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People's Republic of China (PRC) national standard
Code for design of low-voltage distribution equipment and lines
GBJ 54-83
(Trial)
Editor-in-Chief: Ministry of Machinery Industry of People's Republic of China (PRC) and China
Approved by: People's Republic of China (PRC) State Planning Commission.
Date of trial: 1 June 9841.
Compilation and interpretation
This specification is based on announcement number. The former National Capital Construction Committee 150(7 1) was compiled by the former No.8 Design Institute of the First Machinery Department and relevant units in the United Nations.
In the process of compiling, we conducted extensive investigation and study, summarized the design and actual operation test of power engineering since the founding of the People's Republic of China, solicited the opinions of relevant units throughout the country, and finalized it after repeated review and revision with relevant departments.
The main contents of this specification include: the selection of electrical appliances and wires below 1000 volts, the layout regulations of power distribution devices and the requirements for buildings, the protection of power distribution lines, the wiring of insulated wires, the wiring of bare wires, the installation of plug-in buses and the laying of cables.
As this specification is written for the first time, some contents need to be supplemented and improved in future work. During the trial implementation of this specification, if it is found that it needs to be revised or supplemented, please send your opinions and relevant materials to the Eighth Design and Research Institute of the Ministry of Machinery Industry, and send a copy to the Design and Research Institute of our department for reference in future revision.
Ministry of machinery industry
1983 1 1 month
Principal symbol number
-temperature correction coefficient;
-Ambient temperature of the laying site;
-Maximum operating temperature of the conductor;
-Ambient temperature used in current-carrying data.
Chapter I General Principles
Article 1.0. 1 In the design of low-voltage distribution equipment and lines, the national technical and economic policies must be seriously implemented to ensure personal safety, reliable power supply, qualified power quality, advanced technology and economy.
Article 1.0.2 The design of low-voltage distribution equipment and lines shall be convenient for installation and maintenance.
Article 65438 +0.0.3 The design of low-voltage distribution devices and lines should save nonferrous metals, and the technical policy of replacing copper with aluminum should be seriously implemented.
Article 1.0.4 This specification is applicable to the design of power distribution devices and lines below 1000 volts for new projects.
Article 65438 +0.0.5 The design of low-voltage distribution equipment and lines shall still comply with the provisions of existing relevant national standards and norms.
Chapter II Selection of Electrical Appliances and Conductors
Selection of the first stage power supply
Article 2. 1. 1 When selecting low-voltage appliances, the following requirements shall be met:
First, meet the requirements of working voltage, current, frequency, accuracy level and use environment;
Second, the distribution appliances should try their best to meet the dynamic stability and thermal stability under short circuit conditions;
Three, electrical disconnect short-circuit current, should try to meet the short-circuit condition of on-off ability.
Article 2. 1.2 To check the on-off ability of electrical appliances under short circuit conditions, the effective value of the periodic component of short circuit current should be adopted, and the feedback influence of the motor should be considered.
Article 2. 1.3: The calculation wiring mode used to determine the short-circuit current shall be the normal wiring mode where the maximum short-circuit current may occur. At the same time, only the impedances of high-voltage system, transformer and low-voltage line can be considered, and the short-circuit current of low-voltage side will not be attenuated when short-circuit is considered.
Section 2 Selection of Conductors
Article 2.2. 1 The models of insulated conductors and cables shall be selected according to the requirements of working voltage and service environment.
Article 2.2.2 When selecting the conductor section, the following requirements shall be met:
First, the allowable current carrying capacity of the conductor should not be less than the load calculation current of the line;
Second, the line voltage loss from the low voltage side bus of transformer to the receiving end of electrical equipment generally does not exceed 5% of the rated voltage of electrical equipment;
Three, the minimum cross section of insulated wire core, should comply with the provisions of article 2.2.7 of this specification.
Article 2.2.3 The allowable current carrying capacity of neutral wire in three-phase four-wire system should not be less than the maximum unbalanced load current in the line, and it should also comply with the provisions of Articles 4.0.3 and 4.0.4 of this specification. The zero line conductance used for zero protection should not be less than 50% of the phase line conductance in this line.
Article 2.2.4 The allowable current carrying capacity of the conductor shall be revised according to the ambient temperature of the laying place. The temperature correction coefficient shall be determined as follows:
(2.2.4)
Where-temperature correction coefficient;
-Maximum working temperature of conductor (℃);
—— Actual ambient temperature of laying place (℃);
-Ambient temperature (℃) used in current-carrying data.
In addition, it should be corrected according to the number of wires laid in parallel.
Article 2.2.5 The following temperature values shall be adopted for the ambient temperature of conductor laying:
1. For cables directly laid in soil, the monthly average temperature in the hottest month in the calendar year should be adopted;
2. For bare wires laid in the air, the average maximum temperature in the hottest month in the laying area shall be adopted outdoors; The average maximum temperature in the hottest month of indoor installation site (all take the total average of ten years or more).
Article 2.2.6 When laying insulated wires and cables along paths with different cooling conditions, when the length of the section with the worst cooling conditions exceeds 5m (10m when crossing the road), the section of insulated wires and cables shall be selected according to the conditions in this section. However, it is also possible to use only insulated wires and cables with large cross sections in this part.
Article 2.2.7 According to the requirement of mechanical strength, the section of insulated core wire should not be less than the values listed in Table 2.2.7.
Table 2.2.7 Minimum Section of Insulated Conductor Core
Note: For indoor lighting lamps in industrial and civil buildings, if hanging chains or hanging pipes are used, and the down conductor of the lamp cap is a copper cord, the cross section can be appropriately reduced.
Chapter III Distribution Equipment Layout
The first part is the general rules.
Article 3. 1. 1 The normally uncharged metal parts of the power distribution device must have reliable electrical connection with the grounding device.
Both ends of each column of switchboard shall be connected to the ground wire or zero wire.
Article 3.65438 +0.2. Distribution equipment room, should not be through the pipeline has nothing to do with the distribution equipment.
Article 3. 1.3 When installing the floor-type distribution box, the bottom should be higher than the ground. When installed outside the house, it should be more than 0.2 meters above the ground.
Article 3. 1.4 When high and low voltage power distribution devices are installed in the same room, they shall comply with the relevant provisions of Code for Design of Industrial and Civil Substations Up to 10 kV.
Article 3. 1.5: Generally, the width of indoor passage of distribution equipment shall not be less than the following values:
1. When the distribution board is arranged in a single row, the channel in front of the screen is1.5m;
2. When the distribution panel is arranged in double rows, the channel in front of the panel is 2m;
Third, the channel behind the screen is 1 m, which can be reduced to 0.8 m when it is difficult.
Article 3. 1.6 The clear distance between the indoor exposed conductive part and each part of the power distribution device shall meet the following requirements:
1. In the channel behind the screen, when the height of the exposed conductive part is less than 2.3m, it should be shielded, and the height of the channel after shielding should not be less than1.9m; The width of the shielding channel shall meet the requirements of Article 3. 1.5 of this specification.
2. The exposed conductive part of the channel passing through the screen shall have a height of not less than 2.5 meters.
Article 3. 1.7 When the length of power distribution equipment is more than 6m, two exits leading to this room or other rooms shall be set behind the screen. If the distance between two exits exceeds 15m, the exits should be increased.
When the primary load power supply is supplied by the same power distribution equipment room, there should be a fire partition or partition in the bus section, and the cables supplying the primary load power supply should not pass through the same cable trench.
Article 3. 1.8 When the exposed conductive part is blocked by a fence, the clear distance between the fence and the exposed conductive part shall meet the following requirements:
A, with mesh is not more than 20 x 20×20mm fence cover, should not be less than100 mm;
Two, with a flat fence shielding, should not be less than 50 mm. ..
Article 3. 1.9 protective power distribution devices shall be adopted for power distribution devices installed in production workshops or public places.
When the power distribution device is turned on, when the height of the exposed conductive part is less than 2.3 meters, a fence should be set up. The clear distance from the fence to the exposed conductive part should not be less than 0.8m, and the height of the fence should not be less than1.2m. The channels in front of and behind the screen of the power distribution device in the fence should comply with the provisions of Article 3. 1.5 of this specification.
Note: Fence refers to fence, net fence or plate fence.
Section 2 Building requirements
Article 3.2. 1 The fire resistance rating of the power distribution room shall not be lower than Grade III.
Article 3.2.2 There shall be two exits in the power distribution equipment room with a length greater than 8m, and they shall be arranged at both ends of the power distribution equipment room as far as possible. When both upstairs and downstairs are power distribution rooms, the power distribution room located upstairs should have at least one exit to the outside.
Doors should be opened outward except for rooms leading to high-voltage electrical equipment.
Article 3.2.3 The ceiling of the power distribution room should be painted, and the wall should be plastered and painted. The ground is generally leveled with cement and calendered.
Waterproof measures should be taken for cable trench.
Article 3.2.4 The power distribution equipment room with people on duty should adopt natural lighting as far as possible. Heating devices should be installed in cold areas, and measures such as heat insulation should be taken in hot areas.
Chapter IV Protection of Distribution Lines
Article 4.0. 1 distribution line shall be equipped with short circuit protection. All levels of protection in distribution system should cooperate selectively. When this requirement cannot be met, the primary protection on the low voltage side should be operated selectively as far as possible.
Article 4.0.2 The rated fusing current of the fuse or the setting current of the automatic overcurrent release should be as close as possible but not less than the calculated load current of the protected line. At the same time, the protection device should not disconnect the protected line when there is normal short-term overload (such as motor starting or self-starting in the line).
Article 4.0.3 When fuses are used for short-circuit protection of distribution lines, the selection of melt or conductor section shall meet the following requirements:
A, the rated current of fuse melt should not be greater than 2.5 times the allowable current-carrying capacity of cable or tube-penetrating insulated conductor, or 1.5 times the allowable current-carrying capacity of bare insulated conductor.
Second, when the following short circuit occurs at the end of the protected line, the short circuit current value should not be less than 4 times the rated current of the fuse melt.
1. Single-phase grounding short circuit in power network with neutral point directly grounded;
2. Two-phase short circuit in neutral ungrounded network.
Article 4.0.4 When the automatic switch is used for short-circuit protection of distribution lines, the setting current shall meet the following requirements:
A, when using automatic switch with instantaneous or short delay overcurrent tripping device, the setting current of tripping device should avoid short-term overload current, and the ratio of setting current to allowable current carrying capacity of conductor is not specified.
Second, when using an automatic switch with a long-delay overcurrent release and an instantaneous or short-delay overcurrent release, the setting current of the long-delay overcurrent release shall not be greater than 1. 1 times the allowable current-carrying capacity of insulated wires or cables according to the requirements of return current, and its action time shall avoid the duration of short-time overload current.
3. When the following short circuit occurs at the end of the protected line, the short-circuit current should not be less than 1.5 times of the setting current of the instantaneous or short-delay overcurrent trip of the automatic switch.
1. Single-phase grounding short circuit in power network with neutral point directly grounded;
2. Two-phase short circuit in neutral ungrounded network.
Article 4.0.5 When the single-phase short-circuit current of the terminal is difficult to meet the requirements of Article 4.0.4 of this specification, the automatic switch protection circuit can adopt zero-sequence protection or automatic switch with long-delay overcurrent release. If a long-delay overcurrent release is selected, its action time should not exceed 15 seconds under the action of short-circuit current.
Article 4.0.6 The following lines shall be equipped with overload protection:
Lighting lines of residential buildings, important warehouses and public buildings;
Two, power lines that may be overloaded for a long time (excluding bare wires);
Three, in the flammable or refractory building structure, the use of external flame retardant layer of insulated wire surface mounted circuit.
Article 4.0.7 The allowable current carrying capacity of insulated wires and cables of distribution lines equipped with overload protection shall not be less than 1.25 times of the rated current of fuses or 1.25 times of the setting current of automatic switch delay overcurrent release.
Article 4.0.8 Protective appliances shall be installed at the places where the conductor section of distribution lines is reduced, at the branches of distribution lines or at places where protection must be selected. However, it does not conform to Article 4.0.9 of this specification.
The protection device shall be installed at the junction of the protected line and the power supply line. If it is difficult, it can be installed within 3 meters from the connection point, which is convenient for operation and maintenance.
When the branch line is led down from the higher trunk line, the protective equipment can be installed within 30 meters from the branch point, which is convenient for operation and maintenance. However, it should be ensured that when a single-phase (or two-phase) short circuit occurs at the end of the branch line, the protective appliances closest to the short circuit point can act, and the branch line should have an irresistible outer layer or be laid through pipes.
Article 4.0.9 In the distribution line, in any of the following circumstances, it is not necessary to install protective appliances at the place where the conductor section is reduced or at the branch of the distribution line:
1. The protection device in the previous section of the line has been able to protect the line section or branch line with reduced cross section;
Two, the use of 20 amps and below the protection of electrical circuits;
Third, the power distribution device is connected from the bus to the branch line of the protection appliance;
Four, outdoor overhead distribution lines.
Article 4.0. 10 When using fuses to protect distribution lines, the fuses shall be installed on ungrounded phases or poles.
Fuses should not be installed on the neutral line for zero protection.
Article 4.0. 1 1 When the automatic switch is used to protect the distribution line, its overcurrent release shall be installed on each ungrounded phase or pole.
In the distribution line of neutral ungrounded network, an overcurrent trip can be installed in two phases of a three-phase three-wire system. In DC two-wire system, the overcurrent trip can be installed on one electrode. At this time, in the same power supply distribution line, the overcurrent trip should be installed in the same phase or pole.
Chapter V Laying of Distribution Lines
Section 1 Wiring of Insulated Conductors
Article 5. 1. 1 Direct wiring is generally suitable for indoor places in normal environment.
When wiring directly, sheathed insulated wires should be used, the cross section should not be greater than10mm2, and the spacing between wiring fixing points should not be greater than 200mm.
Article 5. 1.2 porcelain (plastic) clip wiring is generally applicable to indoor places under normal environment and outdoor places under overhangs.
The wiring of drum insulator and pin insulator is generally suitable for indoor and outdoor places.
Article 5. 1.3 adopts porcelain (plastic) clips. When the drum insulator and pin insulator are connected indoors and outdoors, the distance between the insulated conductor and the ground shall not be less than the values listed in Table 5. 1.3.
Article 5. 1.4 When drum insulators and pin insulators are used for indoor and outdoor wiring, the distance between insulated conductors shall not be less than the values listed in Table 5. 1.4.
Article 5. 1.5 When the insulated wire is exposed to high temperature radiation or corrosive to the insulated wire, the minimum spacing between wires and between wires and the building surface shall not be less than the values listed in Table 5.2.4 of Article 5.2.4 of this specification.
Article 5. 1.6 The distance between the insulated conductor of outdoor wiring and the building shall not be less than the values listed in Table 5. 1.6.
Article 5. 1.7 Metal pipeline wiring is generally applicable to indoor and outdoor places, but not to places where metal pipelines are seriously corroded.
On the ceiling of the building, metal pipes should be used for wiring.
Article 5. 1.8 For wiring of metal pipes laid in damp places or underground, water and gas steel pipes shall be adopted. Wires and steel pipes can be used for metal pipe wiring in dry places or workshop floors.
Article 5. 1.9 When wires and pipes are laid on the same side as hot water pipes and steam pipes, they should be laid below the hot water pipes and steam pipes. In case of difficulty, it can be laid on it, and its clear distance is generally not less than the following values:
1. The pipeline is 0.2m below the hot water pipe and 0.3m above it.
2. When the pipeline is laid under the steam pipe, it is 0.5m, and when it is laid above, it is1m..
When the above requirements cannot be met, heat insulation measures should be taken. For steam pipes with thermal insulation measures. The upper and lower clear distance can be reduced to 0.2 meters.
The parallel clear distance between wires and pipelines and other pipelines (except flammable gas and flammable liquid pipelines) should not be less than 0.1m. When laying on the same side as the water pipe, it should be laid on the top of the water pipe.
Article 5. 1. 10 Hard plastic pipe wiring is generally suitable for indoor places and places with acid and alkali corrosive media, but not for places that are vulnerable to mechanical damage.
Article 5.65438 +0. 1 1 When the hard plastic pipe is laid in the dark or buried, measures should be taken to prevent mechanical damage to a section of pipeline outside the ground (building).
Article 5. 1. 12 When the pipes of metal pipe wiring and hard plastic pipe wiring are long or bent, cable boxes should be installed properly to make the distance between two cable points meet the following requirements:
First, for roads without bends, it shall not exceed 45 meters;
Two, there is a bend between two points, not more than 30 meters;
Three, there are two bends between two points, not more than 20 meters;
4. There are three bends between two points, not exceeding12m.
Article 5. 1. 13 The voltage level of insulated wires and cables laid through pipes shall not be lower than 500 volts AC.
Article 5. 1. 14 The total cross-sectional area of insulated wires (except two wires) or cables passing through the pipe (including the outer sheath) shall not exceed 40% of the cross-sectional area in the pipe.
Article 5. 1. 15 When the AC line passes through the metal pipe, when the load current is greater than 25 A, in order to avoid eddy current effect, all insulated wires in the same circuit should pass through the same metal pipe.
Article 5. 1. 16. Lines with different circuits should not be worn in the same pipe, except in the following cases:
A, the voltage is 65 volts and below the circuit;
Two, the power cord and control circuit of the same equipment or the same assembly line equipment have no anti-interference requirements;
Third, all the circuits for lighting lanterns;
Four or several roads of similar lighting, but the total number of insulated wires in the pipe does not exceed 8.
Article 5. 1. 17 steel cable wiring is generally suitable for indoor and outdoor places, and anti-corrosion measures should be taken for the corroded parts of steel cables.
Article 5. 1. 18 Cable wiring shall meet the following requirements:
1. When the insulated wires are used for bare wiring of indoor steel cables, porcelain (plastic) clips or drum-shaped insulators should be used and pin-shaped insulators should be fixed: when sheathed insulated wires, cables, metal pipes or rigid plastic pipes are used for wiring, they can be directly fixed on the steel cables.
Two, outdoor cable wiring with insulated wire exposed, the application of drum insulator or pin insulator fixed; When wiring with cable, metal pipe or hard plastic pipe, it can be directly fixed on the cable.
Section 2 Bare Wire Wiring
Article 5.2. 1 Bare conductor wiring is generally applicable to industrial enterprises.
Article 5.2.2 The distance between the bare conductor and the ground shall not be less than 3.5 meters; When using a mesh fence, it should not be less than 2.5 meters.
The distance between the barrier and the exposed conductor shall be the value specified in Article 3. 1.8 of this specification.
Article 5.2.3 When the bare conductor is laid on the same side as the pipeline that needs frequent maintenance, the bare conductor shall be laid on the top of the pipeline.
The clear distance between the bare conductor and the pipeline requiring frequent maintenance (excluding combustible gas and combustible liquid pipelines) should not be less than 1 m, and the clear distance between the bare conductor and the production equipment should not be less than 1.5 m. ..
If the above requirements cannot be met, it should be covered.
Article 5.2.4 The clear distance between the bare conductor and the building surface (excluding the fixed points) shall not be less than the values listed in Table 5.2.4.
The distance between the fixed points of hard conductors should meet the requirements of dynamic stability when passing the maximum short-circuit current.
Article 5.2.5 The clear distance between the bare conductor above the crane and the crane ceiling shall not be less than 2.2m Otherwise, a fence shall be installed on the crane or under the bare conductor.
Except for the auxiliary conductor of the overhead line itself, the bare conductor should not be laid on the same bracket as the overhead line of the crane.
Section 3 Installation of Plug-in Busbar
Article 5.3. 1: Plug-in buses are generally suitable for indoor dry places without corrosive gas.
Article 5.3.2 The distance between the plug-in bus and the ground shall not be less than 2.2m When there is no lead-out wire and lead-in wire at the plug-in bus terminal, the terminal shall be closed.
Section 4 Cable Laying
Article 5.4. 1 When laying cables indoors, try to lay them openly. When cables pass through walls or floors, they should pass through pipes or take other protective measures.
When the cable is buried indoors, it should pass through the pipeline, and the inner diameter of the pipeline should not be less than 1.5 times of the outer diameter of the cable.
Article 5.4.2 When unarmored cables are exposed indoors, the distance from the horizontal laying to the ground shall not be less than 2.5 meters; Vertical laying shall not be less than1.8m; Otherwise, measures should be taken to prevent mechanical damage. However, unless it is exposed to a special electrical room (such as power distribution room and motor room).
Article 5.4.3 The spacing between cable supports or fixed points shall not be greater than the values listed in Table 5.4.3.
Article 5.4.4 When the cable is hung horizontally on the wire rope, the maximum distance between the fixed points of the power cable is 0.75m; The maximum spacing between control cable fixing points shall be 0.6m ..
Article 5.4.5 When cables with the same voltage are laid side by side, the clear distance between cables shall not be less than 35 mm, except when they are laid in the line trough.
Power and control cables below 1000 volts are usually laid separately from power cables above 1000 volts. When laying side by side, the clear distance should not be less than150 mm.
Article 5.4.6 The clear distance between the bare overhead cable and the thermal pipeline shall not be less than 1 m, otherwise heat insulation measures shall be taken. The clear distance between the cable and the non-thermal pipeline should not be less than 0.5m, otherwise, measures should be taken to prevent the cable section close to the pipeline and extending 0.5m from both ends of the section from mechanical damage.
Article 5.4.7 Cable laying in cable trench and tunnel shall meet the following requirements:
1. When laying cables in cable trenches and tunnels, there should be no jute or other combustible outer coating.
Second, when laying on the bracket, the power cable should be placed on the upper layer of the control cable, but the power cable and the control cable below 1000 volts can be laid side by side.
Three, in the cable trench, tunnel, when there are cable supports on both sides, the power cable and control cable below 1000 volts should be laid on different supports as far as possible with the power cable above 1000 volts.
Four, the height of the cable tunnel is generally 65438 0.9 meters; When there are difficulties, it can be appropriately reduced in some areas.
Five, the length of the cable bracket, in the cable trench should not be greater than 350 mm; The tunnel should not be more than 500mm.
Six, cable laying in cable trench, tunnel, the net distance, should not be less than the values listed in table 5.4.7.
Article 5.4.8 Cables shall not be laid in tunnels or passages with flammable gas or flammable liquid pipelines.
Article 5.4.9 Cable trenches and manholes shall not be located in areas where molten metal may flow or in substances that damage the outer sheath and sheath of cables.
Article 5.4. 10 When the length of the cable tunnel is more than 7m, both ends shall be provided with exits (including manholes). If the distance between two exits exceeds 75m, the exits should be increased, and the diameter of manhole should not be less than 0.7m. ..
Article 5.4. 1 1 Cable tunnels and cable trenches shall be equipped with waterproof and drainage facilities.
Article 5.4. 12 The cable tunnel shall be equipped with lighting, and its voltage shall not exceed 36V.
Article 5.4. 13 The depth of outdoor directly buried cables shall not be less than 0.7m, and the outdoor directly buried cables shall be paved with bricks or similar protective layers.
Article 5.4. 14 When directly buried, the clear distance between parallel or cross-laid cables and various facilities shall not be less than the values listed in Table 5.4. 14.
Article 5.4. 15 When the cable is exposed outdoors, direct sunlight should be avoided as far as possible.
Article 5.4. 16 The ratio of the bending radius of cable laying to the cable outer diameter shall not be less than the values listed in Table 5.4. 16.
Note: ① Cables should be buried outside the building apron.
(2) When the insulation layer is installed between the cable and the hot ditch, the parallel clear distance can be reduced to 0.5m ..
(3) When the cable crosses the pipeline or when the cable crosses the intersection within 1 m before and after the pipeline (or separated by a partition)
Open), the cross gap can be reduced to 0.25m. ..
(4) When the cable crosses the thermal ditch, if the cable is protected by asbestos cement pipe, its length should be extended.
2 meters on both sides of the hot ditch, when there is insulation protection, it should be more than two layers of hot ditch and cable.
Each side1m.
⑤ When the cable is parallel to the water pipe and compressed air pipe, the height difference between the cable and the pipe is not more than 0.5m. ..
, the parallel clear distance can be reduced to 0.5 meters.
⑥ When cables cross roads and railways, they should be protected by passing through pipes, and the protection pipes extend out of subgrade 1 m..
Note: ① What is not indicated in the table includes armored and unarmored cables;
② Power cables include oil-impregnated paper insulated cables (non-dripping cables) and rubber-plastic insulated cables.
Cables and other cables refer to control signal cables and so on.
The explanation of a word in the appendix
Plan 1- 1
Appendix II Description of terms used in this specification
First, the strict degree of implementation of the provisions of the wording should be written as follows:
1. is very strict. If you have to do this:
Positive words generally use "must";
The negative word is generally "forbidden".
2. Strict requirements, what should be done under normal circumstances:
Positive words generally use "should";
Negative words generally use "should not" or "should not".
3. Words that allow a little choice should be done first if conditions permit:
Positive words generally use "appropriate" or "general";
The negative word is generally "inappropriate".
It means that this should be done under normal circumstances, but at present, due to the limitation of national technical and economic level, it is difficult to enforce it, so "as far as possible" can be used.
The word "may" is used to allow this under certain conditions.
Two, the provisions must be implemented in accordance with the specified standards, norms or other relevant provisions, the text is "in accordance with the implementation" or "in line with the requirements". If it is not necessary to comply with the referenced standards, specifications or other regulations, it is written as "reference ……".
Note: The words used in this specification are "unified words and expressions" as stipulated in Circular No.387 of the former State Construction Committee, Unified Format and Symbol of Technical Standards and Specifications for Design and Construction.
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