EMC – Electromagnetic Compatibility

Environmental condition of functional electrical and electronic systems do not suffer from any outside electromagnetic interference that can prevent its correct operation nor cause interference which can affect the operation of other devices.

EMC environmental conditions are achieved from the scientific knowledge of electromagnetic phenomena, metrology and application of techniques and technologies specific to the design of devices, filtering, shielding, surge protection and grounding.

CEM techniques and technologies are applied upstream in the design of devices and equipment, and downstream in electrical electronics and telecommunications systems in the processes of generation, transmission, distribution and facilities in buildings, vehicles, boats and aircraft.

EMC conditions are also ensuring the protection and safety of the general public against electrical shock, electrocution, burns or explosions in all facilities with electrical and telecommunications equipment .

Electrical Safety

Grounding and its effect

In the universe, all matter consists of atoms which seek to maintain their equilibrium electrostatic nature, i.e., an equal number of positive and negative charges. Since the mass of the planet consisting of a mixture of different substances whose atoms, taken together, seek equilibrium electrostatic this causes the land is electrically neutral.

An atom loses its neutrality when it gains or loses electrons by friction, induction or contact generating an electric field around it.

It should be borne in mind that the atmosphere surrounding the Earth also contains atoms and interacting with atoms of the earth. This phenomenon leads to some negative charges of the earth are attracted by ionosphere to making the planet slightly positive, which for us is irrelevant. Evidence of the existence of this phenomenon is the atmospheric discharges, lightning, that at any moment occurring on the planet.

Moving the man standing on the floor that makes the body normally remains at the ground electric potential. So that there can be electrical safety is necessary to ensure that whatever man can touch or handle has a grounding.

The way to achieve grounding consists in a ground electrode rod vertically buried deeply connected by a cable to the electrical bonding bar installation or directly to a lightning rod.In an installation which is either equipotential should only be a single network circuit ground.

The arresters are devices mounted on masts on top of buildings or antenna towers, grounded by a ground conductor himself to the currents of lightning have a preferred path for the land and protect the infrastructure where is installed.

In the absence of discharge currents to earth, the ground electrode is at ground potential but in the event of discharge current values ​​of currents and earth resistance will determine the value of the potential of the ground electrode at the time of discharge and should therefore, the value of ground resistance be as low as possible to avoid having high potentials.

With the mandatory use of protective difference to the input of the electric low-voltage regime in the earth TT, it can be said that there is not a reference value for the resistance value to earth, what is required is that the its value should ensure action unequivocal differential protection against indirect contact considering a touch voltage of 50V (25V in some other countries) and a maximum current of nominal protection IΔn indicated in circuit breaker. (R(máx.)=50V/IΔn).

If the purposes of a grounding protection are the infrastructure and security of people, their functions are to dispel chains and to eliminate potential differences between different surfaces to ensure your equipotentiality.

Exposure to Electromagnetic Radiation

Ionizing and Non-Ionizing

Introduction

The electromagnetic radiation can have a natural or artificial origin and are constituted by photons, atomic particles possessing energy whose value is proportional to the radiated frequency. This feature of increasing energy did divide the electromagnetic spectrum in ionizing and non-ionizing radiation below and above the wavelength of 100nm respectively (3x10¹⁵ Hz). Ionizing because at these frequencies the energy levels are so high (>12eV) they can ionize atoms and molecules of matter, so they are extremely dangerous because they can damage the DNA structure of a living being.

Non-Ionizing

Radiation emitted by overhead high voltage power lines (50Hz/60Hz), all radio transmission systems (9 kHz to 300 GHz), the infrared optical fibers (750nm to 1mm), visible light (400nm to 750nm) and part of ultraviolet radiation (100nm to 400nm).

Examples of non-ionizing radiation natural sources are the rays produced by lightning and the sun's rays.

 The effects from exposure to non-ionizing radiation are:

· Direct: electrocution and thermal effects sunburn, skin aging, blindness, etc.;

· Indirect: fire and explosion;

· Non-thermal effects: a category created for cases without apparent explanation.

The non-ionizing electromagnetic radiation is present everywhere, at home, at work or on the street, along the electric, electronic and telecommunication systems wireless, telephone, Internet, radio, terrestrial television, cable, satellite, by sunlight, etc..

The maximum radiation emitted by an antenna follows its axis in one direction in a manner analogous to focus of a flashlight and level of radiation decreases inversely with the square of the distance. The two combined effects ensure that the levels of radiation exposure are, in most cases, relatively weak. Behind and below the antennae radiation levels are also weaker.

With the introduction of digital radio systems, the power levels required for transmission are substantially smaller than those employed in analogic technology.

The levels of population exposure to non-ionizing radiation, including those issued by antennas (0Hz to 300GHz or in wavelength > 1mm) are regulated internationally by ICNIRP guidelines.

(*) ICNIRP - International Commission on Non-Ionizing Radiation Protection

Radiações Ionizantes

Spectrum of ionizing radiation comprises the ultraviolet (10nm to 100mm), the alpha, beta and gamma (X-ray) and the cosmic rays. Some natural substances emit ionizing radiation. The granite, for example, liberates radioactive gas, radon, by the uranium contained therein.

Ionizing radiation is extremely dangerous for the ability to ionize atoms and molecules and so can damage the cell structure of the DNA of a living being, causing cancers and leukemias. Ionizing radiation is used to cell destruction in cancer treatment in hospital premises.

Final Thoughts

This document is not to argue that non-ionizing electromagnetic radiation are harmless or its opposite. Apparently these radiations are not the cause of cancers although its thermal effect, with levels in excess, may accelerate the metabolism of an existing one. In biochemical laboratories, ovens serve to accelerate the process of cell replication as refrigerators serve to delay.