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PROCESS
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Most people think that the 3R’s are “Reading, ‘Righting, and ‘Rithmitic.” The 3R’s
of the distribution rehabilitation business are Re-evaluate, Rejuvenate, and Replace.
The relationships of these three R’s is shown in the illustration nearby.
The 3R's of rehabilitation include: Re-evaluate, Rejuvenate,
and Replace. The 3D's (Database, Distribution hierarchy of
needs, and Diagnostics are input tools to perform the
re-evaluation step.
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Continual re-evaluation of the population of at-risk cables surrounds the process.
Those cables, which are most likely to fail and which have the greatest impact on
reliability, are identified and segregated from the entire population. For almost
all conceivable circumstances, state-of-the-art rejuvenation requires less than
half of the capital required to replace cables. Modern rejuvenation extends reliable
cable life to a par with the anticipated life of new replacement cable. Because
of its inherent capital efficiency, rejuvenation is applied to the majority of the
identified population of at risk cables. However, a small portion of those cables
may not be practically treatable, and hence, some of the identified population must
be replaced. Replacement is so much less capital efficient than rejuvenation, a
tactical plan is required to minimize the added cost of the replacement portion
of the rehabilitation plan.
The 3Ds drive the re-evaluation process, starting with the database of failure statistics
including the "demographics" of the cable, while requiring some effort to collect
and verify, these data are an inexpensive and reliable diagnostic. These statistics
empower the circuit owner to thoughtfully assess the probability that a subset of
cables is likely to fail, at what rate they are likely to fail, and most importantly,
how fast that rate changes with time. The second "D" is the Distribution 5Ps. The
concept of the 5P’s of the distribution hierarchy of needs is described in
"Underground Distribution Reliability: The 5Ps". The 5P’s focus attention
and resources on the sub-population of cables, which have the largest impact on
circuit-owner-defined reliability requirements. The third "D", diagnostics, has
only limited applicability. In
"Diagnostics Testing of Stochastic Circuits" it was shown that currently
available diagnostics generally fall outside either or both the economic test criterion
and/or the thermodynamic test criterion. Advancements in diagnostics are likely
to continue, and future tests may become integral parts of the re-evaluation process.
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The integrated rehabilitation method maximizes capital efficiency
and reliability.
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The top portion down to the "Rehab?" diamond of the nearby flowchart, recaps the
re-evaluation process. Cable’s that will not be rehabilitated in the current planning
cycle are recycled back into the at-risk-population to be re-evaluated in the next
cycle.
Those that will be rehabilitated move on to the "Identify splices and corrosion"
process. This process involves visual inspection of the cable and its components
and high resolution time-domain reflectometry to locate splices and neutral corrosion
issues. Typically about half of the cables tested will have no splices or significant
neutral corrosion. The next decision diamond divides the population of cables to
be rehabilitated into two approximately equal sub-populations: Those with no splices
or corrosion and those with 1 or more splice or corrosion issues.
Cables that fall in the first category are immediately treated with sustained pressure
rejuvenation, which yields a cable likely to provide reliable service for 40 more
years. Cables in the second group advance to a more complete analysis. The analysis
identifies and pinpoints all buried splices or corrosion issues and is labeled,
"Pinpoint splices or corrosion". Using a multi-antenna radio frequency (RF) locator,
a signal is impressed upon the conductor and perturbations in the RF field near
splices and neutral corrosion sites allow the pinpointing of splices or corrosion.
On average, the population of pre-1985 vintage, North American bare-concentric neutral
cables have less than a 2% incidence of significant neutral corrosion.
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The tactic with greatest benefit-to-cost ratio (sustained pressure
rejuvenation) is executed as often as possible. The second best tactic (unsustained
pressure rejuvenation) is applied as often as possible to the leftovers. The residual
is replaced as a last resort at the highest capital intensity.
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Typically the lion’s share of the rehabilitation population can be treated with
the most robust sustained pressure rejuvenation (SPR), a small amount is treated
with unsustained pressure rejuvenation (UPR), and an even smaller residual is replaced.
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Cables must be grounded to assure the safety of line
and injection personnel.
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 TDR.jpg)
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A time domain reflectometer (TDR) allows the identification of splices and neutral
corrosion.
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A radio frequency receiver (RF) is used to pinpoint splices or corrosion issues.
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Pinpoint all splices, severe cable bends, and level 2, 3, or 4 neutral corrosion
sites utilizing a high-resolution TDR and a state-of-the-art radio frequency locator
with a combination of multi-directional antennas, active trace frequencies, and
low frequency band widths together with a proprietary impedance streamliner.
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For cables which have no splice or corrosion issues, advance to the SPR process
(sustained pressure rejuvenation). For cables with splices or significantly corroded
neutrals refer to Excavation Guidelines which are based upon an economic analysis
of rehabilitation options to determine if sites identified in the Pinpoint Splices
step should be excavated. If the defects are not economically addressable, perform
an air test to determine if the splices will support flow.
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Air or fluid flows from the strand interstices around a compression
connector and back into the
strand interstices at a typical molded splice at pressures between 10 and 30 psig.
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If splices support flow, advance to the UPR process (unsustained pressure injection).
If the splices do not support flow, schedule the cable for replacement.
The integrated rehabilitation method maximizes capital efficiency and reliability.
For detailed step-by-step instructions on how to optimally choose the right rehabilitation
option, see NRI-60 Tailored
Injection.
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These excavation guidelines are typical for single phase North American
URD cable. Actual values
are based upon a detailed economic analysis performed by Novinium and the circuit
owner
and included in Exhibit F of the rehabilitation contract.
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Sustained Pressure Rejuvenation
SPR may be applied to any injectable cable to extend its life. Only Novinium’s patented
SPR process may be applied post-failure and still receive capital treatment from
the FERC (Federal Energy Regulatory Commission). For a video overview of SPR click
on the one of the two video windows below. There is one version for post-failure
rejuvenation and another version for all other cases including preventative, proactive,
preemptive, and problematic rejuvenation.
Remove Old Components
Remove and discard all old components (terminations and splices) and old component
compression connectors. Where conductor length is in short supply, old compression
connectors may be removed with a connector cut-off tool, or repair length terminations
and splices may be utilized.
Install Injection Adapters (IAs)
Position new compression connectors and injection adaptors. If there is a splice
position the new splice body on the cable.
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Swage injection adaptors and connectors in a single operation. Compared to standard
crimping techniques, this swage provides superior ampacity.
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Cut-away of 1000 kcm splice connector illustrates the tenacity of
the swage. Ampacity is assured. Fluid-tight seals at the compression connector and
on the insulation assure fluid never leaves the confines of the cable interstices.
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45-ton circumferential swage
is applied to the injection
adaptor and compression
connector in one operation
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Inject
Inject sub-segments at sustained moderate pressure. Typical lengths and conductors
require only a few minutes and are attended. Longer lengths, 7-strand or compact
conductors may require greater injection times and can be rigged for unattended
injection. Fluid flows from the feed tank, which is available in various sizes for
different conductor configurations and cable lengths, to a rotometer which provides
continuous flow measurement. From the rotometer the fluid passes through a ball
valve and into the injection tool or IT. The IT provides a fluid tight seal with
the injection adaptor (IA) installed in the previous step. When the cable is filled
with the right amount of fluid, the IT is used to insert permanent fluid-tight metallic
plugs in the IA access port. The IT is then removed.
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An Injection Tool (IT) is mated to the Injection adapter (IA)
and provides leak-tight fluid access to the cable interstices
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Rotometer
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3-liter feed tank
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Install Components
Complete the installation of Novinium Certified terminations and splices. To learn
the rigor required to earn the Novinium Certified label click the link:
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Standard elbows, splices and live-front terminations already approved by your standards
department are installed right over the injection adapters. To see a list of Novinium
Certified components click the link: www.novinium.com/templates.aspx
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With all personnel clear, grounds are removed and the cable is reenergized.
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Re-energize the cable. Restore any excavations.
Enjoy like-new reliability within days. Safer … faster … better.
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Unsustained Pressure Rejuvenation
Sustained Pressure Rejuvenation or SPR outlined on the previous tab is the preferred
injection method as it provides the best reliability and the longest life. UPR may
be applied to any injectable cable to extend its life in less demanding circumstances.
Only Novinium’s patented fluid technology allows the injection of URD cables with
the UPR process, but without the need for a soak period and its extra risks. Because
of Novinium’s advanced technology both SPR and UPR are available only from Novinium
and Novinium partners. For a video overview of the UPR process click on the video
link below.
Process Steps
Remove old elbows or terminations from both ends of each cable segment. Install
injection elbows on dead-front systems and live-line operable injection adapters
on live-front systems.
Inject fluid into the cable and through any splices at 10-30 psig of pressure. A
vacuum is drawn on the other cable end to increase the net driving force, which
urges the fluid through the strand interstices. Fluid typically flows overnight
along 328 foot (100 meter) URD cable segments.
 002.jpg)
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Cut away of typical injection elbow. The access port provides a fluid interface
to the strands. A proprietary reticular flash preventer (RFP) is positioned in the
throat of the injection port to prevent flashovers that otherwise might occur were
it not present.
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Pressurized gas bottle in the foreground provides the driving force to push fluid
from the supply tank into the access interface installed on an injection elbow.
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After the fluid has filled the cable from end-to-end, the access interface (AI)
is removed and a permanent and shielded cap is put in place. Injection equipment
is typically removed within a day or two of the start.
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 005.jpg)
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Vacuum is applied to a plastic receiving vessel at the far end of the cable. A small
amount of fluid will collect in the bottle before the injection port is sealed.
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A shielded cap completes the dead-front configuration of the injection elbow. The
central pin of the permanent cap safely displaces the RFP into the conductive insert.
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