Dry-type transformer failures versus liquid transformer failures

In this "Cut the Copper" installment, Guentert explains how, when properly installed, liquid-filled transformers in data center power systems are more reliable than air-cooled dry-type transformers.

05/09/2012


I stated at the outset of this series that it would be controversial, and might receive a backlash of unfavorable response. Here is my most controversial statement, as clearly as I can state it:

In my opinion, after having carefully watched this situation develop over 35 years of my professional life, I’ve concluded that properly designed liquid-filled transformers, when installed in properly designed data center power systems, are more reliable than air-cooled dry-type transformers, when switched fairly frequently by upstream vacuum breakers, at voltages of 10 kV and above, by a factor of at least 50.

How’s THAT for being politically incorrect? Whenever I make this statement to a new client or to a group I’m presenting to, the immediate response is usually, “Show us some hard data to back up that terribly assertive claim you just made.”

The hard data don’t exist, I admit. I think that this is mostly because no data center owner ever reports its failures to any sort of a registry or information clearing-house, nor do transformer manufacturers want to report their failures, either. All I can do here is report my own personal experiences:

--I have personal knowledge of more than 75 failures of dry type transformers installed in data centers (95% of them VPI’s) under the switching circumstances described previously, over 35 years of experience. I’d have to believe that there are many, many more I haven’t heard about.

--I’ve personally investigated more than 30 failures of dry-type transformers under these conditions, at various sites—some at the request of my clients and employers, and some just out of my own curiosity.

--I have personally witnessed the failures of 5 indoor dry-type substation transformers at the instant of occurrence, while standing with 30 ft of each of them at the time, inside electrical rooms of active data centers. (Blinding flash, loud “BLAM!!!,” small flames, heavy black smoke, fire alarm callouts, fire companies running into electrical rooms with water hoses. Two of these failures occurred simultaneously, with a single breaker closure, in one data center.)

--I work closely with a select group of large general contractors, who specialize in construction of large data centers, and who have probably collectively built at least $8 billion of large new data centers in the past 5 years. Their guys know of my passion for this topic, and I generally receive about 5 or 6 phone calls or e-mails per year from them. E-mails like, “Hey, Joe. Two more today, at a data center in Virginia, about 1:30 p.m. Simultaneous loud flashover of two 2.5 mVA 12.47  kV VPI units, with a single breaker closure, during final Integrated Systems Testing. No snubbers were installed.”

--I’m aware of at least two manufacturers of dry-type and cast coil transformers who declared bankruptcy and closed up shop, under the weight of warranty claims and litigation from similar failures.

I’ve observed a fairly recent shift in attitude of the remaining major dry-type transformer manufacturers. On a failure of a 2.5 MVA VPI unit in a data center just two months ago, I heard the manufacturer’s response to a request to IMMEDIATELY provide a replacement transformer at no charge under warranty terms. Paraphrasing slightly:

“Warranty claim replacement is denied. This is not a manufacturing defect in our transformer covered by warranty…it’s a widely known systems problem with dry-type transformers switched by upstream vacuum breakers. There was no snubber installed on this transformer. Go speak with your consulting engineer about his system design problem.”



No comments
Consulting-Specifying Engineer's Product of the Year (POY) contest is the premier award for new products in the HVAC, fire, electrical, and...
Consulting-Specifying Engineer magazine is dedicated to encouraging and recognizing the most talented young individuals...
The MEP Giants program lists the top mechanical, electrical, plumbing, and fire protection engineering firms in the United States.
High-performance buildings; Building envelope and integration; Electrical, HVAC system integration; Smoke control systems; Using BAS for M&V
Pressure piping systems: Designing with ASME; Lab ventilation; Lighting controls; Reduce energy use with VFDs
Smoke control: Designing for proper ventilation; Smart Grid Standard 201P; Commissioning HVAC systems; Boilers and boiler systems
Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Consulting-Specifying Engineer case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.

Protecting standby generators for mission critical facilities; Selecting energy-efficient transformers; Integrating power monitoring systems; Mitigating harmonics in electrical systems
Commissioning electrical systems in mission critical facilities; Anticipating the Smart Grid; Mitigating arc flash hazards in medium-voltage switchgear; Comparing generator sizing software
Integrating BAS, electrical systems; Electrical system flexibility; Hospital electrical distribution; Electrical system grounding
Cannon Design’s blog is a place for the many voices of the firm to share thoughts and news related to current projects...
As brand protection manager for Eaton’s Electrical Sector, Tom Grace oversees counterfeit awareness...
Amara Rozgus is chief editor and content manager of Consulting-Specifier Engineer magazine.
IEEE power industry experts bring their combined experience in the electrical power industry...
Michael Heinsdorf, P.E., LEED AP, CDT is an Engineering Specification Writer at ARCOM MasterSpec.