May 28, 2015 URD Webinar # 2 Notes
Presentation pages 5 and 6, Q1 and Q2 (Cable Failure Rates and Rehabilitation Policies):
Tucson Electric: We have a relatively low cable failure rate overall. We are averaging 80 to
120 cable failures per year throughout our system, which translates to about 1 failure for 10-20
miles of installed cable. Most of the failures occur on our older non-jacketed concentric neutral
cable and we are seeing a slight increase in the numbers for that vintage of cable. Most of the
failures occur at termination points.
We have a policy to replace all three phases of 600 amp substation feeder exit cable after we
have experienced a total of 3 failures on any phase. We do not have any such policy for single
phase URD cable. When it fails, we repair it through splicing if possible. When we replace, we
pull out the old cable and pull new cable into the existing conduit. We inspect all of the
equipment that we open during the cable repair or replacement process and perform any
needed maintenance and/or replace badly damaged equipment components, if warranted.
When we are replacing cable, if we are not able to pull the old cable out of the existing duct, we
dig up both the conduit and old cable and install new conduit and cable. We have generally
been able to pull new cable into our old 1960’s-1970’s vintage transite duct. If not, we have just
been abandoning and decommissioning that duct.
Oncor: Our overall cable failure rate is 0.2 failures per mile per year. Our problems are mostly
with pre-1993 unjacketed cable where we are experiencing about 5 cable failures per mile per
year. The overall rate is increasing as larger percentages of our cable approach an age of 30
years or more. We do not have any data that tracks cable failures by root cause.
We now track all of our cable failures by cable segment. After 2 failures have occurred, we
include the segment in our cable rehabilitation program to either treat it, if possible, or replace it.
When we do replace cable, we pull new cable into the existing conduit, if such conduit is there
(our earlier construction was direct buried). We install spare conduit only on feeder exits and
mainlines, not on residential or commercial distribution lines. We inspect equipment that we
open during the cable repair or rehabilitation process and perform maintenance and/or replace
damaged equipment components, if warranted. We decommission our old direct buried cable,
after replacing it with new cable in conduit.
SCE: We are seeing an increasing number of cable failures on our residential URD systems on
cable installed from the 1970’s to mid-1990’s. We do not have specific data available on cable
failure rates or trends by root cause.
When we experience a cable failure, we normally repair the existing cable unless we are aware
that the cable segment has failed multiple times, in which case we bring out crews to replace
the cable. When we need to do that, we often install portable generation to provide electric
service to customers while we are replacing the bad cable. We pull new cable into the existing
conduit if at all possible. Sometimes roots have grown into the conduit so we need to install in
new conduit. Also, we have experienced problems in pulling cable out of and into our existing
CIC systems. Initially these problems lead us to abandon the CIC entirely and install new cable
in regular plastic conduit. Now, if we are able to get the old cable out, we pull in new cable
which has a smaller diameter. We do not attempt to pull new cable into our old transite or
orangeburg duct that was installed in the early 1960’s. We just leave that duct in the ground
and install cable in new plastic conduit.
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May 28, 2015 URD Webinar # 2 Notes
KCP&L: Currently our average failure rate overall is 0.05 failures per mile per year. We don’t
track failure rates by cable type but do track by vintage. Most of our failures are now occurring in
cable installed between 1972 and 1977. The rates are increasing. We don’t track failure rates
by root cause.
After 2 failures have occurred in a segment, we replace the segment as part of our reactive
replacement program. We have been doing that since 1994. When we do replace cable, we
pull new cable into the existing conduit, if such conduit is there (our pre-1983 construction was
direct buried). We do not install a spare conduit. We did an economic study on live front
transformers and determined that is cost effective for us to replace those older transformers
when we replace cable. So we are doing that as well as performing inspections and
maintenance on other equipment when we are replacing cable. We decommission our old direct
buried cable after replacing it with new cable in conduit.
CPS Energy: Our overall average failure rate 0.35 failures per mile per year. Most of the
failures are occurring on our older XLPE, unjacketed cable. Since 2012, our failure rates have
been on a downward trend as a result of our proactive cable rehabilitation programs. In 2012 we
experienced a total of 220 failures. This year to date we have experienced only 13 failures.
Through our proactive programs, we have treated or replaced about 1,600 miles of that older
vintage cable to date and have only about 108 miles still left to rehabilitate. We have a group
that tracks our URD system failure data by root cause. 95% of our URD system failures are
cable-related, including failures of the cable, elbows and splices.
Currently, any single failure within a radial tap or loop will result in a future proactive
rehabilitation project to either treat or replace the entire tap or loop. Most of the cable that we
are replacing is direct buried so we are typically installing new cable in new 2.5” conduit and
abandoning the existing cable. We not install spare conduit. When replacing cable, we inspect
both the transformers and secondary enclosures and perform any needed maintenance.
ComEd: Our overall cable failure rate was 0.27 failures per circuit mile in 2014. We do not
maintain data that breaks down the rates by cable types or vintages. We believe that the
majority of our failures are occurring on pre-1985 XLPE unjacketed cable. Our failure rate has
been decreasing as a result of our proactive cable rehabilitation program. We just started to
track failures by root cause and do not have any data to share on that breakdown at this time.
We do not have any specific policy to treat or replace cable after one or more failures have
occurred. We will splice and reuse a cable segment until it becomes completely unserviceable.
We do not use conduit for any URD installations. When we replace cable, we abandon and
decommission the existing direct buried cable
CenterPoint: We are not tracking our per mile failure rates of URD cable.
We are now focusing our attention and resources on a proactive cable assessment and
replacement program. Historically we had a policy to replace URD loops on a reactive basis
after we experienced 3 or more failures. We are not doing that any more. When a failure
occurs, we repair the bad cable segment through splicing and identify a potential future project
to replace the entire loop, which is rolled into our proactive program and prioritized alongside
other potential replacement projects. We have been going back and forth over the years on the
issue of whether we install URD cable direct buried or in conduit. Our most recent switch back
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May 28, 2015 URD Webinar # 2 Notes
to conduit installation was 2.5 years ago. When we replace cable, we install it in the existing
conduit if that conduit is 3” in diameter or larger (Some of our older conduit was only 2”) When
we replace cable, we also replace all terminations and all existing live front transformers. All
existing direct buried cable and existing bad cable that was installed in 2” conduit is abandoned
and decommissioned.
BGE: Rachel: We not track our cable failure rates on a per-mile basis. Our biggest issues are
with pre-1985 cable and those failures are decreasing as a result of our current aggressive
cable replacement program. We were tracking cable failures by root cause in the past and
found that the great majority of failures were due to electrical treeing on XLPE cable.
We now track our cable failures by cable segment and our replace versus repair criteria is
based on a rolling in 18-month period. If 2 failures occur in a segment within 18 months, we will
replace the cable segment. We do not use conduit on our URD installations. Most of the
replacement work is done through directional boring. When we replace cable, we install new
terminations on both ends, inspect and perform routine maintenance on all equipment and also
replace any older live front equipment with dead front equipment. The existing direct buried
cable is left in the ground and decommissioned.
Presentation pages 7 and 8, Q3 and Q4 (Proactive Cable Treatment and Cable
Replacement Programs):
TEP: Treatment: We are not treating any cable. We have been approached by the various
cable treatment vendors, but determined that cable treatment options wouldn’t provide us with
any significant savings since our failures rates are relatively low and essentially all of our
existing cable is installed in conduit, and is therefore relatively easy to replace.
Replacement: In the last few years, we have been budgeting $3 million per year for cable
replacement work on our 10% worst performing feeders. We use SAIDI, SAIFI and CAIDI
statistics to prioritize which feeders will be addressed and also look at the type and vintage of
underground cable, giving higher priority to replacing non-jacketed concentric URD distribution
cable which is older than 30 years. We also place a high priority on replacing our pre-2000
vintage 500kcmil aluminum feeder cable that has a tape shield. We do as much cable
replacement as we can each year with the $3 million budget and defer the rest to be prioritized
and addressed in future years. When we replace cable on a worst performing feeder, we also
replace any live front equipment on that circuit and any other equipment that is showing signs of
imminent failure. We do not have any regulatory requirements related to this work but believe
that what we are doing will allow us to show our regulator that we’ve been addressing the issues
and help us avoid any future regulatory mandates in this area.
Earlier this year, we hired UtilX to test some of our 600 amp feeder cable which was largely
500kcmil tape shield. They used their CableWISE condition assessment testing process, to help
us prioritize which specific segments to replace. We do not do any diagnostic testing of URD
distribution cable. We are using mostly internal company labor on the cable replacement work
and do not perform any post-construction testing to verify the quality of workmanship.
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May 28, 2015 URD Webinar # 2 Notes
Oncor: Treatment: We are treating cable segments selectively based on failure history. The
priorities can be related to cable vintage, but the ranking criteria is really just failure history. We
typically treat just selected cable segments, but may do an entire loop or subdivision if there is a
lot of bad or marginal cable and we think we would gain some economies by doing all of it at the
same time. We inspect all the equipment that we open up during the treatment process,
perform routine maintenance and replace any transformers, arrestors and terminations, etc.,
that are in poor condition. We do not have any regulatory requirements related specifically to
the cable treatment work but do need to show our regulator that we are addressing problems on
our worst performing feeders.
We have used both UtilX CableWISE testing and IMCORP partial discharge diagnostic testing
to prioritize treatment work on our mainline underground feeders. On URD distribution, we do
not perform any diagnostic testing regarding the cable insulation, but do test the concentric
neutral strength as part of the process for determining whether a segment should be treated or
replaced. We will not treat cable that has less than 25% of the original neutral strength
remaining. We are currently using Novinium products in our treatment program. The biggest
issues that we encounter in the field are access problems in areas where the existing cable was
installed in rear lot lines. We perform air-flow tests before attempting to push the treatment fluid
through splices and often do need to replace some splices before starting the treatment. Our
average treatment cost including splice clearing is about $15 per foot, which is about 1/3 of our
average cable replacement costs per foot.
Replacement: Our replacement program is focused on pre-1993 unjacketed cable. As with our
treatment program, we prioritize individual segments based on failure history and typically only
replace individual bad segments. We use IMCORP partial discharge testing to select and
prioritize replacement work on mainline feeders but do not do any diagnostic testing to prioritize
replacement work on URD distribution lines. The replacement work is done by contract labor
and mostly through directional boring. The biggest issues that we encounter in the field are
access problems due to rear lot line construction and congestion with other underground utilities,
which requires us to do a lot of “potholing” to determine the precise locations of those other
utilities before we attempt any to do any directional boring. Our average replacement cost
including potholing costs is about $45 per foot.
We do not do any post-construction acceptance testing, but since 2008 we have been
maintaining a database that tracks the history of every cable segment on our system including
all cable treatment, repair or replacement work that was done by our crews or by one of our
vendors/contractors, and what cable failures have occurred since the cable was last repaired,
treated or replaced. When failures occur, we use this information to initiate follow-up actions
and/or warranty claims with the vendors and contractors that were involved in the previous work,
when warranted.
SCE: Treatment and Replacement: We are focusing our treatment and replacement work on
pre-2000 vintage cable on our worst performing feeders and are using IMCORP to do partial
discharge testing to select the specific segments or radial taps that will addressed. Typically
50% of the cable segments that we test are found to be good, so we can save a lot of money by
just concentrating our rehabilitation work on the segments that test bad. We do not have any
regulatory requirements that are specific to this work, but we do need to report all of the
remediation work that we are doing on our worst performing feeders
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May 28, 2015 URD Webinar # 2 Notes
Treatment: Our treatment program just started. We are using the Novinium products and their
“unsustained” method of rejuvenation. We just completed a pilot project with them involving
40,000 feet of cable. Before attempting to treat the cable, used partial discharge testing data to
locate all of the splices in each segment. We did not attempt to treat any segments that had 3
or more splices. We are in the process of evaluating the results of that pilot project. The biggest
problems that we encountered in the field were related to our outdated maps.
Replacement: Our replacement program is focused on our worst performing feeders. For those
feeders, we perform partial discharge diagnostic testing on all of the underground segments in
each radial tap. If 4 or more segments in a tap test bad, we replace the entire tap. Otherwise,
we just replace the specific segments that tested bad. We replace in the existing conduit if at all
possible. We were having difficulties removing and replacing cable in our existing CIC runs and
initially we were often just abandoning the CIC and installing new cable in new 4” conduit. In
order to reduce the replacement cost on CIC runs, we eventually specified a smaller diameter
cable with a smoother jacket that we can more easily pull through the CIC conduit, after/if we
were able to get the old cable out. When we are replacing cable under our proactive cable
replacement program, we also replace all of the older live front transformers. We use
contractors to perform the replacement work including a portion of the required switching work.
Our per foot replacement cost has been averaging about $100 per foot but we expect that to go
down now that we have found a less costly method for replacing our existing CIC segments
KCP&L: Treatment: We are currently engaged in a large scale treatment program based on
cable vintage. Within each vintage, we prioritize individual cable branches based on failure
history. We generally treat just individual circuit branches but may do entire subdivisions if the
failure data shows that we have a lot of marginal cable throughout a subdivision. During the
treatment process we replace a lot of elbows but do not typically replace any other components
unless they are showing signs of imminent failure. We do not have any regulatory requirements
specific to this work.
We are not doing any diagnostic testing to weed out individual cable segments that may not
need to be treated. We are using contractors to perform the treatment work using Novinium’s
products and methodologies. About half of the cable is being treated using their “sustained”
method and half using the “unsustained” method. The biggest obstacles that we encounter in
the field when performing this work are switching and hold-off clearance delays, difficulties in
getting the fluid to flow through some extremely tight cable bends that we have on our
connections to low profile padmount transformers, and some problems clearing splices. We do
not do any post-treatment acceptance testing. We have had seen a 66% reduction in failure
rates on the cable that has been treated compared to the performance of similar vintage cable
that has not yet been treated. Our average treatment cost is about $25 per foot, which is about
half of our average per foot replacement costs.
Replacement: Our proactive replacement program is focused on those circuits that have the
most cable failures per mile. The work prioritization after that is based mostly on cable vintage.
Beginning just this past August, we have been using IMCORP to perform partial discharge
testing on our highest priority replacement projects to allow us to weed out individual cable
segments that don’t actually need to be replaced. Now we are replacing just those individual
segments on the highest priority cable replacement projects that tested bad. When we replace a
cable segment, we also replace any live front transformers on that segment as well as
inspecting and performing any required maintenance on other equipment. We use contractors
for the replacement work and all of it is done through directional boring. The biggest field issues
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May 28, 2015 URD Webinar # 2 Notes
that we encounter on the cable replacement work are switching and hold-off clearance delays
and encountering solid rock during the boring operations. Our replacement cost per foot doubles
if we need to bore through solid rock. We do not do any post-construction acceptance testing.
Our replacement cost has been averaging about $50 per foot.
CPS: Treatment: The budget for our cable treatment program has been $2.5 to $3 million per
year over the past several years. To date we have treated 451 miles of cable. We treat entire
loops and do not perform any partial discharge testing to weed out segments that do not need to
be treated. We are currently using the Novinium products and methods but have also used UtilX
products and methods in the past. The biggest issues that we encounter in the field are
physical obstructions and the work required to dig up and replace splices that we are not able to
push fluid through. We have experienced less than a 1% annual failure rate on the cable
segments that we have treated. Our average treatment cost has been about $20 per foot of
cable treated.
Replacement: Our current plan is to replace 35 miles of cable per year under an $18.5 million
annual budget. We are replacing entire subdivisions. We are not doing any diagnostic testing to
weed out cable segments that don’t actually need to be replaced. When we replace cable in a
subdivision, we inspect all of the transformers and secondary equipment, perform any required
maintenance and replace any components that are showing signs of an imminent failure. There
are no specific regulatory requirements associated with this work. We use both internal labor
and contractors for the replacement work. Most of the work is done through open trenching
rather than boring. The biggest problems that we encounter in the field are related to easement
encroachments. We do not do any post-construction acceptance testing. We have seen a
dramatic decrease in cable failures as a result of this work. Our replacement cost has been
averaging about $100 per foot.
ComEd: Treatment and Replacement: We have an integrated cable rehabilitation program that
encompasses and utilizes both cable injection and replacement. We address entire loops, which
are selected and prioritized based upon three criteria: # of outages, # of customers, and
duration of outages. We do not do any diagnostic testing nor any other type of field cable
evaluation before attempting injection. For each cable segment, we first attempt to perform an
injection. If injection is not feasible, we immediately replace the cable segment. We do not
inject on our 3 phase lines – all of that cable is replaced. We started this integrated program in
2007 and plan to complete it in 2017. So far we have injected or replaced about 5,000 miles of
cable.
There aren’t any regulatory requirements associated with this work. We use contract labor for
all of the switching and field construction activities (including cable replacement) and use
UtilX/Novinium technicians for the treatment work using the low pressure injection method. The
field work is contracted on a turnkey basis under a unit price format. The contractor has the
option to use either boring or trenching methods, but typically does all of replacement work
through directional boring. Since we are contracting the work on a turnkey basis, ComEd does
not have to deal directly with any field issues but we do know that homeowner obstructions are
a major issue for our contactor. We have done some post treatment/post construction PD
testing to assess work quality in the past, but that isn’t a regular part of our current program.
Our current failure rate on loops that have been injected is 1.5% per year. We have started to
track the failure history of the loops that have been replaced but we have only collected a limited
amount of data so far. I am not authorized to share data on our treatment and replacement
costs, but can say that our per foot injection costs are about 1/3 of our per foot costs for
replacing cable. When we treat or replace cable loops, we also inspect and perform any
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May 28, 2015 URD Webinar # 2 Notes
required maintenance of the attached equipment, replace lightning arrestors, if needed, and
install fault indicators. When we are treating cable, we do not replace any equipment unless the
equipment is showing signs of imminent failure. When we are replacing cable, we do replace
any live front transformers including our “siloed” (semi- submersible) transformers.
CNP: Treatment: We are not treating any cable. We looked into this option in the past but
concluded that it would be costly and difficult for us, primarily because of splice issues.
Replacement:. We now have a proactive cable assessment and replacement program through
which we are addressing 450-500 URD loops per year. Loops are chosen from a loop ranking
report that rates each loop based on age, type of construction (direct buried or in conduit) the
number of equipment failures, and the number of cable failures that have been experienced.
The loops that we select from that list are then tested by IMCORP using their “Factory Grade”
partial discharge testing methodology to identify the specific cable spans that need to be
replaced. IMCORP guarantees the accuracy of their results for any spans that pass their testing.
For cable that was installed prior to 1970, we do not perform any diagnostic testing and just
replace the entire loop. Through this program we replaced at total of 1,156 cable spans in 2014
and are planning to replace 2,000 spans in 2015. When we replace individual cable spans, we
also replace all of the terminations and any live front transformers associated with that span. If
we are replacing an entire loop, we also replace all of the live front transformers on that loop.
There aren’t any regulatory requirements specific to this work. The replacement work is done by
a contractor using directional boring methods. The most challenging issues in the field are
getting access to rear lot line facilities and working in areas where there is concrete cover. We
do not do any post-construction testing on this replacement program but the field work is
monitored by our QA inspectors. Our program is only two years old so we don’t have any data
to share now on the benefits and costs. We are planning to develop a more formal process to
monitor the cost effectiveness of this program.
BGE: Treatment: We just started a formal treatment program this year after completing a pilot
project last year. We are proceeding cautiously on this program because we have tried cable
injection in the past and did not have much success. This year we only budgeted for 5 miles of
injection. We are proactively looking for cable spans of certain vintages to inject. Prior to 1985,
we were using hand wrapped splices on all of our URD cable. We don’t plan to treat any of that
cable because we would need to replace all of those splices before attempting injection. We are
focusing our treatment program this year on post-1985 cable spans that have experienced 2 or
more failures We are doing this work with a combination of company and contract labor and
are using the UtilX low pressure injection process. The most significant challenge that we
encounter in the field is interference/congestion with other underground utilities. We are not
performing any post-treatment acceptance testing. Since our program just started, we do not
have any data to assess the costs or effectiveness of our treatment program..
Replacement: We do not have a proactive cable replacement program but we have had a
large budget over many years to support the replacement of cable segments on a reactive basis,
based on our 2 failures in rolling 18 months criteria. We do not do any diagnostic testing. Our
program is totally reactive, based on failure history. When we replace a cable segment, we also
replace any live front transformers that are on that section of cable. We also replace any leaking
or badly damaged dead front equipment. The replacement work is all done with contract crews
and 99% of the work is done via directional boring. We use a combination of company and
contractor crews for the switching and energizing work. Our biggest field challenge is
interference/congestion with other utilities. We do not do any post-construction acceptance
testing but do have field inspectors that oversee the contracted work. We have definitely
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May 28, 2015 URD Webinar # 2 Notes
experienced a reduction in cable failure as a result of our large investment in cable
replacements. We don’t have data to share regarding our average replacement cost per foot of
cable replaced.
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