Mr. Chetan Redasani, Prof.Dr.P.D.Patil, Prof. H. G.Patil / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 3, May-Jun 2013, pp.341-344
Stability of “Gas Insulated Switchgear” by using node beam method Mr. Chetan Redasani (ME Mechanical) Prof.Dr.P.D.Patil (Principle COE Shahada) Prof. H. G.Patil (Professor in Mechanical Engineering Dept.) P.S.G.V.P.Mandal’s D.N.PATEL College of Engineering, SHAHADA Dist: Nandurbar (Maharashtra)
Abstract The essential requirement of switchgear is to isolate the electrical circuit in case of unfavorable operating conditions and protect the electrical equipments from failure, Gas insulated switchgear is the device, which bridges the gap between protection system and space requirements of substation. In current scenario the urbanization taking place at glance. There is increasing demand of land in city areas to cope up this, GIS is best fit. Every GIS is having various electrical components starting from Circuit Breaker, Disconnector, Ear thing switch, CT, VT, and many more and configured in various arrangement, which generates large mechanical and electrical stresses in GIS due normal and abnormal service conditions, This stresses generates reactions and moments on GIS, which needs to transfer to foundations for proper operation of GIS. To achieve this various methods are used by different manufacturers, in current paper we utilize to do this by means of node beam method. This method gives very realistic and optimized results.
Over view of GIS and node beam method Gas insulated switchgear is the heart of protection system, the basic need of GIS is to protect the power transformers. It has lot of electrical and mechanical components the combine functioning of these all will make the GIS reliable. This mechanical and electrical components will creates lot of stresses, which are responsible for generating the reactions and moments about fixed load points in GIS. This reactions and moments need to transfer to foundation for safe operation of GIS. Various methods are used to achieve the said process; in this attempt the node beam method is considered. In this method the centre of gravity of the component is identified and the weight of the component is applied on it, based on actual loading conditions the loads are applied, vig. Point load, UDL, UVL, etc. After applying the loads various load conditions and combinations are consider for calculations of reactions and moments. The calculations also give the values of deflections and various mechanical stresses. Based on these values we approach for selection of thermal compensators, different mechanical structures to stabilize the GIS.
Introduction- In this Paper the calculations for mechanical stability are performed by using the software ROBOBAT, the project selected is 145 kV CAN-PACK India site. Following figure gives the overview of the 145kV Gas Insulated Switchgear.
Fig 2. Section view of GIS
Fig 1. 145 kV Gas Insulated Switchgear 
1. Integrated local control cubical 2. Current transformer 3. Bus bar I with disconnecting and ear thing switch 4. Circuit Breaker interrupter unit 5. Bus bar II with disconnecting and ear thing switch 6. Spring stored energy mechanism with CB control unit 7. Voltage transformer
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Mr. Chetan Redasani, Prof.Dr.P.D.Patil, Prof. H. G.Patil / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 3, May-Jun 2013, pp. 8. Make proof ear thing switch (high speed) Calculations for Bay E05 Section A-A 9.
Outgoing module with disconnecting and ear thing switch. 10. Cable sealing end.
The section view of bay E05 is as shown below. Section E-E is typical as per section A-A. Therefore for only one bay the calculations are performed.
Overview of case study project As discussed above we have consider the 145kV product used in CAN- PACK India project. This has 6 total bays, out of which 2 bays are typical. Plan view and section views are shown in annexure. Based on the plan and sectional view the models are created in ROBOBAT software.
Methodology of calculation In this method of node beam calculations the proper sequence is followed. As shown in flow chart. Based on the actual values of deflections and stresses it needs to refine the calculations by applying some additional supports and thermal compensators. After stabilizing the bay it gives the final values of reactions and moments, which are the input for the civil designer. Based on this input he will design his building and slab.
Fig 4. Sectional view of Bay E05 Stage ICreation of line diagram of bay in Robobat for Bay E05 The selected project is three phase single core encapsulated one. All three phases are kept in single bus duct.
Create the line diagram as per actual bay configuration
Define the appropriate sections and apply dimensions to line diagrams
Select the materials if required and apply the loads at centre of gravity of individual component
Select different load conditions for calculations
Fig 5. Line diagram of Bay E05 Stage II- Defining the appropriate sections and connections of line diagram. Perform calculations and review of results
Following figure shows the sectional and connectional details of bay E05. The structures are added at suitable position to take care of deflections and stresses.
Validation and publication of results
Fig 3. Flow chart of ROBOBAT calculation method.
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Mr. Chetan Redasani, Prof.Dr.P.D.Patil, Prof. H. G.Patil / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 3, May-Jun 2013, pp.
Fig 6. Sectional and connectional diagram. Stage III- Applying the loads at center of gravity of sections Various types of loads are applied at various sections. Some of them are point loads, some of them are universally distributed load, and values of each load are defined by manufacturer. It may be vary based on design. All loads are applied in terms of kN except thermal loading which is in degrees.
Fig 8. Deflection of Bay E05 The same way the stresses can be achieved. Stage V â€“ Finding out the reactions and moments about fixed points. After several iterations and limiting the deflections and stresses, we can find out the reactions and moments for Bay E05 as below.
Fig 9. Bay E05 with fixed points Fig 7. Loading diagram of Bay E05 Stage IV - Analyzing the deflection and stresses due to applied load conditions After running the calculations we have certain values of deflections and stresses. Based on it we need to provide the stiffeners to resist it to the desired value. At each node we will have the deflection values; also it shows the maximum value of deflections in red box. The deflected position of bay E05 is shown in different lines, where as original position is as it is as earlier.
General definitions of individual load cases (ILC) are as follows ILC1: ILC2: ILC3: ILC4: ILC5: ILC6: ILC7: ILC8: ILC9: ILC10:
Dead load Load by thermal expansion Static Conductor Tension Wind Load in X-direction Wind Load in Y-direction Short circuit forces Switching forces Earthquake load in X-Direction Earthquake load in Y-Direction Earthquake load in Z-Direction
Combinations of load cases. Combinations for normal load case LC1: LC2: LC3:
ILC1 Combination of (ILC1, ILC2, ILC3, ILC4) Combination of (ILC1, ILC2, ILC3, ILC5)
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Mr. Chetan Redasani, Prof.Dr.P.D.Patil, Prof. H. G.Patil / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 3, May-Jun 2013, pp. Combination for abnormal/exceptional load cases LC4: LC5: LC6: ILC10) ILC7: ILC10) Note:
Combination (ILC1, ILC2, ILC6) Combination (ILC1, ILC2, ILC3, ILC7) Combination (ILC1, ILC2, ILC3, ILC8, Combination (ILC1, ILC2, ILC3, ILC9,
1) Earthquake - Acceleration at centre of gravity Horizontal â€“ 0.6 g, Vertical- 0.4 g 2) Wind load - Maximum wind pressure 700N/m2 Corresponding to maximum velocity 120 kmph
overview of the structure, how stiff it is. Also it will give us an idea about the stability of the bay.
Discussion on results In this method the initial stage is creation of nodes each node is connected with other one by means of bars also called as beam, this is very simple method of stabilizing the GIS substation. It gives very realistic results. The critical issue in GIS stabilization is thermal dilatation, which can be solved by choosing appropriate thermal compensators. Which are capable to take loads in lateral directions only; there are few special compensators which are capable to take longitudinal loads during installation and commissioning. The results are highly comprehensive and optimized. Bay E05 uses very few structures to stabilize. There are some cross bracings used along the diagonals to arrest the longitudinal and lateral movement of the GIS based on requirement. The same calculation methodology can be applied for other bays as well.
References: . . . .
Gas Insulated Substations by M.S.Naidu IEC61936-1 IEC62271-100 Software used- Autodesk Robobat
Fig 10. Plan view of project Can Pack with complete bays The above table shows the values of reactions Fx, Fy and Fz in kN. Where as the moments as Mx, My and Mz in kN-m. These values of the reactions and moments are very important inputs to civil designer of the building. Also these values can give the
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