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Dispelling the Old Myth’s of Winding Hot Spot Measurement Using Fiber Optics
Today Fiber Optic Temperature Measurement is Critical to the Health of Transformers

Brett Sargent, Sr. Director of Energy Solutions, LumaSense Technologies, Inc.

LumaSense (formerly Luxtron) has been measuring winding hot spot temperatures accurately and in real time for more than 20 years. Since LumaSense was one of the pioneers in using fiber optic technology to measure hot spots, we have been on the leading edge of development and have had the opportunity to listen to our customers concerns for two decades. As with any new technology, there were “growing pains”, but we have been in a unique position of working with your customers to successfully develop a sound, robust system that is now being used in more than 1,000 transformers globally.

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Transformer life management [1] is an essential part of a modern power operation system. Oil filled transformer technology has been used for more than 100 years. The principle of operation has not changed over many decades. Many transformers that were built and installed in post World War still remain in service. A properly maintained power transformer can function for 50 to 75 years. However, the maintenance of the insulation system largely determines the extent of a transformer’s life. Future transformers will no doubt have increased capacity and size and their design may require the use of new materials. Transformers may operate at higher temperatures and in turn demand transformer oils of greater stability.

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Technical Paper on Use of Virtual Agents to Effect Intelligent Distribution Automation

Doug Staszesky of S&C presented this paper at the 2006 IEEE PES General Meeting, which took place in Montreal on June 18-22, 2006. Distribution automation has long been applied to improve reliability on distribution circuits. Its typical application has been to effect supervisory control of the system in one fashion or another. Unfortunately, such centralized control schemes lack the flexibility and adaptability required to meet the ever increasing needs of the electric power user.

Electric power distribution companies need the next step – Intelligent Distribution Automation (IDA). IDA takes advantage of advances in computing technology and communication to move the intelligence closer to the problems that need to be solved. But, distributing the intelligence requires innovative command and control strategies to ensure the multiple intelligent devices effectively share information and deliver a consistent and helpful result for the power distribution system. Virtual agents are the ideal method for implementing this control. This paper reviews practical examples of the use of such agents and give the reader a better feel, on a technical level, of how this is being done in the real world – today.

Click here to read the complete technical paper.

Through-Fault Current Calculator: A Resource for Selecting a Substation Transformer Protective DeviceOne criterion in selecting a distribution substation transformer protective device is its ability to protect the transformer from secondary-side limited faults . . . or “through-faults.” These faults are difficult to detect by the overcurrent relay of the line-terminal circuit breaker, because the magnitude of the fault current is relatively low—being limited by the impedance of the transformer. These faults are a challenge to clear as well, because of their high transient recovery voltage.

That’s why a stand-alone protective device such as an S&C Circuit-Switcher is typically applied at each transformer. S&C has tested each of its distribution transformer protective devices—Series 2000, Mark V, and Mark VI Circuit-Switchers, and Trans-Rupter II® Transformer Protector—specifically for this duty, and assigned a secondary-fault interrupting rating to each device.

This formula can be used to determine the secondary-fault interrupting rating required for the substation transformer protective device, to properly protect a particular size and impedance of transformer:

I = (57.8P) / [(%Z)E]
The formula assumes an infinite (zero-impedance) source.

See the program in : http://www.sandc.com/webzine/032707_1.asp

A protective device is appropriate for the application if its secondary-fault interrupting rating is equal to or greater than the value for “I” calculated above.

EXAMPLE:
The inherent secondary-fault current for a 20/40/50-MVA, 115-kV, 8%-impedance transformer would be:

I = [(57.8) (20 000 kVA)] / [(8) (115 kV)] = 1257 A

Check out these other resources for selecting a substation transformer protective device:

“Selection Guide for S&C Substation Transformer Protective Devices”
The selector table in this publication lets you compare the features and capabilities of S&C’s substation transformer protective devices, so you can select the appropriate device for your application.

“Primary-Side Transformer Protection”.
This paper offers a complete overview of transformer protection, including typical protection schemes, a discussion of transient recovery voltage and why secondary-side faults are difficult to interrupt, and criteria for selecting a device appropriate to a particular application.

How to Coordinate Transformer Primary-Side Fuses with Feeder Reclosers Using Coordinaide™ — The S&C Protection and Coordination Assistant

This series of articles explains how to coordinate transformer primary-side fuses with a secondary-side automatic circuit recloser, such as in a utility substation. In Part I, we use the “conservative” coordination method, which ignores the effects of fuse cooling during the reclosing time intervals (contacts open) of the recloser. Part II repeats the exercise using the more precise “Cooling Factor” coordination method. Future articles will address source-side recloser/load-side fuse applications.

View Part I of the series.
View Part II of the series.

Coordinaide™ — The S&C Protection and Coordination Assistant

Technical paper: Primary-Side Transformer Protection.

Peter J. Meyer, S&C Electric Company, Chicago, Illinois
Presented at the Doble “Life of a Transformer” Seminar; Laguna Beach, California February 21 – 25, 2005

There are many different protection schemes used today for distribution substation transformers, covering a wide range of expense and complexity—from high-end ring bus and breaker-and-one-half schemes, to low-end flash bus and grounding switch schemes. Given the pressure to increase the continuity of service, more advanced protective devices are called for than a motor-operated disconnect switch to initiate a fault. Today, the best practice is to individually protect each transformer with a local protective device. Doing so eliminates the need to take off-line all transformers connected to the transmission line, when only one transformer has experienced a fault . . . unnecessary interruptions to service are avoided.

This paper details the process of selecting primary-side transformer protection. It also examines the problem of transient recovery voltage and how and why you should select a device tested for its secondary-fault interrupting rating. Click here for the full paper in Adobe PDF format.