11.2 Installation of hard busbars, wall bushings and pillar insulators

1. Production and installation of busbars

In the power transformation and distribution device, the current sent from the power supply will first be concentrated on the busbar, and then the current will be distributed from the busbar to various lines for users to use. Since the busbar is a conductor that collects and distributes current, it plays an important role in power transformation and distribution devices.

The busbar is also called the busbar. It is divided into three types according to material properties: copper, aluminum, and steel. However, considering the conductivity, resource reserves, price, etc., it is more reasonable to use aluminum as the busbar material. Steel is mostly used for grounding and zero busbars.

The specifications of TMY type hard copper busbar are shown in Table 11-10. The specifications of LMY type duralumin busbar are shown in Table 11-11.

(1) Production of busbar

Before installing the busbar, it is generally necessary to perform processing such as correction, measurement, cutting, bending, drilling, contact surface processing, welding, installation and painting. Before processing the busbar, you must first conduct an appearance inspection to see if there are any defects such as pores, scratches, pits, cracks, etc. on the surface of the busbar. Those with defects and insufficient cross-sections should be removed and not used. At the same time, a comprehensive inspection of the busbar performance and specifications should be carried out to see if it meets the design requirements.

Correction (straightening) of D busbar. Since the construction busbars transported to the site are often not very straight, they need to be corrected before installation. There are two methods of correction: manual and mechanical. When correcting by hand, you can place the busbar on a platform or a straight steel section, and use a hard wooden hammer to directly hit it straight. If you use an iron hammer, you must use a straight hardwood or metal backing plate to back it up and then hit it indirectly. Straight, the force should be appropriate when knocking, not too hard, otherwise it will cause the busbar to deform.

If the busbar has a large processing volume or a large cross-section, a busbar straightening machine needs to be used for straightening, as shown in Figure 11-23. When correcting, the uneven part of the busbar should be placed on the platform of the straightening machine, then the operating disc is rotated, and the screw rod pressure is used to straighten the busbar section by section until the effective length reaches the straightness requirement.

Figure 11-23 Busbar straightening machine

2 busbar measurement. Since the processing dimensions of the busbar are generally not marked on the design drawings, the actual installation dimensions of the busbar should be measured directly on site before cutting the busbar. When measuring, you can use tools such as a line hammer, square tape measure, etc. For example, when installing a busbar on two insulators with different vertical surfaces, you can follow the method shown in Figure 11-24. First, place a wire hammer on each insulator that is in contact with the busbar, and use a ruler to measure the distance between the vertical surfaces of the two insulators. The distance between A1 and the center lines of the two insulators is A2, and the dimensions of B1 and B2 can be determined according to the actual situation. Then draw a large pattern on the platform. Iron wire can also be bent into a template and used as a basis for bending the busbar.

Figure 11-24 Measuring the installation dimensions of the busbar

1-Support insulator: 2-Wire hammer: 3-Flat ruler; 4-Level ruler

When processing the busbar, the convenience of maintenance and disassembly should be considered. Sections should be connected with bolts at appropriate locations, but bending should be minimized.

3 busbar cutting off. The cross-sectional shapes of aluminum busbars are divided into rectangular, tubular, trough, rhombus, etc. Busbar sections below 10kV are mostly rectangular. The long-term allowable carrying capacity of rectangular aluminum busbars is shown in Table 11-12.

Table 11-12 Long-term allowable current carrying capacity of rectangular aluminum busbar (unit: A)

Before cutting the busbar, use a pencil to draw a line on the busbar according to the pre-measured size, and then cut it. When cutting busbars with small cross-sections and small quantities, a hacksaw can be used, as shown in Figure 11-25 (a). When cutting busbars with a large cross-section (250mmx90mm) or above, an electric circular tooth saw can be used, as shown in Figure 11-25(b). The burrs at the busbar break must be removed with a hammer or other cutting tools. When the busbar needs to be bent, it is best to cut it after bending it.

Figure 11-25 Busbar cutting

1 - bracket; 2 - handle; 3 - motor; 4 - protective cover; 5 - busbar

When cutting the busbar with a hand saw or an electric circular tooth saw, in order to prevent the rectangular busbar from being imprinted by the jaws of the bench vise, the jaws should generally be padded with a thin copper sheet or a hard flat object. The distance between the cutting seam and the side of the jaw should be approximately 20mm to prevent vibration during sawing. In order to improve the cutting efficiency, when cutting the busbar by hand, the saw blade usually uses coarse teeth. Pay attention to safety when using an electric circular saw, and wait until the circular saw has stopped spinning before loosening the busbar.

④Bending of the busbar. Busbar bending is a highly demanding link in busbar processing technology. There are usually three situations for rectangular busbar bending: flat bend, vertical bend and twisted bend (twist bend).

The distance between the bent part of the busbar and the connection should be more than 30mm, and the distance from the bend to the insulator support point should be more than 50mm, but should not exceed 0.25L (L refers to the center line of the busbar between the supporting insulators at both ends of the bend) distance) to ensure that the curved part of the busbar is installed firmly.

a. Flat bend of rectangular busbar. The flat bending of rectangular busbars is generally done with a flat bending machine. The busbar flat bending machine is shown in Figure 11-26.

Figure 11-26 Busbar flat bending machine

1-handle; 2-pulley; 3-pressure screw; 4-busbar

When bending, first lift the handle 1, pass the busbar that needs to be bent between the two pulleys of the flat bending machine, and then place the bent part on the roller. After the correction is correct, tighten the screw rod of the press, and finally slowly press down the flat bending machine. The handle of the bending machine makes the busbar bend. Do not use excessive force during operation to avoid cracks in the busbar. When the busbar is bent to a certain extent, you can use the previously made sample to review it to achieve the appropriate degree. The minimum allowable bending radius of the busbar flat bend is shown in Table 11-13.

Table 11-13 Minimum allowable bending radius of busbar flat bend

Note: b is the busbar thickness

A bench vise can also be used when bending small busbars. When bending, first place the busbar in the jaws of a bench vise, but the jaws should be padded with aluminum or hardwood to avoid pinching the busbar, and then pull the busbar by hand to bend the busbar to a suitable angle.

b. Vertical bend of rectangular busbar. The vertical bending of the busbar can generally be completed using a vertical bending machine, as shown in Figure 11-27

Figure 11-27 Busbar vertical bending machine

1-jack: 2-channel steel; 3-elbow; 4-plywood; 5-busbar; 6-stop; 7-angle steel; 8-plywood screws

When bending, first put the bent part of the busbar on the plywood of the vertical bending machine, then put on the elbow, tighten the splint screws and make the correction correct, then operate the jack to bend the busbar vertically. The bending radius of the vertical bend cannot be too small, otherwise cracks and wrinkles will occur on the busbar. The minimum allowable bending radius of busbar vertical bend is shown in Table 11-14.

Table 11-14 Minimum allowable bending radius of busbar vertical bend

Note: h is the busbar thickness.

The schematic diagram of flat bend and vertical bend of rectangular busbar is shown in Figure 11-28.

Figure 11-28 Schematic diagram of flat bending and vertical bending of rectangular busbar

c. Twisting of rectangular busbar. Twist bending is also called twist bending. A twisting machine is usually used to perform twisting during construction, as shown in Figure 11-29.

Figure 11-29 Busbar twister

When twisting, first fix one end of the twisted part of the busbar on a bench vise, and place a hardwood or aluminum block liner on the vise mouth. Then clamp the other end of the busbar with a twister, and then turn the handle of the twister with both hands to make the busbar reach the required shape. This method is generally only applicable to aluminum busbars of 8mmx100mm and below. For large-area busbars, heating is required before bending, and the temperature should not exceed the regulations listed in Table 11-15. When the busbar is twisted at 90°, the total length of the twist should be controlled at about 2.5 times the width of the busbar, as shown in Figure 11-30.

Figure 11-30 Rectangular busbar twist diagram

Table 11-15 Busbar heating temperature

Acetylene gas, gas and kerosene blowtorches can be used to heat the busbars. In order to make the heating temperature and curvature of the aluminum busbar meet the requirements, black paint can be painted on the surface of the bend and heated until the surface of the busbar turns red. If it is a bent cast aluminum busbar, the busbar cannot be moved while heating and can only be bent after cooling to avoid brittleness of the busbar.

d. Drilling of bus bars. Before drilling the busbar, you should first draw the location of the hole, punch a hole in the center of the hole with a punch, and then use a bench drill or hand drill to drill. When drilling, the difference between the diameter of the hole and the diameter of the connecting bolt should be no more than 1mm, and the hole should be vertical. After the hole is drilled, the burrs at the hole should be removed. If the busbar needs to be welded, the welding work should be done before drilling and after bending. Because the welding size is not easy to be very accurate, if welding is done after drilling, the hole position on the welded part often needs to be modified.

⑤ When connecting hard busbars, the following points should be noted:

a. When connecting busbars to busbars, busbars to branch lines and electrical terminals, the treatment of the overlapped surfaces should comply with the following regulations

Copper-copper: It can be connected directly in a dry room. It must be tinned outdoors, in a room with high temperature and humidity, and in a room with corrosive gases to the busbar.

Aluminum to aluminum: can be directly connected under any circumstances, and should be tinned if possible

Steel - Steel: in all cases must be tinned or galvanized

Copper-aluminum: Copper conductors should be tinned in dry rooms, and copper-aluminum transitions should be used outdoors or in particularly humid rooms.

Steel to Copper or Aluminum: In any case the steel overlap must be tinned

The overlapping surface of closed busbar bolts should be silver-plated

b. When connecting rectangular busbars by lap connection, the drilling size and the distribution size of bolts on the busbar should comply with the requirements in Table 11-16.

Table 11-16 Overlap requirements for rectangular busbars

legend	category	Connection size		Drilling requirements			Bolt specifications
		b₁	b₂	ɑ(mm)	∅(mm)	numerical value
	Straight line connection	125	125		19	4	M18
		112	112		17	4	M16
		100	100		17	4	M16
		90	90		17	4	M16
		80	80		17	4	M16
		71	71		16	4	M12
	vertical connection	125	125		19	4	M18
		125	71~112		17	4	M16
		112	71~112		17	4	M16
		100	71~100		17	4	M16
		90	71~90		17	4	M16
		80	71~80		17	4	M16
		71	71		13	4	M12
	Straight line connection	63	63	95	13	3	M12
		56	56	84	13	3	M12
		50	50	75	13	3	M12
	Straight line connection	45	45	90	13	2	M12
		40	40	80	13	2	M12
		35.5	35.5	71	11	2	M10
		31.5	31.5	63	11	2	M10
		28	28	56	11	2	M10
		25	25	50	11	2	M10
	vertical connection	125	40~63		13	2	M12
		112	40~63		13	2	M12
		100	40~63		13	2	M12
		90	40~63		13	2	M12
		80	40~63		13	2	M12
		71	40~63		13	2	M12
		63	25~50		11	2	M10
		56	25~45		11	2	M10
		50	25~45		11	2	M10
	vertical connection	63	63~56	25	13	2	M12
		56	56~50	20	13	2	M12
		50	50	20	13	2	M12
		45	45	15	11	2	M10
		125	35.5~25	60	11	2	M10
		112	35.5~25	60	11	2	M10
		100	35.5~25	50	11	2	M10
		90	35.5~25	50	11	2	M10
		80	35.5~25	50	11	2	M10
	vertical connection	40	40~25		13	1	M12
		35.5	35.5~25		13	1	M10
		31.5	35.5~25		11	1	M10
		28	28~25		11	1	M10
		25	22		11	1	M10

c. The method of using bolt overlap for rectangular bus bars is shown in Figure 11-31.

Figure 11-31 Busbars are overlapped by bolts

L - the distance between the two support points of the busbar

d. The diameter of the busbar connector hole should be 1mm larger than the diameter of the bolt, and the error in the center distance between the holes should not be greater than 0.5mm.

e. Installation of the bolt overlap surface between busbars or busbars and electrical terminals. The installation should meet the following requirements: connection fasteners should use galvanized bolts, nuts and washers; the contact surface should be smooth and clean, and coated with conductive paste or neutral vaseline; when the busbar is laid flat, the through-bolts should be passed from bottom to top. In other cases, the nut should be placed on the maintenance side, and the length of the bolt should expose 2 to 3 buckles of the nut; washers should be installed on both sides of the bolt, and spring washers or locking nuts should be installed on the nut side. After the bolts are tightened, the electrical terminals should not be subject to additional stress; the contact surface connection should be tight and can be checked with a 0.05mmx10mm feeler gauge. Busbar widths of 63mm and above must not be plugged in > 6mm; busbar widths of 56mm and below must not be plugged in 4mm ; The pressure of the fastening bolts should be appropriate and not over-tightened. If the bolts are tightened too much, the busbar will expand due to the heat generated during operation. Since the expansion coefficient of the bolts is smaller than that of copper and aluminum, the copper-aluminum rows under the washers will be compressed. If there are dents, gaps will appear after cooling, which will weaken the pressure and increase the contact resistance. Generally, during installation, you should first tighten the nut with greater force, then loosen it, and then tighten the nut until the spring washer is flattened.

⑥ Treatment of busbar contact surface. The busbar contact surface refers to the surface of the contact part when the busbar is connected to the busbar or the busbar to the equipment terminal. The flatter the contact surface is, the greater the mutual pressure, the more contact points, the smaller the contact resistance, and the more even the current distribution. Generally, the contact resistance of the bolted busbar contact surface cannot be greater than 20% of the resistance of the busbar itself of the same length. If the contact resistance is too large, overheating will occur when the rated current passes through the contact surface, and the busbar contacts may even melt, causing an accident. Therefore, the processing of the busbar contact surface is one of the keys to ensuring the quality of busbar installation.

The processing content of the contact surface is mainly to eliminate the oxide film, wrinkles and bulges on the surface of the busbar, making the contact surface smooth and slightly rough. Processing methods usually include mechanical processing, hand processing, etc. Mechanical processing uses a milling machine or a cutting machine. Although this method is efficient, it requires on-site conditions. The processing method of hand hammer is simple, but the efficiency is low, and it requires skilled benchwork skills. After the busbar contact surface is processed, the cross-sectional area is reduced. It should be noted that the cross-section reduction value should be controlled within the following range: the busbar should not exceed 3% of the original cross-section, and the aluminum busbar should not exceed 5% of the original cross-section. In order to make the busbar contact surface smooth without reducing the cross-sectional area of the busbar, busbar flattening machining can be used, as shown in Figure 11-32.

Figure 11-32 Busbar smoothing machine

This kind of machine has a simple structure and can generally be homemade. It uses two copper plates of 150mmx150mmx50mm, polish them with a grinder, and place them on the top of the jack as a mold for flattening the busbar. When operating this machine, the end of the busbar should be placed between the two molds, as shown in Figure 11-32. Then operate the jack to tighten the two tools and flatten the busbar. After pressing, use a flat ruler to check whether it meets the requirements. If it is flat, use a wire brush to remove the oxide film on the busbar connection part to make the busbar slightly rough. For aluminum busbars, a layer of neutral Vaseline paste should be applied immediately to isolate the contact surface from the air. If not installed immediately after processing, the joints should be wrapped in paper.

If a copper busbar is used, after processing the busbar joint, use a wire brush to remove rust and dirt, apply a layer of solder paste, and immerse it in a melted tin pot to make the tin adhere to the surface of the busbar. When taking the busbar out of the tin pot, use a clean rag to wipe away any scum on the surface to make it look silvery. If not installed immediately after processing, the joint part should be wrapped in paper

When tinning the busbar, you can use the flame of a blowtorch to heat the tinned part of the busbar until the color is copper and blue, then use a fine steel wire brush to remove the surface oxide layer, apply solder paste, melt the tin to the busbar, and then use Just wipe off the surface scum with a rag.

⑦Welding of bus bars. Welding the busbar can overcome the shortcomings of bolted connections and greatly reduce the contact resistance. There are many busbar welding methods, including gas welding, arc welding (carbon arc welding) and gas shielded welding. Before processing and installing the busbar, the appropriate welding method should be selected according to the construction conditions and specific requirements. Since the welding process of busbars is demanding, especially the welding process of aluminum busbars is more complicated, the welding of busbars should usually be done by skilled full-time welders.

Commonly used welding connections for busbars include butt welding and overlap welding, as shown in Figure 11-33. For aluminum busbars, clean the welding area with clean water after welding to avoid corrosion of the solder. The busbars connected by welding must be reliable and must not have holes or cracks. After welding, the busbar must be kept in a straight line without distortion.

Figure 11-33 Busbar welding

(2) Installation of busbar

Before installing the busbar, the support frame of the busbar should be buried in the wall or fixed on the building components. When installing the bracket, first use a level ruler to level and correct it, and then fix it with bolts or grout it with cement mortar. If the busbar is installed on a steel structure, electric welding can be used to directly weld the bracket firmly. The distance between busbar support points is shown in Table 11-17.

Table 11-17 Distance between busbar support points (unit: mm)

After the bracket is installed, the insulator should be fixed to the bracket with bolts. If there are many brackets installed in a straight section, in order to install the insulator neatly, you can first pull an iron wire through the bolt holes of the brackets at both ends, and then fix the insulator on each bracket along the iron wire. Finally, fix the busbar to the insulator.

① Fixing the busbar on the insulator. There are two types of insulators for fixed busbars: high voltage and low voltage. The high-voltage busbar is fixed with high-voltage insulators, and the low-voltage busbar is fixed with low-voltage insulators. Whether it is a high-voltage busbar or a low-voltage busbar, there are usually three ways to fix it.

a. Use bolts to tighten the busbar directly on the insulator, as shown in Figure 11-34. Using this method, oval holes must be drilled on the busbar in advance. The long axis of the oval hole must be along the direction of the busbar so that when the temperature of the busbar changes, the busbar has room to expand and contract without damaging the insulator.

Figure 11-34 Directly fix the busbar with bolts

1-busbar; 2-spring washer; 3-M10 hexagonal bolt; 4-washer: 5-pillar insulator

b. Use plywood to fix the busbar to the insulator, as shown in Figure 11-35. Using this method, there is no need to drill holes for the busbar. You only need to pass the busbar through the middle of the plywood and tighten it with bolts on both sides. The busbar plywood specifications are shown in Table 11-18

Figure 11-35 Fixing the busbar with plywood

1 - bolt, 2 - plywood; 3 - busbar

c. Use clamp plates to fix the busbar on the insulator, as shown in Figure 11-36. Using this method, you only need to put the busbar into the clamp and twist the clamp at a certain angle to clamp the busbar. The busbar clamp specifications are shown in Table 11-19.

Table 11-18 Busbar plywood specifications (unit: mm)

Figure 11-36 Fixing the busbar with a clamping plate

1 one busbar clamping plate; 2 one flat head bolt; 3 one pillar insulator: 4 one high voltage busbar: 5 one clamping plate

表 11-19 母线卡子规格(单位: mm)

d. The busbar terminals are fixed on the insulator as shown in Figure 11-37. When the insulator is installed horizontally, it should be connected with right-angled plates. The side where the right-angled plate is connected to the busbar is usually processed into an oval hole. If the connecting bolt is M10, the round hole is about 24mm long so that the busbar can expand and contract freely after the temperature of the busbar changes. When the insulator is installed vertically, the busbar terminal should be processed into a notch with a mouth length of about 40mm, and the busbar should be fixed to the insulator with bolts.

Figure 11-37 Terminal fixation of busbar on insulator

1 - washer; 2 - spring washer; 3 - card plate: 4 - busbar; 5 - M10 hexagonal bolt; 6 - pillar insulator

The busbar can be placed flat or vertically on the insulator, depending on the need. If there are several busbars of the same circuit on the insulator, special busbar clamps should be used to fix the busbars whether they are placed flat or vertically. When the busbar is placed flat, support sleeves should be put on the bolts fixing the plywood to maintain a gap of 1~1.5mm between the busbar and the upper plate; when the busbar is placed vertically, there should be spacers between the busbars to ensure that the upper plate Keep a gap of 1.5~2mm between the busbar and the busbar so that when the busbar is heated and expanded by the load current, it can expand and contract freely without damaging the insulator.

Figure 11-38 Busbar expansion joint production dimensions

Installation of busbar expansion joints. The busbar should be equipped with expansion joints (also called compensation devices) according to the design requirements. If there is no clear provision in the design, the design can be as follows: Install an expansion joint every 20m along the length of the busbar. Expansion joints should also be installed at the expansion joints of the building. The expansion joint can be made of the same material as the busbar, laminated with copper sheets or aluminum sheets (for aluminum busbars) with a thickness of 0.2~0.5mm. Its appearance and specifications are shown in Figure 11-38 and Table 11-20. The thin sheets of the expansion joint must not have cracks or wrinkles, and the oxides must be carefully removed. In addition, copper sheets should be tin-lined, and aluminum sheets should be coated with neutral petroleum jelly. After being stacked, it is riveted with copper or aluminum plates. The total cross-sectional area of the finished telescopic device shall not be less than the cross-sectional area of the busbar.

Table 11-20 Dimensions of expansion joints for busbar connection

Since the busbar expansion joint sheet welding process is high and the welding is complicated, finished busbar expansion joints are often used.

③ Bolt connection of busbar. The bolt connection methods of busbars are divided into three types: lap connection, butt connection and pressure plate connection, as shown in Figure 11-39.

Figure 11-39 Bolt connection of busbar

1-bolt; 2-nut; 3-washer; 4-busbar; 5-pressure plate (connecting plate)

The bolt connection method is only suitable for flat busbars. This method is simple to connect. When connecting, you only need to overlap and drill holes at the overlap of the two busbar sections, pass them with bolts, and tighten the nuts, as shown in Figure 11-39 (a). The overlapping processing technology requirements of various rectangular busbars are shown in Table 11-16. Butt connection refers to arranging the ends of two sections of busbars end-to-end, using a pair of splints (connecting plates) to connect the busbar joints up and down, and then drilling holes and tightening them with bolts, as shown in Figure 11-39 (b). The pressure plate connection is similar to the overlapping method. A special pressure plate is used to overlap the connected busbars. There are fixed screw holes on the pressure plate. Overlap the busbars that need to be connected, put in the pressure plate, tighten the pressure plate screws, and use a pressurized The method is to compress the busbar tightly, as shown in Figure 11-39 (c)

The following points should be paid attention to when constructing the busbar bolt connection.

a. When installing, first tighten the bolts with greater force, then loosen them. The second time, tighten the bolts until the spring washers are flattened. After a period of operation, recheck the tightness and contact surface conditions.

b. The bolts, nuts, flat washers and spring washers used for connection should be of appropriate size, and all except the spring washers should have an anti-rust layer (galvanized or blued). The thickness of the flat washer should not be less than 3mm. When installing bolts, flat washers should be placed on both sides of the bolt first, and then spring washers and nuts should be installed on the nut side. Then tighten them one by one. The tightened bolts should expose the nut (3~5) pitch.

c. The bolts should be tightened appropriately. Moderate means that the spring washers are just flattened by force. If it is too loose, the contact resistance will increase; if it is too tight, the plane pressure at the busbar connection will be uneven, which will deform the busbar contact part after being heated, which will increase the contact resistance. Generally, a 0.05mm thickness gauge should be used for inspection. When the busbar width is above 60mm, the insertion depth should not exceed 6mm; when the busbar width is below 50mm, the insertion depth should not exceed 4mm.

d. When connecting the busbar with a pressure plate (connecting plate), it is best to use copper bolts. When using plywood, iron bolts are not allowed to be used at the four corners at the same time. Two copper bolts should be used on one side of the square plywood. It is best to use non-magnetic splints to reduce eddy current losses.

e. When connecting the busbar to the equipment terminal, if it is a copper-aluminum connection or a copper busbar and an aluminum busbar, a copper-aluminum transition plate should be used. If there is no suitable copper-aluminum transition plate, a thin copper sheet can be tinned and placed on the copper-aluminum joint.

f. After the busbar is connected with bolts, in order to ensure that the connection part is well sealed, the grease on the joint part must be wiped off, and (2~3) layers of transparent varnish that can produce an elastic film should be applied on the surface and gaps of the joint to ensure The contact seal is good.

④Install the tensioning device. Low-voltage hard busbars installed in workshops are usually laid along walls, across columns, beams or roof trusses. The lines are generally long and the distance between brackets is also large. Therefore, terminal and middle tensioning should be used at the busbar terminals and middle sections respectively. device, as shown in Figure 11-40. The tensioning device can be assembled on the ground first and then installed. During installation, one end of the tensioning device is connected to the busbar, and the other end is fixed on the bracket with stud bolts. The place where the busbar and the tensioning device are bolted should be padded with a backstop gasket. The nut should be crimped after tightening to prevent loosening.

Figure 11-40 Busbar tensioning device

1-pull plate; 2, 3, 4, 9-plywood: 5-stud bolts; 6-tightening insulator; 7-busbar; 8-connecting plate; 10-stop washer; 11, 14-bolt; 12 , 15 - nut; 13, 16 - washer

(3) Arrangement and coloring of busbar phase sequence

In general design drawings, the busbar phase sequence arrangement is stipulated. If there is no stipulation, it can be arranged according to the following requirements.

①Vertically installed busbar. AC: U, V, W phase sequence is arranged from top to bottom; DC: positive and negative poles are arranged from top to bottom.

②Horizontally installed busbar. AC: U, V, W phase sequence is arranged from inside to outside (facing the bus); DC: positive and negative poles are arranged from left to right

③Arrangement of down-leads. AC: U, V, W phase sequence is arranged from left to right (facing the bus); DC: positive and negative poles are arranged from left to right.

④The phase sequence configuration of busbars of various voltage distribution devices should be consistent with each other. After the busbars are installed, they must be painted. The paint should be mixed well, not too thin or too thick, so that it can be applied evenly and beautifully. Painting the busbar can prevent oxidation of the busbar and enhance heat dissipation. Another function of painting is to identify the phases of the busbars and use different color marks to distinguish the phases. According to the color used for power, the busbar coloring should be carried out according to the following regulations.

a. Three-phase AC bus: U phase is painted yellow; V phase is painted green; W phase is painted red. The single-phase busbar derived from the three-phase AC busbar should be the same color as the lead-out phase.

b. DC bus: positive painted pig color; negative painted blue

c. AC neutral line busbar and DC voltage equalizing busbar: those that are not grounded are painted purple, and those that are grounded are painted purple with black horizontal stripes.

d. All sides of the single-piece busbar, all visible surfaces of the multi-piece busbar, and the steel base material (regardless of the number of pieces that can be installed and the type of current) should be painted.

e. The busbar bolt connection or busbar plywood (clamp) connection, as well as the connection welds should not be painted. The connection between busbars and equipment, as well as the connection parts of all busbars and the places within 10mm from the connection parts shall not be painted.

f. The unpainted length of the contact surface for the portable grounding wire connection should be equal to the width or diameter of the busbar but not less than 50mm, and should be separated from the painted part of the busbar by a black edge with a width of 10mm. Areas covered with thermometric paint should not be painted.

g. The busbar operating temperature is generally 70C. Since the contact resistance of a connection point is always greater than the resistance of the same length, in order to monitor the operation of the busbar, green (70°C) or red (80°C) temperature indicating wax sheets should be affixed to each connection point. When the busbar is running, if the temperature indicator wax is found to be melted, measures can be taken in time.

2. Installation of wall bushings

High-voltage wall bushings are used in power stations and substation and distribution devices of 6~35kV three-phase AC systems to allow conductors to pass through partitions, walls, etc., and play the role of insulation and fixed connection of external conductors.

Wall bushings are divided into indoor ordinary type, outdoor and indoor ordinary type, outdoor and indoor pollution-resistant type, etc. The meaning of the model is:

(1) Appearance and technical specifications of wall bushings

The appearance of the wall bushing is shown in Figure 11-41~ Figure 11-45, and the technical specifications are shown in Table 11-21~ Table 11-25.

Figure 11-41 10kv indoor copper conductor (row) pollution-resistant wall bushing

Figure 11-42 35kV copper conductor wall bushing

Figure 11-4310kV outdoor indoor pollution-resistant aluminum conductor (row) wall bushing

Figure 11-44 10kV indoor aluminum conductor wall bushing

Figure 11-45 35kV outdoor aluminum conductor wall bushing

(2) Specific installation of wall bushings

① Inspection should be carried out before installation. The porcelain parts and flanges should be complete and without cracks. The filling at the glued joint should be complete and the connection should be firm. It should be qualified after testing according to national standards.

② During installation, the base or flange must not be embedded in the concrete or plaster layer. The top surface of the wall bushing installed on the same plane or vertical surface should be on the same plane, and its centerline position should meet the design requirements.

③The hole diameter of the wall casing should be at least 5mm larger than the embedded part, and the maximum thickness of the concrete installation plate should not exceed 50mm.

④ When the wall bushing with a rated current of 1500A and above is directly fixed on the steel plate, there should not be a closed magnetic circuit around the bushing.

⑤ When installed vertically, the flange should be upward, and when installed horizontally, the flange should be outside.

⑥The metal splint (except fasteners) at the end of the busbar wall bushing of 6600A and above should be made of non-magnetic material. There should be metal connection between it and the busbar, and the contact should be stable. The thickness of the metal splint should not be less than 3mm. When the busbar is When there are two or more pieces, the busbars should be fixed

⑦ When installing the oil-filled pipe sleeve horizontally, the oil storage tank and oil sampling pipeline should be free of leakage. The oil level indication should be clear. The position of the oil filling and sampling valve should be installed on the patrol monitoring side. The oil injected into the casing must be qualified.

⑧The grounding terminal of the bushing and the unused voltage extraction terminal should be reliably grounded