PE of busbar trunk belongs to protect the lives of power transmission lines, it relates to the busbar fault current and fault current branch circuit all evacuated to the grounding device, to ensure contact with the body parts voltage does not endanger the personal safety while but also to protect the control circuit signaled to quickly cut off the power supply, so the PE line with the standard requirements should be specified relative to the ratio of line conductors, see GB GB7251.1-2005.7.4.3.1.5 and 22.214.171.124.7 (Table 3 Protection sectional area of the conductor PE, PEN), the standard is equivalent to IEC60439.1-1999.
Phase conductor cross-sectional area S
Corresponding to the minimum cross-sectional area of protective conductors SP (PE, PEN)
|S ≦ 16||S|
|35||S / 2|
|800||S / 4|
1.1 GB50303-2002 "Building Electrical Construction Quality Acceptance" refers to: a base insulator, bushing flange, protective net (hood) and close to the bus stand and so should not be used as a conductor bare ground or zero conductor connection . The provision of individual quality inspection station network (cover) understood as Busway shell, thus not allowed to use it as a PE ground lines, because of the standard analysis in place, which led to some Chinese enterprises to new technologies, new products When the total time to market by the resistance.
1.2 GB50303-2002 11.1.1 provisions stating very clearly written, the bus is powered from the main trunk, where the associated accessible bare conductor to ground or zero main reasons are: the accident occurred when the leakage current can be imported Ground device to ensure that the contact voltage does not endanger personal safety, while protecting signal the control circuit to prevent ground or in series between zero extension, so provision can not serve as the middle ground or zero conductor, ie: without a stable network connection cover, PE metal parts can not be used as the main trunk.
1.3 GB7251.1-2005 "Low-voltage switchgear and control equipment - Part 1: Type-tested and partially type-tested assemblies" is equivalent to IEC standards IEC60439.1-1999.
1.3.1 GB7251.1-2005 126.96.36.199.5a provisions say very clearly that when a part of complete sets of equipment when it is removed from the housing, for example, routine maintenance, equipment to protect the rest of the circuit should not be cut off.
If the measures adopted to ensure lasting protection circuit has good conductivity and current carrying capacity sufficient to withstand the equipment ground fault current flowing, then the assembly of complete sets of equipment of various metal parts are considered to be able to effectively ensure continuous protection circuit sex.
1.3.2 GB7251.1-2005 188.8.131.52.5.d if the housing as part of the protection circuit is used, the cross-sectional area specified in 184.108.40.206.7 minimum cross-sectional area of the conductive capacity should are equivalent.
1.4 Standard analysis
These two criteria are specified in 1.4.1: Case for PE wire must have a stable connection, for routine maintenance, PE line protection circuit should not be cut off. So GB50303-2002 and GB7251.1-2005 is no conflict. Case for PE line must meet the following two requirements:
(1) Requires a reliable connection; (2) To meet GB7251.1-2005 220.127.116.11.1.7 Table 3 provides protective conductor cross-sectional area equivalent value, which is equivalent conductivity.
1.4.2 In the short-term thermal stress caused by current circumstances to protect the conductor cross-sectional area is calculated:
Subject to the duration of the thermal stress of about 1s current protection conductor cross-sectional area shall be calculated as follows.
SP-sectional area, mm2;
I-negligible impedance fault in the case of protection of electrical flow through the fault current value (root mean square value), A;
t-protecting electrical breaking time, s;
Note: The impedance of the circuit should take into account the role and current limiting protection device limiting capability (J).
k-factor, which depends on the protective conductor, insulation and other parts of the material and the initial and final temperatures.
|protective conductor or cable insulation jacket|
|PVC||XLPE, EPR, bare conductor||butene rubber|
|final temperature||160 ℃||250 ℃||220 ℃|
|Note: Conductor assumed initial temperature was 30 ℃.|
1.4.3 GB50303-2002 11.1.1 refers mainly mesh (cover) class components, without a stable connection for PE nets are not lines, busbar on the network (cover) is what? It should be said busbar connections and connection cover plates can be said to cover, check the connection head because the part may have to open; some places when installing isolation busway fence, can be said network; belong screw connections Busway cover overhaul easily removed, can be said to cover.
Five kinds of programs, there is bus independent internal PE line, see Figure A program and E programs; external independent PE line, see Plan B and D programs; and overall connectivity shell do PE lines.
Above all for busbar aluminum shell, except A program, other programs are in line PE line conductor busbar current standard PE wire cross-sectional area. Do you think that there are several qualified? Which most secure?
2.1 A program, market common products. PE wire inside the bus, each with the shell is not connected, only shell between paragraphs 16mm2 wire jumper. When a certain phase busbar enclosure leakage or short circuit occurs when, for example, the third paragraph of accidents busbar current, from 2-3 and 3-4 two evacuation, but the two can not meet 200A protective conductor busbar fault current evacuation . Therefore, the scheme does not apply to more than 200A busbar. Standard PE conductor cross-sectional area of the line the most important, is a busbar fault current evacuation itself, to ensure that touches its voltage busbar enclosure without endangering personal safety play a protective role, and timely feedback to the control of the power distribution cabinet bus segment bus switching off the power. If only the branch circuit fault current evacuation, PE can meet the main trunk branch circuit, the maximum rated current of the accident is not required by current evacuation phase conductor busbar configuration PE wire cross-sectional area ratio, so the provisions of the PE wire conductor busbar primarily to ensure an equivalent cross-sectional area to evacuate busbar fault current, so that the voltage does not reach compromise personal safety.
2.2 E scheme differs from Option A, each PE busbar enclosure with a jumper wire. If Option A case of an accident, PE line and shell from 3 # jumper wire, shell paragraphs and paragraphs 2-3 and 3-4 by the jumper wire, combined to meet the criteria in Table 3 protective conductor cross-sectional area ( PE, PEN) specifications comply with the standard. The problem is that not ensure that the internal bus # 3 jumper cable with PE conductor size, its cross-sectional area of how and whether each has a jumper, which is also worth considering.
2.3 B and D programs as a separate program PE line, set out in PE busbar lines can clearly see the cross-sectional area of the wiring is in line with the standard, non-secret operations. But D program has a problem, because the flat iron shots Route PE line, if the bus current exceeds 500A, the main trunk of the PE line can not meet the national standard GB7251.1-2005 18.104.22.168.7 Table 3 marked the equivalent cut-off area. Precisely D program is used more in recent years in engineering practice, this issue deserves special attention.
2.4 C program, two units are connected busbar aluminum alloy, the aluminum row welded mechanical connection by connecting the head, as the protective circuit PE ground, the ground line as a PE shell as a whole. The program just make sure connectors are mechanically connected, confirm the connection of PE and PE wire welding lines and the primary side of the cross-sectional area to meet the national standard GB7251.1-2005 22.214.171.124.7 Table 3, the cross-sectional area of the protective conductor (PE, PEN ) equivalent cross-section can be, but also because of the overall housing as a PE ground lines, its cross-sectional area of the column is much larger than the standard value, is the most security programs, should be introduced.
2.5 Shell as PE line to meet the following conditions:
2.5.1 Busway two units connected, the connection with the independent PE line the same way, with A, B, C, N lines simultaneously with the mechanical connection.
2.5.2 Has lapped parts and connectors for the PE must have a reliable connection, the overhaul should not be cut off.
2.5.3 Beginning of the line section box with plug inserted PE line interface to do Copper transitional technical processing; plug box of pins to be inserted in the copper to prevent oxidation of different metals copper and aluminum.
2.5.4 Spanned between the two units and PE PE wire and cable cross-sectional area of the overall housing to meet the national standard GB7251.1-2005 126.96.36.199.7 Table 3, the cross-sectional area of the protective conductor (PE, PEN ) equivalent cross-sectional area (equivalent to IEC standards IEC60439.1-1999).
Zhuhai Guangle GLMC Series Busway won the national patents, busbar enclosure doubles as a PE grounding line, the product is the use of aluminum alloy shell do PE busbar line units of the main busbar side ends welded aluminum row as PE line. Bus when two units are connected, PE line and A, B, C, N phase conductor while using mechanical connection as a PE grounding lines. Welded aluminum row and busbar jumper whole shell is greater than GB7251.1-2005 188.8.131.52.7 Table 3 shows the equivalent cross-sectional area. GLMC Series Busway When the shell as a PE grounding line, the equivalent is the standard cross-sectional area several times.
GLMC series All products have passed the national compulsory product certification (3C certification), in line with national standards GB7251.2-2006 is equivalent to IEC standards IEC60439.2-2000. This series of products per square millimeter through 2A current limit temperature rise is less than 30K, its line loss than ordinary busway reduced by 60%, the fault current evacuation Busway faster than ordinary, shell hit a low voltage accidents, safety performance is far Over independence for the PE line busbar busbar. Compare five-phase five-wire power supply scheme, shell doubles as a PE line PE line fault current program than independence Busway faster evacuation. Because there is no cross-sectional area of wire and connection stability issue, the housing for the PE line PE line security and stability than independence, while saving copper resources, reducing the project cost; because of reduced PE busbar inside a row, in the middle copper away from the shell closer, bus internal temperature also decreased, reducing the power consumption, but also to adapt to China's current energy policy to reduce exhaust.
Hope the QC inspection personnel-depth understanding of the meaning of the standard on how to achieve the PE line protection circuit continuity purposes, and how to do the most secure and reliable products to conduct research into, in order to reduce China's modernization and energy conservation Consume more contributions.