By Rajeev Shevgaonkar, Managing Partner, North Star
The Central Electricity Authority (CEA) has issued the standard specifications for power transformers and reactors in April’ 2021. This 486 page long comprehensive document lays down in details the standard requirements of power transformers and reactors of voltage class including and above 66 KV.
In our country, Electricity generation and supply is a state
subject. All states have their own set up of power generation, transmission,
and distribution along with central govt. companies like NTPC, NHPCL, PGCIL
etc. These bodies independently operate and have their own set of technical
standards and specifications. Further, for example in context of transformers
and reactors, OEM have their own design, manufacturing, and other practices.
These makes the whole thing overly complex and rigid.
This document by CEA is aiming to address this by way of
introducing standard uniform specifications which can be used by all the
electricity companies and equipment manufacturers in India across the
boundaries of states. Considering the vastness of our country this task was a herculean
one. The CEA has done a commendable and impressive work by devising this
document. As a large number of stake holders including manufacturers of
transformers and accessories, Experts and users were consulted by CEA to gather
the concerns, challenges and ideas, the document has high possibility of its
acceptance by all of the concerned organizations.
OBJECTIVES OF THE MANUAL
This manual is expected to meet below major objectives:
1. ONE NATION-ONE SPECIFICATION
2. Availability of reliable, un-interrupted, high quality electricity.
3. Long and trouble-free service of transformers and reactors
4. Facilitate faster replacement of failed equipment and quick restoration of supply.
5. Make the whole power system future ready to meet the anticipated huge surge in power demand.
6. Optimize inventories of transformers and reactors.
7. Simplification of procurement
8. Shortening the delivery periods
9. Providing level playing field to all the manufacturers
10.Incorporate best design practices and state of the art technologies
SCOPE OF THE MANUAL
The document has covered all the areas of Transformers and
Reactors and touched up on all such avenues which in some way or other helps in
improving the performance and utilization of this costliest equipment of the
power system. Some of the areas which this document addresses are as follows:
1. Standardization of ratings and technical specifications for country wide application.
2. Standardization of energy losses and other guaranteed technical parameters.
3. Eliminate the need of capitalization of the losses by standardizing the same.
4. Adopt standard Manufacturing Quality Plan to ensure uniform quality levels.
5. Improvement of manufacturing and testing facilities/ practices
6. Inspection and Testing
7. Transportation challenges
8. Erection, commissioning, and testing
9. Standardization of foundation to bring inter-changeability of transformers of different makes
10.Warranty period disputes
11.Condition monitoring.
12. Remaining Life assessment
13. Incorporation of new technologies/solutions to improve reliability
HIGHLIGHTS OF THE MANUAL
The manual is very vast and deals in great details with the
topics. The comprehensive nature of the manual is justified considering the
complexity and enormity of the power system. The key points of the manual are
as under:
1. The manual is having 6 chapters and 23 annexures. The topics covered in the chapters are-
a. Introduction
b. Technical Specifications for Transformers and Reactors
c. Design review
d. Quality assurance program
e. Transportation, erection, testing and commissioning
f. Condition monitoring and Life cycle management
2. The document is applicable to transformers/ reactors of 66 KV and above voltage class.
3. Among others the manual is not applicable to inverter transformers for Renewable generation, transformers for furnace, welding, testing, traction and mining applications, static VAR compensation and static compensation.
4. The ratings of the transformers are standardized. Standardization is based upon existing popular ratings and common practices in the country.
5. Smallest standard rating is 12.5 MVA, 66/11 KV.
6. The losses including auxiliary losses are fixed. The method of calculation of these losses is given in the annexure. The calculation methods given in the manual will be very helpful to the user to verify flux density, weight of core and copper, current density, no load loss, load loss corresponding to guaranteed particulars.
7. A provision of penalty to the manufacturers has been made if the tested losses are found to be within 2% of the specified values. If losses found to be more than this than the equipment may be rejected. The rate of penalty is also specified at Rs 10 Lakh and Rs 8 Lakh per extra KW for No load loss and load loss or auxiliary loss respectively.
8. The tertiary winding of 3 limb transformers up to 200 MVA, 220 KV has been removed to reduce failures and overall equipment cost.
9. OLTCs are advised to be removed and make the transformers without taps for 400 KV and 765 KV voltage class. To start with ICTS of 765/400/33 KV are to be made without OLTC. This is to reduce the failures, improve reliability and reduce overall cost.
10.In place of OIP bushings, RIS or RIP bushings are to be used. RIS is the best alternative. However, availability of RIP or RIS bushings in India is still a challenge. Bushing manufacturers have to gear-up to discourage import of the same.
11.Design review has been given a great importance. However, an option is given to use the design review done by some other utility for a specific transformer of same design of a particular make if accepted by manufacturer. The onus of conducting design review is kept with the Purchaser. They can appoint an external expert to do the design review on their behalf.
12.The manufacturing facility is expected to be of global standard. A period of 2 years from release of this manual has been given to upgrade the same if it is already not. Dust controlled winding shops, Vapour phase drying, Air castors are some of the topmost high investment items. Annexure G provides a list of equipment/facilities which manufacturer should have.
13.The manual considering the changing times approves virtual inspection/FAT. A detailed procedure has been given about the same under chapter 4 - Quality assurance program.
14.To enhance interchangeability of transformers at site and facilitate jacking of different make units, block foundation design with portable metal plates etc., has been suggested.
15.The type of tests, their frequency and threshold values of parameters has been given for condition assessment of the transformers. The trend monitoring and analysis has been emphasized.
16.The transformers older than 15 years are to be subjected to remaining life assessment. Furan Analysis, DP test are to be used to assess age of cellulose-based insulation along with other diagnostic techniques. Health Indices may also be used for this purpose.
17.Superior alternative liquid like natural and synthetic ester fluids in place of petroleum-based mineral oil can also be used with appropriate allowance for temperature rises.
18.The manual also covers other important things like control cable of 1.1 KV, BDV test set, On-line Insulation Drying System (molecular sieve based), Portable DGA Kit, Sampling Syringes and bottles.
19.In the annexure W, it has included list of all the applicable standards/codes/regulations/publications which will be very useful to all the concerned stake holders.
20.The manual recognises that there could be an increase in the cost of transformers or reactors but emphasizes that, if these guidelines are adopted then total life cycle cost will outweigh the initial cost.
21.The manual puts a lot of emphasis on maintaining and operating the equipment in correct manner by use of diagnostic and life assessment techniques and periodic trend analysis of the test results and other data. If these practices are followed, then the transformer or reactor will surely serve its designed life of 35 years or more.
22.The topics like Quality management, Erection, testing commissioning, condition monitoring, life cycle management are covered in great deal in their respective chapters. The depth of the information given makes this manual a very useful reference book and ready reckoner.
POINTS OF CONSIDERATIONS TO MANUFACTURES/ SUPPLIERS
1. Standardized specifications will increase participation as pre-qualification criteria will be same and if you are qualified for one board, no need to comply with different needs of other board especially short circuit test requirement for specific voltage ratio and impedance.
2. It is not clear from the document that pre-qualification criteria (other than technical specs) is also made uniformed? If not, then it should as it will prevent undue favor which happens by tweaking specs for small things.
3. Design standardization will reduce the burden of Designers.
4. Type testing of transformers would be reduced as type tests done on one rating made for one utility will be applicable for all other utilities.
5. The credentials would be more widely referenced and thus will increase the reach of the manufacturer to wider customer bases.
6. Inventory levels will reduce as raw materials will also be standardized and variety will get reduced.
7. Better utilization of plant capacity.
8. Turn over time from raw material to finished goods will shorten. As a result, delivery periods will shrink and more, number of equipment can be produced within same amount of time.
9. The manual requires that winding shop should be dust proof of clean room class ISO 9 or better as per ISO 14644-1, humidity controlled and positive atmospheric pressure. This and other such facilities related requirements are to be built within two years from now. This would call for a sizeable amount of investment.
10.The inclusion of elaborative design review process and keeping it with the purchaser, may increase the drawing approval period, which already a concern to the manufacturers.
11.The manual gives calculation methods to verify various performance parameters. These methods are useful to the purchaser/utility and brings good deal of transparency, however, leaves little scope of manufacturing margins.
12.Virtual customer inspection/FAT is going to be a thing of coming days. It is favorable to manufacturers for-
a. Saving of time.
b. Cost saving as travel, lodging etc of inspectors is eliminated.
c. Saving in manpower.
13.Suppliers of accessories like OLTCs and OIP bushings may get adversely affected as these are likely to be phased out to reduce failure rate of the transformers and reactors.
14.Incorporation of smart features like regenerative breathers, online drying systems and advanced materials like ester fluids will be helpful in reducing the pre-mature failure and ensuring in trouble free service life of transformers and reactors. It will also ease out warranty period troubles of manufacturers.
EPILOGUE
This manual has not left any aspect untouched and hence it is
a very thorough and widely implementable document. It brings many benefits, to
the nation, power system, utilities/ users, manufacturers, and other stake
holders.
To the manufacturers who are migrating from distribution to
power transformer range, this standard will provide a boost as with lesser
number of credentials/ type-tested designs they can approach larger customer
base.
The IS1180 was introduced some years back which is applicable
for transformers up to 2.5 MVA, 33 KV with the similar objectives of bringing standardization.
This manual covers transformers from 12.5 MVA, 66 KV and above. So, with this
document entire rage of transformers, except a narrow band of 3 MVA to 10 MVA,
is addressed for standardization, reliability, and effectiveness of the power
system.
The provisions made in the document are welcome and address
the challenges rightfully. The key to success lies in implementation. The
manual is “advising” for implementation and hence provisions of the same are
not binding on the stake holders.
Although it is not appropriate to draw parallels with BIS
1180 implementation level, however, it is in every one’s interest that this
manual should get really incorporated for the common benefits.
Compared to transformers of 2.5 MVA and below ratings, number
of manufacturers of 12.5 MVA and above are very few. From that angle, the hopes
can be kept high, however there are other challenges and still a long way to
go.
Nevertheless, CEA and all the members of the standards committee deserves great complements for bringing out this wonderful document and leading the country towards ONE NATION- ONE SPECIFICATION objective.
The Manual is available at CEA web site www.cea.nic.in
