MIDWEST Blog

SSF16B216 General Electric Circuit Breaker

On a recent Saturday afternoon, one of our field service supervisors received a call on his cell phone while he was at home.  MIDWEST offices are closed on the weekends, but the supervisor was on-call; as such, our phone system redirects incoming calls to whoever is on-call.

The person on the other end was frantic. We finally got the facts from him. We found out he was an electrician from a division of a huge four billion dollar fortune 500 company. He said he had an emergency there. He had been calling dozens of electrical firms all over the country. He said not a single person answered, during which he had grown more and more desperate.

Apparently a model SSF16B216 (1600 Amp 600 Volt) General Electric circuit breaker had been turned off to perform some routine maintenance on downstream devices.

As can be seen from the picture, this “Insulated Case” style breaker has a 10” long silver pump handle that compresses a huge spring (think of a small version of a car’s suspension coil spring) through gearing, a pawl and a ratchet. The user then pumps the long handle 5 or 6 times. Each pump compresses the very strong spring a little more; the pawl and ratchet hold the spring back for the next pump. Once the spring is fully pumped up (compressed), the spring is said to be “charged”. Then the user presses the little black button labeled “PUSH ON”, which releases the spring, causing the main contacts to forcefully slam together, thus closing the breaker. The contacts need to forcefully slam together so as to minimize contact bounce, which would cause unacceptable arcing during the bounce. This same action also charges smaller springs that will cause the breaker to open when the current exceeds the trip settings or if manually opening is required which is accomplished by pressing the little red button labeled “PUSH OFF”.

Now that the maintenance work was finished, they had tried to close the breaker, as their next shift was starting. But no matter what they tried, the breaker would not charge the closing spring, so the plant could not operate. As such, they were losing $2,000 per minute ($120,000 per hour, or $3,000,000 per day). It’s easy to see why they were frantic to get some help.

Upon learning the company’s plight, our supervisor walked the customer through the necessary steps to reset the breaker. It turned out that the reason the customer could not reset the breaker originally, is because a part on the breaker had failed. Fortunately, MIDWEST has seen this same failure before, so we knew exactly how to circumvent the problem. Decades of use (and heating) had degraded a large, elastomeric end-stop called a “spring bumper”. Its purpose is to limit the travel of the pawl on the ratchet gear which charges the main actuator spring. The defective spring bumper caused the pawl to go into an over-travel situation so it couldn’t contact the ratchet tooth to pump up the closing spring. Thus, the breaker was made incapable of being closed again.

On the phone, we walked the customer through an improvised procedure that allowed him to manually circumvent the degraded spring bumper, and to finally charge the closing spring and close the breaker, powering up his factory. The customer was absolutely ecstatic. Not only was he finally able to get a real live person to talk to on a Saturday, but we knew exactly what to do to get him over his emergency, right then and there.

Afterwards, we looked at the times of the telephone call, starting from when we first picked up the phone to when the customer successfully closed the breaker and ended the call. From beginning to end, the call was only 50 minutes. And on a Saturday when we are closed!

On Monday, he called back to profusely thank us in very glowing terms.

Our experience and dedication saved the day again.

Bus Plugs

Safety Disconnect Switch

This is the first in a series of blogs that outlines a detailed analysis of the corrosion problems found in a piece of equipment needing refurbishing.

At MIDWEST, a portion of our business is refurbishing electrical switchgear.  Refurbishing old equipment includes electrical, mechanical and cosmetic reconditioning of used switchgear.  For example, this includes reconditioning.

Most importantly, our shop wizards fully dissemble the functional electrical and mechanical innards and recondition and / or replace them as necessary, in order to bring the equipment back to full functionality, just as it was brand new from the factory.  This often includes plating electrical parts with a thick coat of pure silver.

And of course, each and every item is tested to our stringent standards before it is shipped out to a customer.

As far as just the cosmetics of the metal enclosure goes, for years I have watched our shop perform miracles.  They can take an old, corroded enclosure, sand it down to bare metal, prime it, and respray it in one of our paint booths, and have it come out looking just as good as if it were new. Their technical knowhow never ceases to amaze me.

Fusible Panelboard Switch

MIDWEST Field Services was at a manufacturing facility in South Central Wisconsin performing inspections and testing of 15KV load break switches along with 480V indoor substations.  The services were being performed as part of scheduled electrical maintenance services.  During our inspection of the outdoor 15KV load break switches it was discovered that one of the fuse holder assemblies was not installed correctly resulting in excessive heat being generated and the fuse holder overheating to the point that it melted down and nearly fell out of the fuse assembly.  Had that occurred the 15KV fuse would have likely fell out of the holder resulting in a single phase condition and the potential for damage to the downstream equipment.  After a hard-focused inspection of the damaged fuse holder assembly it was determined that the threaded assembly was either cross-threaded or the threads in the cast part were defective leading to the assembly being hard to turn which one may have mistaken for it being tightened properly.  Catastrophic failure would have occurred if this deficiency hadn’t been corrected and was certain to occur if the regularly scheduled electrical maintenance services had not been performed.  In conclusion, we believe the old adage an ounce of prevention is worth a pound of cure holds true here because the cost of performing regularly scheduled electrical maintenance services was far less than the cost of damaged equipment as a result of the catastrophic failure to this fuse holder assembly, fuse(s), switches and associated switchgear.  Add those costs with the cost due to the loss of production resulting from the unscheduled outage would result in what is known in today’s production world as unacceptable.  The photo below shows the damaged part along with a complete part to show how much damage occurred.

Damaged Part Versus Complete Part

MIDWEST Field Services was at an educational facility in the Western United States performing inspections and testing of 15KV load break switches and indoor dry type transformers.  The services were being performed as part of an insurance claim.  The electrical distribution system had experienced a failure of some components within the system and the customer was having issues after replacing the damaged components and re-energizing the system.  Our services included but were not limited to performing hard-focused inspections, making minor adjustments to mechanisms, performing insulation resistance testing, contact resistance testing, and winding resistance testing.  No deficiencies were found with any of the equipment so all of the cover panels were installed and the equipment was energized.  It was at this time that the transformers secondary phase-to-phase and phase-to-ground voltages were measured and found to be fluctuating by as much as 50% below the expected voltage.  The equipment was shut down and the 15KV fuses for each of the load break switches were removed and the internal resistance was measured.  The manufacturer has a range for this fuse between 24.871 mΩ and 33.6 mΩ.  The fuses that were in service had resistance values that were nearly twice the manufacturer’s maximum tolerance.  These fuses were replaced with fuses that were within the manufacturer’s resistance tolerance and the equipment was again energized.  The secondary voltages for all of the transformers were again measured and found to be constant and within 1% of the nominal voltage.  One of the original 15KV fuses was opened up and found that the fusible link inside was connected by a small fragment of its original configuration.  The fuses were literally holding on by a thread inside which caused the increased internal resistance and translated into the erratic voltages seen on the secondary of the transformers.  Long story short, the entire electrical distribution system was exposed to the short circuit and while other components ultimately failed this event reinforced that the electrical stresses were experienced by the entire distribution system and caused other components (fuses in this instance) to be compromised to the point they were unacceptable for continued service.

The Worst Hollowed Out Electric Pole in 40 Years

When this electric pole (see image) was cut down, it exploded into a hundred pieces when it hit the ground. This was for a private overhead service along a roadway to remote buildings and was replaced with an underground service. It was obvious the pole was very old, but one would never guess it was so hollow, unless you tapped it with a hammer. And that could have been a mistake if the lines were still energized. The overhead lines may have been holding the pole up. This was the worst of the worst electric poles we have seen in 40 years. And no there were no 4 legged critters living in the pole. Just bugs, now homeless.

MIDWEST sells reconditioned, used and new Circuit Breakers.  Call today at 800.803.9256! 

All manufacturer’s available – Cutler Hammer, General Electric, ITE, Siemens, Square D, Westinghouse, ABB, Airpax, Allen Bradley, American, ASEA Brown Boveri, Bryat, Bulldog, Challenger, Crouse Hinds, Federal Pacific, Fuji, Gould, Heineman, Kraus Naimer, Merlin Gerin, Milbank, Mitsubishi, Moeller, Murray, National, Sace, Sylvania, Telmand, Thomas and Betts, Trumbull, Tyco, Vois Worth, Wadsworth, Zinsco, etc.

MIDWEST sells reconditioned, used and new Bus Plugs.   All manufacturer’s available – Square D, ITE, General Electric, Westinghouse, Cutler Hammer, Bull Dog, Continental, Federal Pacific, Gould, Siemens, etc.  Call today 800.803.9256!  http://www.swgr.com/store/Bus-Plug-Home.aspx

The Arc Flash Department at MIDWEST is asked all the time about the life span of the batteries for the Arc Flash Hoods with cooling fans.  The cooling fans are powered by eight (8) AA batteries.  The batteries have a lifespan of 6 to 8 hours of continuous use.  Click on the link and you will find a list of all the Arc Flash Hoods that MIDWEST carries.  http://www.swgr.com/store/Protective-Clothing-And-Equipment/Hoods.aspx

Hazard Risk Category 4 – ARC RATING 65 cal/cm² Style Hood with Cooling System

MIDWEST Infrared Scans miles of bus duct and thousands of bus plugs every year. By using our large real time Infrared (Thermographic) Scanners, this is a very practical and valuable service. Our Thermographers are frequently asked what the most common serious problem they find on bus plugs. The answer is heating at the disconnect fingers. The disconnect fingers are spring loaded contact clips located on the back side of the bus plug. Depending on the size of the bus plug, for example a Square D PQ3603 (30 amp bus plug), the disconnect fingers may be the size and appearance of small clothes pins or as big as your fist for a large bus plug, like a Square D PTQ36120 (1200 amp bus plug). If the mechanical connection of the disconnect fingers to the bus bar in the bus duct is deficient or outright defective, the heating at the connection can be enough for our experienced Thermographers to detect. The same for heat due to poor contact surfaces between the bus bar and contact tips of the disconnect fingers. Sometimes the disconnect fingers are not even clipped on to the bus bar, but are bent under or over the bus bar. These defects may be present for years and not manifest themselves until the circuit becomes more heavily loaded. MIDWEST’s Thermographers are trained and experienced in reconditioning and testing bus plugs in our Switchgear Service Shop. They may have even melted a few disconnect fingers on one of our high current test sets, just for fun of course, when no one was looking. Actually that is what we call ‘real world’ training.

Locating these problems on energized bus plugs is extremely important because of the damage that can occur to the bus duct itself. We can repair or recondition a 400 amp Cutler Hammer ITAP 365R bus plug, but the bus bar in bus duct is more costly and time consuming.  So finding this common problem with in-service bus plugs is also finding a more serious problem involving the bus duct. Both very important.

General Electric AC364RG Bus Plug – Inside View

MIDWEST’s Switchgear Engineers and Technicians receive calls for technical help with bus plugs every day, day after day. It’s a big part of the service MIDWEST provides to those purchasing electrical switchgear. Sometimes the questions are more about electrical power than equipment. Most of the questions deal with details about the equipment and problems associated with installation. But sometimes we get simple blunt non technical requests that surprise us and we have to think for a moment to realize why it’s important to the person requesting the information. An example is a purchasing agent that wanted the availability, cost, and pictures of a GE General Electric AC364RG bus plug. That was it. His name was Pat and that’s all he wanted and he wasn’t interested in any technical questions. After some conversation about many images available in GE catalogues and lots of images on the internet, Pat was getting a bit impatient. Polite but impatient. After a couple more quick questions, a number of things became suddenly clear. First, Pat was not Mr. Pat, but Ms. Pat, with a raspy voice. Pat’s job was simply to get a GE General Electric AC364RG fast. Availability, price, and images that was all she needed. Simply procurement and she seemed pretty good at it. But she was instructed to get pictures specifically of the inside of the bus plug and the back side of the bus plug. Could we get her the pictures or not? Our answer was yes. Her response was ‘Thank you.’ Done.  Purchasing agents frequently operate at hyper speed and have little time for conversation. She got the price, availability, and images she wanted. We got the order and a surprise by how fast it happened.