technical documentation of fires caused by electrical "hot shorts" due
to cable damage

Hello wjo-ga:

Well, this is an interesting area of discussion. I have found many
documents discussing your broad question.

 The most interesting thus far is exploding manhole covers. I quote
from Engineering – Electrical World:

http://www.platts.com/engineering/issues/ElectricalWorld/0111/0111ew_distexplosion.shtml

“Road salt: Silent assassin? 
Age and loading are not prime suspects at Con Edison, however. "We
examine the cables that are involved in these events and we don't find
anything relating to age as a cause," says Michael Miller, senior
engineer for Con Edison in Manhattan. "The cables we install are
designed to last 100 years, and many are capable of exceeding that
considerably.

Instead, Miller says he sees a one-to-one relationship between manhole
events and the use of rock salt on city streets to provide traction
during winter months. We have a five-year average (over the last five
years) of 1372 events," Miller reports. "The number varies year to
year based on the severity of the winter. In 1998 we had a very mild
winter, so we had very few events. That was the lowest level of rock
salt applied during any of those five years.

Miller says that underground events are precipitated by cable damage,
typically caused by the normal flow of heavy vehicle traffic on city
streets and by external vendors--cable TV, telephone, gas, water,
street, or sewer workers. Once a cable is compromised--the insulation
is ruptured in some fashion--this allows the salt or salt-water
solution to get into the cable where it acts as an electrolyte and can
form an arcing fault producing gas, says Miller. The gas we find
mostly present is hydrogen. If hydrogen rises above 4% that's an
explosive mixture . . . it either ignites and burns, or explodes,
depending on the concentration of oxygen in the mixture."

Many, many articles dealt with fire problems in Nuclear plants, with
poorly designed cable systems, or sub standard cables.

From: UNITED STATES NUCLEAR REGULATORY COMMISSION

A discussion and a reference to a technical paper on this type of
problem in the Nuclear industry.

http://www.nrc.gov/reading-rm/doc-collections/gen-comm/info-notices/1999/in99017.html#_1_6

Post-fire Safe Shutdown Circuit Analysis is discussed in this paper
from the same site:

http://www.nrc.gov/reading-rm/doc-collections/insp-manual/71111-05.html

A PDF document cited below, is very specific in its recommendations
for power plant design , specifically cable routing.


http://www.insc.anl.gov/current/obn2000/P15.pdf

The link below is also a PDF document, a copy of a letter to PECO
energy in Wayne, PA about the NRC concerns about circuit induced fire.
The cite the NRC’s  "Rules of Practice, which is available here:
(large file!)

http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0386/sr0386.pdf

In relation to design of aviation systems this technical document,
gives a lot of design guidelines to avert fire problems caused by
cabling.

http://www.generalaviation.org/download/AC33.28-1-Electrical-Controls.pdf



The Nuclear Energy Agency has an in depth report on fire risk analysis
and fire spreading.


Here is an abstract from that report:

“Numerous fire PSAs (probabilistic safety assessments) have shown that
fire can be a major contributor to nuclear power plant risk. However,
there are considerable uncertainties in the results of these
assessments, due to significant gaps in current abilities to perform
realistic assessments. These gaps involve multiple aspects of fire
PSA, including the estimation of the probability of important fire
scenarios, the modeling of fire growth and suppression, the prediction
of fire-induced damage to equipment (including the effects of smoke),
and the treatment of plant and operator responses to the fire.”

And:

“Regarding the treatment of failure modes, all fire PSAs address
fire-induced circuit failures that lead to loss of function; some also
address failures that can lead to spurious actuation of plant
equipment or to an
alarm. The latter failure mode, typically assumed to be caused by «hot
shorts» (i.e., electrical faultsbetween cable conductors without a
loss of conductor integrity or a simultaneous short to ground), has
been shown to be an important and sometimes even dominant contributor
to fire risk in a number of U.S.
studies. In such cases, the scenarios often involve the spurious
opening of one or more valves in theprimary system boundary and a
subsequent loss of coolant accident (LOCA).”

Here is the link to the full document (PDF) described above:

http://www.nea.fr/html/nsd/docs/1999/csni-r99-27.pdf


I hope this helps you in your research, as always I will welcome any
clarification you require.

Sincerely,


Colin







Google search query:
fires caused by "cable damage"

There are also a number of interesting and detailed technical reports
at:

http://www.usfa.fema.gov/applications/publications/pubs_display.cfm?p_media_code=36&p_subject_code=18

(This is from FEMA's US Fire Administration, and most of the reports
are
 intended to illustrate a specific point related to emergency response
 and fire safety.)

Hello wjo-ga,

The United Kingdom Air Accidents Investigation Branch
(http://www.aaib.dft.gov.uk) has covered a couple of cases where
inflight electrical fires have started in wiring looms.

The most serious case, meriting a full formal report, occurred to
N653UA - a Boeing 767 - on the 9th January 1998. The report can be
found at:

http://www.aaib.dft.gov.uk/formal/n653ua/n653ua.htm

(see especially the remarks under 'Causal factors')

In this case, it was believed to be the incorrect installation of a
chiller unit  which had caused insulation damage to the wiring loom.
The presence of aliminium swarf from drilling operations was
considered to be a contributory factor to the  overheating, and
consequent tripping of circuit breakers.

As an appendix, the above report cites an earlier case, where drilling
swarf was believed to have caused insulation damage and shorts in a
wiring loom. On this occasion, the consequent fire ddestroyed any
possible evidence:

http://www.aaib.dft.gov.uk/bulletin/oct97/gvgin.htm

There are other cases of electrical fires listed, but these two
specifically mention cable damage and consequent short circuits as
factors. The analysis of N653UA is particularly detailed.

I hope this provides some useful material for you.