12.2 General Items
12.2.1 When connecting the busbar，the joint shall be in accordance with the following requirements:
1 If the bus is overlap jointed，the contact surfaces shall be grounded in accordance with those specified in Table 12.2.1-1.
Table 12.2.1-1 Requirements for faying surface of bus
2 Overlap joint of rectangular bus shall be in accordance with those specified in Appendix C of this code.
3 The joints shall be fastened:all bolts shall be arranged correctly，and the screw thread shall be 2-3 turns higher than the nut.Minimum clearance between adjacent gaskets shall be 3mm.The bolts shall be tightened using a torque spanner with the tightening torque specified in Table 12.2.1-2.
Table 12.2.1-2 Tightening torque（N·m）for steel bolt
4 Welding of joints:the material of welding rod shall be the same as that of the bus.There shall be 2-4mm reinforcement on the top of the butt weld of bus，and both sides of weld seam shall respectively protrude 4-7mm.The weld shall be free from defects，e.g.cracks and lack of penetration.Clean up the welding agent left over.
12.2.2 The bus shall be free from cracks and crinkles when being bent.
12.2.3 The insulators and busbar support shall be arranged squarely with even spacing.The fittings for fixing the busbar shall be correct and complete.
12.2.4 Refer to Table 12.2.4 for allowable deviation and bending radius for installation of the bus.
Table 12.2.4 Allowable deviation and bending radius for installation of the bus
Note:δ refers to the thickness of bus while b refers to the width of bus.
12.2.5 Electrical joint compound shall be applied to the contact face of bus joint.The bolt shall be under an even load，and there shall be no additional stress on the connection terminals of electrical apparatus.
12.2.6 During installation of bus，the safety clearance between indoor and outdoor power distribution units shall be in accordance with those specified in Appendix D of this code.
12.2.7 The fastening of bus shall be in accordance with the following requirements:
1 The fixture of bus shall be fastened with the insulator securely and the fixture shall not form a closed magnetic circuit.
2 When the bus is placed horizontally，there shall be a 1-1.5mm clearance between the bus and the upper pressing plate of the busbar clamping plate.If the bus is placed vertically，the clearance between the bus and the upper pressing plate shall be 1.5-2mm.
3 When the bus is connected to equipment，it shall be clamped securely at the last porcelain insulator.
12.2.8 If there are no design requirements，the arrangement of phase sequence of bus shall be in accordance with the following requirements:
1 For the AC busbars that are arranged up and down，the sequence shall be phase A，B and C from top to bottom.For DC busbar，the positive pole is at the top and negative pole is at the bottom.
2 For the AC busbars that are arranged horizontally，the sequence shall be phase A，B and C from back to front of the panel.For DC busbar，positive pole is at the back and negative pole is at the front.
3 For the AC busbar of downlead，the sequence shall be phase A，B and C from left to right.For DC busbar，positive pole is at the left and negative pole is at the right.
12.2.9 The color of panting for busbar shall in accordance with the following requirements:
1 For three-phase AC busbars，phase A is yellow，phase B is green and phase C is red.The singlephase AC busbar shall be the same color as the leading-out phase.
2 DC busbars:the positive pole is ocher and the negative pole is blue.
3 DC equilibrium busbars and AC neutral busbars:those that are not grounded are purple；and those that are grounded are purple with black stripes.
4 Closed busbars:lusterless black paint shall be applied to the outer surface of busbar and the inner surface of the casing.Light color paint shall be applied to the outer surface of the casing.
12.2.10 Applying of phase paint to the busbar shall be in accordance with the following requirements:
1 For indoor flexible busbar and enclosed busbar，phase paint shall be applied to both ends and appropriate part at the middle.
2 Phase paint shall be applied to all faces of single-strip busbar and all the visible faces of multistrip trough-shaped and tubular buses.
3 Anti-corrosive phase paint shall be applied to all surfaces of steel bus.
4 The paint shall be applied evenly without flaking and crinkles.
12.2.11 Phase color paint shall not be applied to the following positions of the busbar:
1 Bolt connection and connection of support，connection between busbar and electrical apparatus，as well as the positions within 10mm from all the connections.
2 The contact face for connection of portable earth wire，the length of the part that can't be painted shall be equal to the width or diameter of busbar，and not less than 50mm.And a 10mm wide black mark zone shall be painted on both sides.
12.2.12 The installation of the multi-strip rectangular busbar shall be in accordance with the following requirements:
1 The minimum clearance between buses shall be equal to the thickness of the bus.
2 Flexible cable should be used for connecting the busbar with equipment，and its section shall be not less than that of the busbar.
3 For butt welding of bus，the weld height shall be in accordance with those specified in Item 4 of Article 12.2.1 in this code.
12.2.13 The installation of plug-in enclosed busbar shall be in accordance with the following requirements:
1 Where it is installed by hanging，the hook shall be equipped with adjusting bolts，and the fixing distance shall not be greater than 3m.
2 The ends of the bus duct shall be provided with a closing cap，and the cap for lead hole shall be complete.
3 Each section of bus duct shall be securely connected，and the plugs shall be connected closely and reliably.
12.2.14 The installation of the busbar in the tunnel and vestibule shall be in accordance with the following requirements:
1 Where the busbar is installed with bracket，the distance between brackets shall be in accordance with design requirements.If the backbone cable is laid crossing the beam，column or along the roof truss in the workshop，the distance between brackets shall not exceed 6m.Tension device shall be securely fastened，and the difference of sag of the busbars within the same span shall not be more than 10%.
2 The busbar support in the low-voltage workshop shall be fixed together with the roof truss with clamps and must not be directly welded.
3 If the length of bus is more than 300-400mm，make a circulatory transposition.The transposition location of trough-shaped bus may be connected by a rectangular bus.
12.2.15 The installation of heavy current line of electrical furnace shall be in accordance with the following requirements:
1 The combined spacing of bus tie shall be the same，and the spacing between the mounting clamp plates should be 0.6m.The insulating clamping bolt shall be well insulated，and the suspension devices shall be the same in height.
2 The mobile collector ring shall be well connected to the copper wire，and the flexible cable shall be long enough to allow the platform to rise and lower.The connection of water-cooled pipe of the busbar shall be watertight.
3 The pressure for braking shall be in accordance with design requirements，and the clamps used for the bus end and the calandria shall be anti-magnetic.
12.2.16 The installation of insulator and sleeve shall be in accordance with the following requirements:
1 Support insulator:the porcelain parts shall be free of cracks，and the packing material at the glued joint shall be firm.
2 The support insulator shall be fixed securely with its top surface in line with its center line，with a deviation not more than 2mm.
3 Rubber or vulcanized fiber paper washer shall be used for between the low-voltage support insulator and the metal contact surface.
4 The diameter of the hole for installing the porcelain sleeve shall be at least 5mm larger than that of the embedded part.
5 Where the sleeve rated 1500A or above is installed on the steel plate or reinforced-concrete outlet plate，the hole in the plate shall not form a closed magnetic circuit.
6 The metal clamp at the end of the busbar sleeve rated 600A or above shall be non-magnetic.If the busbar sleeve is installed through the wall in an environment that is humid or sealing is needed，its both ends shall be sealed.
7 Both earth terminal of oil-filled sleeve and the idle voltage tap terminal shall be securely grounded.