First, the classification of electrical safety helmet
Classification of helmets according to the scope of application can be divided into Y class (general purpose), and T category (special use) two kinds. Y-helmet is of such products should conform to national standards set forth in the basic technical requirements, while the T type helmet addition to Y-helmets should meet basic performance requirements, product standards should be provided with a special performance requirements . The power industry require helmets with insulating properties to prevent electric shock accidents, power (electrical) safety helmets, safety helmet shall be T4 category. Electrical safety helmets in accordance with its additional features of the different divided into near electric alarm (device) Electrician helmet and general electrical safety helmet. Near electric alarm (device) Electrician T4 helmet that is in the general category of internal installation of a safety helmet "near electric warning device."
Second, the use of scientific knowledge of electrical safety helmets
1. Electrical safety helmets work environment "to adapt to the universality of the environment: helmets national standard (GB2811-2007) A.4 provides (T4 category) Electrical insulation helmets," adapted to possible exposure to the following three-phase AC 400 V working environment. " that may come into contact the following three-phase AC 400 V working environment operating personnel should wear T4 class of electrical insulation helmets. China's current users are most terminals in the power transformer are generally from 10 kV three-phase AC transformer for the 400 V three-phase alternating current, so "the following three-phase 400-volt alternating current work environment" is a very common environment, not only the needs of a professional electrician electrician helmet, that is, ordinary buildings. oil. chemical. shipbuilding and other industries also need a state specification is necessary; 2 is a multi-functional protective layer of insulation and more secure.
2. The scope of protection and the principles of electrical safety helmets: helmets national standard (GB2811-2007) requirements, electrical insulation standards for helmets: When the helmet contact with 400 volts and below voltage, safety helmets to the head of the leak current of less than or equal to 1.2 milliamperes (Su-star brand electric helmet of 0.2 mA, that the insulation performance is better than the national standard 6-fold), thereby protecting the safety of persons wearing. Therefore, the main electrical safety helmets to protect principle is 400 volts and below voltage contact of the insulation protection. 3. Near electric alarm (device) Electrician scope of protection of helmets and Principle: Alarm electrical safety helmet addition to having the above (2) above the ordinary insulation protection, but also has the following 400-volt electrical contact or near an early warning function; in particular, with 400-volt more "safe distance" outside near power early warning function. T4 category in accordance with national standards require that helmets electrical voltage of 400 kV or more contacts can not afford absolute protection role, especially as more than one kilovolt high-voltage discharge can occur without contact such as electric shock accident. Therefore, nearly electric alarm (device) Electrician helmet on the emerged and played a "near power warning" feature. Near electric alarm (device) Electrician helmets main protection principle is "near power warning" prompt function, rather than contact with insulation function. 4. Near electric alarm (device) Electrician helmet to use: Use the former, voltage selector switch placed in the appropriate voltage profile, and then hold down the self-test, which could give roar (voice) signal, you can normally use. Optional 220-volt electricity to nearly -500 kV voltage range, as worn near electrical alarm (device) Electrician helmets to enter preset voltage range, that is issued nearly automatic electric roar audible alarm or a live voice alarm, to alert Do not wear a person close to the electrically charged objects, so as to avoid an electric shock.
5. General Electric alarm Near (device) Electrician's use of helmets: (1) 200 V -380 volt overhead power cables, alarm distance: 0.4 meters -0.6 m; (2) 10 kV overhead power cables, alarm distance: 0.8 m -1.0 m; (3) 35 kV overhead power cables, alarm Distance: 1.8 m -2.0 m;
3, electrical power helmet-related scientific knowledge
1. Three-phase AC: the average family are single-phase AC electric power, but the current large-scale production and distribution, as well as most of the industrial use of electricity, they were all in the form of three-phase AC circuits. High-voltage transmission lines, usually four lines. Unit kV voltage (KV) / V (V), current unit of a thousand (KA) / An (A) / milliamps (mA).
2. Safety voltage: 36 volts. In addition to rules of order of the high-voltage, low two kinds of voltage, there is a safe voltage. The so-called safe voltage: It is relative to the high-pressure, low pressure, means there is little risk of personal safety voltage. Voltage value is generally 36 volts, 24 volts and 12 volts. In a variety of circumstances, the body's resistance of straight is not the same. Generally about 1-10 million in Europe (but there are also lower), such as Europe by about 800 to consider, experimental analysis shows that the human body allows the frequency limit of current is about 50 mA, or 0.05-an. On this premise, then, according to Ohm's law calculation, that the human body to withstand the maximum allowed limit frequency voltage of about 40 volts. It is generally taken as a safe voltage 36 volts.
3. Safety current: 10 mA (mA).
The body of the current reflects:
8 ~ 10MA hand from the electrode is already feeling the difficulties and pain influenza (finger joint).
20 ~ 25MA hand the rapid paralysis, can not automatically get rid of electrodes, difficulty in breathing.
50 ~ 80MA difficulty breathing, atrial began to tremble.
90 ~ 100MA respiratory paralysis, three seconds after the heart began to paralysis, to stop beating.
4. A safe distance from other states:
High-pressure: According to the "Safety" of data, at all levels of voltage and the human body a safe distance from
500kV: 5m 220kV: 3m 110kV: 1.5m
35kV: 1m 10kV: 0.7m low voltage what is a safe distance from the basic need