leakage is carried out through the insulating layer to the conductive elements. From them, along the conductors, it is diverted to the spreading region.
- TN circuit with neutral neutral ground - leakage passes through the REN bus to the input protection device.
- TT system - leakage is carried out through the main insulation from current-carrying to open conductive elements. Through the conductor and the ground electrode, the current is directed to the local ground.
The direction and path of the current in the IT and CT circuits are the same.
Causes of current leakage
Leakage occurs even when the equipment is operating normally, but a hazard occurs when the differential current limit is exceeded. The permissible norm may increase in several cases.
With an electrical appliance in an apartment or house
Voltage arises on the body of household appliances (most often a water heater or automatic machine). The reason is damage to the heater or insulation breaks. In a three-wire or two-wire equipment connection diagram, the phenomenon manifests itself in different ways:
- Three-wire connection of the device according to the TN-C-S scheme. In the event of a breakdown in the grounded enclosure, the leak is routed to the PE bus. The electromagnetic or thermal protection of the circuit breaker on the power line is activated.
- Two-wire connection of the device with grounding type TN-C. A leak will not cause the circuit breaker to trip, and the technician will continue to operate until a differential current is generated. The phenomenon will occur when you touch the body, element of the building or water pipes. The conductor of the leak from the device to the ground will be a person.
The greatest danger to life is a two-wire connection type.
In hidden wiring in a house or apartment
With hidden wiring, there are risks of damage to insulated cable conductors. They occur in such cases:
- Exceeding the regulatory life. The apartment in the building of the 50-90s of the XX century is equipped with aluminum or copper wiring. According to VSN 58-88, copper current-carrying conductors are replaced once every 30 years, aluminum - once every 30 years.
- Misuse.Overloading the mains leads to heating and destruction of the insulation of the power cable.
- Mechanical damage to current conductors. They arise when the installation technology is broken or the walls were drilled incorrectly.
The insulation has a constant resistance value, but should be checked for suspected leakage.
What is dangerous leakage
If the insulating layer loses resistance, a person touching the housing of a household appliance, a sheath of wire, a plug-type plug, a socket, a water pipe or heating pipe, the walls of a residential building will act as a conductor. Through his body, a leakage current will enter the earth. In this case, there are risks of partial damage or death.
Current leakage will affect the quality of energy consumption. Some consumers may not work in the house, but even when the equipment is off, the electricity meter will reflect the consumption of electricity.
Grounding electrical appliances will prevent electric shocks when touching the chassis. In this case, the fixation point of the conductive cable will begin to generate heat intensively, which will cause a fire to the wiring.
Characteristic signs
You can find out the current leak by the following signs:
- slight tingling when touching the wall, pipes, household appliances;
- increased power consumption for no apparent reason;
- starts to knock out plugs when several devices are turned on;
- interference and noise from a working radio;
- electrical appliances do not work when connected to the network;
- electric shocks in the bathroom during water procedures.
To eliminate the phenomenon, it is necessary to identify its cause.
How to check and find the leakage current with your own hands
At home, you can apply a simple method - leakage testing with measuring instruments.
Indicator screwdriver
The tool can find the phase on the objects-conductors. The tip of a screwdriver must touch various areas. A light bulb indicates a violation of the insulation layer.
Work with a multimeter
The device is used in ohmmeter mode to specify resistance indicators. You will need to turn on the multimeter, transfer it to an ohmmeter, use the probes to look at the indicators between the equipment bodies and each of the pins. A leak is indicated by a value greater than 20 mOhm.
A value less than 5 mA is not dangerous with reliable grounding of electrical appliances.
Vertebral megaohmmeter
Household appliances need to be disconnected from the network. Since the device can detect damage on voltage-insensitive equipment, you will need to touch it with probes. Rotating the handle, generate tension. Leakage is detected if the resistance is more than 20 mOhm.
With a sharp voltage jump from 500 to 1000 V, low-current electronics fails.
How to determine if the appliance is damaged
Devices with a metal casing, when phase voltage gets on them, become life threatening. You can identify a leak like this:
- Touch the neon indicator screwdriver to the unpainted metal part. A faint light bulb indicates a leak. Testing is carried out on two connection polarities.
- Turn off the equipment by removing the plug from the network. Switch the indoor switch to operating mode. One probe of the multimeter to touch the device, the other to the outlet. Measurements are made in both polarities.
Do not touch household appliances.
Troubleshooting wiring problems
A damaged hidden wiring circuit often causes electric shock during repair work. Leakage is easy to check with a transistor radio.
The device is configured to capture medium and long waves, wiretapping of the station in silent mode. The radio is turned on at full volume and the search is started by navigating it almost along the wall.The noise of the speaker and background noise indicate damage to communications.
Means of protection
To protect yourself from electric shock, and household appliances from breakdowns, the following protection methods are used:
- grounding of all home appliances and devices;
- installation of SHDUP (tires for additional equalization of potentials) in the bathroom;
- RCD installation, which responds to a total reading of about 100 mA and quickly turns off the devices;
- installation of a difavtomat, disconnecting electricity only in damaged areas;
- replacing the wiring blocks in the shield and connecting them with high-quality terminals;
- laying a new electric line with high-quality insulation.
Organization of protection requires compliance with safety standards and professional skills, so the help of specialists will be needed.
Detection of current leakage will protect a person from injury or death, prevent damage to equipment. Independent changes should be carried out in compliance with safety regulations, and the protection line should be organized with the help of qualified electricians.
