On the dangers of electricity

By Admin | Electrical Light
08 May 2016
"Fully wiring was replaced, however, as shown by the repeated measurements, but the level of the magnetic field was above the recommended values. What do I do next?" - From a letter to the Centre electromagnet tion security.

Electromagnetic ecology electrical building

author raises at first sight is not entirely relevant and not very much clear question.
But only at first and superficial glance.
Indeed, media inform us about these different studies on the negative impact on health of mobile phones and basestations, powerful radio transmitters, power lines, transformers, electrical appliances, etc.

It would seem, with a building's electrical system is as such?
What it could have a negative impact?
What is the physical mechanism of this influence factor?How
massively spread potentially dangerous situation?
And what to protect against such adverse effects?

will try to thoroughly investigate these issues.

well known electromagnetic fields have a negative effect on human health (more is devot
ed to this issue in our next article), and the degree of "severity" is determined by the intensity of the electromagnetic wave frequency, exposure time and other factors.
applied to installations of buildings are the main factor affecting the magnetic field of industrial frequency (IF MP).

magnetic field in the environment created by the current in the conductors.Thus, the cause of the MT inverter near power transformers, motors and so on. N. Obviously.A more complicated situation with a system of cable lines of the building.Total current of the supply lines of single-phase and three-phase loads identically zero for any distribution of loads on the phases, and the magnetic field generated by flowing in such currents in the cable lines laid next to each other conductors also negligible.

But if pave phase and neutral conductor in different routes, in the space between them there is a significant value for the magnetic field (with the same currents in conductors).
Further, if for one reason or another (See below.) Neutral conductor has a galvanic connection to the protective conductor and / or steel structures, a portion of the current conductor "goes" on the PE system (there is leakage current).This imbalance occurs when currents (inequality zero sum current of the cable line) in the surrounding area creates a constant presence of a magnetic field decreases slowly with increasing distance from the cable under consideration.
In addition, the presence of leakage currents in the electrical system of the building leads to a constant leakage current of metal structures and pipeline systems, which is also a reason for the increased levels of MT inverter.

What is the cause of the leakage and how often the above situation?
1. Perform electrical installation of the building in accordance with the requirements of the 6th edition of the SAE (4-wire TN-C system).At the same time there are multiple, leading to the occurrence of leakage currents, galvanic connection PEN - conductor metal structures of the building.In other words, all the buildings, electrical systems which are made of TN-C system in varying degrees, initially subjected to electromagnetic pollution power frequency magnetic fields.
2. It was expected that the introduction of the requirements of the 7th edition of the SAE allow law gradually resolve the situation.Unfortunately, this did not happen.Indeed, p. 543.2.5 GOST R 50571.10-96 states: "The use of the HRC (extraneous conductive parts) as PEN-conductor is prohibited."At the same time n. 1.7.133 of the 7th edition of the SAE in the literal wording "Do not use third-party conductive parts as a single PEN-conductor" one - a single word (certainly justified to ensure electrical TZ) puts leakage currents "outside the law "with all the ensuing consequences (including loss of use of protective devices).
3. It is known that the load is evenly distributed in the circuits of three-phase AC current in the neutral conductor is absent.It really is true for linear electrical load (electric motors, heaters, incandescent lamps, etc.) In fact, the situation may be much worse.The fact that widespread now electroconsumers nonlinear (computers and file servers, computer peripherals, monitors, laser printers, uninterruptible power supply (UPS), copiers and fax machines, discharge lamps, home audio and video equipment, etc.n.) characterized by the presence of higher harmonics in the consumed current waveform.In this case, the current harmonics are multiples of three, is algebraically added in the neutral conductor, whereby the current in the latter is greater than the current in the phase conductors (up to 1.7-fold) even at the absolute equality of loads on phases.Accordingly, leakage current supply lines "computer loads" (and hence the contamination MP power frequency harmonics) will be significantly higher as compared with the case of the same supply network linear electroconsumers / 1 /.
4. Constantly encountered in practice and repetitive installation error zero workers and protective conductors, as well as damage to the insulation neutral conductor / 2 /.

presence of leakage currents in electrical installations of buildings leads not only to the above environmental, and other problems - problems of ensuring the electromagnetic compatibility of facilities / 2 /.

What should I do in this situation?
In our view, the way out of this situation could be the following:
1. To recognize the existence of a serious problem
2. Make the necessary correction to the wording of paragraph. 1.7.133 of the 7th edition of the SAE.
3. Perform a phased reconstruction of electrical installations of buildings, executed by the TN-C system.
4. In case of impossibility of performance of works by n. 3 in full, to perform work on the measurement of levels of power frequency magnetic fields in places of long stay of people, followed by work on the elimination of leakage currents along the cable lines with maximum values ​​of the past.
5. When performing electrical works in newly constructed and capitally reconstructed buildings carry the instrumental error-control installation, leading to the appearance of leakage currents.
6. In order to meet the current requirements to ensure the electrical and fire safety, as well as preventing occurrence of leakage currents during the operation of electric - to use the device (RCD).

Head of department of electrical
Center for Electromagnetic Safety,
Ph.D., a member of the IEEE