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220kV GIS Installation

(2010-04-02) Hits: 1886

By Liu Mei Juan from Guangxi Power Construction Corporation. Liu Zhou city, 545002

【Abstract】 GIS (gas insulated switchgear), as a reliable power transmission & transformation equipment, has been widely used in electric power system. Compared with traditional open-type high-voltage power distribution equipment, GIS has obvious advantages: structural compaction, space-saving, free from the impact of the external environment, and high reliable operation, long maintenance cycle. Since its advent in 1960s, GIS has developed rapidly, and has occupied an important position in the field of power transmission system, especially applicable to high-voltage substation of urban power supply, power plants, large industrial and mining enterprises, petrochemical and railway transportation sectors, etc.. 

【Key words】220kV   GIS  Installation

1 General

220kVGIS Switchgear for Guangzhou Hengyun Power Plant, Phase I (2x300MW) is made by Henan Pinggao Toshiba Corp. and Japan Toshiba Corporation which is composed of SF6 circuit breakers, disconnecting switches, maintenance grounding switches, high speed grounding switches, current transformers, voltage transformer, lightning arresters, busbar tube, terminal bushing, control cabinet, outlet bush, and high-frequency wave trappers etc. The main tie line takes the mode of dual-busbar with 10 bays falling into 4 circles of outgoing line bays, 3 circles of incoming line bays, 1 busbar connection bays and 2 PT bays. Based on the GIS installation experience with this project, combining the company’ past experience in engineering practice, the specific installation steps for GIS is introduced for fellow’s reference.

2 Reference drawings, documents and standards

2.1 drawings, installation procedure and handbook
2.2 GIS design drawings.
2.3 GBJ147-90: Construction and Acceptance Criterion of High-Voltage Electrical Installation for Electrical Equipments
2.4 Electric Installation Part: Power Plant Construction Quality Inspection and Evaluation Criterion
3 Operations preparation and conditions
3.1 All civil works related with GIS have been completed; the foundation construction with embedded channel steel has been completed and accepted after inspection.
3.2 The road for GIS transport is smooth, clean and spacious enough to unload and open the cases. All manufacturers’ supplies are in place (including equipment, spare parts and special tools).
3.3 To obtain relevant technical information, e.g. to learn about the relevant provisions in the manufacturer's "product installation instructions" and "product testing certificate", to be aware of the characteristics, structure, working principles, the installation methods and requirement of the products. To establish the detailed installation plans, including equipment transportation and case-unpacking plan with on-site manufacturers’ technical representatives. The installation personnel need adequately training so that they can know the basic structure of GIS, performance characteristics, and master installation process. Issues concerning safety, environmental protection, technical measures should be emphasized towards the operating personnel prior to construction. 
3.4 The unpacking inspection for equipment should meet the following requirements: all components, accessories, spare parts and special tools and instruments should be complete, be of no damage and deformation as well as being free from corrosion. Porcelain pieces and insulators should be crackless and be of no damage. For units or parts filled with SF6, their pressure values should conform to the specified requirements. Components of the product should be inspected in mechanical & technical terms and necessary defect treatment should be performed.
4 Critical controlling points of construction procedure
4.1 GIS installation is a process of having all GIS assembling components piecing together in a certain sequence which is simple and convenient but the demand is high as far as the operation conditions are concerned, so the ambient conditions should be kept clean and dry to meet the quality requirements.
4.2 Foundation surveying, installation of equipment in bays or their piecing together would be defined as witness point; in installation of breakers in each bay would be defined as hold-point; the time when energized commission operation is conducted is defined as hold-point. 
5  The contents of operating procedures
5.1 Operation flowchart (Figure 1)
Figure 1 Operation Flow Chart
5.2 Foundation installation
5.2.1 To mark off the centerline of breakers, busbar incoming bushing and outgoing bushing according to the foundation layout drawing.  
5.2.2 Installation of circuit breaker, bracket of incoming terminal bushing, along with their alignment and self-inspection & acceptance. 
5.3 Install local control panel
5.3.1 Unpack the cabinet case and clean it; check the specification, model, circuit and arrangement against its design or not; mark it temporarily with its name, serial number and installation location.
5.3.2 Transport the control panel to the embedded channel foundation; arrange it according to the design position, fix it by the means of welding and screws/bolts.
5.3.3 Use plumb and angle Square to examine and adjust the degree of verticality, levelness, and flatness of the control panel to meet quality standards.
5.4 Accumulator/battery installation 
5.4.1 Check whether the enclosure of the accumulator/battery is broken or not, and clean the surface contaminant with alcohol.
5.4.2 Check whether the sealing compound at the sealing edges is torn or not, and check whether the components, such as: connecting strips, bolts, anti-acid explosion-proof cap/screw, fluid injection bolts etc.,, are complete and in good order or not.
5.4.3 Arrange and install it based on the design drawing and the space normally is 25mm according to the manufacturer’s requirements. 
5.4.4 After the installation of the accumulator/battery, they can be connected in series by "+","-" signs and be coated with a layer of Vaseline as protection.
5.5 Position Circuit breaker
5.5.1 According to equipment packing lists and numbers, open the circuit breaker box in order, bind it with a nylon rope and hoist it with the hoisting crane and travelling crane to where it is in place; adjust the centerline and the levelness; the centerline error should be within ± 2mm, the levelness error should be within the 0.5mm. The maximum error of levelness in different phases should not exceed ± 1mm.  
5.5.2 Compare the product mark in the manufacturer’s information, the number of components should be marked in the appropriate position and mark each component number in relevant position and on drawings after unpacking, and then put each component in the corresponding position according to numbers. Identify the accurate centerline and the adjust levelness with vertical plumb bob and level ruler when installing and positioning.
5.5.3 List specific positioning methods in details according to equipment size, location and weight and installation order.
5.6 Installation and connection of Bus
5.6.1 Put the busbar tube to extend where it is about 2000mm away from the fixed busbar tube, then loosen the stop bolt according to the position shown on the manufacturer’s drawing.
5.6.2 Insert the conductor fully into the interface inside busbar tube, and put special rubber pad under the conductor to maintain the conductor in horizontal position.  
5.6.3 Press O-ring coated with sealant into the flange sealing groove, move the outstretched busbar tube gently closer to the original parent tube/busbar tube until their flanges are fully connected.
5.6.4 Slightly adjust the bus conductor at the interface according to the direction shown on the manufacturer’s drawing until the stop bolt hole of the conductor is completely exposed, then put the stop bolt into the hole and tighten it.
5.6.5 When doing outdoor busbar tube connection, first connect it with indoor busbar tube through-wall panels, and the outdoor vacant/protruding part of the tool can be supported by the use of temporary supporting device in order to connect with the outdoor sleeve.
5.6.6 Install the permanent supporting structure of outdoor sleeves before connecting busbar tube and outlet line sleeves. Because of heavy outdoor dust, the hole at the joint should be sealed with adhesive tape before interfacing which can not be removed until connection is done. Care must be taken in resisting moisture because of high outdoor humidity. 
5.6.7When connecting busbar tube, the busbar tube connection, temporary support erection or permanent supporting structure erection should be done simultaneously to avoid busbar tube deformation by gravity. 
5.6.8 The work inside the busbar tube must be done by designated personnel. Wear safety hemlet, mask, buttonless one-piece uniform while working. All tools must be recorded. After the work is finished, check off the tools in case some of them is left behind inside the busbar tube.
5.6.9 When the work inside the busbar tube is over and the busbar tube has not yet been closed, clean it with vacuum cleaner and check it in case tiny articles such as hair, dust etc left behind in it.
5.7 Installation of outlet bushing and incoming bushing
5.7.1 Carry out visual inspection before installation to ensure no cracks and damage on porcelain sleeve.
5.7.2 Mark sleeve name, number and installation location temporarily.
5.7.3 Use manual crane to hoist in order to adjust the sleeve angle and put it in place.
5.8 Installation, adjustment and calibration of the isolating switch, grounding switch and operating mechanism.
5.8.1 Check if the specifications and model meet the design requirements; Indicate/mark the name, number and installation location, and then, lift up the facilities according to design requirements. 
5.8.2 After isolating switch, grounding switch and operating mechanism have been installed, switching-in and switching-off test should be carried out so that switch in-and-off complies with testing standards.   
5.9 Gas treatment and absorbent replacement
5.9.1 Gas treatment should be done together with the installation of other components simultaneously after the circuit breaker is in place
If no special requirements from the manufacturer, firstly vacuumize chamber and then charge N2, and vacuumize again to -0.1Mpa, and then fill SF6 gas to the rated pressure.
5.9.2 Check the O seal groove and flange surface if there are scratches, dents, contaminant, etc. prior to gas sealing, clean the groove and flange by using solvent, and fully dry them. All the solvent should meet the following requirements: use absolute alcohol to clean epoxy resin pieces; and use thinner to clean metal parts.  
5.9.3 The sealant used should be the type of KE-44RTVW or KE-45RTV-W which is waterproof and anticorrosive. A small opening should be cut at the mouth of the pipe before you connect the pipe orifice to the sealant tube. 
5.9.4 Apply a layer of sealant at the corner to the outside of the sealing groove bottom. The inside close to the gas cannot be coated with sealant. it is noted that the sealant must not be used in mixing way.
5.9.5 Smooth the surface of sealant evenly, and make the corner to the outside of the sealing groove bottom covered with sealant.
5.9.6 Check the special O-ring to see whether it is damaged and there is dirt/contaminant in it; wash it with absolute alcohol, and then put it into the outer area of the groove.
5.9.7 Apply a layer of sealant on the conjoint part of the O-shaped sealed ring and the outward top of the sealed groove. Smooth the surface of sealant with hands evenly, and daub the extra sealant on the outer surface of the external flange.  
5.9.8 Apply a 1mm thick sealant on the flange surface extending from the O-ring to the outer edge of the flange surface evenly. Notice that the connection of the flange must be completed within one hour. After the connection, the extra sealant should be removed.
5.9.9 After confirming that the internal is clean enough, the connection can not been done until the internals are confirmed clean enough. Slowly close up two assembly components flange, put on Screw orientation on the two symmetrical flange bolt holes. Passing through the bolts in the order of right angle, first tighten the bolt on flange top, until the two flange surfaces are closely contacted, and then tighten the bolts on the right angle, and finally use torque wrench to tight each bolt until reached the specified torque. 
5.10 Fabrication and installation of grounding wire and short circuit plate
5.10.1 The short-circuit plate should be made of flat copper sheet by bending it and all connections should be coated with anti-rust and corrosion-resistant paint.
5.11 cable laying & wiring 
5.11.1 According to cable construction drawing, secondary wiring connection diagram, etc, formulate relevant methods of the cable tray fabrication and installation. Based on the actual situation on jobsite, work out the construction technical measures for cable laying and wire connection technical requirements.
5.11.2 Cable laying should comply with construction quality standards, so that it can be tidy and beautiful, as a line both of horizontal and vertical, all cables leads to the same direction, with the same curvature, and the cables should be laid in such a way that they are in order both see
5.12 installation of framework device
5.12.1 Before installation, first conduct a visual inspection, cleaning and check the specifications and design models to make sure it is consistent with original design.
5.12.2 Lightning arrester should be connected to main grounding net of the power distribution equipment by the shortest connecting wire. It also should installed Concentrated grounding connection near it in order to avoid that grounding resistance is too large to affect the protective effect.
5.13 In the circuit breaker unit, after the busbar tubes are all installed, it is the time to start pumping-vacuum and gas-filling. These two procedures should follow the procedures provided by the manufacturer:
5.13.1 Sealed chamber vacuum procedure: Open the inlet valve cover of GIS gas sealed chamber → Fix the leather hose joint on the intake valve → start vacuum pumps and open the pipeline valve → when the indication on vacuum gauge achieve to O.1TORR, continue to pump vacuum for 30 minutes → close the intake valve of GIS sealed chamber and stop the vacuum pump → removal of leather hose.
5.13.2 SF6 gas filling procedures: check and make sure that the inlet valve of GIS sealed chamber is closed → open the inlet valve cover of the GIS sealed chamber→ connect safety valves and joints to the GIS inlet valve→connect coupling, adjusting device of SF6 gas, nylon hose to gas cylinder→ Open SF6 gas cylinder valve, then slowly clockwise rotate the handle of adjustment device to pump the SF6 gas out of the nylon hose → connect nylon hose to the safety valve → Open the inlet valve of GIS sealed chamber and adjust the handle of SF6 gas regulation device, pump to GIS chamber → obtain a, ccurate pressure, close the SF6 gas cylinder valve and GIS chamber valve, and remove nylon hose.
5.14 Unless there are specially explanations of manufacturer, vacuum--pumping should always be done before SF6 gas-filling in SF6 gas sealed chamber. If vacuum pump is suddenly stop during pumping, close the relative valves immediately, then check whether the vacuum pump oil is flow back to the hose or SF6 gas seal chamber.
5.15 Two hours after the gas-filling of SF6, water content measurement should be carried out, and within 24 hours, airtight measurement should be executed. 
5.16 After the installation and connection of all the components, bolt connection should fixed according to moment value of Appendix Table 1.
5.17 After finishing adjusting brackets’ centre, position and height, anchor bolt installation and facility grounding could be done according to manufacturer’s picture.
5.18 During GIS components installation, position of the local control box, installation of outdoor bracket and adjustment of facilities can be carried out at the same time.
6  Operation check and quality acceptance standard
6.1 The maximum permissible error the channel beam in each bay should be within ±3mm,  while the maximum error of GIS length should be within ±5mm.
6.2 The civil standard of GIS facilities’ lifting on perching: the error of center distance and height should be within 10mm; the error of embedded bolt central line should less than 2mm; the error of embedded roll or embedded iron center should less than 10mm; the depth of anchor bolts should more than 150mm.
6.3 There should be no crack in porcelain, and no damp, distortion, exfoliation or breakage in the insulators   
6.4 the combination of the electrical components, terminals, connections and the plug connector should be smooth and no corrosion.
6.5 the gas pressure and moisture content of each chamber should be accorded with the technical specification of the products.
6.6 the fastening bolt should be complete and tight, and the bracket and grounding wire should not have damage and corrosion.
6.7 meter passed the test and the explosion-proof membrane kept intact.
6.8 Busbar and line tube are smooth and no burr. Basin-shaped insulators are clear and intact. Connect plug-in should contact the centre of the sockets, no card resistance and insertion depth meet the requirement.
6.9. The installation work should be carried out in the weather without sandy wind, snow or rain the moisture content is less than 80 percent. And adopt dustproof and damp proof measures).
6.10 detergent, lubricant, sealants and cleaning materials must meet the technical requirements.
6.11 seal groove surface should be clean, no scratch marks; the sealant shall not run into the inside of the seal ring nor contact with SF6 gas.
6.12 The surface of the terminals should be smooth and contact, no- oxide film. When connected, coats it with thin electrical composite resin; silver-galvanized parts should not been construed, no burr nor depression in the current-carrying, connection bolts are kept complete and tight.
6.13 Before the gas-filling of SF6 gas, the gas-filling facility and pipeline should be clean, waterless, without oil pollution. There should be no leakage in the pipeline connecting part, and SF6 gas should meet relevant specification.
6.14 When there is SF6 gas with a qualified water content, gas can be supplied directly. The minimum water content of SF6 gas in the equipment should meet following requirements: first, for the electric arc disaggregation compartment, it should be less than 150ppm; second, for the non-electric arc disaggregation, it should be less than 500ppm, with the annual air leakage rate of every air chamber being no more than 1 percent. The measurement of water content and air leakage rate should be carried out 24 hours after the GIS gas-filling.
6.15 Test index and quality standard of basic check, installation of bracket and compartment equipment should meet the requirements when accept inspections.
6.16 The installation of composite apparatus should be solid, the surface should be clean and complete, and action capability should meet the product technique specification.
6.17 Electrical connections should be reliable and in good contact.
6.18 The linkage of composite apparatus and its drive gear should work well, without block. The indication of switching-in-and-off should be correct. The action of auxiliary switch and electric interlocking should also be correct. 
6.19 Bracket and grounding wire should be no rust and damage, grounding should be in good condition.
6.20 The alarm of density relay and locking value should meet the specification, and the transmission of electric loop should be correct.
6.21 SF6 gas’s air leakage rate and the moisture content should meet the specification.
6.22 Paint shall be complete and the color for different phase should be correct.
7 Safety and civilized construction measures
7.1 Inspecting the workplace before construction, carrying out safety construction technology clarification, taking good security measures, and consciously observe the relevant regulations of construction safety.
7.2 The composite apparatus shall not be upside down, roll over and collision during transporting, loading and unloading. It should be marked and transported as per the specified regulation.
7.3 Pay special attention not to pierce hands and feet or scratch equipment by nails, for GIS are frequently unpacked.
7.4 When assemble the internal components of GIS busbar tube inspecting and making sure that all components and tools had been thoroughly cleaned, work has been completed, no tools and debris is left in the busbar tube and all procedures are under the wardship and inspection by some designated person.
7.5 Porcelain sleeve and epoxy resin cylinder should not be over-pressed or shocked.
7.6 While using the lifting equipment, chain hoist should be added to maintain stable and prevent from shaking or collision in the air.
7.7 GIS equipment is easily damaged, so during installation, special attention should be paid to lifting position, weight, and the performance of chain hoist should often be checked to ensure good working condition.
7.8 GIS installation area must be kept clean, dry, dust-free, should be kept to monitor changes in environmental humidity. The assembly should be done under the humidity of less than 80%. Open the protective cover and components of the protective layer, assembly must be completed before off from work. GIS internal components can not be exposure to the air for a long time.
7.9 Safety helmet and bump protection ring of SF6 gas cylinder should be completed. Safety helmet should be tightened and kept in sun-proof, moisture proof, and well-ventilated places. No water and oil can be stuck in the valve and the cylinder can not mix with other cylinder.
7.10 GIS indoor workplace should be cleaned up once before and off work every day, so as to achieve the goal of work completed, material used up, workplace cleaned, equipment, material classified, so that it will not hinder construction and access.
7.11 GIS chamber should have enough extinguishers and fireproofing should be well-done.  
8 Environmental protection measures
8.1 The major risk factors are: high-lift construction, the demolition of metal scaffold, welding sparks flying, and construction power supply.
8.2 Major environmental factors are: abandon of waste oiled cotton and paint.
8.3 Classifying Waste material and rubbish and set the dumping point, cleaning and recycling regularly in order to purify the environment.
8.4 Master GIS related technical data, clarified the product features, structure and working principle. The related installation methods and requirements should combine with on-site situation, implement the organization and responsibilities in and after work, establish management measures, improve the comprehensive management level, make full use of effective resources and reduce consumption.
8.5 Using gas recovery plant to recycle, filter and re-use the SF6 gas N2 gas to prevent pollution.
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