Following topics to be covered; - Internal comm. / Organization of section / shop - Process (flowcharts/quality plans) - Interfaces with other departments
A brief overview of each department in BU-TR has been given in this internship report.
Distribution Distribution Transformers Production & Test Field MAIN ADVANTAGE OF TRANSFORMERS :
To overcome losses, the electricity from a generator is passed through a step-up transformer which increases the voltage. Throughout the distribution system, the voltages are changed using step-down transformers to voltages suitable to the applications at industry and homes. TRANSFORMER PARTS:
The main parts of which the transformers comprise are: • • • • • • • • • • • • • •
Core Winding Conservator tank Radiator High and Low voltage bushing Oil sample valve Oil drain valve Breather Tap changer switch Explosion vent Manhole and Cover Oil pump Terminal board Gas relay
HV Winding
LV Layer Winding
≥100 KVA
Coil Drying Oven Insulation mat. & Wooden parts
Not OK Core Storage Area
Assembly Core + Winding
Ratio Testin g
HV & LV Connections
Cores from Core Sect.
OK
Active Part from Storage Area
GK material from Super market
Vacuum Drying Oven
Final Assembly
Powder coated plates and Red oxide tanks
Steel Parts from surface Treatment/ Oxycoat
Oil Filling
Testing
Dispatch to yard FPP
EXPLANATION FOR TERMINOLOGIES IN PROCESS FLOWCHART: 1. LV WINDING: It is the low voltage winding which is placed on the core beneath the high voltage winding. It is wound in layer and foil format as required in design. 2. HV WINDING: It is the high voltage winding which is wound on the low voltage winding. It is wound in layer and disk format as required. Taps are also carried out from the HV winding. 3. ACTIVE ACTIVE PARE: The active part of transformer consists of core, winding, tab changer, insulation and connections. 4. CORE: The core is made from joining silicon coated steel plates of definite geometrical shapes. The silicon lamination on steel plates prevents from losses inside core material. 5. VACUUM DRYING OVEN: This oven absorbs moisture from insulation of windings and active part. 6. GK MATERIALS: These are the different items from nut bolts, washers, bushing to tools and other inventory items that are required in transformer production.
DISTRIBUTION TRANSFORMERS ROUTINE TESTS: POWER FREQUE FREQUENCY NCY TES TEST T (HV): (HV): This 1. POWER This test test is perf perfor orme med d on prim primary ary side side of the the transformer. It determines HV to earth leakage paths.
2. POWER FREQUENCY TEST (LV): This test is performed on secondary side of the transformer. It determines LV to earth leakage paths. 3. INDUCED OVER VOLTAGE TEST: This test is performed to check inter-turn and interlayer insulation of the windings by applying double of rated secondary voltage and frequency. 4. NO LOAD TEST (OPEN CIRCUIT TEST): This test is done to check the no load current and tolerance level i.e. 15% (IEC standards) on losses by applying rated voltage at secondary side of transformer. 5. LOAD TEST (SHORT CIRCUIT TEST): This test is done to check the rated current by shorting the LV side of transformer. 6. TURNS RATIO TEST: This test verify the turns ratio of the transformer given on the name plate as prescribed by the client. 7. RESISTANCE TEST: This test checks the winding resistance. 8. PRESSURE TEST: Pressure test is performed on t transformer after filling the oil in the transformer tank and sealing it. Nitrogen gas at 15 psi is applied inside the tank to check the tanks leakage if any.
Sales and Marketing This department is concerned dealing with w ith the customers and conveying information to other departments. First of all the inquiry is received from fax, telephone, E-mail etc. then they review the data technically and commercially. Contact customer for further clarifications. Forward the checklist (details of the transformer to be made) to the design Dep. after the design is finalized planning tells time span and some other measures after which sales Dep. tells customer the final date of the delivery and cost is set. Cost can be changed if cost of raw material increases in the market. After that order is placed i.e. production work starts. This Dep. deals in three ways i.e. •
INTERNAL
•
DIRECT / EXTERNAL
•
EXPORT INTERNAL means that if generator or motor dep. needs any thing it will be considered as internal dealing i.e. with in the siemens head office. DIRECT / EXTERNAL means to deal with in the country c ountry with the help of the sales and service offices all over the country or o r to deal with the local customer directly. EXPORT means to deal internationally. At present they are dealing all over the world particularly in Asia.
For each type of dealing they have different group of people.
PEQ (Process Excellence & Quality)/ MTL The PEQ department works for the quality check and fulfillment of costumer requirements. Fulfillment of requirements is achieved by two ways: - Quality is checked (inspected) - Quality is produced (assured) The PEQ department is categorized as:
PEQ PRODUCT QUALITY (Inspection)
PROCESS QUALITY
Receiving Inspection (RI)
QMS Audits
In process Inspection (IPI)
Quality Reporting
Final Inspection (FI)
Quality Training
Material Testing Lab (MTL)
•
Continuous Improvement: (RCA, CA/PA) - RCA: Root cause Analysis
*Continuous Improvement (RCA,CA/PA)
- CA: Corrective action; to prevent recurrence of problem - PA: Preventive actions; to prevent occurrence of problem
•
RECEIVING INSPECTION: Goal: To inspect all material used in manufacturing of product i.e. copper, steel sheets, testers, tap changer, brass parts etc.
The receiving inspection department processes the material as follow:
Supplier
List of important RI Documents: 1- Approved supplier list (Purchase) 2- Sampling Plan (No. of samples) 3- QA Test Plan (What to & how to do?) 4- MIR Material Inspection Report. 5-RMTR (Lab Testing) 6- Request for Testing (Shop Checking)
Challan Receive stocks
Good Report (GR) RI
Approved Supplier List
BAP (Purchase)
QA Work Instructions (Sampling Plan)
QA Test Plan What to do how to do?
Material Inspection Report (MIR)
Lab RMTR or Shop Ref. testing
Checked as per specifications Good Report Status
Passed
Rejected
MATERIAL TESTING LAB (MTL): • • • •
This lab is open for all business units in siemens. This lab is the part of BU-TR. It also provides services to external costumers. It works its results on RMTR document after testing materials. RMTR gives specifications / tests to be performed on the material.
The Tests performed in this lab are:
Viscosity test for transformer coolant oil Pour point test of oil. Enameled Copper breakdown voltage Tin coating test Viscosity test of oil Density test of oil Flash point of oil Acidity of oil Aging test for Rubber /Insulations Hardness tester of steel(nuts& bolts) Tensile & Elongation test of steel/copper parts Resistance Test of copper wire Spring back angle Test Brinell hardness of metal Weighing test by precise weighing balance Rubber hardness test Paint tests i.e. flow, density, adhesiveness, scratch, bend tests.
Power transformers Production & Test Field PRODUCTION If the rating of the transformer is more than 10 MVA then it is considered as Power transformer and is manufactured here. This is one of the biggest shops of SIEMENS. There are cranes ranging up to 200 20 0 tones. Machines used here are mostly of CHINA, Stoll Berg or of SIEMENS GERMANY. This SHOP is divided into three main parts i.e. 1)
CORE SECTION.
2)
WINDING SECTON.
3)
ASSEMBLY SECTION.
Each section has an in charge that runs the section according to the schedule given. This shop is also proud to manufacture the Auto transformer of the largest rating ever made in Pakistan of 160 MVA. Its customer is WAPDA. It is expected to be launched by this year. Brief view of each section is given. g iven.
CORE SECTION Cutting Of Sheets: Dimensions given by the design Dep. are feed in the cutting machine which then cuts the IRON SHEETS to the required size. These sheets are of 0.27 mm in thickness having a layer of silicon over it. Along with the cutting Punching is also being done. Sheets are cut at 45o and 90o angle, this is done to achieve maximum flux linkage. FOUR different types of sheets are being cut i.e. inner, outer, upper and lower sheets.
Step Formation:
Each type of sheet decreases width wise gradually to achieve a step wise construction. Step wise assembly is required to have a round figure of the core. Where steps are being made we place strips of round wood in- odder to have a complete round assembly of core, also to avoid damage of wire by the sharp edges of step, and technically to avoid concentration of the Magnetic Density around the step which would result in greater leakage flux.
Core Assembly: The core is arranged very carefully by the worker i.e. making proper arrangement as required with leveling of the sheets being placed on each other and achieving the step wise assembly. Each step contains a number n umber of sheets as per rating of the transformer. After the sheets are being properly arranged the core is then coated by b y RED-OXIDE to avoid it from rusting.
Core Frame: Core is enclosed from upper and lower sides in a frame.
WINDING SECTION Following types of winding are made here: 1)
L.V (Low Voltage) Winding.
2)
H.V (High Voltage) Winding.
3)
TAP Winding.
4)
Tertiary Winding.
INSULATION OF WIRE: Wires are insulated with a paper known as PRESS PHAN. The quality q uality of this paper is that it doesn't swell in the oil and can be gained in any thickness. Along with all this it is a good insulator.
1) L.V Winding: As it is a low voltage winding, the current here is high so we use a thick copper wire. It is a LAYER TYPE WINDING i.e. it increases axially. As the wire is thick so to have layer la yer winding is easy. The number of conductors (rolls of wire) to be used depends upon the rating. So the ends of wire coming out of the winding depend on the rating.
2) H.V Winding:
High voltage so less current i.e. thin wire, As it is required to have greater number nu mber of turns on than L.V winding and that to on the same length so we apply DISC TYPE WINDING. In this winding increase radially i.e. after completeness of o ne disc we move to the other. There is a strip of same paper containing thick pieces of the same paper (press pan) which is placed with in the disc to make easy flow of oil through the disc for cooling purpose. There are two stages before a disc is ready:
1) Build Up Disc: As we move from one disc to the other the wire has to move from top to bottom which disturbs the symmetry of winding. To avoid that we first make a disc in which wire is brought down with the help of a wooden piece whose diameter decreases gradually and the disc is made as the number of turns are required in a disc.
2) Simple Disc: This disc is then opened and is rebuild in opposite direction so the starting wire i.e. wire coming from the other disc is at the top. This is the final disc.
3) TAP Winding: This type of winding has thin wire and it is electrically connected to the H.V winding. TAP changer is not made here it is imported from SIEMEN Germany. It is on-load and off-loads both tap changers. In tap winding the taps are coming out after some number of turns as designed which help us to adjust the voltage accordingly. It is also layer type winding.
4) Tertiary Winding: This winding is placed inside the L.V winding. As when ever there is a short circuit take place L.V winding is burned so to avoid we introduce this and more over we can have much higher voltage across tertiary winding then L.V winding. Final Adjustment of Windings: Finally windings are packed tightly in wood frame from top and bottom so that they don't loosen up, and dried in the oven. The height of the winding is adjusted so that the required Tolerance could be achieved.
ASSEMBLY SECTION Here core and windings are arranged and a connection of tap changer with tap winding is done. Or in simple words active part is prepared. First we place an insulating sheet made of press pan paper around the core, then L.V winding is placed and adjusted so that it does not rotate around the core. After that another insulating sheet is placed and then H.V winding is placed. After it we
place tap winding which is electrically connected with the H.V and then to the tap changer. The active part is then placed in the oven for 3 to 4 days and approximately 20 2 0 to 22 litters of water is drained out. Then all the connections with the tank are made i.e. of bushings, with the terminal board, with sensors etc. BUSHINGS: These are insulators made of PORCELANE. In case of WAPDA on H.V side there are 4 bushings and 4 on the L.V side. In KESC 4 on the H.V but on L.V side there are 6 due to tertiary winding. Oil filled bushings are used for HV side.
SENSORS/INDICATORS: There different type of sensors or indicators as;
1) 2) 3) 4)
OIL LEVEL INDICATOR (On the conservator). TEMPERATURE INDICATOR (winding and Oil both). OIL LEVEL INDICATOR (Tank and Tap changer). BUCHOLZ GAS RELAY.
POWER TRANSFORMERS TEST FIELD After the filling of the oil finally the transformer is set for the tests. Tests which are normally done on the transformer are given below.
ROUTINE TESTS: These are the tests which are done on every transformer. They are listed below. 1) 2) 3) 4) 5) 6) 7) 8) 9)
Meas Measur urem emen entt of the wind windiing resi esistan stance ce.. Meas Measur urem emen entt of volt voltag agee rati ratio o & chec check k of pha phase se dis displ plac acem emen ent. t. Meas Measur urem emen entt of of sho short rt circ circui uitt imp imped edan ance ce and and loa load d los losse ses. s. Meas Measur urem emen entt of no load load loss oss and and cur current rent.. Induce uced ov over vo voltage wi withstand te test. Sepa Separa ratte sour source ce vol voltage tage wit withsta hstand nd tes test. Test on on on-load tap ch changer. Ligh Lighttning ning impuls pulsee vol volttage age wit withs hsttand and tes testt. Measurement of partial dischar harge.
TYPE TESTS: These tests are performed not on all the transformers but on some which are representative of the other. These are normally done only on customer demand. 1) 2)
Temperature Rise Test. Ligh Lighttning ning Impul pulse Vol Voltage tage Wit Withsta hstand nd Tes Test
SPECIAL TEST: These tests are not normally done but only on customers demand. These are;
1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 10)
Capacitances de determination. Transient vo voltage tr transfer cha charracteristics Short circuit withstand test Sound level determination Meas easurement of of ha harmoni onics of of th the no no lo load cu current. nt. Meas easurem uremen entt of of the the powe powerr tak taken en by the fan fan and and oil oil pum pump p mot motor ors. s. Measurement of of insulation re resistors. Meas Measur urem emen entt of diss dissip ipat atio ion n fac facto torr of the the insu insula lati tion on syst system em.. Meas easurement of dielectric strength gth of oil. Meas easurem uremen entt of of ind induc ucttance ance of the the wi windi ndings. ngs.
PLANNING This department is considered as the heart of the BU-TR.As it co-ordinates directly with every department. PURPOSE:
To prepare a documented procedure to define production planning functions. The mission of this dep. is to plan, execute, monitor and control all activities of product realization for greater customer satisfaction required quality and delivery reliability at optimum cost. The main areas that are covered during planning are; •
DELIVERY CAPABILITY.
•
DELIVERY RELIABILITY.
•
INDENT CONFIRMATION.
•
PRODUCTION DOCUMENTS DELIVERY.
WORKING:
The abbreviations normally used here are; I/C = Incharge. P.O = Purchase order. W.O = Work order. P.R = Purchase Requisition. BOM = Bill of Material. Similarly there are many other. They provide the whole plan i.e. how much time is required, work division to each section e.g. winding, core, tank etc. PICK LIST or in simple words the details and quantity of the raw material to be issued from the store is also given by the planning dep. if some material is to be purchased it is also decided by this dep. There working
flow charts are shown.
STEEL FABRICATION This shop is concerned with all the steel parts which are used in transformer i.e. •
EXTERNAL PARTS
•
TANKS.
•
TOP COVER.
•
CONSERVATOR.
•
PIPING ARRANGEMENT.
•
RADIATOR.
INTERNAL PARTS •
CORE FRAMES.
•
BASE PLATES.
•
HANGING ARRANGEMENT.
•
TENSION STRIPS. There shop is divided into some parts as;
•
MACHINE SHOP:
All the steel parts are set here according to the dimensions given by the design dep. such as the machines used here are;
• • • •
SHEARING. PUNCHING. BENDING WELDING.
WORKING: First the sheets of mild steel are cut. Usually sheets up to 10mm are cut by shearing machine and rest by GAS CUTTING. Then these sheets are set for punching. The punching holes are of the shapes such as circle, oval and square. The holes diameter varies from 10mm to 90mm. Some of the punching is done by drilling also. Then the sheets are moved for bending.
•
RADIATOR PLANT: PLATE TYPE RADIATORS:
Thin sheets are cut and designed and then two are joined together from center by welding known as SPOT WELDING, and from the sides by SEAM WELDING. These radiators are tested. Air is passed through them with pressure and they are immersed in water to check any kind of leaking. Then they are coated with red oxide to prevent from rusting.
PIPE TYPE RADIATORS: These are in shapes of pipe and are quite large in number. They are prepared by bending and welding. Then they are shot blasted and coated with red-oxide.
TESTING OF TANKS: Oil named as PENETRATING OIL is poured just on the inside walls of the tank and after 5 to 6 hrs it is tested from outside with the help of test lamp for any kind of leakage.
SHOT BLASTING: In case of DT this is done in a machine with in 15 minutes. At a time two transformers are put in the machine and are fired with small balls of iron to remove any kind of rusting. This is done before coating of red-oxide. In case of PT it is done manually. Worker wearing oxygen kit moves into a room where PT tank is placed and shot blasts it. FINAL ASSEMBLY OF DT AND PT:
Both DT and PT are prepared in different areas of the shop. After all these steps the tanks are sent for paint and then are dispatched to the required shops. EFFICIENCY OF WORK:
This shop provides 100% to DT 2, DT 3 & DT 4. Where as instead of tanks all other material is given to DT 1. It deals PT 80%.
MAINTENANCE & TOOL ENGINEERING This department deals with the maintenance work of the machines that are being used in the production of the transformer. They have h ave distributed there work into three main areas. •
BREAK DOWN MAINTENANCE.
•
PREVENTIVE / CHARACTIVE MAINTENANCE.
•
PREDECTIVE MAINTENANCE.
More over them have categorized their machines into three areas as A, B & C. A type machines are given YEARLY maintenance. 87 in number B type machines are given MONTHLY maintenance. 39 in number C type machines are given QUATERLY maintenance. 8 in number WORKING:
If some machine goes out of order any time time they respond to that and immediatel immediately y move their crew crew to the machine machine for quick maintenance maintenance and to make it work as soon as possible possible so there is no delay in work. Most of the times they take help from lifters. They also co-ordinate with the manufacturer of the machine if required. Manual of the machine is also given a reading at times. As SIEMENS is a manufacturing plant and not a process plant so there is no shut down maintenance. Heavy and light machines are tuned and checked accordingly to their category. If there is some major fault they co-ordinate with the respective dep. and to the planning dep. for maintenance or a change. So the back bone of the production area is this dep. If any machine goes down this mean the chain of work has broken so for this purpose maintenance puts in its effort to chain up the work wo rk again.
DESI DESIGN GN DEPA DEPART RTME MENT NT This area is responsible for the design of the required TRANSFORMER. The design is made according to the requirement of the customer. They receive their data from the SALES dep. The design of the Transformer comprises of following main steps. 1) Search of the pre-existing pre-existing data. 2) Electrical and Mechanical calculations. The first step as they get the CHECK LIST i.e. the details of the Transformer to b e designed, put the data and compare it with the already designed transformer, if it matches or some of the features are the same then they continue their work from there otherwise they start designing it. The first step of the design is ELECTRICAL calculations. These calculations are done using two soft wares. 1) Excel Sheets. 2) CADWIG software software (made by SIEMENS). From here we get the information that how many numbers of turns are to be use, Length of the coil, Diameter of the winding etc. If Round coil winding is to be done then Excel Sheets are used and if Foil (using copper sheets) winding is to be used then CADWIG software is applied. These calculations complete the electrical part of the Transformer. The kind o f the windings designed here are HV, LV & TAP winding. If required then TERTIARY winding is also d esigned (only in case of K.E.S.C).
Then come the design of the Mechanical part i.e. the CORE and the TANK. Core is design keeping in view the value of the losses. The core is design in the form of the layers of the steel sheets to control the losses and its size varies with the rating of the transformer. The TANK is designed leaving some spaces from the windings from all sides, keeping in view all the parameters. The CONSERVATOR, RADIATORS, HEAT and other SENSORS along with the BREATHER are also designed i.e. giving all the information of the dimensions of each part the tank. All the design work is done do ne on the software named AUTOCAD. Then the final file is forwarded to the respective departments.
