APPENDIX 2: EXAMPLE OF QUESTIONNAIRE
16 SERVICE PERFORMANCE
Several surveys have been published during the last thirty years or more aimed at determining the incidence of transformer failures and identifying the generic causes. The CIGRÉ survey on transformer failures published in 1983 is notably the most comprehensive and together with other later national or regional focused surveys, the general consensus has been to separately derive the primary causes of failure from the actual types of faults e.g.:
Primary fault causes
Defects in design, manufacturing, materials, poor specifications and inadequate testing, commissioning, maintenance, condition monitoring and protection; abnormal network and environmental effects, operations and events.
Transformer fault categories
These are usually classified into four main categories; electrical, mechanical, thermal and operational and apply to sub-categories, comprising for example, as illustrated in table 1:
Windings, core, bushings, tap changers, tank, insulating fluids, corrosion, materials, fittings and abnormal operation such; excessive harmonics, system over-voltage, overloads, ambient temperatures, weather.
It is apparent that in order to obtain some worthwhile assessment of the service performance of a transformer manufacturer’s product, some record of the performance of that product or his similar products is required. Such a record would need to be
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formulated in a regular and universally applicable manner and the duty to compile and maintain the record would appear to involve both the manufacturer and the previous purchasers of the product.
Nowadays it is very difficult for factories to trace long term service data since the operators do not routinely provide service related feedback after the warranty period has ended.
Therefore it is the operators that have the primary data by which to determine the Mean Time between Failure (MTBF), which must still be considered today.
The data that can normally be obtained during the warranty period should be used by factories to derive a service performance summary that identifies failure frequency and causes of failure in terms of their product population and service history. Data derived from beyond the warranty period if obtainable can be considered and may indicate the way corrective actions have been introduced by the factory to improve service performance or even product design and manufacture.
Part Sub-structure
Windings HV / LV / Tapping / Tertiary
Location Inner, middle, outer Axial position Radial position
Insulation Major (winding to winding) (winding to ground) Minor (turn to turn)
(disc to disc) Stress control Electrostatic shields
Inter-disc connection Capacitance shields
Magnetic circuit Core Leg (wound, unwound)
Yoke (upper, lower) Magnetic shunts Tank
Windings Supporting structure Clamps Mechanical structure Windings
Leads
Clamping Cleat bar
Bushings HV
LV
Ceramic / core / oil Ceramic / oil
OLTC Type
Selector Mechanical Control system
In-tank / separate compartment Single/double compartment Drive motor / couplings
Tank Flanges Shields Turrets Welded / bolted Magnetic conducting HV / LV
Table 1 – Potential failure locations in a transformer Reference: Prof. D J Allan, Consultant: “Transformer Failures” ©. EA Technology Ltd; “Transformers for Power Systems”, March 2009.
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Appendix 1: Quality management system
The ISO 9001 Standard provides common basic requirements and guidance to develop implement, use and maintain a Quality Management System leading to better performance of processes and to an acceptable level of quality of products. This means full conformity with specified requirements resulting in customer satisfaction. The following section explains the basic stipulations of the ISO 9001 Standard.
A1.1 Quality Management System, Document Requirements (ISO9001-2000, chapter 4)
The Quality Management System is a set of principles, rules, documents and actions which aims at improved quality of the product and customer satisfaction.
In order to manage quality, the factory should:
define processes involved in the transformer manufacturing perform, check and monitor the processes in terms of quality establish and control quality documents:
a. Quality Policy and Quality objectives b. Quality Manual
c. documents required by the ISO 9001 Standard
d. documents needed by the factory to influence processes (guidelines, procedures ….)
e. records proving conformity and proper function of the QMS
establish a quality management organisation (quality manager, auditors,…) the top management level should be personally involved in QM issues
(Management Responsibility)
A1.2 Management Responsibility (ISO9001-2000, chapter 5)
The Quality Management System should be managed under responsibility of the Company Top Management, who should be committed to:
promote the importance of determining and meeting purchaser requirements throughout the organisation
establish and promote the company quality policy ensure that the quality objectives are established
conduct management reviews and decide on necessary corrective and preventive actions
ensure the availability of resources necessary for quality management
A Quality Manager is appointed as a member of the company management team with clear authority and responsibility for all quality matters is to be appointed. The Quality Manager is basically responsible for:
all processes needed for the QMS and their function
reporting to the top management – performance of QMS, continual improvement
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A1.3 Resource Management (ISO9001-2000, chapter 6)
The factory should determine and provide all resources (Human, Infrastructure, Work Environment etc.) needed for:
Quality Management System development and continual improvement, enhancing the customer satisfaction by meeting purchaser requirements A1.4 Product Realisation (ISO9001-2000, chapter 7)
A1.4.1 Planning of product realisation
The factory has to plan the product realisation, by determining the following, as appropriate:
quality objectives and requirements for the product
necessary processes, documents and resources needed for the product realisation
ways and means of verification, validation, monitoring, inspection and testing, criteria for product acceptance
maintaining records needed to provide evidence that the transformer meets the above mentioned requirements
A1.4.2 Purchaser related processes The factory should determine and consider:
all requirements stated by the purchaser
all requirements not specified but necessary for the intended use
all statutory and regulatory requirements related to the transformer (legal, normative and other aspects)
any additional requirements determined by the factory
It is recommended to use the latest CIGRÉ guides for technical specification and design review.
A1.4.3 Review of requirements related to product
All requirements must be reviewed prior to the factory commitment to supply the product (i.e. submission of offers, acceptance of contracts…).
It must be made clear that:
all product requirements are defined
all contract or purchase order requirements have been resolved the factory has the ability to meet the defined requirements A1.4.4 Purchaser communication
The factory should implement effective ways of communication with purchasers in relation to:
54 product information
enquiries, contracts and order handling purchaser feedback
A1.5 Design and Development
The factory has to plan and control the design and development of the product. It has to determine design and development stages, define necessary reviews, verifications and validations appropriate to every stage, determine responsibilities and authorities in the design process. It is very important to manage the interfaces (e.g. mechanical, electrical, thermal design). The design plan has to be updated as appropriate, as the design and development progresses.
Design Inputs
All necessary information arising from purchaser requirements, applicable standards and regulations, previous similar designs and designer experience, have to be taken into account and reviewed for adequacy.
Design Outputs
Design outputs have to be provided in a form that allows for verification against the input and shall be approved accordingly. They have to provide appropriate information for purchasing, manufacturing and servicing, set up product acceptance criteria, and specify the product characteristics that are essential for its proper use.
Design Reviews
Design reviews should be performed at suitable design stages. This is one of the most important parts of the factory capability assessment which strongly influences the quality of the purchased transformer. (For details see the appropriate chapter of this guide). There is a CIGRÉ guide for design review, which is recommended for use during factory assessment.
Design Verification
The purpose is to verify, that the completed or partial design meets the input requirements. Records of design verification are to be maintained.
Design Validation
Design validation should prove that the manufactured product fulfils all intentions and design parameters required. Records of design validation (i.e. test reports) are to be maintained. A good proof of design validation is the reference to similar products manufactured before.
Design Changes
Design changes shall be identified and records maintained. Design changes shall be reviewed, verified and validated in the same way as the original design.
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A1.6 Purchasing
The factory should ensure that the requirements for the purchased product are properly specified and that the purchased product (material, service) conforms to them. This applies also to subcontractors.
The factory should evaluate and select factories based on their ability to supply products in accordance with its requirements. Criteria for such evaluation should be established; records including arising actions should be maintained.
purchasing information
a. specification of the product to be purchased
b. requirements for approval of the purchased product, manufacturing procedures, processes and equipment
c. requirements for qualification of personnel d. Quality Management System requirements verification of the purchased product
A1.7 Production and service provision
A1.7.1 Production Control The factory should ensure:
availability of all necessary information on the required product availability of work instructions, as necessary
availability and use of suitable equipment (machines, tools…)
For details see the appropriate chapters of this guide.
availability and use of monitoring, measuring and testing devices
For details see the appropriate chapters of this guide
suitably qualified trained production personnel
For details see the appropriate chapters of this guide
release, delivery (transport) and post-delivery (installation, commissioning and service) activities
For details see the appropriate chapters of this guide
A1.7.2 Production Process Validation
Results of manufacturing processes, which cannot be verified by measuring or testing directly on the transformer, should be validated.
A1.7.3 Product Identification, Traceability
Where appropriate, the factory should identify the product during its realisation - (labelling). The label should not only identify the product, but also its status in respect to monitoring, measurement and test requirements.
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A1.7.4 Purchaser property
The factory should identify, verify, protect and safeguard property provided for use or for incorporation into the product. In case of damage, loss etc. the purchaser must be notified and a record must be made. (Property may include intellectual property). A1.7.5 Preservation of product
The factory has to preserve the conformity of his product during manufacture and delivery to the intended destination. The preservation should include identification, handling, packaging, storage and protection.
A1.7.6 Monitoring and Measuring Devices
The factory should determine the monitoring and measurement to be undertaken and the monitoring and measuring devices needed to provide evidence of product conformance to determined requirements.
Where necessary to ensure valid results, measuring and testing equipment must be: calibrated or verified at specific intervals or prior to use against
measurement standards traceable to national or international standards adjusted or readjusted as necessary
the calibration and its validity (expiration) should be identified on the equipment
safeguarded from adjustments that would invalidate the measurement results
protected from damage and deterioration during handling, maintenance and storage
A1.8 Measurement, analysis and improvement (ISO9001-2000, chapter 8) Transformer manufacturing is a plan-do-check-act process.
The factory should plan and implement monitoring, measurement, analysis and improvement processes needed to:
demonstrate conformity of product with the specification and design requirements
ensure conformity and effectiveness of the quality management process continually improve the effectiveness of the quality management system Such measurement process should determine applicable methods including statistical techniques and the extent of their use.
A1.8.1 Customer Satisfaction
As one of the measurements of the performance of the quality management system, the factory should monitor information related to purchaser perception as to whether the factory has met the purchasers’ requirements. The factory should develop methods for obtaining and use of such information.
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A1.8.2 Internal audits
The factory should conduct internal audits at planned intervals to determine whether the quality management system
conforms to the planned arrangements for the product, to the requirements of the ISO 9001-2000 standard and to the quality management requirements established by the factory
is effectively implemented and maintained
The factory should establish an audit program that takes into account the importance of the processes to be audited as well as results of previous audits. Internal auditors should be selected. The auditing program should be independent and auditors should not audit their own processes. Non-conformities detected during internal audits should be eliminated together with their causes. Follow up actions should be taken in order to verify the elimination.
Note: Guidance for internal auditing can be found in ISO 10011-1, 2 and 3.
A1.8.3. Monitoring and measurement of processes
The factory should apply methods that measure of the quality management process. The methods should demonstrate the ability of the processes to achieve planned results. When planned results are not achieved, corrective actions should be taken to improve the processes and ensure conformity.
A1.8.4. Monitoring and measurement of product
The factory should monitor and measure the characteristics of the product to verify that requirements have been met. Such measurements should be taken at appropriate stages of the manufacturing process and evidence of compliance with requirements and with acceptance criteria should be recorded.
Records should identify the persons authorising release of the product. Final product release should not be permitted until all criteria are met and the planned checks have been completed unless otherwise approved by the purchaser.
A1.8.5. Control of non-conforming product
The factory should ensure that the product which does not conform to product requirements is identified (red tag) and controlled to prevent its unintended use or delivery. The controls and related responsibilities should be defined in a special documented procedure.
A1.8.6 Analysis of data
The factory should determine, collect and analyse appropriate data to demonstrate the suitability and effectiveness of the quality management systems and to continually improve the effectiveness of the system. This data should include data obtained by monitoring and measurement of processes and products.
The analysis of data should provide information on customer satisfaction
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characteristics and trends or processes and products suppliers
A1.8.7 Improvement
The factory should continually improve the effectiveness of its quality management system by improving quality policies, quality objectives, audit results, analysis of data, corrective and preventive actions and management reviews.
A1.8.8 Corrective action
The factory should take action to eliminate non-conformances in order to prevent recurrence. Corrective action should be taken to eliminate the consequences of non- conformances.
A1.8.9 Preventive action
The factory should take preventive action to eliminate the cause of non-conformances in order to prevent recurrence and avoid further non-conformances.
More information on ISO9001-2000 in Appendix 2
Examples of questions that need to be asked during the Quality
Management System review are presented in the Questionnaire –
Appendix 2
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Appendix 2: Example of Questionnaire
A2-36 Example of Capability Assessment Questionnaire Evaluation criteria
Chapter Information required Excellent Good Poor Unacceptable Comments
3 MANAGING QUALITY
Does the manufacturer have a valid ISO 9001 certificate?
Does the manufacturer have a valid ISO 14000 certificate?
Does the manufacturer have a valid OHSAS 18000 certificate?
4 TECHNOLOGY BASE
Transformer Type produced by the Factories
What type of transformer design is manufactured, core and/or shell?
Origin of Technology Base
Is the owner of the technology a global, regional, or local supplier?
Where or from whom is the origin of the technology?
Is the technology owned or licensed?
Familiarity and Compliance with applicable Industry Standards
4
DOCUMENTATION OF THE DESIGN AND MANUFACTURINGTECHNOLOGY BASE
Investigations and R&D Reports
Does the factory have 5 to 10 years of R&D Reports that can be used
for the assessment?
How does the knowledge and competence get maintained and
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Evaluation criteria
Chapter Information required Excellent Good Poor Unacceptable Comments
4 Basic Design Theory
Is the basis for the transformer design calculations clearly described
and documented?
Have origins of rules and criteria's been documented?
Do technical standards provide adequate geometric details between
adjacent components - windings, core, insulation systems, etc.?
How are materials and components specified for purchasing?
Does the factory have a drawing numbering system?
Are the manufacturing methods, processes, tools and equipment
clearly described and visualised?
Is there documentation that confirms the validation of computer
design programs?
4 Product Design and Manufacturing Rules and Instructions
Product Design Rules
Dielectric Rules
Does the factory have documented evidence describing how the
knowledge of electrical breakdown is transferred into design rules?
Does the factory have a documented insulation system?
Magnetic Core Performance Rules
Can the factory clearly calculate no-load losses, inrush and exciting
currents, harmonics, temperatures?
Does the factory historically analyse performance data versus
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Evaluation criteria
Chapter Information required Excellent Good Poor Unacceptable Comments
4 Acoustic Sound Rules
Does the factory have tools to calculate core vibration modes and
resonances at different frequencies?
Are sound levels calculated for both no-load and loading conditions?
Load Losses and Load Temperature
What thermal design calculation computer programs does the factory
use?
Have the thermal calculations been validated by fibre optic
measurements?
Are hot spot temperatures calculated for windings, core, internal
clamping structures and the tank at worst case operating conditions?
Short Circuit Strength and Mechanical Integrity Rules
Does the factory demonstrate short circuit withstand capability by
design calculations in accordance with IEC 60076-5?
What criteria are used for axial and radial strengths of the windings?
Has the factory performed short circuit tests?
If yes, what has been the experience?
What criteria are used to calculate transport and seismic capabilities?
Design Methods and Tools
How does the factory optimise the transformer designs?
Does the factory calculate dielectric stresses down to single turns?
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Evaluation criteria
Chapter Information required Excellent Good Poor Unacceptable Comments
Manufacturing Technology in Production Standards
How are production and process methods documented?
What accuracy and uncertainty does the factory have in:
Loss measurements? Sound level measurements? Temperature measurements? Impedance measurements? Partial discharge measurements?
Does the factory have an equipment calibration process and appropriate certification for its instruments?
4
Other means of Evaluating the technical capabilities of a factory
How many engineers and technicians does the factory have?
Does the number seem adequate?
Is there a formalized training and development program for the
engineers?
Has any of the factory staff written industry papers?
5 DESIGN PROCEDURES AND IT TOOLS
Design Experience of Market
Does the factory have experience with different specifications based
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Evaluation criteria
Chapter Information required Excellent Good Poor Unacceptable Comments
Design Experience of Product Range
Does the factory have experience with any of the following types of
transformer :
Grid step down transformers?
Generator step up transformers?
Transmission autotransformers?
Phase-shifting transformers?
Arc furnace transformers?
Rectifier transformers?
HVDC transformers?
Shunt reactors?
High voltage?
High current?
High leakage flux?
5 Specification Understanding and communication
Is the factory capable of understanding the user’s specification in the
original language?
How is communication between the user and the factory’s engineers
organised?
How direct are the lines of communication between engineers?
How many steps are there?
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Evaluation criteria
Chapter Information required Excellent Good Poor Unacceptable Comments
Design Process Quotation and Order
Is there an adequate post award review process (minutes, actions
followed-up)?
Internal (with commercial-, design- and manufacturing departments)?
External (with customers and their representatives)?
Are there defined hand-over points between electrical design and
mechanical design?
Is there an adequate design review process (minutes, actions