This standard specifies the safety measures provided to personnel and equipment of the low-voltage system in case of a fault between the high-voltage system and the ground on the high-voltage side of the substation supplying power to the low-voltage system. GB 16895.11-2001 Electrical installations in buildings Part 4: Safety protection Chapter 44: Overvoltage protection Section 442: Protection of low-voltage electrical installations against temporary overvoltages and faults between the high-voltage system and the ground GB16895.11-2001 Standard download decompression password: www.bzxz.net

GB16895.11—2001
Articles 442.1.2, 442.1.3, 442.2 to 442.8 of this standard are mandatory, and the rest are recommended. This standard is part of the series of standards "Electrical Installations in Buildings" and is equivalent to IEC60364-4-442:1993 "Electrical Installations in Buildings Part 4: Safety Protection Chapter 44: Overvoltage Protection Section 442: Protection of Low-voltage Electrical Installations against Temporary Overvoltages and Faults between High-voltage Systems and Earth" and its 1st Amendment (1995) and 2nd Amendment (1999). The national series of standards for "Electrical Installations in Buildings" includes the following 7 parts: Part 1 Scope, purpose and basic principles Part 2 Definitions Part 3 General characteristics evaluation Part 4 Safety protection Part 5 Selection and installation of electrical equipment Part 6 Part 7 Requirements for special installations or locations IEC60664-1:1992, which is cited in the technical content of IEC60364-4-442, has been adopted as the corresponding national standard GB/T16935.1-1997 "Insulation coordination of equipment in low-voltage systems Part 1: Principles, requirements and tests". Appendix A of this standard is a suggestive appendix. This standard is proposed by the China Electrical Equipment Industry Association. This standard is under the jurisdiction of the National Technical Committee for Standardization of Electrical Installations in Buildings. This standard was drafted by the China Academy of Mechanical Sciences, Beijing Labor Protection Research Institute, Guangzhou Electric Science Research Institute, and China Electronic Engineering Design Institute.
The main drafters of this standard are Li Shilin, Guo Ting, Zhu Deji, He Weien, and Huang Deming. GB16895.11—2001
IEC Foreword
1) IEC's formal resolutions or agreements on technical issues are formulated by technical committees composed of national committees that are particularly concerned with these issues, and express international consensus on the issues involved as much as possible. 2) These resolutions or agreements are used internationally in the form of standards and are accepted by various national committees in this sense. 3) In order to promote international unification, IEC hopes that all national committees will adopt IEC standards in their respective national regulations under the conditions permitted by their domestic conditions. If there are any inconsistencies between IEC standards and corresponding national regulations, they should be clearly pointed out in the national regulations as much as possible.
This standard was drafted by IEC Technical Committee 64. The text of this newspaper is based on the following documents.
Six Months Rule
64(CO)175
Full information on the approval of this standard can be found in the voting report in the table above. Appendix A is for reference only.
Voting Report
64(CO)213
IEC Foreword to the First Amendment
This amendment was prepared by IEC Technical Committee 64. The text of this amendment is based on the following documents.
Draft International StandardbzxZ.net
64/748/DIS
Voting Report
64/795/RVD
Full information on the approval of this amendment can be found in the voting report in the table above. IEC Foreword to the Second Amendment
This amendment was prepared by IEC Technical Committee 64. The text of this amendment is based on the following documents.
Draft International Standard
64/1046/FDIS
Voting Report
64/1061/RVD
Full information on the approval of this revised document can be obtained in the voting report in the table above. 90
GB 16895.11—2001
IEC Introduction
The provisions of this standard do not apply to systems that are wholly or partly under the jurisdiction of a public power company (see the scope in IEC364-1). Fault currents flowing through the earthing electrodes of exposed conductive parts of a substation cause a significant increase in the potential of the exposed conductive parts of the substation to earth, i.e., the fault voltage, the magnitude of which depends on: the magnitude of the fault current, and the resistance of the earthing electrodes of the exposed conductive parts of the substation. Fault current may cause:
General increase in the potential of the low voltage system to the ground, i.e. stress voltage, which may cause the insulation of the low voltage equipment to be broken down; General increase in the potential of the exposed conductive parts of the low voltage system to the ground, which may cause an increase in the fault voltage and contact voltage. Note: The term "high voltage (HV)\" in this standard refers to the voltage exceeding the upper limit of voltage segment I. The term "low voltage (LV)\" refers to the voltage not exceeding the upper limit of voltage segment 1.
National Standard of the People's Republic of China
Electrical installations of buildings--Part 4: Protection for safety-Chapter 44: Protection against overvoltages-Section 442-protection of low-voltage installationsagainst temporary overvoltages and faults betweenhigh-voltage systems and earth442.1 General
GB 16895.11—2001
idt IEC 60364-4-442:1993
Note: The clauses of this standard only consider the following four situations, which are usually the causes of the most serious temporary overvoltages (defined in IEC604-03-12). Faults between high-voltage systems and earth. Explanatory notes to the relevant clauses are given in Appendix A, Disconnection of the neutral conductor in low-voltage TN and TT systems (see Clause 442.6); - Accidental earthing of low-voltage IT systems (see Clause 442.7); Short circuit in low-voltage electrical installations (see Clause 442.8). 442.1.1 Scope and purpose
This standard specifies the safety measures to be provided to personnel and equipment in low-voltage systems in the event of a fault between the high-voltage system and earth on the high-voltage side of a substation supplying the low-voltage system. 442.1.2 Fault voltage
The fault voltage or touch voltage caused by an earth fault in the high-voltage system shall not exceed in magnitude and duration the values ​​given by curves F and T in Figure 44A.
442.1.3 Stress voltage
The power-frequency stress voltage on low-voltage equipment in a consumer's electrical installation caused by an earth fault in the high-voltage system shall not exceed in magnitude and duration the values ​​given in Table 44A.
1 The power-frequency stress voltage is the voltage present across the insulation. 2 If the insulation level of the low-voltage equipment is appropriate and meets the conditions specified in Article 442.3, the low-voltage equipment in the substation is allowed to withstand higher stress voltages. Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on November 21, 2001 92
Implementation on November 1, 2002
GB 16895.11—2001
Table 44A
Allowed AC stress voltage in low-voltage electrical installations, VU. +250 V
U. +1.200 V
Cut-off time, s
When the (maximum) nominal voltage of the low-voltage system to ground is less than U due to special reasons (such as one phase conductor in the system is grounded), the stress voltage shall be specified separately.
2 The values ​​in the first row of the table are used for systems with longer cut-off times, such as impedance-grounded high-voltage systems; the values ​​in the second row are used for systems with shorter cut-off times, such as directly grounded high-voltage systems. The above two rows of values ​​are the guidelines for appropriate insulation design of low-voltage equipment taking into account temporary overvoltage factors (see 1.3.7.1 of GB/T 16935.11997). When low-voltage equipment is connected to a TN system in which the neutral conductor is connected to the protective earthing electrode of the high-voltage system of the substation and is used outside the area affected by the total equipotential bonding, its basic, double and reinforced insulation will experience these AC temporary overvoltages. When low-voltage equipment is used in the total equipotential bonding area, the total equipotential bonding is connected to the protective conductor of the TN system at the power supply line end of the building installation, and these overvoltages will not occur.
442.1.4 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T13870.1-1992 Effects of current passing through the human body Part 1: Common parts (neqIEC60479-1: 1984) GB14821.1—1993 Protection against electric shock of electrical installations in buildings (egvIEC60364-4-41: 1992) GB16895.1-1997 Electrical installations in buildings Part 1: Scope, purpose and basic principles (idtIEC60364-1: 1992) 442.2 Grounding system of substation
The substation should have a grounding system, which should be connected to the following objects: grounding electrode,
transformer box;
metal sheath of high-voltage cable;
metal sheath of low-voltage cable. However, the neutral conductor has been grounded through an independent grounding electrode; grounding conductor of the high-voltage system;
exposed conductive parts of high-voltage equipment and low-voltage equipment; conductive parts outside the device.
442.3 Grounding Rationing of Substations
If 442.3.1 or 442.3.2 can be met separately or simultaneously, the conditions listed in 442.4 and 442.5 can be considered to have been met. If neither 442.3.1 or 442.3.2 can be met, the requirements of 442.4 and 442.5 shall be met. 442.3.1 The substation is connected to
a high-voltage cable with a suitable metal sheath that has been grounded; or a low-voltage cable with a suitable metal sheath that has been grounded; or a high-voltage and low-voltage mixed cable with a suitable metal sheath that has been grounded. And in all cases:
The total length of the above cables exceeds 1 km.
442.3.2 The grounding resistance of the exposed conductive parts of the substation shall not exceed 1Q93
GB 16895.11—2001
442.4 Grounding configuration related to the system grounding type in low-voltage electrical installations 442.4.1 Symbols
The symbols used in this standard are:
Im: ground fault current flowing through the grounding electrode part of the exposed conductive parts of the substation in the high-voltage system; R: grounding electrode resistance of the exposed conductive parts of the substation, U.: voltage of the phase line to the neutral point of the low-voltage system; U: line voltage of the low-voltage system,
Ut: fault voltage between the exposed conductive parts and the ground in the low-voltage system; UI: stress voltage in the low-voltage equipment of the substation; U2: stress voltage in the low-voltage equipment of the user system. 442.4.2 TN system
a) When the fault voltage RXIm can be cut off within the time given in Figure 44A, the neutral conductor of the low-voltage system can be connected to the grounding electrode of the exposed conductive parts of the substation (see TN-a in Figure 44B). Note: If the exposed conductive parts of the low-voltage equipment of the electrical installation in the building are connected to the main equipotential bonding with a protective conductor, the touch voltage is actually ov.
b) If condition a) is not met, the neutral conductor of the low-voltage system should be grounded through an electrically independent grounding electrode (see TN-b in Figure 44B). In this case, the requirements of 442.5.1 should be met. 442.4.3 TT system
a) When the relationship between the stress voltage (R×I.+U.) and the cut-off time given in Table 44A is suitable for the insulation level of the low-voltage equipment of the user system, the neutral conductor of the low-voltage system can be connected to the grounding electrode of the exposed conductive parts of the substation (see TT-a in Figure 44C). b) If condition a) is not met, the neutral conductor of the low-voltage system shall be grounded via an electrically independent grounding electrode (see TT-b in Figure 44c). In this case, the requirements of 442.5.1 shall be met. If the exposed conductive parts of the low-voltage equipment of the electrical installation in the building are connected to the main equipotential bonding with a protective conductor, the touch voltage is actually 0 V.
442.4.4IT system
a) If it can be cut off within the time given in Figure 44A under the fault voltage (RXI), the exposed conductive parts of the low-voltage equipment in the user's electrical installation can be connected to the grounding electrode of the exposed conductive parts of the substation (see Figures 44D, 44J and 44K). If this condition cannot be met, the exposed conductive parts of the low-voltage electrical equipment in the low-voltage electrical installation shall be connected to the grounding electrode of a grounding system that is electrically independent of the exposed conductive parts of the substation (see Figures 44E to 44H). b) When the exposed conductive parts of the low-voltage equipment in the user's electrical installation are grounded through an electrically independent grounding electrode from the substation, and when the relationship between the stress voltage (R×Im+U.) and the disconnection time given in Table 44A is suitable for the low-voltage equipment of the user's electrical installation, the neutral point impedance of the low-voltage system (if any) should be connected to the grounding electrode of the exposed conductive parts of the substation (see Figure 44E). If the above conditions cannot be met, the neutral point impedance should be grounded through an electrically independent grounding electrode (see Figures 44F and 44H). In this case, the requirements of 442.5.2 should be met. 442.5 Limitation of stress voltage in low-voltage equipment in substations 442.5.1 TN system and TT system
When the neutral conductor of the TN system and the TT system is grounded through a grounding electrode electrically independent of the exposed conductive parts of the substation (see TN-b in Figure 44B and TT-b in Figure 44C), the stress voltage (RXI+U.) should be cut off within a time corresponding to the insulation level of the low-voltage equipment in the substation.
Note: The insulation level of the low-voltage equipment in the substation may be higher than the value given in Table 44A. 442.5.2 IT system
GB16895.11—2001
When the neutral impedance of the IT system (if any) and the exposed conductive parts of the user's electrical equipment are grounded through an earthing electrode electrically independent of the substation (see Figures 44F, 44G and 44H), the stress voltage (RXIm+U.) should be cut off within a time corresponding to the insulation level of the low-voltage equipment in the substation. 442.6 The stress voltage caused by the open circuit of the neutral conductor in TN and TT systems should take into account that when the neutral conductor of the three-phase TN or TT system is open circuited, the basic, double and reinforced insulation and components that withstand the rated voltage between the phase conductors can temporarily withstand the line voltage. The stress voltage at this time can reach U=√3U. 442.7 The stress voltage caused by accidental grounding of the IT system should take into account that when a phase conductor of the IT system is accidentally grounded, the basic, double and reinforced insulation and components that withstand the rated voltage between the phase conductors can temporarily withstand the line voltage. The stress voltage at this time can reach U=3U. 442.8 The stress voltage caused by the short circuit between the phase conductor and the neutral conductor should be considered. When the phase conductor and the neutral conductor are short-circuited, the stress voltage can reach 1.45U within 5s. 95
GB 16895.112001
Figure 44A The maximum duration of the fault voltage F and the touch voltage T caused by the earth fault of the high-voltage system
6701000
Voltage.v(acrms)
Substation
GB 16895. 11—2001
U, U.
U = R× Im+Uo
Figure 44BTN-system
Low-voltage electrical installation
U= U,= U.
U= R× Im
Uz = Uo
Ur = 0
Substation
GB 16895. 11--2001
U,= Uo
U# R×1m+Uo
Figure 44CTT-System
Low-voltage electrical installation
Uz == R× Iα+U.
Uz Ue
GB 16895.11-2001
U, U.
Uz = U, = Uo
U,= R×Im
1． There is no fault in the low-voltage system
U,= Ua/3
U, = U,=UoN3
U=R×Im
2. There is the first fault in the low-voltage system
Figure 44DIT-system, example a
GB 16895.11--2001
U, = Uo
U, = R× 1m+U.
1. There is no fault in the low-voltage system
U,= Ua/3
U2 = R× Im+ Uo/3
U+=RAXIJSUL
2. There is a first fault in the low voltage system
Figure 44EIT-system, example b
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