“Snubber” Networks - Are they effective?

Installing RC snubbers connected directly to the transformer primary windings is a common recommendation, but can snubbers really produce the desired result?

07/12/2012


Figure 1: A typical RC snubber network mounted inside a VPI dry-type enclosure. Courtesy: J. GuentertOver the last 10 or so years, the entire data center industry has become much more aware of the problems with switching medium-voltage (MV) distribution transformers with vacuum breakers, especially after some very high-profile failures of dry-type transformers in data centers around Manhattan and New Jersey, although there have been dozens of other similar failures around the country.

A number of Institute of Electrical and Electronics Engineers (IEEE) committees have performed some solid research, papers have been published, and new IEEE guidelines proposed and issued in IEEE C57.142. There is finally a good understanding of the full nature of the problems, and the steps then can be taken to mitigate. There have been some excellent papers by David Shipp of Eaton Corporation and a number of presentations made by him to various IEEE conferences, as well as some excellent papers and presentations by Phil Hopkinson, owner of HVOLT.

I’ve closely followed David’s and Phil’s works (and IEEE’s work) on this topic since their very beginning, because of my 30+ years of keen interest in this problem. The recommended solution always seems to be the installation of RC snubbers connected directly to, or very close by, the transformer primary windings.

Can snubbers be effective, and produce the desired result? Emphatically, “yes.”

But I think this is the wrong question to be asking, and it begs the more fundamental question: “Why install a data center substation transformer in the first place that requires a snubber in order to survive for a normal lifetime?”

Even the most ardent proponents of use of snubbers generally add a post-script of advice, saying something like “RC snubbers - while useful and often necessary - will likely become points of failure at some time, when the capacitors eventually fail. A systems study should be performed to determine whether a snubber is actually required at any particular transformer. If a snubber is not required, then don’t install one - what’s not there can’t fail.”

I’ve read a number of such system studies performed by study engineers for various projects. They generally end with a conclusion and recommendation that goes something like this:  

Transformers T15 and T16 do not require use of snubbers. Transformers T1 and T2 do require snubbers, because of the very short lengths of the primary feeder cables. Transformers T3 through T14 are ‘borderline’. Prudence suggests that it might be wise to install snubbers on these twelve transformers.

After reading a recommendation like this one from the study engineer, most data center owners and their consulting engineers wouldn’t be able to sleep at night until after they had made a decision like “Why don’t we just install snubbers on every transformer?” (And, who could argue with the logic of that conclusion?)



No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2013 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
The true cost of lubrication: Three keys to consider when evaluating oils; Plant Engineering Lubrication Guide; 11 ways to protect bearing assets; Is lubrication part of your KPIs?
Contract maintenance: 5 ways to keep things humming while keeping an eye on costs; Pneumatic systems; Energy monitoring; The sixth 'S' is safety
Transport your data: Supply chain information critical to operational excellence; High-voltage faults; Portable cooling; Safety automation isn't automatic
Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Plant Engineering 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.

Maintaining low data center PUE; Using eco mode in UPS systems; Commissioning electrical and power systems; Exploring dc power distribution alternatives
Synchronizing industrial Ethernet networks; Selecting protocol conversion gateways; Integrating HMIs with PLCs and PACs
Why manufacturers need to see energy in a different light: Current approaches to energy management yield quick savings, but leave plant managers searching for ways of improving on those early gains.

Annual Salary Survey

Participate in the 2013 Salary Survey

In a year when manufacturing continued to lead the economic rebound, it makes sense that plant manager bonuses rebounded. Plant Engineering’s annual Salary Survey shows both wages and bonuses rose in 2012 after a retreat the year before.

Average salary across all job titles for plant floor management rose 3.5% to $95,446, and bonus compensation jumped to $15,162, a 4.2% increase from the 2010 level and double the 2011 total, which showed a sharp drop in bonus.

2012 Salary Survey Analysis

2012 Salary Survey Results

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.