Grounding - One of the most importanttechnological methods of protection against electric shock when working with electrical appliances. For proper wiring upgrades or repairs need to accurately represent what the grounding system is used at the facility. On this depends the safety of the person and the normal operation of equipment. Also, information is important in reconstructing the project. Accordingly, the need to explore all available grounding systems differ from each other as well as their installation technology.
- Classification of earthing systems
- TN system and its variants
- What is a TT system
- IT System: features
- Grounding Systems Technology unit
- Traditional technology and materials
- Modular grounding system progressive protection circuit
Classification of earthing systems
The International Electrotechnical Commission (IEC) and the State Standardization Committee established types of grounding systems.
They are all listed in the EMP (Electrical Installation Regulations). There are:
- System TN (subsystems TN-C, and TN-S, and finally, TN-C-S);
- System TT;
- IT System.
They differ according to the source of electricity and a method of grounding electrical equipment. Grounding system type denoted by the letters:
1. In the first letter is defined as grounded power supply:
- if T - there is a direct connection between neutral conductor (neutral) power source to the ground;
- if I - the neutral energy source is connected to the ground only through the resistance.
2. In the second letter is determined by the grounding conductor exposed parts of the electrical installation of the building:
- the letter T is the local (remote) grounding of electrical equipment and power supply;
- letter N indicates that the power source is grounded, but a grounding consumers occurs through PEN-conductor.
3. The following letter N is determined for a functional method in which arranged the neutral and the protective conductor:
- if there is a S - means working function (N) as well as protective (PE) conductors are provided with separate conductors;
- if there is a C - means a function of the zero workers and protective conductors are provided with a common conductor (PEN).
TN system and its variants
TN system is distinguished by the earthedNeutral: exposed conductive parts connected to any electrical specific earthed neutral point of the power supply by means of special protective conductors.
The term "neutral to earth" means that the neutral (zero) at the transformer substation is connected directly to the earthing circuit (ie, grounded).
The main condition of electrical TNIt is as follows: the value of the current between the exposed conductive part of the phase conductor and the short-circuit must be greater than the value of the protection device operation electric current for the specified time.
Demanded subsystem TN-C
Partition TN-C is a TN, whereinconductors (the neutral and protective) throughout the system combined (in the PEN conductor 1), ie, made protective earth and neutral. This is the most used variety of TN from the Soviet era. However, this system is now outdated. Of the modern electrical installations, it is found only in street lighting (in order to save as well as reduced risk). For the new housing it can not be recommended. Now replaced by a more modern system.
Ground Option TN-S
TN-S subsystem is TN, whereinconductors (the neutral and protective) are separated throughout the system. It is modern, the safest, but the most expensive system. She has a long history used in telecommunication networks (notably, when using non-interference in the low-current network).
TN-C-S - Device specifics
Subsystem TN-C-S - can be attributed tointermediate option. In it the neutral and protective conductors are combined only in any one part of it. Usually - the main board of the building (where the protective earth supplemented protective earth and neutral). Throughout the building below the conductors separated. The system is optimal from the standpoint of the ratio of price - quality. This scheme is currently the principal, which can be implemented in some parts of the electrical installations in the reconstruction. Other electrical grounding systems do not allow this. The cross sections of the conductors are chosen based on the current value (calculated), flowing through them. Cross-sectional area (minimum) PEN-conductor is 4 mm2. It is necessary to provide that the switchboard had separate clips on the bus PEN (for each wire - N and PE). In the application of a single wire or stranded as PEN-conductor insulation its color must be exceptionally yellowish green.
What is a TT system
This system is characterized in that zero sourceit is grounded, and the exposed conductive part of any installation connected to the ground, which is electrically independent from the grounded zero (neutral) power source. In other words, the facility applies its ground loopWhich has nothing to do with zero. To date, this system is used as the main mobile facilities such as cabins, houses, cars, etc. (Where it is not always possible to mount the earthing in accordance with the required standards). It is noteworthy that approval of its application runs much harder than TN. Becomes mandatory application of the RCD, also need high-quality ground (namely 4 ohms at 380), there are many features in the selection of the required circuit breakers.
IT System: features
This system is characterized in that zero sourceIt is isolated from earth or earthed through devices that have greater resistance, and electrical conductor exposed parts are grounded using grounding devices. IT is rarely used. Basically - in electrical special purpose buildings. For example, emergency lighting and power supply in hospitals. In general, where there are increased requirements for safety and reliability.
Grounding Systems Technology unit
There are several technologies ground loop installation. The most used are two: the traditional and modular Whip grounding system.
Traditional technology and materials
Grounding is made of black metal: corners, pipe bands, and so on. n. The installation will start by creating a project that reflects the place where it will be constructed grounding circuit arrangement of technical communications in the ground. Then, focusing on the object into the soil to a depth of 3 m, a distance of about 5 meters al. Digged other metal products (electrodes) of a particular cross section (not <3). Thereafter, these electrodes are welded together in the general contour perimeter by a metal strip.
This basic technology has been for manydecades. However, it has several drawbacks (eg, metal corrosion, the complexity of the installation, etc.), so now it is trying to replace other, more modern and perfect grounding technology.
Modular Ground System
What is included?
- It consists of a rod made ofstainless steel and coated with copper. They are arranged in the ground vertically. Each of these rods reaches about half a meter in length and the diameter - 14 mm, weight 1 of element - not more than 2 kg. On both sides of each rod is coppered thread cutting 30 mm in length.
- The steel elements of the system are interconnected using brass couplings.
- Complete modular system includes groundand brass clamp is used for horizontal connections (special steel strips or copper wire, extending from the distributor panel directly to the grounding circuit of the system) and vertical (copper-clad steel rods) earth elements.
- Also included two steel tip,which will be attached to the rod by screwing on the copper plating thread. Select tips will have, depending on the soil (particularly hard or normal). It will take all of this device is the building grounding system.
- For corrosion protection of all elements of the earth is usually attached protective paste, which handled all elements of the future earthing system.
- For a more secure and reliable connection of horizontal and vertical components using masking tape (for example, PREMTAPE).
How does the installation?
Installation of modular pin grounding system consists of several stages:
- Fits first vertical steel pin.
- Held froze intermediate resistance.
- Mounted remaining vertical pins.
- Laid horizontally earthing.
- Then connect the elements and handled with protective tape.
The advantages of a modular pin grounding system
- It allows you to save area (can settle for 1 m2).
- A simple, does not require time-consuming excavation.
- You do not need welding.
- Use a ground can be in any form of soil
- Achieved great depth - 50 m.
- Used stainless steel wires.
- There is no need for special equipment.
- Long service life.
From the foregoing it can be concluded thatToday is the most efficient use of the system TN-C-S and module-pin technology its installation. All the evidence suggests that the latest generation of the grounding device technology in many ways superior to traditional. Their use reduces the duration of the work, reducing the financial costs, increase the service life of the grounding elements.