Asset Management of Power Transformers

Transcription

1 Asset Management of Power Transformers Prof. Dr.-Ing. C. Neumann TRANSFORM Partner

2 Claus Neumann Study of electrical engineering at Technical University of Aachen, Germany Dr.-thesis at Technical University of Darmstadt, Germany Till 2010 head of Operative Asset Management at Amprion, former RWE TSO Since 2010 active as a freelance Senior Consultant; fields of activities: network development, asset management, design and diagnostics of gas-insulated systems Honorary professor at Technical University of Darmstadt, Germany, lecture in HV switchgear and substations Asset Management of Power Transformers Page 2

3 Asset Management of Power Transformers 1. Introduction 2. Basic tasks and functions of asset management 3. Renovation strategy, life cycle assessment 4. Risk assessment 5. Maintenance, condition monitoring & assessment, life estimation 6. Design optimization based on evaluation of service experience 7. Conclusions Asset Management of Power Transformers Page 3

4 Introduction In the course of liberalisation of the electricity market significant changes in the regulatory framework strong impact on network business Intensive efforts of grid operators for optimized exploitation of the system and the equipment installed with regard to technical and economical aspects Introduction of management methods known from property management & insurance-trade asset management and risk management Application of these methods for control of economy & reliability of HV systems distinct technical aspects modifications necessary Fundamental functions of asset management examples, mainly related to power transformers duties & tools; Asset Management of Power Transformers Page 4

5 Fundamental functions of asset management Preparing of the key decisions for the network business, managing the relationship with internal and external partners maximising long term profitability and business success Revenues in network business mainly grid charges, more or less fixed optimisation of grid costs, improvements in efficiency, cost reduction (OPEX, CAPEX) Development and implementation of strategies quality of supply at minimised cost expenditure guarantee a given Ensure the asset rent ability Preservation of the existing network - maintenance, condition assessment & life estimation; future network development Work on technical & management oriented subjects Asset Management of Power Transformers Page 5

6 Costs Relation between costs and quality of supply costs in total Δ C costs for interruption of supply Δ Q costs for quality of equipment Quality of supply Ref.: G. Balzer, C. Schon: AM für Infrastrukturanlagen; Springer Verlag 2011 Asset Management of Power Transformers Page 6

7 Asset Owner, Asset Manager, Service Provider Asset Owner corporate planning financial responsibility, legal duties corporate management Asset Manager preservation & extension of the grid, preparation of the key decisions of the grid operator, optimisation & guarantee of asset rent ability Service Provider execution of AM s work orders, erection, assembly, maintenance operation Asset Management of Power Transformers Page 7

8 Asset Owner, Asset Manager, Service Provider Ref.: CIGRE Brochure 309, Dec Asset Management of Power Transformers Page 8

9 Asset management process Business policy, financing Budget, authorisation Business development Regulatory management Links to authorities, legal rules Financing management Links to customers Maintenance strategies, refurbishment Risk management R & D, new technologies Budget management Maintenance management Project realisation Commissioning, maintenance, Purchasing, stock management Operation, service functions Stand-by duty, fault diagnosis Ref.: G. Balzer, A. Gaul, C. Neumann, C. Schorn: The general AM process. CIGRE Symposium Osaka, Nov. 2007, Report 212 Asset Management of Power Transformers Page 9

10 Technical & management oriented subjects Replacement, renovation & extension Risk management Maintenance, condition monitoring & assessment, life estimation New technologies Service experience, reliability Performance measurements Environmental interaction Know-how & skill retention and development Consideration under technical & economical aspects with special regard to power transformers Asset Management of Power Transformers Page 10

11 Replacement, renovation & extension Decision making for investment by Life Cycle Cost Assessment: In the past: Decision making mainly based on Investment costs Spatial & environmental considerations Today: Decision making also affected by Service costs Lifetime considerations Life cycle cost assessment for finding the most economic solution Asset Management of Power Transformers Page 11

12 costs Different shares of LCC over years of service decommiss., disposal unplanned maintenance erection, acquisition renewal year of service scheduled maintenance, losses All payments in future to be represented as present values to year 0 Discounting interest rate: 10 % / a; inflation rate: 2,0 % / a Asset Management of Power Transformers

13 LCC cost shares related to invest costs in total IC Life Cycle Costs (LCC), 380/110 kv transformer 180% 160% 140% losses renewal unplanned mainten. scheduled mainten. balance of plant equipment 120% 100% 80% 60% 40% 20% equipment balance of plant scheduled mainten. per year unplanned mainten. per year renewal after 50 a loading 80% IC 20% IC 0,11% IC 0,36% IC 80% IC 50% P r 0% transformer 350 MVA losses IC investment costs 6 ct/kwh Asset Management of Power Transformers Page 14

14 LCC cost shares related to invest cost LCC cost shares related to invest cost LCC: 380 kv transformer 380 kv cable system 180% 160% 140% losses renewal unplanned mainten. scheduled mainten. balance of plant equipment 120% 100% losses renewal unplanned mainten. scheduled mainten. interface structure cables 120% 100% 80% 80% 60% 60% 40% 20% 40% 20% 0% transformer 350 MVA 0% cable system Asset Management of Power Transformers Page 15

15 LCC cost shares related to invest cost LCC cost shares related to invest. costs LCC: 380 kv transformer 380 kv GIS, AIS 180% 160% 140% 120% losses renewal unplanned mainten. scheduled mainten. balance of plant equipment 160% 140% 120% losses renewal unplanned mainten. scheduled mainten. balance of plant system, equipment 100% 100% 80% 80% 60% 60% 40% 40% 20% 20% 0% transformer 350 MVA 0% GIS AIS Asset Management of Power Transformers Page 16

16 bad Renovation and equipment end of life assessment Decision making process using an approach based on condition c and importance i of the equipment c Maintenance & renovation measures: sequence depending on urgency d: region I Urgency d depending on condition c and importance i d region II region III E. g. renovation measures equipment 3 first, equipment 2 secondly, equipment 1 depending on the budget available E.g. maintenance measures: high i equipment 5 will be maintained prior to equipment 4 Asset Management of Power Transformers Page 17

17 Assessment of condition and importance parameters 1. Assessment of condition parameters Actual condition quantities: taken from inspection & condition assessment, interval to next planned maintenance activity General condition quantities: service experience (e. g. after-sales service quality, maintenance costs), type related and individual failure rates assessment by school marks 2. Assessment of importance parameter Derived from the loading of the transformer in question related to the nominal power Weighted by a factor reflecting the relevance of the station in the system 3. Condition and importance parameters normalised to 100 Asset Management of Power Transformers Page 18

18 condition Condition & importance of 110 kv transformers Population of von 640 transformers maintenance maintenance replacement replacement d r2 d r d m2 d m importance Asset Management of Power Transformers Page 19

19 Dringlichkeit urgency Sequence of transformer replacement measures according to urgency Priorität Priority 11 Priorität Priority 22 Priorität Priority transformer Trafo Asset Management of Power Transformers Page 20

20 Technical & management oriented subjects Replacement, renovation & extension Risk management Maintenance, condition monitoring & assessment, life estimation New technologies Service experience, reliability Performance measurements Environmental interaction Know-how & skill retention and development Consideration under technical & economical aspects with special regard to power transformers Asset Management of Power Transformers Page 21

21 Risk assessment process Time after commissioning respect. service Result of reliability calculation Ref.: G. Balzer, C. Neumann, et al. : SELECTION OF AN OPTIMAL MAINTENANCE AND REPLACEMENT STRATEGY OF H.V. EQUIPMENT BY A RISK ASSESSMENT PROCESS; CIGRE-Report B3-103, 2006 Asset Management of Power Transformers Page 22

22 Risk assessment, value at risk (VaR) method Conventional risk assessment methods => assessment of risk factors of various equipment, e. g. different frequencies & consequences of failures, by mean values Stochastic characteristics of risk factors neglected => risk can be under- or overestimated VaR method => risk factors considered as stochastic distribution functions => Fig. a VaR summarizes the expected maximum (financial) loss within a given confidence interval over a target horizon => Fig. b a) 0,04 b) f(t) 0,03 failure rate 0,25 f(t) 0,20 Financial loss per a 0,02 0,01 0,15 0,10 0,05 Critical value at confidence level of 95% 0 0,0 0,2 0,4 0,5 0,6 0,8 [1/a] 1, [Mio ] 20 Asset Management of Power Transformers Page 23

23 Example: Population of 110kV/MV transformers Risk factors to be considered: Energy costs Transmitted power Outage time * Value of the equipment, investments Repair costs * * stochastic quantities Failure frequency * Outage time Repair costs Failure frequency Outage time & failure frequency => non-availability => costs for repair & corrective maintenance Ref.: G. Balzer, C. Schon: AM für Infrastrukturanlagen; Springer Verlag 2011 Asset Management of Power Transformers Page 24

24 Costs related to max. costs Result of VaR calculation: Loss costs in the period under consideration 100 [%] % probability 58% % probability 11% probabilty [%] Ref.: G. Balzer, C. Schon: AM für Infrastrukturanlagen; Springer Verlag 2011 Asset Management of Power Transformers Page 25

25 Technical & management oriented subjects Replacement, renovation & extension Risk management Maintenance, condition monitoring & assessment, life estimation New technologies Service experience, reliability Performance measurements Environmental interaction Know-how & skill retention and development Consideration under technical & economical aspects with special regard to power transformers Asset Management of Power Transformers Page 26

26 (Transformer) Lifetime model strength refurbishment, corrective maintenance maintenance failure, outage new condition condition after refurbishment minimum strength stress service life age Maintenance strategy has impact on loss of strength Refurbishment can compensate loss of strength Definition of minimum strength Assessment of actual strength Asset Management of Power Transformers Page 27

27 Maintenance & diagnosis strategy for power transformers Stepwise diagnosis* ) routine diagnosis * ) in addition to a quarterly visual inspection and periodical servicing no yes failure indication? Special diagnostic measurements no yes inadmissible impact? precautionary withdrawal from service, repair actions Asset Management of Power Transformers Page 28

28 Stepwise diagnosis strategy for power transformers comp. diagnosis method online offline off site remark active part bushing tap changer oil ageing X routine dissolved gas analysis (DGA) X routine resistance measurement X after indication (DGA) PD measurement X after indication (DGA) imdepance measurement X after short circuit transfer function measurem. X after short circuit PDC measurement X condition assessment furan analysis X condition assessment DP measurement X condition assessment capacit. / tan measurem. X routine DGA X condition assessment PD measurement X condition assessment diverter switch inspection X routine torque measurement X condition assessment Asset Management of Power Transformers Page 29

29 Stepwise diagnosis strategy for power transformers comp. diagnosis method online offline off site remark active part bushing tap changer oil ageing X routine dissolved gas analysis (DGA) X routine resistance measurement X after indication (DGA) DGA most important diagnostic tool for transformers PD measurement X after indication (DGA) In case of larger populations expert system imdepance measurement X after short circuit transfer function measurem. X after short circuit Classification of DGA results & condition based determination of sampling intervals PDC measurement X condition assessment furan analysis X condition assessment DP measurement X condition assessment capacit. / tan measurem. X routine DGA X condition assessment PD measurement X condition assessment diverter switch inspection X routine torque measurement X condition assessment Asset Management of Power Transformers Page 30

30 Stepwise diagnosis strategy for power transformers comp. diagnosis method online offline off site remark active part bushing tap changer oil ageing X routine dissolved gas analysis (DGA) X routine resistance measurement X after indication (DGA) PD measurement X after indication (DGA) imdepance measurement X after short circuit transfer function measurem. X after short circuit PDC measurement X condition assessment Short circuits in the vicinity of transformer terminals mechanical impact on windings danger of winding displacements furan analysis X condition assessment DP measurement X condition assessment TF measurements displacements diagnostic tool for detection of winding capacit. / tan measurem. X routine DGA X condition assessment PD measurement X condition assessment diverter switch inspection X routine torque measurement X condition assessment Asset Management of Power Transformers Page 32

31 TF2(f) TF 1 (f) TF 2 (f) TF 2 (f) TF1(f) TF 1 (f) ) Dauersberg Trafo 21 TF measurements for detection of A 0.0 Kelsterbach Trafo 23 winding displacements b.) 16.0 fo afo afo Measurements on 12 transformers of the same type (k ) Frequenz f MHz Hz Osterath Trafo 22Osterath Trafo 22 MHz Walsum Trafo Frequenz 21Walsum f Trafo 21 Pfalzdorf Trafo 22Pfalzdorf Trafo 22 Pfalzdorf Trafo 21Pfalzdorf Trafo 21 Osterath Trafo 22 Opladen Trafo 24Opladen Trafo Walsum 24Trafo 21 Pfalzdorf Trafo 22 Dünnwald Trafo 23 Dünnwald Trafo Pfalzdorf 23Trafo 21 Opladen Trafo 24 Ibbenbüren Trafo VIbbenbüren 21 Trafo 21 Dünnwald Trafo 23 Lüstringen Trafo Lüstringen 23 Trafo 23 Lüstringen Trafo 23 Ibbenbüren Trafo Ibbenbüren 22 Trafo 22 Mündelheim Trafo Mündelheim 23 Trafo 23 Fühlingen Trafo 22 Fühlingen Trafo 22 Fühlingen Trafo 22 St. Barbara Trafo St. 21Barbara Trafo MHz MHz 1.0 MHz Frequenz frequency f f Frequenz frequency f b.) a.) 2.0 A V Brauweiler Trafo 22 Limburg Trafo 22 Brauweiler Trafo 22 Dauersberg Trafo 21 Kelsterbach Trafo MHz 1.0 Frequenz f d.) b.) b.) d.) A Pfalzdorf Trafo 22 Pfalzdorf Trafo 21 Opladen Trafo 24 Dünnwald Trafo 23 Ibbenbüren Trafo 21 Lüstringen Trafo 23 MHz Ibbenbüren Trafo 22 Mündelheim Trafo 23 Fühlingen Trafo 22 St. Barbara Trafo Frequenz f V Ibbenbüren Trafo 21 Ibbenbüren Trafo 22 Mündelheim Trafo 23 St. Barbara Trafo MHz Frequenz f 0.70 Asset Management of Power Transformers Osterath Trafo 22 Page 33

32 TF I-1N/U-2V (f) TF I-1N/U-2W (f) TF measurement on a 220/110 kv transformer after short circuit on May kv windings 2.5 m (f) 1.5 I-1N/U-2U phase U TF of I-1N/U-2U on TF of I-1N/U-2U on measurem. Oct measurem. May 2005 TF MHz frequency f 2.5 m phase W TF of I-1N/U-2W on TF of I-1N/U-2W on m2.0-1 phase V TF of I-1N/U-2V on TF of I-1N/U-2V on MHz frequency f MHz frequency f Asset Management of Power Transformers Page 34

33 TF I-1N/U-2W (f) TF measurement on a 220/110 kv transformer after short circuit on May 2005 measurem. Oct measurem. May 2005 Winding displacement 2.5 m TF of I-1N/U-2W on TF of I-1N/U-2W on phase W MHz frequency f Asset Management of Power Transformers Page 35

34 comp. diagnosis method online offline off site remark active part bushing tap changer oil ageing X routine dissolved gas analysis (DGA) X routine resistance measurement X after indication (DGA) PD measurement X after indication (DGA) imdepance Failure statistics measurement on transformers X ~15% of after all failures short circuit caused transfer by failures function on measurem. bushings X after short circuit Measurements of capacitance and dissipation factor tan delta PDC measurement X condition assessment diagnostic tools to detect ageing phenomena and to prevent furan failures analysis X condition assessment DP measurement X condition assessment capacit. / tan measurem. X routine DGA X condition assessment PD measurement X condition assessment diverter switch inspection X routine torque measurement X condition assessment Asset Management of Power Transformers Page 36

35 Delta C / % tan / % Ageing behavior of resin bonded paper bushings: Delta C & tan 10 capacitance C 2,0 dissipation factor tan 8 1, ,0 2 0,5 0 0, age / a age / a Asset Management of Power Transformers Page 37

36 Technical & management oriented subjects Replacement, renovation & extension Risk management Maintenance, condition monitoring & assessment, life estimation New technologies, e. g. monitoring systems Service experience, reliability Performance measurements Environmental interaction Know-how & skill retention and development Consideration under technical & economical aspects with special regard to power transformers Asset Management of Power Transformers Page 38

37 Basic requirements for monitoring systems Monitoring systems valuable data and information for condition assessment of the system and the equipment installed Variety of data recorded and transmitted may cause problems when the information has to be evaluated and presented for the user Standardisation needed, basic requirements to be defined: Autonomous system, no inadmissible interference of the transformer in case of an outage Modular structure, which can be updated; monitoring server as well as sensors Uniform operator environment, independent from the transformer manufacture and type Asset Management of Power Transformers Page 39

38 Modular structured sensors manufacturer s test tap responsibility connector adapter standardised bushing coupler unit temperature measuring device moisture in in oil oil measuring device analogue intelligent gas in in oil oil measuring intelligent device gas in in oil oil monitor (subsystem) transformer bus link plugs analogue intelligent oil oil level indicator intelligent subsystem Asset Management of Power Transformers Page 40

39 Standardised visualisation of power transformer monitoring data information for system management operation asset management Asset Management of Power Transformers Page 41

40 Technical & management oriented subjects Replacement, renovation & extension Risk management Maintenance, condition monitoring & assessment, life estimation New technologies, e. g. monitoring systems Service experience, reliability => design optimisation Performance measurements Environmental interaction Know-how & skill retention and development Consideration under technical & economical aspects with special regard to power transformers Asset Management of Power Transformers Page 42

41 Failures on 220 & 380 kv power transformers 15% 10% Interturn fault 25% 30% Displacement by short circuit stress 20% OLTC bushing Carbonized-oil formation Asset Management of Power Transformers Page 43

42 Transformer failures: tripping compon. 18% an on angeschloss. compon. connected Komp. 50% outside of transf. 53% main tank 29% other causes 18% caused by animals 82% an on Trafo- transf. terminals Klemmen or od. bar Verschien. connections 50% 50% cable connection Asset Management of Power Transformers Page 44

43 Transformer failures: Alarm & warning signals others 17% Buchholz gas main tank 39% Buchholz gas component. 44% fault gas 34% miss signal 4% no findings 62% dry type bushing Asset Management of Power Transformers Page 45

44 Optimized transformer design 250 MVA, 400/120/30 kv resin impregnated paper bushing (RIP) with composite insulator (oil free design, no special protection device) tertiary winding with cable connection and plug in arresters (protection against external short circuits) Plug in cables Plug in arresters self supporting natural cooling unit (maintenance free) No external condensers! monitoring system Further features: On load tap changer with vacuum switching device, maintenance free air drying units Asset Management of Power Transformers Page 46

45 Conclusions Grid operators seek for asset rent ability asset management strategies and tools optimization by an adequate Technical as well as management oriented tasks, e. g. renovation, risk assessment, maintenance & condition assessment, new technologies, service experience, design optimization Renovation => LCC assessment, RCM method Risk assessment => VaR method Maintenance and condition assessment => multi-stage diagnosis: Basic diagnosis routine measurements; depending on the findings more sophisticated diagnostic investigations New technologies, e. g. monitoring systems => standardisation & definition of basic requirements Evaluation of service experience => design optimization, reduction of maintenance expenditure Asset Management of Power Transformers Page 47

46 Thank you for your kind attention! Asset Management of Power Transformers