by Thermo 8. September 2011 16:27
Neutral Ampacity & Re-closers
 
Hey Thermo, a couple of questions from your home state of Michigan – Northern Michigan, beautiful country, lots of insects.
 
In Exhibit E of your proposal you state that cable replacement should be utilized rather than cable injection if the “cable neutral has lower than required ampacity …”  I was able to find on Novinium’s website the limits for neutral corrosion, but nothing on the neutral ampacity limits. What are the neutral ampacity limits? Keep in mind that on three phase cable installs we use one-third neutrals.
 
In Exhibit F of your proposal you define “Abnormal Operational Excursion(s).”  One of the identified excursions, item (3), is “repeated operations of re-closers.” We use re-closers on all of our circuits. Does this mean that the warranty is void?
 
Signed,
 
Northern Michigan Coop
Dear Michigan-
 
I don’t know where you got the idea that I am from Michigan.  I was born in a pond in Federal Way, Washington near Novinium’s global headquarters.  I recently moved my home to the nearby lovely community of Gig Harbor, still in Washington State. Click here to check out the short version of my life story. Click here to check out my Facebook wall. With Novinium extending the life of cables in most of the United States, most of the Canadian Provinces, and at locations around the globe, I get opportunities to travel widely, so I can attest that Michigan insects are indeed plentiful during the warm summer months.  Now, to your two questions …
 
There are three primary purposes for neutral wires:
 
1.  Provide a low resistance path for fault currents to protective devices.
2.  Assure a grounded and uniform potential to the insulation shield, which in turn provides uniform electrical stress along the cable axis and circumference.
3.  Carry the return current of unbalanced loads.  Since multi-phase circuits have lower unbalanced loads, lower-ampacity neutrals such as your one-third neutrals are possible in many applications.
 
Each circuit owner must decide upon an appropriate value for the required neutral ampacity.  This analysis is required on a case-by-case basis. That neutral ampacity requirement is communicated to Novinium so that candidate cables for rejuvenation can be screened for their neutral condition. If a circuit owner requires guidance on appropriate requirements for a specific circuit, they need only ask the world’s foremost rejuvenation experts.  They are all at Novinium.  Typically less than 2% of a population of candidate cables do not meet circuit owner neutral ampacity requirements.
 
With regard to “Abnormal Operational Excursion(s)” I have reproduced the full definition below and I have underlined the portion about repeated re-closer operations. Note that the recloser operations are abnormal only if the recloser is operated to clear overhead faults.  Most frogs and people would agree that this is not a “best practice.”  Life insurance doesn’t payout if the insured commits suicide and neither does the Novinium warranty.  If the recloser operates normally, but is not abused in an attempt to burn a branch on an overhead line, then the warranty is not suspended.
 
Reassuringly yours,
 
Thermo
 
Abnormal Operational Excursion(s) includes non-routine maintenance or operations prior to the segment failure such as:  (1) conductor currents or neutral current greater than circuit design constraints; (2) operating temperature greater than circuit design; (3) repeated operations of re-closers, whether manually or automatically operated, as a method to clear overhead faults; (4) physical manipulation of the segment including dig-ins; or (5) any other operational practice inconsistent with the cable’s original manufacturer’s specifications, act of a third party, or act of God (except lightning strikes), which is believed to degrade the reliability of connected circuits

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Warranty Reflections

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9/26/2011 12:14:40 PM #

Northern Michigan Coop

Thermo,

We would like further clarification on “Abnormal Operational Excursions” as it applies to our typical scenarios. We have an underground substation exit that feeds about 10 miles of overhead line. The substation circuit uses a recloser to clear temporary and permanent overhead faults. The recloser is programmed for 2 fast operations and 2 slow operations. All taps off the three phase line are fused such that the substation recloser will operate 2 times before the fuse opens. Is this type of method an acceptable practice or does it violate the “Abnormal Operational Excursions”?

Thanks,
Northern Michigan Coop

Northern Michigan Coop United States |

9/26/2011 5:29:09 PM #

Admin

Dear Michigan-

Upon further review, I can see our language is confusing.  Since a recloser, by definition, involves repeated closing operations, the phrase “repeated operations of recloser” seems redundant. I have asked our contract folks to improve the language as follows:

(3) manual resetting of a recloser, such that it cycles through more than a single cycle of reclosing operations;

This pithy language better describes the intent and I believe it provides the clarity you seek and deserve.

The reason this language is necessary can be traced to a failure of a submarine cable at Tanner Electric Cooperative (TEC) in Washington State’s Puget Sound.  The failure report can be accessed at:

http://www.novinium.com/pdf/failures/00000179.pdf

Not explicitly stated in this report, the circuit owner manually reset the recloser many times in an attempt to burn the tree/branch that fell onto the overhead lines on the island community served by the submarine cable. Large fault currents were repeatedly carried by the compromised copper tape neutral shield. It was almost certainly the abuse of the neutrals that caused an otherwise serviceable cable to fail. This case was the poster child for “Abnormal Operational Excursion.” At Novinium, a deal is a deal, so we wrote a $136,421.40 check to TEC.

Fair to a fault,
Thermo

Admin United States |

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