10 Commandments

Dear All-knowing Frog,

I read with great interest your June 9, 2010 post describing the greatest rejuvenation safety risks at …

www.novinium.com/frogblog/post/2010/06/09/Greatest-Rejuvenation-Risks.aspx.

It is clear that injection is much safer than replacement and that the steps Novinium has taken to make rejuvenation safer still are substantial and impressive, but what can be done to mitigate the risk of electrical contact?  Do you have any rules or insights from which I may learn?

Signed,

Praying in Provo

Dear Devout-one,

I sought, and was granted, guidance by the highest of authorities.  When it comes to safety we share all of our best practices with anyone that would like to learn.

The very first Novinium Value is Safety.  It states: 

“Safety is our first priority.  We provide an ever–improving safe work environment for our team members, our customers, and the public.”

The greatest safety risk we face is electrical contact.  If the ten commandments below are followed the team will be safe from all known electrical hazards.  If an individual decides to ignore one or more of these commandments that individual is not welcome on the Novinium team.  Ignoring any of these 10 commandments endangers life. More...

Neutral Corrosion - How much is too much?

Dear Ms. Frog,

I am looking for some guidance on what percent of bare concentric neutral corrosion can be tolerated on an underground primary cable before it needs to be replaced.  I wondered if the technical staff at Novinium happens to have any ideas as to where I may get some information on this subject.

Colorado Corrosion Concern

Dear Concerned-

I have access to millions of feet of records of treated cable.  Together, my colleagues and I have analyzed over 70 million feet of rejuvenated cable that had been scanned with a time-domain reflectometer (TDR).  The incidence of neutral corrosion is way less than many suppose.  In an August 1996 article, “Neutral Corrosion Problem Overstated” in Transmission & Distribution World, Bob Gurniak of Pennsylvania Power & Light (PP&L) described this overstatement using data from the AEIC Cable Report and IEEE ICC Task Force on Cable Neutral Corrosion (6-21).  There are two notable exceptions in North America … the Appalachian Mountain Region (in PP&L territory) and Wisconsin suffer more than the normal amount of corrosion because of the low soil electrical conductivity in those regions.  The T&D article is available at …

http://tdworld.com/mag/power_neutral_corrosion_problem/index.html

... without the Table and Figures in the printed version.  I have recreated that table below and provided similar Figure 1 and Figure 2 illustrations.

Fig. 1. Technician Analyzes the TDR readout to pinpoint bad sections of cable.

Fig. 2. Waveform from the TDR.

As a rule of thumb, most circuit owners with 100% neutrals accept up to 50% local loss of neutrals.  What I mean by local loss is that neutral corrosion is almost always limited to just a few feet as shown in the photograph above.  The purposes of the neutral, enumerated in Section 4 of IEEE 1617-2007 (Guide for Detection, Mitigation, and Control of Concentric Neutral Corrosion in Medium-Voltage Underground Cables) are not compromised.

The reason for the locality of typical neutral corrosion is that the predominant cause of concentric neutral corrosion is differential aeration which is an inherently local phenomenon.  See Section 6.4 of IEEE 1617-2007.

Kindest corrosion-free regards,

Thermo