This section describes general issues related to domestic electrical installations, according to standard specifications ELEC NCH 4 / 84 currently in effect. It is worth mentioning here that all electrical installations should be planned and executed by an electrician approved by the Superintendency of Electricity and Fuels, and that the information contained in this page is for reference purposes only.
The electrical panel electrical panel in a concentrated protection devices and switching of electrical circuits of the installation (note: for more background see NCH ELEC Electrical Code 4 / 84). For residential installations this board usually consists of a box within which are mounted respective breakers.
To achieve a safe electrical installation, you must have protective devices operating in the time when a fault (short circuit, overload or fault isolation) at some point in the circuit. This will avoid both the risk for people to have "electrical accident" as the overheating of conductors and electrical equipment, thus preventing material damage and possible causes of fire.
Service Security
When designing the electrical system, you should distribute the burdens of several "circuits" as to possible failures (In operation) is interrupted only by the respective circuit without affecting the continuity of service in the rest of the installation. For example, in a house is recommended to install at least three circuits, one exclusively for lighting, one for plugs and a third for special plugs in the kitchen and laundry. Types
electrical faults failures according to their nature and severity are classified as:
Overload: This occurs when the magnitude of the tension (voltage) or current exceeds the preset as a normal (nominal value). Typically these overloads are caused by excess consumption in the electrical installation. The overloads produce overheating in conductors, which may mean the destruction of their isolation, even arriving at fires cause inflammation.
Short: It is caused by the accidental union of two uninsulated power lines, between which there is a difference in electrical potential (phase-neutral, phase-phase). During a short circuit the value of the current intensity rises so that the electrical conductors may melt at the point of failure, generating excessive heat, sparks and flames, with the respective risk of fire.
insulation failure: These are caused by the aging of insulation, cuts a conductor, isolated mismatches, etc. These failures do not always rise to short circuits, but in many cases means that electrical metallic surfaces are energized (with dangerous voltages), with the consequent risk of electric shock to users of those devices.
protection elements
There are several different types of protections, so then explains the most important devices used to achieve electrical continuity of service and security for people:
a) Fuses (thermal protection)
These devices interrupt the electrical circuit due to an overcurrent burning a filament conductor located inside, so it must be replaced after each performance to reset the circuit. Fuses are used as protection against short circuits and overloads.
b) circuit breaker or circuit breaker
These switches have a magnetic system for rapid response to abrupt overcurrent (short circuit), and thermal protection based on a bimetallic strip that off to slow occurrence overcurrent (overload). These circuit breakers are used to protect each circuit of the facility, its main function to protect the electrical conductors to surges that can cause dangerous temperature rises.
c) Switch or Differential Protector
The circuit breaker is a component to the protection of persons against indirect contact. Is installed in the switchboard after the circuit breaker to be protected, usually plugs circuits, or it can be installed after the general breaker of the installation if you want to install only one differential protector, if and with concern about the nominal capacity (amperes) general circuit breaker is less than or equal to the differential protector. The circuit breaker
census the current flowing through the phase and neutral, which normally ought to be beaten. If an insulation fault in any electrical appliance, ie the phase conductor is in contact with a metal part (conducting), and results in grounding, then the current flow through the neutral will be less than that flowing through the phase. Given this imbalance the circuit breaker operates, disconnecting the circuit.
These protections are characterized by their sensitivity (current operation), ie the leakage current level at which they begin to operate, typically this value is 30 milliamps (0.03 A). It is very important to note that these protections should be supplemented with a sistemas de puesta a tierra, pues de no ser así, el interruptor diferencial solo percibirá la fuga de corriente en el momento en que el usuario toque la carcaza energizada de algún artefacto, con lo que no se asegura que la persona no reciba una descarga eléctrica.
Dimensionamiento de los conductores
Los conductores eléctricos se dimensionan en base a dos criterios: Intensidad de corriente que impone la carga y caída de tensión que se produce en la línea.
Según el diámetro de cada conductor, este tiene asociada una capacidad de trasporte de corriente (en amperes), en la cual también tiene que ver su la aislación (recubrimiento) y el método de canalización to be used (tubing, tray, etc). Thus a conductor of 1.5 mm2, NYA insulated type, channeled into pipes, can carry up to 15 A, while the same driver, but lying outside, can carry up to 23 A. Different types of insulation available for drivers is related to the application and environment in which they will place them, ie they can be resistant to water, corrosive liquids, UV, etc.
However, the premise of the sizing of drivers you can set:
< I disy < I cond
where I load, I load, nominal load current or power consumption
I DISY: Current rated circuit breaker protects the circuit
I cond: Maximum current carrying conductor selected.
The second criterion (voltage drop) is related to the fact that while farther away the point of consumption of the supply, the voltage drop at the end of the line will be higher. This can be solved by using drivers with a wider diameter originally selected (as per transmission capacity).
A household level, commonly used insulated wires NYA rate of 1.5 mm2 for lighting circuits and 2.5 mm2 for outlet circuits.
It requires the use of standard colors to identify The different conductors: the phase conductors must be blue, black or red, the neutral must be white and the driver of the grounding protection must be colored green or yellow green: Pipes
There is a wide variety in the types of pipes, as referred to above rule. It is noteworthy that in residential installation a common means of channeling the conductors are PVC or metal pipe (usually galvanized steel). Offices are also used as a method of channeling for sockets, and even current weak (telephone, computer or network signal), or molding plastic trays. Basically
dimensions of the channels are defined according to the quantity and size of wire to use, which is normal. Earth
service grounding of service corresponds to a method of protection against elevation of tension caused by faults in the distribution system (neutral cut power lines.) The "land of service" is basically grounding the neutral of the electrical system, usually at the point of junction, using a copper electrode, or a mesh.
Protective Earth Grounding
protection is one of the most important elements of an electrical installation, in regard to protection of persons against indirect contact.
This system consists of grounding all conductive elements (frames) of the equipment under normal conditions, should not present dangerous contact voltages. It is for this that plugs come three wires (phase, neutral and ground), which allows each device that is plugged into an outlet can be connected to earth ground.
A good grounding protection assures us that in an insulation fault (Phase conductor in contact with exposed metal parts of a device such as a washing machine) occurs grounding protections operate if the fault is not dormant, waiting for someone to touch the surface to be channeled through that person, electrocuting her. The proper functioning of the earth depends on the electrical resistance value is achieved at installation.
In practice, such as land protection system used electrodes made of copper or Copperweld type bars, or entangled in copper wire, buried at depth. Strength results are achieved for the "land of protection" depend on the type soil (moisture and salts containing), surface covering the ground, and certain electrical parameters of the system.
Effects of electricity on the human body
The effects of electricity on the human body depends on:
intensity current through it
Duration of contact (time of exposure to electric shock)
Resistance body electric.
Effects of electricity on the body, according to the intensity that crosses
current in milliamps (mA) Effects on the body
to 1 Undetectable to humans
2 3-tingling in the exposed area from 3 to 10
involuntary contraction. The subject usually gets rid of the contact, however the current is not fatal.
10 to 50 Current is not fatal if applied at decreasing intervals with increasing intensity, otherwise the breathing muscles are affected by cramps that can cause death by suffocation. 50-500 Current
decidedly dangerous increasing function of duration of contact resulting in ventricular fibrillation (irregular heart operation with very frequent and ineffective contractions), which constitutes a serious risk to life.
over 500 Decreases the possibility fibrillation, but increases the risk of death from paralysis of nerve centers and internal burns.
human body's electrical resistance
In general, the human body's electrical resistance varies with the physical and psychological (mood) of subject and condition of your skin. And a person is "stressed" or nervous is more "electrically conductive" a quiet person, as well as a person with skin "wet" is more conductive than a person with dry skin.
As general estimate assumes a human body resistance of 3,000 Ohms, Low Voltage, and 1,000 Ohms for high voltage, being extremely variable course data for the reasons described
Source:
http://www.eclipse.cl
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