My Transfo 2004

Turin, the 20th and 21st October 2004

Interventions and abstracts

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[toggle title=”STATE OF THE ART FOR NEW IEC AND CENELEC STANDARDS” state=”opened”]

A. de Pablo

International standards are key elements to facilitate worldwide trade by eliminating technical barriers and promoting the development of new markets and the economy in general. A proof of such importance is given by the “Agreement on Technical Barriers to Trade” reached in the context of the Uruguay Trade Negotiation Round of the World Trade Organization and signed and ratified by more than 100 governments.
Moreover, such agreement establishes that international standards must be prepared, adopted and applied according to the “Good Practices Code”, also known as the WTO Standards Code.
On the other hand, international standards constitute an excellent media to disseminate technical knowledge and the common frame of work for all those involved in a specific task.
Based on these principles, IEC TC 10 initiated in 1997 a process to revise and update the most important standards of the Committee. This process consumed many of the committee limited resources (experts), thus making almost impossible to initiate new works.
During last months, however, the revision of the committee most important standards, i.e. 60296, 60422, 60567 has been successfully accomplished (see tables 1 to 4) and TC 10 has decided at its last meeting held in Funchal in July to initiate the new standardisation works that are described hereafter.
On the other hand, by the end of 2003, CENELEC set up a new committee with the task “to prepare a guide for the inventory, control, handling, decontamination and/or disposal of electrical equipment and insulating fluids containing PCBs”.
This document briefly describes the up-to-date advances on these areas.

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[toggle title=”Revised IEC standards for supply and maintenance of insulating oil”]

Prof. Pahlavanpour and Dr Eklund, Nynas Naphthenics Ltd UK

The international organization responsible for producing standards for electrical material is International Electro Commission (IEC) and member countries have their own national committee. Liaison is maintained with International Standards Organization (ISO) to prevent duplication in borderline area of mutual interest. Within IEC, Technical committee 10 (TC10) is responsible for fluid for electrical application, which covers over 46 standards. Among these standards and specifications there are three very important standards namely:
  • IEC60296 “Unused mineral insulating oils for transformers and switchgear
  • IEC60422 “Guide for the supervision and maintenance of mineral insulating oils in electrical equipment
  • IEC60599 “Mineral oil-impregnated equipment in service- Interpretation of dissolved and free gases analysis 
 
International standard IEC60296 is used in electrical industry for purchasing and supply of unused mineral insulating liquid. The previous issue was revised and published in 1982 and since then quality of the oil and expectation for performance of the oil in service has improved tremendously. It is one of the most widely used standards for supply of oil in the electrical industry. Although it is well established, the limits and expectations are very low, therefore many low quality oils may pass the requirements of this standard. Both users and producers realized this shortcoming, there for during IEC TC10 general meeting in 1998, it was decided to revise this standard. This standard was revised and published November 2003.

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[toggle title=”Test sull’Olio per determinazione del Fingerprint (condizioni iniziali). Applicazione di strumenti EPSS ……”]

Test sull’Olio per determinazione del Fingerprint (condizioni iniziali). Applicazione di strumenti EPSS e dell’incertezza di misura su previsioni dello stato di degradazione di oli e apparecchi in esercizio

R. Maina

I trasformatori elettrici sono apparecchiature strategiche, sia nella catena di generazione, trasmissione e distribuzione dell’energia, sia per gli utenti finali dell’industria e dei servizi. Una eventuale interruzione di erogazione dell’energia causata da un fuori servizio accidentale, più o meno grave, può assumere conseguenze economiche pesanti, sia in termini di penalità imposte dall’Authority, sia a causa dei danni indiretti da mancata produzione.

La capacità di individuare precocemente sintomi e cause del degrado dei trasformatori e dei fluidi in essi contenuti permette agli utilizzatori la pianificazione delle azioni manutentive localizzate. Questa strategia operativa prende il nome di manutenzione predittiva (Prognostica), o manutenzione basata su condizione (CBM – Condition Based Maintenance).

La capacità di stimare le condizioni di degrado medio e la vita utile residua di parchi macchine (più o meno numerosi) è una strategia operativa sovente inapplicata, quando non totalmente ignorata. Essa consente all’utilizzatore una attendibile e precoce stima dello stato di degrado attuale del parco macchine (Degradation Assessment), e permette di effettuare in tempo utile l’allocazione delle risorse tecniche, umane ed economiche (Asset Management).
La capacità di effettuare previsione dei tempi di degrado su singoli apparecchi o sul parco macchine è una strategia attualmente in corso di definizione, ma che sta divenendo sempre più importante, a causa della necessità (da parte degli esercenti di grandi parchi macchine pubblici e privati) di effettuare validazione e verifiche continue sullo stato di degrado dell’Asset tecnico globale. Questa strategia è la chiave di lettura della gestione prossima e futura dei parchi trasformatori, e può essere definita Asset Degradation Forecasting.
Alcuni tra gli strumenti operativi attualmente disponibili per un corretto approccio a queste strategie sono l’applicazione del concetto di fingerprint dell’apparecchio (o della famiglia di apparecchi), l’utilizzo di opportuni strumenti E.P.S.S. per la registrazione e il valido utilizzo dei dati, le tecniche statistiche previsionali.

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[toggle title=”LIFE MANAGEMENT TECHNIQUES FOR POWER TRANSFORMERS”]

V. Sokolov ZTZ-Service Co, Ukraine

Cigre published brochure № 227 “GUIDE for Life Management Techniques for Power Transformers,” prepared by CIGRE WG A2.18. This document of guidelines follows basically the two branches of transformer life:

1) Condition monitoring and assessment and 2) Operations and correction.
The contribution in the first branch has been in condition classification, definition of aging factors, recommendations on failure identification and on monitoring methodology, either two-step condition-based or functional-based, recommendations on diagnostic and monitoring techniques and assessment of typical problems based on a Catalogue of Defects and Faults. In the second branch a Catalogue of Operations has been introduced along with concepts and methodology of insulation rehabilitation and life extension and methods and support for insulation processing. 
Presented paper discusses several specific subtopics, which are important from both technical and economic points of view, namely
  • Consideration in many faces of transformer life;
  • Nonuniformity of insulation aging and contamination;
  • Functional –based diagnostic methodology and condition –based ranking the transformer population
  • Transformer design review as diagnostic tool
  • How to extend transformer life

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[toggle title=”Gestione Manutentiva Integrata applicata a TRASFORMATORI DI POTENZA”]

H. Pisani TRANSBA S.A.

E’ l’azienda di Trasporto dell’Energia Elettrica della provincia di Buenos Aires, Argentina. La nostra impresa gestisce il mantenimento di 5989 km di linee da 500, 220, 132 e 66 kV, 81 stazioni di trasformazione con 178 trasformatori di potenza e una potenza totale installata di 4363 MVA.

La quantità di impianti in concessione fanno di questa azienda la DISTRO (Impresa di Trasporto per Distribuzione Troncale), più importante del settore elettrico in Argentina e l’argomento di questo documento è la nostra esperienza rivolta alla Gestione dei metodi e dei processi applicati alla manutenzione dei trasformatori di potenza.

NOZIONI GENERALI

Il trasformatore, elemento principale nella catena di servizio, è una componente di grande valore economico, dove un guasto interno comporta dei costi di sostituzione e di riparazione eccessivi: nel nostro caso, nel 1989, erano dell’ordine delle centinaia di migliaia di euro annui. D’altra parte dalla sua disponibilità o meno, dipende la quantità di energia che non viene fornita ai clienti.

La necessità di migliorare la disponibilità di questi elementi ci ha portato all’inizio all’impiego di metodi statistici, per l’identificazione dei problemi e per la distribuzione delle risorse, e successivamente alla ripianificazione dei processi e dei metodi usati nei lavori di manutenzione.

Queste tecniche di gestione della manutenzione progrediscono costantemente sotto l’impulso del mercato sempre più competitivo, che obbliga a migliorare la disponibilità e a ridurre i costi operativi. Nel caso delle aziende fornitrici del servizio, come la nostra, bisogna tenere presente inoltre la richiesta di qualità da parte dei clienti.

In particolare l’adozione del sistema di qualità ISO 9000 da parte di TRANSBA (Certificazione ottenuta con BVQI, il 09/07/97), ci ha offerto il contesto necessario per completare l’organizzazione della manutenzione.

La regolazione di ogni intervento secondo protocolli di manutenzione e le “Procedure Generali per la Manutenzione dei Trasformatori” formano un insieme di elementi che permettono di mantenere questa attività sotto controllo con registri e tracciabilità.

Il risultato della gestione è stato positivo, considerando che il parco dei trasformatori della nostra azienda è completamente sotto controllo, in accordo con gli obiettivi di miglioramento ed i livelli di manutenzione stabiliti annualmente. Questo contributo, con registri di tracciabilità controllati tramite audit esterni ed interni stabiliti nel sistema di assicurazione della qualità, è sicuramente una strategia di gestione che può essere imitata, e che permette di fare delle esperienze utili agli specialisti di questa attività.

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[toggle title=”Applicazione ed interpretazione dei test elettrici per la diagnostica dei guasti su trasformatori”]

C. Serafino Terna – Italia

L’oggetto della relazione è illustrare a livello generale le due principali attività di verifica dello stato di affidabilità dei trasformatori ed autotrasformatori che la Terna esegue sul parco macchine di propria competenza.

·        Misura della induttanza di dispersione degli avvolgimenti
Lo scopo è trarre informazioni sullo stato degli avvolgimenti valutandone le rispettive deformazioni meccaniche attraverso il parametro “Induttanza di dispersione in corto circuito“.
Tali deformazioni sono spesso dovute a stress elettromeccanici derivanti da funzionamento su guasto ( corto circuito in rete ) e possono costituire motivo di allerta nell’esercizio della macchina in quanto possibile causa di indebolimento strutturale degli avvolgimenti stessi.
·        Misura del livello di Scariche Parziali
Lo scopo di questa misura, assai meno routinaria della precedente, è valutare o meno la presenza di fenomeni di scariche parziali, o di ionizzazione, che si abbiano a manifestare all’interno della macchina con conseguente ed indesiderata produzione di gas nell’olio.
La presenza di Scariche Parziali, o di fenomeni di ionizzazione, è sempre evidenziata da un particolare e ben preciso quadro gascromatografico dell’olio. Esse possono essere originate da danneggiamenti delle parti isolanti, derivanti da stress elettromeccanici, o dalla perdita accidentale di equipotenzialità di componenti tenuti invece saldamente a potenziale.

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[toggle title=”Assessment of environmental risk for the electrical substation”]

G. Pedoja
Objectives

The present work establish a methodology to manage existing environmental contaminations and prevent possible or new impacts in the future, derived from the maneuvers made in substations of electrical companies.
The project contemplates to visualize, to analyze, to register and to present before the organisms of control, the real risk derived from the contaminated facilities and the future plans of action.
The implementation of this methodology represents a technical, legal and economic benefit.

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[toggle title=”ASSESSMENT OF RELATIVE OXIDATIVE STABILITY AND PHYSICAL PROPERTIES OF BIOGENIC INSULATING OILS”]

S. Kapila 1, R. Seemamahannop 1, H. Shi 1, K. Kittiratanapiboon 1, V. Koneni 1, Ranjith Kolli 1, V. Flanigan 1 and V. Tumiatti 2

1Center of Environmental Science and Technology
University of Missouri-Rolla, MO 65409
2Sea Marconi Technologies, Turin, Italy

Introduction

The flow of current through a conductor invariably leads to resistive heating which in turn leads to a rise in temperature of the electrical devices such the transformers, capacitors and bushings. At equilibrium, the heat generated is equal to the heat dissipated. However, if the heat generated is not rapidly dissipated, temperature in the device can rise to unacceptable levels leading to the degradation of insulating materials in the device and ultimately failure of the device. Liquids are often used as heat transfer and insulating agents to maintain temperatures of electrical devices at optimal operating levels and prevent failure of devices. Insulating liquids or the “electro-technical” liquids are necessary for the generation, transmission, distribution and industrial utilization of electrical power. Properties of the liquids, in conjunction with those of solid insulating materials are important criteria in the designing electrical transmission and distribution equipment with an acceptable performance, life expectancy and minimal environmental impact at low costs (1).
            The desired properties of ideal insulating and heat transferring liquids in transformers and other electrical devices include:
·                   High electric strength, impulse strength
·                   Low dissipation factor
·                   High specific heat and thermal conductivity
·                   Excellent chemical stability and gas absorbing properties
·                   Good low temperature flow properties and low viscosity
·                   Low volatility and high flash point
·                   Low viscosity
·                   Good arc quenching properties
·                   Non-flammability
·                   Low cost
·                   Rapid degradability in the environment
No single liquid possesses all the desired properties; thus, compromises have been made in selecting insulating liquids. The criteria for compromises are the economics, equipment design, power rating, and criticality of uninterrupted operation as well as the health and environmental concerns. Different organic liquids have been used as insulating liquids.

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[toggle title=”LIFE ASSESSMENT OF POWER TRANSFORMERS TO PREPARE A REHABILITATION BASED ON A TECHNICAL-ECONOMICAL ANALYSIS”]

P. Boss 1, T. Horst 1, P. Lorin 1; K. Pfammatter 2; A. Fazlagic 3, M. Perkins 3

[1] ABB Sécheron, Geneva / Switzerland
[2], Algroup Alusuisse, Steg / Switzerland
[3] ABB Power T&D Company Inc., St-Louis/Mo, US 

This paper presents an overview of studies performed to establish the condition of transformers, connected to the grids of USA and Switzerland, based on diagnostic techniques and calculation methods developed in ABB. These units include Generator Step-up (GSU) transformers installed at power plants in USA and industrial transformers in Switzerland. The purpose of the studies was to assess the condition and status of these 10-40 year old transformers as part of a reliability and load management process. The assessment included an engineering design review and an evaluation of critical parameters linked to the life and reliability of the transformers. These parameters included dissolved gases in oil, the aging of components based on furanic compounds or the loading and thermal history, the condition of the insulation, the short-circuit analysis of the transformer windings, the operating conditions, the failure history and the preventive maintenance plan. The concept of Asset Management and the associated significant economical benefits are described in general terms. An overview of the methods used by ABB for condition assessment of medium and large power transformers, in particular, the advanced diagnostic methods used for that purpose, are then given and some representative results of these tests are presented. Finally, methods used for the economic evaluation of the different rehabilitation alternatives are discussed and a significant life assessment case-study is presented along with the calculations performed to estimate the economical impact (Benefits vs Cost) of the different recommended scenarios).

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[toggle title=”Economics of transformer management”]

Ryszard Sobocki 1; Pierre Boss 2

[1] Polish Power Grid, 2 Mysia Str. , PL-00-496 Warsaw/Poland
[2] ABB Sécheron SA, Geneva/Switzerland
[2] members of WG A2-20 of CIGRE

In a time of increasing competition and deregulation within the field of electrical power supply, increasing attention has to be paid to cost cutting, and thus also to economical issues. Transformers are important elements of a power system. They are important not only to power system performance and reliability of supply, but also to the financial performance of companies. The technical complexities of transformers, as well as their high capital costs and long lifetimes are important elements in the power system asset management process.

In order to support the work of asset managers, CIGRE has within the Study Committee A2, “Transformers”, appointed the Working Group WG A2-20 1), “Economics of Transformer Management”. Its main purpose is to develop a guide that is supporting the mentioned managers in performing evaluations (mainly based on economical considerations) and developing optimal solutions. The main target group for the guide are transformer managers. Nevertheless, the guide, and in particular, certain parts of it, can also be used by technical and organisational experts. The guide can be purchased at CIGRE Central Office (see also WEB site).

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[toggle title=”Maintenance, repaires, refurbishment of power transformers and feedback”]

P. Voorspoels, Pauwels Trafo Service

After describing the different stages in the life of reparable systems, we will examine how a power transformer can be likened to a system of this type.  We will then look at the difference between repairs and reconditioning.  The second part of this report will attempt to highlight the criteria used to decide whether to repair or recondition.

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[toggle title=”Insurance coverage for transformers’ economic management”]

D. S. Shubert

What are your chances for a transformer event?

Since 1996, more than 70 evens have been associated with large main auxiliary, or start-up power transformers. Several, such as the Quad Cities event, had significant station impact. More than 30 reactor scrams, numerous plant shutdowns, and several power reductions were associated with the transformer events. Many resulted in lost production and high repair costs.

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[toggle title=”Premature Insulating Oil Ageing and Remedial Action”]

(Mr M Meddins, National Grid, UK; Prof. B Pahlavanpour, Nynas Naphthenics AB, Sweden

The prime function of insulating oil is cooling and insulation. Specifications, standards are used for purchasing insulating oil. In service the oil is subjected to heat and electrical stress in which the oil is oxidised acid and sludge are produced. Recent experience shows that some oil age faster in service than others in a similar condition

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[toggle title=”LTR? Technology: PCB Transformer Decontamination for Re-Use Recycling of PCB free Transformers”]
Helmut Bergel Envio Germany GmbH & Co. KG, Kanalstr. 25, 44147 Dortmund, Germany

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