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Intelligent condition diagnostics for transformersWith SITRAM® DIAG from TLM™ – Transformer Lifecycle Management™
www.siemens.com/energy
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You have to know the condition before you can improve it
A transformer’s condition cannot be assessed without a comprehensive understanding of the electrical, physi-cal, and chemical processes that occur during operation. Binding standards for evaluating electrical parameters measured on site are practically nonexistent. Based on our expert knowledge and more than a century of experi-ence manufacturing transformers, we at Siemens have developed a modular diagnostics program for power transformers – SITRAM® DIAG.
SITRAM® DIAG consists of three levels of analysis and many additional stand-alone modules for the selection and examination of irregular transformers in ever greater detail:
� Level 1: Basic package without interruption of service � Level 2: Electrical measurements with short-term decommissioning
� Level 3: Mobile test field, performance testing, high-voltage testing, partial discharge testing
During the 1970s, many industrialized countries made large investments in their power generation and distri-bution infrastructures. Now that the average age of these installed transformer fleets exceeds 30 years, many transformers have already been in service longer than was originally planned. Due to failures and load shifting, what were once reserve transformers have long been used in normal operation and the average utilization of transformers has increased.
As a result, previously available redundancies are now gone and the operative risks are growing. The potential economic consequences could be dramatic.
To avoid unplanned outages and their consequences, the operating condition of installed transformers must be assessed more frequently as they age, and expenses must be kept within reasonable limits. In addition to taking accu-rate measurements, this involves evaluating the individual data, correlating it, analyzing the trends, and documenting the findings.
SITRAM® DIAG helps prevent breakdowns while optimizing utilization and availability. It isn’t a matter of having the oldest transformer in the net-work, but of knowing exactly what operating reserves are available and of maximizing power throughput until a planned decommissioning.
SITRAM® DIAG ensures the availability of transformers – and thus the supply of power to entire infrastructures.
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Assessments during normal operation
Basic module: � Analysis of insulation liquid (chemical/physical, DGA, furanic components, corrosive sulfur, etc.)
Optional additional modules: � Determination of relative oil humidity � Thermograph scans � Partial discharge measurement and localization � Noise measurement (vibration measurement)
SITRAM® DIAG Level 1 The cost-effective management of maintenance budgets requires that existing transformer fleets be selected with-out unreasonable expense and that the more expensive evaluations be reserved for irregular transformers and those that are of particular importance. The Level 1 mod-ule was developed for transformers in normal operation. It focuses on the analysis of insulation liquid – an effi-cient tool with a decades-long track record that allows us to draw well-founded conclusions about the “health” of your transformers.
Evaluation of the results of the analysis is based both on established standards and on the experience of our experts, as well as on the assessment of a unique dataset. Ideally, the relative oil moisture is immediately deter-mined from the sample (additional module for SITRAM® DIAG Level 1). This value can then be used to determine the relative paper moisture. Taking into account addi-tional parameters and sophisticated models, reliable find-ings on operating safety are then possible.
SITRAM® DIAG is part of the SITRAM® family, which includes modular solutions that extend the availability and service life of your transformers. Together we define the right solutions for your requirements.
A Level 1 assessment basically involves com-prehensive oil diagnos-
tics, supplemented by stand-alone modules
(e.g. thermograph scans) and performed on ener-
gized transformers.
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Analysis of individual transformers
Basic components of SITRAM® DIAG Level 2: � Ratio and phase angle � Winding resistance � C-tan delta (windings and bushings) � Insulation resistance and polarization index (PI) � Impedance � No-load current and losses at low voltage � Dielectric testing (insulation condition) � SFRA (Sweep Frequency Response Analysis)
Optional: � Bushing tests � Testing of built-in converter � All modules from Level 1 � Special tests by prior arrangement
SITRAM® DIAG Level 2 Level 2 includes electrical tests performed on transformers that are deenergized and disconnected from the network. Suitable electrical measurements serve to verify irregulari-ties in transformers that are either especially important or were selected from Level 1. They also serve to detect and evaluate changes in the parameters defined in the manu-facturer’s test protocol.
In addition, new methods yield both condition findings and parameter sets that then form the basis for future (compara-tive) measurements. Transformer breakdown often results from the failure of built-in components, which is why important components such as bushings and on-load tap changers are also included in transformer testing. However, the module is also available for testing components sepa-rately, for example following a replacement.
After the transformer has been disconnected
from the network, irregularities can be
examined more closely.
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Mobile high-voltage and performance testing on site
SITRAM® DIAG Level 3 Following on-site repairs, extensive refurbishments (component replacement), and conversions, mobile performance and high-voltage tests are required in order to verify a transformer’s readiness for service before the actual power-up.
At the same time, a growing number of operators and insurance companies are requiring that tests be repeated on site (SAT – Site Acceptance Tests) to ensure that valu-able new devices were not damaged during transport or installation. Our mobile HV and performance test field is designed to perform these tests.
As a trailer or container solution, the test field can be flexibly deployed and is easy to relocate and transport using standard means of transportation.
When partial discharges in the transformer are suspected, a test with infeed from a variable voltage and frequency source is necessary. Reactive power compensation and the filtering of interference signals require complex and sophisticated systems engineering, including the requisite power components and feedback loops.
Basic components of SITRAM® DIAG Level 3: � No-load currents and losses (frequency- dependent, if required)
� Load losses and impedance (frequency- dependent, if required)
� Applied overvoltage test � Induced overvoltage test (variable frequency) � Long-duration tests, PD measurement (frequency-dependent, if required)
Optional: � DC testing (additional module required) � All modules from Levels 1 and 2
A mobile test field requires sophisticated equipment and expertise.
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Hundreds of measured values result in one concrete recommendation
FTNR Trafo1 Trafo2 Trafo3 Trafo 4 Trafo5
gE – Electrical 0.0 0.0 0.0 0.0 0.0
gT – Thermal 0.0 0.0 0.0 2.0 0.0
gS – Stresses 0.0 0.0 0.0 0.0 0.0
gA – Aging 0.0 1.3 0.0 1.3 0.3
gF – Moisture 0.0 0.0 0.0 0.0 0.0
Total grade 0.0 1.3 0.0 2.1 0.3
If result is yellow or red
Maintenance recommendations
Limit values
DGA Oil Actual condition when sampled
Visual inspection
Offline mea-surements
Load profile events
Input parameters
Time-dependent data Static dataGas Visual
inspectionLoad profile
eventsOil Actual condition when sampled
Data from rating plate
Design data
Manufacturer’s test report
Maintenance strategy
Offline mea-surements
Physical groupsElectri-
calThermal Stresses Aging Moisture Bushings Me-
chanical
Analysis
Electrical Thermal Stresses
Correlation?E, T, S, A, M, B
Aging Moisture Bushings
With SITRAM® DIAG, you: � Select your transformer fleet. � Receive concrete recommendations for action. � Make efficient use of your maintenance budget. � Can utilize transformers more efficiently without shortening their service life.
� Schedule maintenance procedures or decommissioning. � Have access to a structured procedure for determining the condition of your transformers and for archiving measurement data.
The system is based on standardized specifications, the experience of our experts, the results of numerous “post mortem” assessments, and targeted laboratory experiments.
Clarity at a glanceAn intuitive color coding indicates the condition of each physical group and provides clear recommendations for action:
� Green: standard maintenance � Yellow: additional assessments or simple maintenance procedures
� Red: prompt action required to avoid breakdown
SITRAM® DIAGHigh-quality measuring instruments, careful measurements, and experienced employees who select the tests from our portfolio that best suit each individual transformer – these are the only possible basis for reliable diagnostics and con-dition assessment.
Other processes to be considered as part of cost-effective transformer diagnostics include the preparation and evalua-tion of the extensive measurement data, as well as this data’s archiving together with the analysis results.
Analysis and evaluation means comparing each measured parameter with its limit value and determining its signifi-cance and correlation with other parameters, and thus developing an overall picture of the transformer’s condi-tion. For this purpose, SITRAM® DIAG assigns the measured parameters to physical groups and weights them differently.
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Operating information
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Physical groups/Compaction Grade Significance
Electricalis based on quantities which could indicate problems in the electrical insulation system
0.0 0.0
Thermalprovides information about possible thermal faults (excessive temperature rise in the insulation)
2.0 1.7
Stressesdescribes external impact due to ambient temperature, loading, cooling, contamination of oil and effective age
0.0 0.5
Agingincludes aging-sensitive quantities and components due to degradation of oil and solid insulation
1.3 0.0
Moistureestimates the moisture distribution in the windings including relative moisture and contribution to bubbling
0.0 0.0
Total 2.1 1.7
Result/Recommendation
Thermal fault – DGA monthly, assignment no-load operation or load? If load, then reduction.
Oil regeneration is recommended!
Integrated fleet managementBased on the procedures described above, SITRAM® DIAG already allows you to select transformers from within a fleet as of SITRAM® DIAG Level 1.
The color coding clearly indicates the places in your power plant or distribution network requiring more than just standard maintenance, thus enabling you to make tar-geted use of your maintenance budget.
Experience has shown that when the number of “yellow” transformers in a distribution network is between 10 and 20%, the number of “red” transformers is in the low single-digit percentage range. Knowing exactly which transformers are involved is essential for making cost-effective maintenance decisions and strategic decisions in asset management.
Automated application of the same evaluation criteria guar-antees that the same evaluation standard will always be applied, without reliance on “gut feelings.” Models running in the background permit well-founded predictions based solely on the familiar use-of-life curve from the relevant standards.
In addition to diagnostic measurements, SITRAM® DIAG also systematically registers and evaluates other factors, such as resource data and operator information. This means that you as operator can have a major influence on the quality of the analysis results. The more concretely the algorithms are supplied with reliable historical data (typical load, typical temperatures, events, maintenance procedures, etc.), the more applicable the findings.
Database-supported forecastsWith SITRAM® DIAG, data is entered into a diagnostics database that already contains existing historical data for the specific device and data from comparable devices. This means that in addition to the basic findings, the his-torical trend is also evaluated and the absolute analysis data is mapped onto a comparable population.
The TLM condition assessment tool reliably indicates transformers with irregular values. If a breakdown appears likely, the color coding and the associated recommendations help you take the necessary action in a timely manner.
[email protected] www.siemens.com/energy/TLM
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All rights reserved. Trademarks mentioned in this document are the property of Siemens AG, its affiliates, or their respective owners.
Subject to change without prior notice. The information in this document contains general descriptions of the technical options available, which may not apply in all cases. The required technical options should therefore be specified in the contract.
Published by and copyright © 2011 Siemens AG Energy Sector Freyeslebenstr. 1 91058 Erlangen, Germany
Siemens AG Energy Sector Transformer Lifecycle Management™ Katzwanger Str. 150 90461 Nuremberg, Germany E-Mail: [email protected] www.siemens.com/energy/TLM
For more information, please contact our Customer Support Center Phone: +49 180/524 70 00 Fax: +49 180/524 24 71 (Charges depending on provider)
E-Mail: [email protected]
Power Transmission Division Order No. E50001-G640-A191-X-4A00 | Printed in Germany | Dispo No. 19200 | c4bs No. 7487 | GB 100988 RP 471964 | WS | 08112.0
