Article 1.0.1  The establishment of this code is on purpose to ensure the construction quality of installation engineering of cable lines, to promote the technical improvement of the construction of cable lines and to ensure a safety work of cable lines.

Article 1.0.2  This code is applicable for construction and acceptance of the installation engineering of electric power cable lines or control cable lines that work with a voltage of 500 kv or lower.

The installation engineering of cable lines with special requirement such as those applicable for mines, ships, metallurgy and Chemistry shall be in accordance with the corresponding rules of the profession.

Article 1.0.3  Installation of cable lines shall be conducted in accordance with approved design.

Article 1.0.4  The transportation and storage of cable and its appendixes shall be in accordance with the requirement of this code.  When the product is with special requirement they shall be in accordance with the requirement.

Article 1.0.5  The storage period of cable and its appendixes before installation shall be not longer than 1 year.  When a long-term storage is necessary, the period shall be in accordance with special regulations of equipment storage.

Article 1.0.6  The adopted cable as well as its appendixes shall be in accordance with the regulations of the running technical standards of the country and qualified certificates shall be available.  The equipment shall be with proper nameplate.

Article 1.0.7  The safety technical measures adopted in construction shall be in accordance with this code as well as the running safety technical standards and product technical documents.  The safety technical measures shall be set down beforehand for important construction projects or procedures.

Article 1.0.8  The practice of the construction projects that are related to cable line installation shall be in accordance with the following requirements:

A．     The constructional engineering quality of buildings and structures that related to cable line installation shall be in accordance with the concerning regulations in the actual national codes of construction and acceptance of constructional engineering.

B．     Before installation of cable lines, the constructional engineering shall meet the following requirements:

a.    The pre-embedded fittings shall be in accordance with design and fixed firmly;

b.    Surfacing and float work shall be finished where there exist cable ducts, tunnels or vertical shafts;

c.    The temporary construction devices, templates and construction rubbish shall be cleared away where there exist cable layers, cable ducts or tunnels; the construction passage shall be unblocked and coverage plates shall be complete;

d.    The construction works that can not be carried out after the laying of cable lines shall be finished beforehand;

e.      Water discharge of cable duct shall be free and the installation of doors and windows of the cable room shall be finished.

C．     The decorating works of construction engineering caused by the necessity of vacancy-filling, boring or reaming for built-in fittings shall be finished before the startup of an installation finished cable line.

Article 1.0.9  Hot galvanized products shall be applied as steel fixing device for installation of cable and its appendixes with exception of anchor-bolt.

Article 1.0.10  The anti-jamming measures shall be adopted according to design regulations for the cable lines with requirement on anti-jamming.

Article 1.0.11  For the construction and acceptance of cable lines, the regulations in this code shall be executed and the actual national standards or codes concerned shall also be observed.

 

Chapter 2   Transportation and storage

 

Article 2.0.1  During transportation, loading and unloading, cable and cable reel shall not be damaged.  It is forbidden to push down the cable reel directly from trucks.  The cable reel shall not be placed flatly during transportation and storage.

Article 2.0.2  Before transportation or rolling of cable, it must be ensured that the cable reel is firm and the cable is coiled tightly on the reel.  For the oil-filled cable, the oil tube between the cable and pressure oil tank shall be fixed and shall not be damaged.  The pressure oil tank shall be firm and the pressure indication shall conform to the requirement.

Should the cable reel be rolled, the rolling must be along the direction which the arrows on the reel indicate or the direction which makes the cable to go tighter on the reel.

Article 2.0.3  When the cable and its appendixes arrives at the site, an inspection shall be conducted according to the following requirements:

A．     The technical documents of product shall be complete;

B．     The type, specification and length shall conform to the requirement of the order and the appendixes shall be complete; the appearance of the cable shall be intact without any damage.

C．     The sealed end of the cable shall be tight.  When there exists suspicion in the visual inspection, estimation or test shall be made whether the cable is affected with damp.

D．     The pressure oil tank, oil tube, valves and pressure gauges for oil-filled cable shall be intact and in accordance with the requirement.

Article 2.0.4  When cable and the related material are not to be installed immediately, they shall be stored according to the following requirements:

A．     A concentrated and classified storage shall be made for the cable; the type, voltage, specification and length of the cable shall be marked and there shall be passages between cable reels; the groundsill shall be solid and when conditions are limited the reel shall be underlayed; there shall be no accumulated water at the storage site;

B．     Measures shall be taken to prevent any damage to the porcelain bushing of the cable terminal during storage;

C．     The damp-proof package for the insulating material of the cable appendixes shall be well sealed and properly stored and kept according to the material performance and keeping requirement.

D．     The fireproof material such as fireproof coating, tape and fire-stopping material shall be properly stored and kept according to the material performance and keeping requirement.

E．      A classified keeping shall be made to the bridge support of cable and the bridge    support shall not be deformed under stress.

Article 2.0.5  During keeping period of the cable, the cable reel and package shall be intact, symbols shall be complete and the sealed ends shall be tight.  Should any defects occur, they shall be disposed in time.

The oil pressure for the oil-filled cable shall be often inspected and recorded and it shall not be lower than the minimum value.  When the oil pressure decreases to zero or vacuum occurs, it shall be disposed in time.

 

Chapter 3   Processing and laying of cable tubes

 

Article 3.0.1  There shall be no perforations, cracks or obvious unevenness on the cable tube and the inner wall of the tube shall be smooth.  There shall be no serious corrosion on the metal cable tube.  The hard plastic tube shall not be applied in locations where temperature is too high or too low.  The piping material with enough strength shall be applied in locations where it is easily to subject mechanical damage or the direct embedding is located where the tube is under larger stress.

Article 3.0.2  The processing of cable tube shall meet the following requirements:

A．     There shall be no burrs or sharp edges at the mouth of the tube and the mouth may be made in the shape of a bugle.   

B．     After bending, there shall not be cracks or obvious concaveness on the tube and the bending flattening may not be larger than 10% of the outer diameter of the tube; the bending radius shall not be lower than the minimum allowable bending radius of the cable inside the tube.

C．     The outer surface of metal tube shall be coated with anti-corrosion paints or asphaltum; for galvanized tube the anti-corrosion paints shall also be applied where zinc layer scales off.

Article 3.0.3  The ratio of the inner diameter of the cable tube to outer diameter of the cable shall not be lower than 1.5; besides this requirement, the inner diameter of the tube made from concrete, argil or asbestos cement may not be less than 100mm.

Article 3.0.4  The number of elbows to be applied to each tube shall not be more than 3 and that of the right angle bend shall not be more than 2.

Article 3.0.5  When the cable tube is laid openly, the following requirements shall be observed:

A．     The cable tube shall be installed firmly; when regulations are not given by design, the distance between support points of the tube may not be larger than 3 meters.

B．     When straight length of the plastic tube is larger than 30 meters, expansion joints may be applied to it.

Article 3.0.6  The connection between cable tubes shall meet the following requirements:

A．     The connection between metal cable tubes shall be firm and with proper sealing, both tube mouths shall be well aligned.  The length of connected short bushing or threaded nipple shall not be less than 2.2 times outer diameter of the cable tube.  Direct butt welding may not be applied to metal cable tubes.

B．     When sleeve joint or insertion joint is applied to hard plastic tubes, the inserting length may be 1.1 – 1.8 times inner diameter of the tube for insertion joint and the inserting surface shall be coated with agglutinant to ensure a firm connection and well sealing; for sleeve joint, both ends of the sleeve shall be sealed by welding.

Article 3.0.7  When the cable tube is led to the equipment, the location of the tube mouth shall be convenient for connecting the tube to the equipment without obstructing the mounting and dismounting as well as moving in and out of the equipment.  Parallel arranged tube mouths shall be tidily and well arrayed.

Article 3.0.8  When the protective steel tube of the cable is used as earth connection, the grounding wire shall be welded beforehand; when pipe connection is threaded, jumper wire shall be welded and the cable shall be put in afterwards.

Article 3.0.9  When the tube made from concrete, argil or asbestos cement is installed, the groundsill shall be solid, flat and even without any caving in.  The installation of the cable tube shall be in accordance with the following requirements:

A．     The imbedding depth of the cable tube shall not be less than 0.7m and when the tube is installed below the pavement, the depth shall not be less than 0.5m.

B．     The cable tube shall be with a water discharge gradient of not less than 0.1%.

C．     When cable tubes are jointed, the tube mouths shall be well matched with a tight connecting seam and any infiltration of underground water or mud shall not be allowable.

 

Chapter 4   Manufacture and installation of cable support

       

Article 4.0.1  The processing of the cable support shall be in accordance with the following regulations:

A．     The steel material shall be straight and flat without any obvious distortion.  The material preparation error shall be within she scope of 5mm and the cutting edge shall be free from any curling or burr.

B．     The support shall be firmly welded without any obvious deformation.  The deviation between the vertical wale-to-wale net distance and its design value shall not be more than 5mm.

C．     Anti-corrosion measures shall be taken to metal cable supports and special anti-corrosion disposal shall be conducted according to the design for areas where exists hot damp, salty mist or chemical corrosion.

Article 4.0.2  When it is not regulated in the design, the minimum distance between layers of cable support may refer to the regulations in Table 4.0.2.  But the net distance between support layers shall not be less than 2 times outer diameter of the cable plus 10mm and the distance shall not be less than 2 times outer diameter of the cable plus 50mm for high voltage cables of 35 kv and more.

Table 4.0.2   the minimum allowable value for distance between layers of cable support (mm)

Notes: h indicates the shell height of the groove box.

Article 4.0.3  The cable supports shall be installed firmly and arranged in good order; the fixing method of brackets, underlaying and hanging supports shall be fixed according to the requirement of design.  The crosspieces in the same layer of each support shall be arranged on the same level and the difference of height shall not be larger than 5mm.  For the arrangement of brackets, underlaying and hanging supports, the deviation from the orientation of the bridge support shall not be larger than 10mm.

When the cable supports are installed in the cable duct or on the building with certain gradient, they shall be arranged to be with the same gradient as the duct or the building.

The distance from the top layer of cable support to the top of cable channel (or ceiling of building) and that from the lowest layer to the bottom of cable channel ( or ground level), if not regulated in design, may not be lower than values given in Table 4.0.3. 

Table 4.0.3   the distance from the top layer of cable support to the top of

cable duct (or ceiling of building) and the distance from the lowest layer

of cable support to the bottom of cable duct ( or ground level)（mm）

 

Article 4.0.4  The vertical deviation of a steel structure silo after assembly shall not be larger than 2/1000 of its length; the horizontal deviation of the support wale shall not be larger than 2/1000 of its width; the deviation of the silo diagonal shall not be larger than 5/1000 of the diagonal length.

Article 4.0.5  The fabrication of cable bridge shall conform the following requirements:

A．     The quality of cable trays, support of cable trays as well as their connecting pieces and fittings shall be in accordance with the actual technical standards concerned.

B．     The specification of the cable trays, the span between underlaying or hanging supports and the type of anti-corrosion measures shall conform to design requirements.

Article 4.0.6  The cable tray shall be firmly fixed on each support; the bolts of the connecting board of cable tray shall be fastened tightly and the bolt nuts shall be arranged outside the tray.

When aluminum alloy cable tray is fixed on the steel support, measures to prevent electrochemical corrosion shall be taken.

Article 4.0.7  When the straight section of a steel cable bridge is over 30m, or the length of aluminum alloy or polyester cable bridge is over 15 m, the expansion seams shall be provided and the connecting board with expansion function may be adopted for connection of the seams; the expansion seams shall be provided where the cable bridge crosses the expansion seams of a building.

Article 4.0.8  The bending radius at the cable bridge turning shall not be less than the minimum allowable bending radius of the cable which, compared with other cables on the bridge, has biggest value of minimum allowable bending radius.

Article 4.0.9  A proper grounding shall be provided along the total length of cable support.

 

Chapter 5   Laying of the cable

 

Section 1  General regulation

Article 5.1.1  Inspections shall be made according to the following requirements before cable-laying:

A．     Cable passage shall keep unblocked and shall be with proper water discharge devices. The anti-corrosion layer for metal part shall be complete. The illumination and venting inside the tunnel shall conform to design requirement.

B．     The type, voltage and specifications of the cable shall be in accordance with design.

C．     The appearance of cable shall be free from any damage and the cable shall be with proper insulation. Should the sealing of cable be under any suspicion, estimation shall be made for damp. Directly embedded cable and under-water cable shall be tested and qualified.

D．     The oil pressure of oil-filled cable may not be lower than 0.15Mpa; the valve that supplies oil shall be set at open position and able to act promptly; the pressure gauge indication shall be free from any abnormity; oil-leakage shall be excluded for all pipe connections; oil sample shall be tested and qualified.

E． The cable releasing racks shall be set stably and the strength and length of their steel shafts shall match the weight and width of the cable reel.

F． Calculations shall be made before cable-laying for the length of each cable according to the design route and actual route; to minimize the number of cable connections, a reasonable arrangement shall be made for each reel of cable.

G．     Reliable safety measures shall be taken when cable-laying is carried out in an electriferous area.

Article 5.1.2  When cable-laying is being conducted, any damage to the water-proof layer of cable duct, tunnel, cable shaft and man shaft shall be excluded.

Article 5.1.3  The 4-core electric power cable shall be adopted in a 3-phase and 4-wire system, any substitution with 3-core cable plus a sing core cable or using the metal sleeve of cable as neutral wire shall not be allowable.

Article 5.1.4  It is proper to adopt same length, type and specifications for parallel connected cables.

Article 5.1.5  To preserve spare length for power cable near terminals and connections is proper.

Article 5.1.6  The distance between supporting points of cable shall conform to design regulations and if not regulated in design, the distance shall not be larger than figures given in Table 5.1.6.

Table 5.1.6  minimum bending radius of cable（mm）

Notes: When total plastic power cable is laid horizontally, if the cable can be fixed along the support, the distance between support points to be set as 800mm is permitted.

Article 5.1.7  The minimum bending radius of cable shall conform the regulations in Table 5.1.7.

Table 5.1.7  the minimum bending radius of cable

Notes: The symbol “D” in the table indicates outer diameter of cable.

Article 5.1.8  The maximum height difference between the highest point and the lowest point of viscous oilpaper insulated cable shall not exceed the regulated values in Table 5.1.8.  When it is not possible to meet this requirement, the cables suitable for larger height difference shall be applied.

Table 5.1.8  the maximum permitted height difference to be laid for

viscous oilpaper-insulated lead-wrapped power cable

 

Article 5.1.9  During cable-laying, the cable shall be led out from the top of the reel and it is not permitted to haul the cable and make it worn on the rack or on the ground.  Any not removed mechanical damage, such as flattening of the cable armour under pressure, twisting of cable or cracking of the protective layer by turning are not allowable.

Article 5.1.10  When cable-laying is conducted by mechanism, the maximum tenacity may refer to the regulations in Table 5.1.10.  The total tensile force subjected by oil-filled cable shall not exceed 27kN.

Table 5.1.10  the maximum tenacity of cable (N/mm²)

 

Article 5.1.11  The speed of cable-laying by mechanism is not proper to exceed 15m/min; when cable of 110 kv and above are laid on rather complicated route, the speed shall be slackened.

Article 5.1.12  When cables with larger section area are laid mechanically under complicated conditions, construction organization and design shall be made thus to determine method of laying, positions to set up reel support rack and orientation of cable traction and to recheck the traction and lateral stress, as well as to make arrangement for personnel and tools for laying.

Article 5.1.13  When cables are laid mechanically, twiddling-prevention devices shall be installed between the drawing head or steel mesh sheath and the tractive wire rope.

Article 5.1.14  When cables of 110 kv or above are laid, the lateral stress at turnings shall not exceed 3 kN/m.

Article 5.1.15  When the oilpaper insulated power cable is cut off, the cut ends shall be lead-sealed immediately; the plastic insulated cable shall be equipped with reliable anti-damp sealing ends; after cutting off, the oil-filled cable shall also meet the following conditions:

A．     In any case, any part of oil-filled cable shall be equipped with a pressure oil tank so as to keep oil pressure.

B．     When connecting the pipeline, the air in the tube shall be expelled and oil-spray connection shall be applied.

C．     The position where the oil-filled cable is cut off shall be higher than the cable at both sides.

D．     No metal dust or dirt shall enter the cable during cutting.

Article 5.1.16  During cable-laying, the lowest allowable laying temperature and the mean temperature in 24 hours before laying as well as the temperature at laying site shall not be lower than the regulations in Table 5.1.16; corresponding measures shall be taken when temperature is lower than the regulated values given in Table 5.1.16.

Table 5.1.16  the lowest allowable temperature for cable-laying

 

Article 5.1.17  The arrangement for power cable connections shall conform the following requirements:

A．     The connection positions for cables laid in parallel shall be staggered from each other.

B．     The connectors of openly laid cables shall be fixed by supporting boards.

C．     Protective hood shall be provided outside the junction box of directly embedded cable so as to prevent mechanical damage (with exception of epoxy resin junction box).  For junction boxes located under frozen earth, asphalt shall be filled in the box.

Article 5.1.18  During laying, the cable shall be arranged tidily and properly fixed. Intercross laying of the cable is not proper.  Signboards shall be installed in time.

Article 5.1.19 The setting up of sign boards shall conform the following requirements:

A．     Sign boards shall be installed on the cable at places such as the end of cable terminals, connections and turning points of cable, inside of interlayers, both ends of vertical shafts and tunnels and inside of man shafts.

B．     The route number shall be marked on the signboard.  When route number is not available the type, specification as well as the beginning and end positions of the cable shall be written clearly on the signboard; the parallel arranged cables shall be provided with serial number.  The writing on the signboard shall be legible and not easy to drop off.

C．     The style of signboards shall be unified.  The signboard shall be corrosion-proof and installed firmly.  

Article 5.1.20  The fixing of the cable shall conform the following requirements:

A．     The cable shall be fixed in following locations:

a.    Every support for vertically laid or aslant (over 45°) laid cables; at intervals of 2m on the bridge support;

b.    At both ends of a cable, a cable turning and a cable connection for horizontally laid cables; at intervals of 5 – 10m when space between cables is regulated;

c.    Locations for fixing the single-core cable shall be in accordance with the requirement of design.

B．     The fixing device shall not form a closed magnetic circuit for single-core cable in AC system or misphasing lead sheath cable after phase splitting.

C．     The fixing position of naked lead (aluminum) sheath cables shall be protected by soft pad.

D．     When the protective layer of cable is required to be insulated, insulating pad shall be provided where the cable is fixed.

Article 5.1.21  The metal protection layer or metal protection pipe of openly laid cable along electrified railroad or the bridge through which the electrified railroad passes shall be insulated with the metal support or metal structures of the bridge along its total length.

Article 5.1.22  When cable enters cable ducts, tunnels, vertical shafts, buildings, panels (cabinets) or passes through pipes, the inlet (outlet) or the mouth of the pipe shall be sealed.

Article 5.1.23  For the lighthouse equipped with lightning rod, the cable-laying shall conform to the concerning requirements in the actual national standard《Code for construction and acceptance of the grounding devices in electric equipment installation engineering》.

 

Section 2  Laying of the cable inside production buildings or in tunnels or ditches

Article 5.2.1  The arrangement of the cable shall meet the following requirements:

A．     Power cable and control cable shall not be arranged on the same layer of support.

B．     High and low voltage power cable, strong current and weak current controlled cable shall be arranged on different layers according to priority.  Normally they are arranged from above to below, but when high voltage cables containing 35kv and above are led into the panel or cabinet, they may also arranged from below to above, so as to meet the requirement of bending radius.

Article 5.2.2  For the power cable laid in parallel, the net distance between each other shall meet design requirement.

Article 5.2.3  The cable-laying on the support shall meet the following requirements:

A．     The control cable laying on normal support shall not exceed one layer and shall not exceed 3 layers on bridge support.

B．     Laying of the AC 3-core power cable on normal support shall not exceed one layer and shall not exceed 2 layers on bridge support.

C．     The AC single-core power cable shall be arranged on the support at the same side and if it is arranged as closely adjacent triangles, the cable shall be firmly packed by binding tape at intervals of 1m.

Article 5.2.4  The net distance between cable and heat pipe or heat equipment shall not be less than 1m when they are arranged in parallel and the distance shall not be less than 0.5m when they go across each other.  When conditions are limited the heat insulating measures shall be taken.  The cable passage shall keep away from the kiln eye of boilers and the explosion-proof door of milling system.  When conditions are limited, the heat insulating and fireproof measures such as applying protective tube or closely sealed trays shall be taken.  To lay the cable on top of heat equipment or heat pipe in parallel is not proper.

Article 5.2.5  For the cable with flax protective layer openly laid in the building or in cable duct, tunnel and vertical shaft, the flax layer shall be stripped off and the anti-corrosion measures shall be taken for its armour.

Article 5.2.6  When cable-laying is finished, all irrespective matters shall be cleared up and the cover plates shall be properly closed.  When necessary, the seams of the cover plate shall be sealed.

 

Section 3  Laying of the cable inside tubes

Article 5.3.1  At the following locations, the protective tube with certain mechanical strength shall be provided with for the cable or the protective hood shall be installed:

A．     The places where the cable enters buildings or tunnels or passes through floor stabs or walls;

B．     Cable led from cable duct to wire poles, equipment, outer surface of wall or in the building where personnel may access easily i.e. the section below the height of 2m above the ground;

C．     Other locations where the cable may subject to mechanical damage.

When the protective tube of the cable is embedded into the non-cement ground, the embedding depth shall not be less than 100mm; the length of the protective tube stretched outside the apron slope shall be not less than 250mm.  The root part of the protective hood shall not be higher than ground level.

Article 5.3.2  There shall be no accumulated water in the internal of the tube and foreign matters blocked in the tube is also not permitted.  When cable goes through the tube the protective layer of the cable shall not be damaged, therefore, lubricants (powder) may be applied.

Article 5.3.3  The cable tube shall be dredged and foreign matters in it shall be cleared up before cable-laying.

Article 5.3.4  The quantity of the cable laid into shall meet design requirement; AC single-core cable shall not be put into the tube separately.

 

Section 4  Laying of directly embedded cables

Article 5.4.1  The areas in the route of the cable lines where it is possible to make the cable subject to harms such as mechanical damage, chemical effects, underground current, vibrations, heat influences, humus, insect and rat shall be properly protected.

Article 5.4.2  The embedding depth of the cable shall meet the following requirements:

A．     The distance between cable surface and ground level shall not be less than 0.7m and when the cable goes under the farm fields the distance shall not be less than 1m. The cable may be embedded not too deep when it is led into the building, or it goes across or by underground structures, but the protective measures shall be taken.

B．     The cable shall be embedded below the frozen earth zone and when conditions are limited, measures to prevent the cable from damage shall be taken.

Article 5.4.3  The minimum net distance between cables or between cable and other devices such as  piping, road and building when cables are laid in parallel with (or across ) each other or in parallel with ( or across) these devices shall be in accordance with the regulations in Table 5.4.3.  It is strictly forbidden to lay the cable over or under pipeline in parallel.  In special cases, following regulations shall be executed:

A．     When cable goes through tube or it is separated by clapboard, the net parallel distance between power cables and between power cable and control cable or between cables of different departments that employ these cables may be decreased to 0.1m.

B．     When cable goes through tube or it is separated by clapboard, the net cross-distance in scope of 1m before and after the cross point between power cables, control cables and between power cable and control cables or between cables of different departments that employ these cables may be decreased to 0.25m.

C．     Although the net distance between cable and heat pipeline (channel), oil pipe (channel), pipeline (channel) of flammable gas (liquid), heat equipment or other pipeline (channel) may meet the requirement, the maintenance of the pipeline is possible to damage the cable, the protective measures shall be taken in a scope of 1m before and after the cross point.  When the net cross distance does not meet the requirement, cable shall be put into tube, then the net distance may decrease to 0.25m.

D．     When cable is laid in parallel with ( or across) heat pipeline(channel), or heat equipment, heat insulation measures shall be taken so as to make the temperature elevation of the earth around the cable not higher than 10℃.

E． When DC cable is laid in parallel with (or across) the rail of electrified railroad and the net distance does not meet the requirement, measures shall be taken to avoid electro chemical corrosion.

Table 5.4.3   the minimum net distance between cables or between cable and

other devices such as  piping, road and building when cable goes in parallel

with (or across ) each other or in parallel with ( or across) these devices (m)

Notes: ① In special cases, the net distance between cable and highway may be extenuated when they go in parallel.

      ② The net distance in the Table shall be calculated from the outer wall of the tube or of the protective device when cable is laid in tube or with protective devices such as heat insulating layer etc,.

Article 5.4.4  Cable shall be laid in firm protective tube or tunnel when it goes across railways, highways, city streets or factory roads.  Both ends of the cable shall stretch out of the sides of roadbed for 2m and of gutters for 0.5m; they shall also stretch out of driveways.

Article 5.4.5  The upper and lower part of directly embedded cable shall be paved with soft earth or sand layer of not less than 100mm and covered with protective board.  The coverage width shall exceed both sides of the cable for more than 50mm and the protective board may use cement plate or brick.

There shall exist no stone or other hard foreign matters in the soft earth and sand.

Article 5.4.6  For directly embedded cable, obvious marks or marking stakes shall be set up at an interval of 50 – 100m for straight reaches, as well as in places such as connecting points, turnings of the cable and where the cable enters the building.

Article 5.4.7  Before back filling, the directly embedded cable shall be inspected and qualified as concealed work.  The back-filled earth shall be tamped in separated levels.

 

Section 5  Laying of underwater cables

Article 5.5.1  The underwater cable shall be formed by a whole piece.  If the whole piece of cable exceeds the capability of the manufacturer, the cable may be connected by soft connectors.

Article 5.5.2  The cable laid in rivers shall be in locations where the riverbed is stable or the river bank less subjected to water scour.  When cable is laid in locations such as piers, anchorage ground, loughs, ferries and places where watercrafts may anchor, reliable protective measures must be taken. The cable shall be deeply embedded if possible.

Article 5.5.3  The underwater cable shall be laid horizontally on the bottom of water and suspending laying shall be not allowable.  The cable may be embedded deeper than 0.5m below riverbed or seabed if possible.

Article 5.5.4  The space between underwater cables when they are laid in parallel is not proper to be less than 2 times the water depth of the highest water level.  The space shall be determined according to the embedding mode or the work and activity capability of the embedding machine when cable is embedded under the riverbed or seabed.

Article 5.5.5  The protective measures such as protective tube or cover plate etc, shall be taken to the part of the underwater cable that is led to the bank.  The lower end of the protection scope shall be the position where vessels pile up or where a pole cannot reach and the upper end shall be the highest flood level.  The cable shall be fixed at the lower end of the protection scope. 

Article 5.5.6  When cable lines go across brooklets or streams they shall be put into tube or embedded under riverbed with enough depth.

Article 5.5.7  The connections between underwater cable and land cable at the bank shall be equipped with anchoring devices.

Article 5.5.8  The choice and design of construction organization for laying mode and laying vessel of underwater cable shall be determined according to factors such as the length, outer diameter and weight of the cable to be laid as well as water depth, velocity of flow and landform of the riverbed etc,.

Article 5.5.9  For the laying of underwater cable, when reel cable is applied for the total length, the cable reel may be set up on the bank or vessels according to conditions of the water area.  The cable may be supported by buoys during laying.  To haul the cable on the ground under water shall be strictly forbidden.

Article 5.5.10  When it is impossible to apply reel cable for underwater cable-laying, the method of bulk laying shall be applied.  The procedure of laying shall be in this way: firstly the cable shall be coiled in the laying cabin, then it shall be led via the stilt on top of cabin, pulleys and braking devices into a water entry groove and get into water; the cable shall then be bound and hauled by a tugboat and the laying shall be carried out by self-sail or by wire rope draught.

Article 5.5.11  The selection of vessels shall be in accordance with the following conditions:

A．     The volume of the cabin, the area and stability of the deck shall meet the requirements such as the length, weight and bending radius of the cable as well as the requirements of the worksite.

B．     The laying vessel shall be equipped with braking devices and instruments measuring tension, length, immersion angle and water depth, as well as apparatus for navigation and orientation etc. and communication devices.

Article 5.5.12  Laying of the underwater cable shall be carried out in periods when week tide, slab water or low flow occurs and when line of sight is clear and wind power is less than grade 5.

Article 5.5.13  Proper back-reel height shall be kept by the feeding reel on the laying vessel.  The laying tension shall be controlled according to the water depth and the immersion angle shall be maintained within the scope of 30°~60°.  The velocity shall be 20~30 m/min when laying is carried out by draught or pushing and 90~150 m/min by tugboat or self-sail traction.    

Article 5.5.14  Guide posts shall be set up on both banks when underwater cable is under laying. Orientation measuring shall be conducted during laying and the route correction and laying length calibration shall be made in time.

Article 5.5.15  When underwater cable is led to the bank, all the remaining cable shall be float supported on the surface of water and then it shall be led to land.  The float supported cable then shall be sunk to the bottom of water according to the design path.

Article 5.5.16  A dive inspection shall be conducted after laying of underwater cable.  The cable shall be set horizontally and shall not be suspended when riverbed is undulant. The exact location of the cable shall also be examined.  The signboards shall be set up on both banks of the river according to the design.

 

Section 6  Laying of cables above bridge

Article 5.6.1  The cable to be laid on wooden bridge shall be put into the tube.  For other structures of bridge, the cable channel shall be set up under pavement or the cable shall be put into the tube made from refractory material.  Cable may be laid nakedly on the bridge where people is not easy to access, but measures shall be taken to prevent the cable from direct sunlight.

Article 5.6.2  The net distance between suspending erected cable and the trestle structure of the bridge shall be not less than 0.5m.

Article 5.6.3  Anti-vibration measures shall be taken for the cable laid on bridges which often subject to vibration.  Baggy part of cable shall be remained at both ends and expansion seams of the bridge pier.

 

Chapter 6   Manufacture of cable terminals and connectors

 

Section 1  General regulations and preparation works

Article 6.1.1  Manufacture of cable terminals and connectors shall be conducted by trained personnel and they shall be familiar with the process.

Article 6.1.2  The technological process of the manufacture shall be strictly observed during manufacture of cable terminals and connectors; regulations concerning oil and vacuum process shall also be observed for oil-filled cable.

Article 6.1.3  When manufacture of cable terminals and connectors of 6kv and above are proceeded outside the building, the relative humidity of air shall be 70% and below; when humidity is high, the environment temperature may be elevated or the cable may be heated.  When high voltage cable terminals and connectors of 110kv and above is under manufacturing, temporary work sheds shall be set up and the environment humidity shall be strictly controlled, the temperature of 10~30° shall be proper.  When plastic insulated cable terminals and connectors is under manufacturing, dust and foreign matters shall be kept from dropping into the insulation layers.  Construction under fog or rain shall be strictly forbidden. 

Fire-fighting equipment shall be prepared in doors and at construction site of the oil-filled cable.  Temporary power supply shall be set up for construction in doors or in the tunnel.

Article 6.1.4  The manufacture of cable terminals and connectors of 35kv and below shall conform the following requirements:

A．     The type and specification shall be in consonance with the environment requirements and the types of cable such as voltage, number of the core, section area and protective layer structure.

B．     The structure shall be simple, compact and easy for installation.

C．     The material and parts applied shall be in consonance with technical requirement.

D．     The main performance shall conform to the regulations in the actual national standard《The Basic requirement for power cable appendixes with rated voltage of 26/35kv and below》.

Article 6.1.5  For the accessional insulation material applied, besides that its electric specification shall meet the requirement, it shall be compatible with the insulation of the cable itself.  The physical property indexes of the two kinds of material such as hardness, expansion coefficient, tensile strength and elongation at break shall be similar to each other.  Material with high elasticity and favorable adherence shall be applied as accessional insulation material for rubber plastic insulated cable.

Article 6.1.6  The connecting tube and terminal up to standard shall be applied for anchor clamp of the cable core and the inner diameter of the clamp shall closely match the cable core with a clearance not too large; its section area shall be 1.2~1.5 time of the core.  When crimp connection is adopted, the press pincher and mold shall conform to the requirements of the specification.

Article 6.1.7  In following cases, the control cable may be with connections but the connection must be firm and shall not subject to mechanical tensile force.

A．     When laying length exceeds manufactured length,

B．     When installation completed control cable must be extended,

C．     When mulfunction of the cable in use must be removed,

Article 6.1.8  Before the manufacture of cable terminal and connector, the concerning personnel shall get familiar with the installation process data; the conditions shall be inspected and they shall be up to the following requirements:

A．     The insulation of cable shall be in good condition and not affected with damp; no water shall enter the plastic cable; before construction of oil-filled cable, oil samples shall be taken from cable itself, pressure box, oil drum and rolled-paper drum for cable one by one and electrical specification test shall be conducted and qualified.

B．     The specification of appendixes shall be in consonance with the cable; all parts shall be complete and without any damage; insulation material shall be free from damp and sealing material shall be in effect.  The appendixes for shell structure shall be pre-assembled and the inner wall shall be cleaned; the test for sealing and structure dimensions shall be up to the requirement.

C．     The construction machine and tools shall be complete and clean and easy for operation; all consumable material shall be ready for use.  The preparation of the solvent for cleaning the surface of plastic insulation shall observe process instructions.

D．     Test assembly shall be proceeded when necessary.

Article 6.1.9  Copper strand wire or tin-copper plating braided wire shall be applied as earth wire of the power cable and its section area shall be not less than the regulated values given in Table 6.1.9.  The section area for cable of 110kv and above shall meet design regulations.

Table 6.1.9  The section area for earth wire of the cable terminal

Article 6.1.10  The connection between the cable terminal and the connector shall conform to the concerning regulations in the actual national standard《Code for construction and acceptance of the bus line device in electric equipment installation engineering》

Section 2  Manufacture requirements

Article 6.2.1  The manufacture of cable terminal and connector shall be carried out continuously beginning from stripping and cutting the cable till the completion of work thus to shorten the exposure time of the insulation.  The cable core and the remaining insulation layer shall not be damaged during the stripping and cutting of cable.  The wrapping, assembly and pyrocondensation of the accessional insulation shall be proceeded cleanly.

Article 6.2.2  When there exist connectors in oil-filled cable lines, the connectors shall be manufactured beforehand; when there is height difference between both ends, the lower end terminal shall be made before.

Article 6.2.3  Measures of reinforcing insulation, damp-prevention sealing and mechanical protection shall be applied to the cable terminal and connector.  The effective measures to improve the electric fields concentration on the cable shield end shall also be taken for the terminal and connector of the power cable of 6kv and above, besides these, the interphase distance of outer insulation and the distance between outer insulation and ground shall be ensured.

Article 6.2.4  During the stripping and cutting of the core insulation, shield and metal sheath for cable of 35kv and below, the minimum distance between the surface of core insulation and the nearest grounding point (shield or metal sheath end) shall conform to the requirements given in Table 6.2.4.

Table 6.2.4  The minimum distance among the cable terminals and connectors

 

Article 6.2.5  When manufacturing the terminal and connector for plastic insulated cable, the half-conducting shield layer shall be thoroughly cleared up.  For wrapped graphite shield layer, the carbon trace shall be wiped out with solvent and the shield layer shall be squeezed out oppositely; the insulation surface shall not be damaged during stripping and the shield end shall be tidy.

Article 6.2.6  25mm of originally wrapped insulation shall be remained for 3-core oilpaper insulated cable without any damage.  After stripping off the shield soot carbon paper, the end shall keep tidy.  Even strength shall be applied when bending the wire core without damaging the insulation paper; the bending radius of the wire core shall not be less than 10 times its diameter.  During wrapping, injecting or filling of the insulation material, the gas gap at the core branch shall be removed.

Article 6.2.7  When accessional insulation is wrapped to the terminal and connector of the oil-filled cable, the pressure tank shall not be closed completely.  During the manufacturing and vacuum disposal, the oil effused from the cable shall be discharged in time, not allowed to remain and accumulated inside the porcelain sleeve or shell.

Article 6.2.8  During connecting, the wire core of the cable, the oily soil and the oxidation layer shall be removed from the wire core and the inner wall of the connecting tube.  The impaction mold and the anchor clamp shall match with each other properly.  The compression ratio shall be up to the requirement.  After impaction, the convex trace on the terminal or the connecting tube shall be repaired and made smooth and no burrs shall be remained.  When the copper core is connected with tin weld, the neutral solder paste shall be applied and the insulation is not allowed to be damaged with burning. 

Article 6.2.9  The metal shield layer (or metal sleeve) and armour layer of the cables at both sides of the 3-core power cable connector shall be separately connected properly without any interruption and the section area of the jumper shall not be less than the regulated value for the section area of the grounding wire given in Table 6.1.8 of this code.  Anti-corrosion measures shall be taken to the metal shell of the connector for directly embedded cable and the metal protective layer of the cable.

Article 6.2.10  The metal protective layer at the terminal of the 3-core power cable shall be grounded properly; The grounding of the copper shield and steel armour of each phase of the plastic cable shall be tin welded.  When cable passes through zerosequence current transformers the metal protective layer and grounding wire shall be insulated to ground; when the grounding point is below the transformer the grounding wire shall be grounded directly; when the grounding point is above the transformer, the grounding wire shall go through the transformer then be grounded.

Article 6.2.11  When the assembly and connection of cable terminal and connector are carried out, the measures of leakage stoppage, damp prevention and sealing shall be taken where different parts match or join each other. When lead sealing is made for lead-wrapped cable, the surface oxide shall be wiped out; too long time for lead adding is not proper and the lead sealing shall be impact without any air vent.  The lead sealing for oil-filled cable shall be conducted two times; the oil shall be stopped and sealed for the first time and formation and reinforcement shall be made for the second time.  The lead sealing for high height difference shall be reinforced with epoxy resin.

The sealing for plastic cable may apply self-sticky tape, adhesive tape or adhesive agent (thermosol); the surface of protective sleeve shall be made coarse and the oily soil on the bonding surface shall be removed with solvent and thus to form a well-bonding.

No leakage shall occur at the cable terminal, connector or in the oil supply pipe.   

Article 6.2.12  The installation of the oil supply system of the oil-filled cable shall conform to the following requirements:

A．     There shall be insulated connectors between the metal oil pipe of the oil supply system and the cable terminal and their insulation strength shall not be lower than that of the outer protective layer of the cable.

B．     When multiple sets of pressure tank have been provided for each phase, they shall be connected in parallel.

C．     Oil pressure monitoring or alarm device shall be provided for each phase of cable line.

D．     The instruments shall be firmly installed; the out door instrument shall be provided with rainproof devices and the instruments shall be adjusted when construction is finished.

E． The oil pressure of the pressure tank shall be adjusted and, in any case, it shall not exceed the allowable pressure range of the cable.

Article 6.2.13  The cable terminal shall be marked with obvious phase color symbol and the symbol shall be in consonance with the phase of the system.

Article 6.2.14  The terminal of the control cable may be bound up in general and damp-proof measures shall be taken for the connectors.

 

Chapter 7   Fire-fighting and flame retardant

measures for cable

 

Article 7.0.1  For cable concentrated locations where it is easy to catch fire as affected by outer factors and the cable circuits which may catch fire and cause serious emergency, the construction must be carried out with fire-fighting and flame retardant measures according to the design requirement.

Article 7.0.2  Following measures shall be taken as fire-fighting and flame retardant measures for cable:

A．     The fireproof plugging shall be applied to tightly seal the holes through which the cable passes through vertical shafts, walls and floors or enters electric panels or cabinets.

B．     In the important cable channels and tunnels, the fire division wall shall be set up in sections or be built with soft refractory material.

C．     The cable applied in the important circuits shall be laid in special duct or fire-resistant sealed groove box separately or be applied with fire-resistant coating or wrappings.

D．     The fire-resistant coating or wrappings shall be applied at both sides of the power cable connectors and the adjacent zone of 2~3 meters long.

E．      The fire-resistant and flame-retardant cables shall be applied.

F．      The alarm and fire extinguisher system shall be established.

Article 7.0.3  Technical authentication or product appraisal for fire-fighting and flame retardant material must be proceeded.

Article 7.0.4  Coatings shall be diluted to certain thickness and agitated evenly and shall be brushed in the direction of the cable length.  The times and thickness to be brushed as well as the time of the interval shall be according to the application requirements of the material.

Article 7.0.5  During wrapping, the tape shall be pulled tightly and wrapped closely; the layers and thickness of wrapping shall meet the requirement of the material application.  After wrapping, the cable shall be banded firmly with intervals of certain distance.

Article 7.0.6   the stoppage of the holes shall be tightly and reliable and no obvious cracks or visible gaps shall be found.  For larger holes, the refractory lining board shall be added firstly then plugging work shall be proceeded.

Article 7.0.7  The fire resisting door on the fire wall shall be tight and the holes shall be plugged; fire-resisting tapes or coatings shall be applied to the cable on both sides of the fire wall.

 

Chapter 8   Hand-over and acceptance of engineering

 

Article 8.0.1  Inspections shall be proceeded in the following sequence during the check and acceptance:

A．     The specification of the cable shall be in accordance with the regulation; the cable shall be arranged in good order without any damnification; the signboard for cable shall be completely established and written correctly and clearly.

B．     The fixing, bending radius and the concerning distances of the cable as well as the wiring of the metal protective layer and the phase sequence arrangement of the single-core power cable shall conform to the requirements.

C．     The cable terminal, cable connector and the oil supply system for oil-filled cable shall be installed firmly without any leakage; the oil pressure and calibrated value of the pointer for oil-filled cable shall conform to the requirements.

D．     The grounding shall be well and the grounding resistant of the oil-filled cable and the protector of the protective layer shall be according to the design.

E． The phase color of the cable terminal shall be correct and the anti-corrosion layers of the metal parts of the cable support, etc. shall be in good condition.

F． With complete cover plates, the cable channels shall be free from any foreign matters; there shall be no foreign matters in the tunnel and the illumination, venting and drainage devices shall be according to the design.

G．     The route symbols of directly embedded cable shall conform to the actual route.  The route symbol shall be written clearly, firmly installed and with proper intervals and shall be in accordance with the requirement in item 5.4.6 of this code.

H．     The symbols and the night illuminating devices on both banks of the underwater cable route and in the anchoring forbidden zone shall conform to the design.

I．  Fire-fighting measures shall be according to design and the construction shall be qualified.

Article 8.0.2  Intermediate reception shall be conducted and signed in during construction for the concealed work.

Article 8.0.3  Following data and technical document shall be delivered in the reception:

A．     Document of agreement the cable circuit route;

B．     Design data and drawings, detailed list for the cable, identification document for design change and completion drawings;

C．     The layout of transmission line for directly embedded cables with a proper scale of 1:500; the scale shall not be lower than 1:100 for areas with concentrated underground pipelines and it may be 1:1000 for areas with few pipelines and a simple landform; One drawing shall be shared by cable lines laid in parallel; the relative locations of different lines shall be marked in the drawing and the profile chart marked with underground lines shall be attached.

D．     The technical documents such as product descriptions, test records, certificates and assembly drawings from the manufacturer;

E．      Technical records for the concealed work;

F．      Original records of the cable lines:

a.    The type, specification as well as total length and subsection length of actually laid cable; the type and installation date of cable terminals and connectors;

b.    The title and type of the insulation material filled in the cable terminal and connector.

G．     Test records

 

Annex 1  Explanations on nouns applied in this code

 

Attached table 1.1  explanations on nouns applied in this code

 

 

Annex 2    Typical calculation formulae for lateral

pressure and traction

 

A.        lateral pressure  P = T/R

  in this formula,  P ---- lateral pressure (N/m);

                 T ---- traction (N);

                 R ---- bending radius (m).

B.  horizontal linear traction               T = 9.8μWL

C.  oblique linear traction                    T₁ = 9.8WL (μcosθ₁ + sinθ₁)

T₂ = 9.8WL (μcosθ₁ + sinθ₁)

D.  horizontal bending traction           T₂  = T₁ e^μθ

E.  vertical bending traction

1.  convex camber   

                        T₂ =  9.8WR[(1-μ² ) sinθ+ 2μ(e^μθ-cosθ)]/( 1+μ²) + T₁ e^μθ

                     T₂ = 9.8WR[2μsinθ+(1-μ² ) (e^μθ- cosθ)]/ ( 1+μ²)+ T₁ e^μθ

2.  concave camber, 

              T₂ = T₁ e^μθ-9.8WR[(1-μ² ) sinθ+ 2μ(e^μθ-cosθ)]/( 1+μ²)

              T₂ = T₁ e^μθ-9.8WR[2μsinθ+(1-μ² ) (e^μθ- cosθ)]/ ( 1+μ²)

in the formulae,           T ---- traction (N)

μ---- friction coefficient (see attached Table 2.1);

W ---- weight of one meter of cable (kg/m);

L ---- length of cable (m);

θ₁ ----the declination angle of the cable when it is subjected to oblique                                linear traction (rad);

θ---- the central angle of the bending part（rad）;

T₁---- traction before bending (N);

T₂ ---- traction after bending (N);

R ---- radius of the cable when it is bending (m).

 

Attached Table 2.1 the friction coefficient under various conditions of traction

conditions of traction	friction coefficient
in steel tube	017 ~ 0.19
in plastic tube	0.4
concrete tube, without lubricant	0.5 ~ 0.7
concrete, with lubricant	0.3 ~ 0.4
concrete tube, with water	0.2 ~ 0.4
draught on roller	0.1 ~ 0.2
draught in sand	1.5 ~ 3.5

Notes: The concrete tube includes asbestos cement.

 

Annex 3    Explanations on terms applied in this code

1.    In order to differentiate the terms of requirement with different extent of exactness during execution of this code, the definitions of these terms are given below:

A.   For terms giving expression of “very exact” and showing that things must be done in that way:

“must” is adopted for positive meaning and “must not” is adopted for negative meaning.

B.   For terms giving expression of “exact” and showing that things shall be done in that way normally:

            “shall” is adopted for positive meaning and “shall not” is adopted for negative meaning.

C.   For terms showing that small scopes of selections are permitted and that will be the first section when possible, “may” or “proper” is adopted for positive meaning and “may

not” or “not proper” is adopted for negative meaning.

2.    When certain items in this code shall be proceeded according to other standard or code, the terms are written as “shall be according to certain standard”, “shall be in accordance with certain code” or “shall conform to certain regulation”.