GOST 50571.5-94 (IEC 364-4-43-77) UDC 696.6:006.354 Group E08 STATE STANDARD OF THE RUSSIAN FEDERATION Electrical installations of buildings Part 4: Protection for safety. Overcurrent protection Electrical installations of buildings Part 4. Protection for safety. Protection against overcurrent OKS 3402 Effective date 01/01/1995 PREFACE 1 prepared and submitted to the Technical Committee for Standardization TC 337 "Electrical residential and public buildings" 2 approved and put into effect by Decision of State Standard of Russia from 21.06.94 № 176 3 This Standard contains the full authentic text of the international standard IEC 364-4-43 (1977) "Electrical installations of buildings. Part 4. Requirements for safety Chapter 43. Overcurrent protection with additional requirements which reflect the needs of the economy four first introduced Introduction This standard is part of the state standards for electrical installations of buildings developed on the basis of the standards of the International Electrotechnical Commission IEC 364 "Electrical installations of buildings". Establishes requirements for the content of the standard is a fundamental, whose provisions shall apply in all areas falling within the scope of the standardization and certification of electrical installations of buildings in the development and revision of standards, rules and regulations on the device, testing and commissioning of electrical installations of buildings. Numbering sections and paragraphs in the standard are in conformity with IEC 364 standards for electrical installations of buildings. The numbering system established in the standards IEC 364, provides an indication of notation numbers of parts and chapters of the international standard IEC designation numbers of sections and paragraphs of private standards. For example, in the notation of paragraph 432.1 of the standard figure 4 represents the part number, 43 - the chapter number, 432 - section number of the international standard IEC 364-4-43 (1977). The use of this numbering system provides vzaimouvyazku requirements of private standards set standards for electrical installations of buildings according to the rules adopted by the IEC Technical Committee 64 "Electrical installations of buildings". Requirements of the "Regulations for Electrical Installation" (RB, Sixth Edition), approved Glavtehupravleniem and Gosenergonadzor USSR Ministry of Energy, are generally consistent with the requirements of this standard. In the EMP (Chapter 3.1) set more stringent requirements on the consistency of the conductors and protective devices in comparison to the 433.2 in the standard requirement (the ratio between the current, ensuring reliable operation of protective devices, and the allowable long-term current conductor), and also provides for the use of protective devices selected by the value of disposable limit switching ability (3.1.3). Guidance on this issue and the concept of "one-time maximum switching capacity of protective devices are missing in the IEC 364-4-43 (1977). In this regard, this standard provides for the application requirements of SEP on these provisions in domestic practice, the design and construction of electrical installations of buildings. 1 Scope This Standard specifies requirements for the implementation of the protection of conductors from overcurrent in order to ensure safe operation of electrical installations of buildings. Scope of Standard - GOST R 50571.1. Additional requirements that reflect the needs of the economy, given in the footnotes to the 433.2, 434.3, 434.3.2 of this standard. 2 Normative references used in this Standard Link: GOST 50571.1-93 Electrical installations of buildings. Key provisions of 43 overcurrent protection 431 General requirements for conductors in electrical installations that are under stress, should be protected by one or more devices automatically turn off the power supply in case of overload and short circuit, except when the overcurrent is limited in accordance with section 436. In addition, protection against overload and short circuit protection must meet the requirements of section 435. Notes: 1 conductor under voltage, overload protected in accordance with section 433, see also protected from damage that can result in current, not exceeding an overload currents. 2 Protection of conductors in accordance with this standard does not necessarily guarantee the protection of the equipment attached to the conductors. 432 Characteristics of protective devices protective devices must be appropriate types listed in 432.1 ? 432.3. 432.1 devices providing protection against current overload and short circuit protection devices must provide any off-current to the expected value of the short circuit current, inclusive, at the point where the device is installed, and comply with the requirements of section 433 and 434.3.1. Such devices may be: ?-breakers with combined releaser; ? fuses; ? breakers in conjunction with fuses. Notes 1 The fuse comprises all the parts that make up a set of protective devices. 2 Application of protective devices, switching capacity is lower than the expected short-circuit current in a place where you installed the protection provided for in 434.3.1. 432.2 devices that provide protection only against overcurrent protection devices are used to overload currents with inverse time current characteristics, the breaking capacity of which may be below the expected value of the short circuit current at the point where the device is installed. Such devices must meet the requirements of section 433. 432.3 devices that provide protection only from the short-circuit protection device from short circuit current can be installed in places where overload protection is achieved by other means or is not required. These devices must provide off the short circuit current up to the expected value of the short circuit current, inclusive. The devices must conform to the requirements of section 434. Such devices may be: ?-breakers with instantaneous protection; ? fuses. 433 Protection against overcurrent 433.1 General requirements for protective devices should turn off any surge current flowing through conductors, before this current could cause a temperature rise of conductors dangerous for insulation, connections, clamps or the environment surrounding the conductors. 433.2 Consistency conductors and protective devices * Performance of any safety device that protects the cable from overload, to the following two conditions: 1) IB ? In ? IZ; 2) I2 ? 1,45 xIZ, where IB ? operating current circuit; IZ ? valid continuous current cable; In ? rated current protection device (for device protection with adjustable characteristics of the nominal current In is selected, the current); I2 ? current that ensures reliable operation of the protection device is practically taken as equal to I2: ? current response at a given time of operation for automatic switches; ? fuse melting current for a given response time for the fuses. Note ? Protection in accordance with this paragraph does not provide complete protection in some cases, such as a long-term current, a smaller value than I2, and do not always economically feasible solution. It is assumed that the electrical network is designed so that small overloads of long duration will not occur often. 433.3 Protection of conductors connected in parallel in the case when the same protection device protects several conductors in parallel, the value of long-term allowable current of these conductors is the sum of admissible currents of individual conductors, provided that the conductors are chosen so that the currents are approximately equal. This requirement can be applied to the ring distribution networks. 434 Protection against short circuit 434.1 General requirements for protective devices should turn off any short-circuit current flowing through the conductors of the protected circuit before this current could cause a danger due to thermal and mechanical effects on the conductors and their connections. 434.2 Determination of the expected short-circuit current expected short-circuit current at each corresponding point of electrical installations should be determined either by calculation or by measurements. ___________ * In the Soviet Union should also fulfill the requirements of "Regulations for Electrical Installation" (Chapter 3.1, paragraph 3.1.11) in terms of consistency of the conductors and protective devices. 434.3 A device for protection against short-circuit protection * Each device must meet the following two conditions. __________ * In the Soviet Union should also fulfill the requirements of "Regulations for Electrical Installation" (Chapter 3.1) in terms of establishing the characteristics of protective devices against short circuits. 434.3.1 breaking capacity shall be not less than the expected value of the short circuit current at the point where the device is installed, except as noted below. Allowed to use devices with lower breaking capacity if other protective device having the necessary breaking capacity is installed on the supply side. In this case, the characteristics of these two devices must be coordinated so that the penetrating power of a short circuit did not exceed that allowed for a device that is installed on the user side and the conductors protected by these devices. ? Note: In some cases it may be necessary to take into account other characteristics, such as dynamic effort and energy of the arc for a device that is installed on the user side. Adjusted data to be reconciled, should be obtained from the manufacturer's devices. 434.3.2 Time off full short-circuit current at any point in the chain must not exceed the time during which the temperature of the conductors reaches the allowable limit. For short circuit duration up to 5 times with t, during which the temperature rise of conductors from the maximum value permitted by the temperature in the normal mode to the maximum allowable temperature * can be roughly estimated by the formula where t ? length, with; S ? section, mm2; I ? rms short-circuit current, A; K = 115 ? for copper conductors with PVC insulation; K = 135 ? for copper conductors, rubber insulated (including the isolation of butyl rubber and ethylene propylene rubber), with XLPE insulation Polyethylene; K = 74 ? "for aluminum conductors with PVC insulation; K = 87 ?" for aluminum conductors, rubber insulated (including the isolation of butyl rubber and ethylene propylene rubber), with XLPE insulation; K = 115 for ? compounds of copper conductors, performed by soldering, which corresponds to a temperature of 160 ° C. Notes 1 For a very short duration (less than 0,1 s), when the current asymmetry is significant, the value of current-limiting devices K2S2 must be greater than the referenced manufacturer values ??(I2t), which characterizes the thermal resistance of the protection device. 2 Other values ??of K are currently being considered for: ? conductors of small cross section (particularly for the cross section of less than 10 mm2); ? short circuit duration St. 5; ? other types of connections of conductors; ? bare conductors; ? conductors with mineral insulation. 3 Nominal current protection devices against short circuit may exceed the allowable continuous current cable. ________ * The maximum permissible temperature of the heating wires short-circuit are given in "Rules of Electrical Code" (Chapter 1.4, paragraph 1.4.16). 435 Reconciliation of protection against overload and short circuit protection 435.1 Protection by a common device If an overload protection device meets the requirements of section 433 and has a breaking capacity not less than the expected short-circuit current at the point where it is installed, you believe that this device also provides protection for the conductor, located on the user side, from the short circuit currents. ? Note: This provision may not be valid for the whole range of short-circuit, checks are carried out in accordance with the requirements of 434.3. 435.2 Protection by separate devices requirements of sections 433 and 434 relate to the overload protection device and the device short-circuit protection, respectively. The characteristics of these devices must be coordinated so that the penetrating power of a short circuit does not exceed a value that can withstand, the overload protection device. 436 Restriction of the supercurrent through the characteristics of the power supply conductors should be considered as protected against overcurrent and short circuit, if power from the source, whose resistance is such that its maximum current can not exceed the allowable continuous current conductors (for example, some transformers to power the phone calls, some welding transformers and certain types of thermocouples). ____________ Key words: electrical buildings, security, protection against overcurrent, the characteristics of protective devices protective devices against overcurrent, protection devices on the current short-circuit breaking capacity, time off the full short-circuit current, consistent protection against overload and short circuit protection Posted on 06/26/2008 GOST on "Electrical, lighting, security systems," GOST 15597-82 Fixtures for industrial buildings. 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