Table of Contents
Grounding of owner-occupied dwelling performs two major functions:
- protection of the person against defeat by electric current;
- protection of household appliances of new generation (microprocessor controlled) from emergency operation in the power supply network.
Emergence of emergency operation, partly, can be provoked by availability in life of the modern powerful equipment raising loading of power supply networks which quality does not meet modern operating conditions.
Function of grounding in holiday villages and villages where problems of power supply are most expressed is especially important. The actual risk of use of powerful household appliances is present at rooms with the increased humidity. Heating electric devices can be used only in the presence of the full-fledged grounding contour.
What is ground loop what it consists of; whether it is possible to mount grounding independently and what for this purpose is necessary? The lightning protection role is how important?
What is ground loop?
Ground loop is the grounding conductor which components are connected with each other for ensuring interaction, all contour located from outer side of the building and covering. If to look at grounding system from above, then, really, it is possible to note that it is located along all walls of the house, from here and there is name “planimetric grounding”. The grounding conductor consists of group of the located closely to each other vertical electrodes established below earth surface. Among themselves the group of electrodes unites the horizontal conductor.
Today owners of owner-occupied dwellings use classical and modern method of grounding.
The traditional (classical) method of arrangement of grounding consists in:
- swamping by means of sledge hammer of pieces of steel corner or armature about 3 meters long to the earth;
- association of vertical elements the steel strip of 4х40 mm stacked on bottom of ditch about 0.6 m in depth by means of electro or gas weldings.
This classical method of grounding has unconditional advantage: it is economic in respect of the cost of materials, for this system new materials are not necessary, it is possible to use second-hand which will manage, almost free of charge. But it is laborious work and if there is no transport and the welding, then it is necessary to employ specialists and the machine. If the object which is subject to grounding is in the region of dense urban development, then for arrangement of such planimetric grounding certain approvals and obtaining permission are required.
Performance of planimetric grounding
For performance of planimetric grounding it is possible to use different ways, we will consider one of them, the simplest: by means of triangular design. For this purpose it is necessary to mount equilateral triangle and to connect it to guard.
It becomes as follows:
1. As directed PUE-7 (Section 1.7) is taken:
- steel corner of 50 х 50 х 5 mm;
- strip steel of 40 х 4 mm;
- round bar steel with a section of 8-10 mm ².
It is impossible to apply armature as presence of its tempered top layer breaks current of current on section as grounding system component parts. Besides, armature quickly rusts, and the system becomes not effective.
2. At distance no more than 1 meter from the base of the house do marking of equilateral triangle with lengths of parties about 1.2 meters.
3. On marking dig out trench about 0.6 meters wide on depth about 1 meter, it is intended for horizontal grounding conductors.
4. The steel corners (3 pieces 2.5 – 3 meters long) sharpened on the one hand (lower) hammer with sledge hammer into the earth on three tops of the planned triangle. For simplification of works it is recommended to drill previously on triangle tops wells and already, then to hammer the corners inserted into them. The corner 3 meters high is problematic to be established at its eminence above the ground completely on all height. Over trench bottom surface the corner has to tower on 25 cm as the horizontal grounding conductor will be welded on it.
5. By means of welding weld steel strip on the ends of corners, creating the closed contour. Welding reliably connects parts, bolted connections, in this case, are not recommended to be done because over time at bolted connection there can be oxidizing processes which will lead to loss of overall performance of system.
6. The collected ground loop is connected to electric board: the steel wire with a section of 8-10 mm is welded on contour and lay it in trench about 0.5 meters in depth. For fastening of the grounding conductor by its end weld bolt of M6 or M8 on electric board.
7. Welding points on end of welding need to be processed anticorrosive structures. Preliminary coloring of system is strictly forbidden to be done! Because metal with the earth has to have good contact, and the coat of paint creates big resistance and all meaning of arrangement of grounding is lost.
8. The trench needs to fill up, condense and level the earth.
Note: in the lower end of each grounding conductor, in this example steel corner, approximately on half a meter, it is recommended to nasverlit not symmetrically 10-15 through holes with a diameter about 7 mm in advance. In hot weather in the absence of rains grounding conductors need to be watered with hydrochloric solution, at the rate of 1 kg of table salt on 20 liters of water. It allows to hold normal spreading resistance.
The linear contour supplied with two sets of grounding conductors is necessary under following conditions:
- the house is equipped any, even at least one of utilities (gas, water, the sewerage, communication);
- input of underground power supply is carried out by means of IB (introduction board);
- simultaneous power consumption over 1 KW can exceed 20 minutes.
The full contour providing grounding on all perimeter is necessary if:
- the area of the house is more than 100 m ²;
- electroinput is carried out by means of VRU or ShchVS;
- the house is provided with back power supply (DGU);
- constant power of consumption is the size of 3 KW and more;
- in the house are used stationary the unit of industrial type (circular saw, the electrowelding machine, etc.).
Why it is necessary to use several grounding conductors?
The earth – the nonlinear conductor, at it is big dependence of resistance on contact area with the grounding conductor and from applied voltage. One grounding conductor cannot provide sufficient contact area, and several grounding conductors form the potential surface providing sufficient contact area. The efficiency of interaction of the earth and system increases in hundreds of times. In order to avoid rupture of potential surface, the grounding conductor it is impossible to carry on too long distance, it should not exceed 1.2 meters.
The modern method is modernized and allows to do without welding and other burdensome processes. The new contour consists of one compound electrode which elements fasten among themselves the threaded connection. Still the copper wire by section 16 or 25 of mm ² for connection of electrode with board is required. The set of the grounding conductor weighs no more than 2 kg and easily is placed in inside of the car, from shop it can be brought also in public transport. Being guided by the instruction one person can build planimetric grounding of new type in the presence of the minimum set of tools.
Whether it is possible most to make grounding?
There are official Rules regulating works on the device of planimetric grounding of residential buildings. In one of them there are no instructions who has the right to make planimetric grounding. That it has to be executed according to all norms, differently any possible check can lead other question to penalty.
There is, certainly, sense to address to the specialized organization and to order from them “turnkey” service. Businessmen estimate such works expensively, business even not at costs of mounting and materials, and that they provide to the user guarantee certificates and if any incident at operation of electrical wiring will take place, the company fitter completely indemnifies the loss caused as a result to state of emergency. The one who decides on independent works automatically loses such advantage.
Whether there are circumstances interfering the grounding device?
To have opportunity to use all advantages of grounding, it is necessary to have three-core wiring in the house. It is important at the same time that connection of wires in sockets (phase-zero-zero) has been executed correctly.
If in the house the two-conductor cable is laid, but there is urgent need of grounding of separate devices, then it is necessary to ground each unit separately. It concerns all houses, including wooden. The modern equipment demands obligatory grounding, it is specified in requirements of the producer. This requirement pursues the aim not only to protect own goods from damage, but also to ensure safety of the user. Therefore if in the house installation of modern household appliances is planned, then at first it is necessary to change electrical wiring, to make grounding and lightning protection.
The existing rules forbid:
- to make grounding on any pipelines, including metalplastic;
- to bring system to earth surface;
- to connect the grounding conductors on unprepared platforms;
- to apply consecutive grounding (to ground installations the friend through the friend) as it causes electromagnetic incompatibility;
- to paint components of planimetric grounding;
- to use iron fittings.
How to be convinced that the system works correctly?
If you observed all recommendations, grounding is obliged to work, but, a priori, it is necessary to be convinced of it by means of devices.
It is strictly forbidden to use for measurement of grounding the milliammeter, mains voltage or the quenching resistor! It represents deadly risk!
Specialists use special devices of old and new sample for this purpose. The private user can measure grounding by the electronic measuring instrument or megger. This electro induction device (shrews) it is reliable and safe in use. Of course, megger it is impossible to test metalcommunication, but the measurement at welded contour is sufficient.
Resistance of spreading can be measured by the following method:
- shrews it has to be included on Ohms;
- two measuring electrodes will be necessary (naked, smoothed out to gloss);
- electrodes have to be located in soil in 12-15 meters from metalcommunication and in 1.2-1.5 meters from each other;
- having connected, by means of the available wires and the shrew system, fix indications of arrow on instrument scale.
The indicators the shrew, the better is less. Requirements of PUE 1.7.62 it is admissible to have energy source ground resistance to 4 Ohms.
The total value of resistance of current of secondary grounding of zero conductor cannot exceed 10 Ohms, no more than 30 Ohms are not time-dependent years, everyone.
Whether the lightning arrester is necessary?
According to Rules and considering that the territory all is affected by such natural phenomenon as thunderstorm, lightning protection is obligatory for the objects supplied with planimetric grounding. It is necessary to understand that grounding can attract natural electric charge. Therefore the lightning arrester for the house with planimetric grounding is obligatory, especially if in the house the system of strengthening of cellular communication is provided.
It is possible to use services of professionals, but it is possible also most to mount lightning arrester. The simplest model: two pieces of armature towering over the rooftop on height about 1.3 meters, connected to contour by means of steel wire with a section of 6 mm and more.