Is It Time To Update Your System Coordination

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Is It Time To Update Your System Coordination?
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The Electric Power Research Institute estimates
annual outage costs to society amount to 119
billion.
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Unscheduled outages cost the average large
industrial customer approximately 40,000.
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Some states are beginning to enforce fines for
poor system performance (primarily in
de-regulated states)
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Is It Time To Update Your System Coordination?
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Approximately 75 percent of all overhead faults
have a temporary cause
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Typical causes of temporary faults

• Lightning
• Animals Birds cause 25 of all overhead outages
  in the U.S.
• Trees or debris
• Vehicles hitting poles (conductors slap
  together)

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A sustained outage is typically defined as an
outage lasting 5 minutes or longer
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Reliability Indices

• Most Common
• SAIDI System Average Interruption Duration
  Index
• SAIFI System Average Interruption Frequency
  Index
• CAIDI Customer Average Interruption Duration
  Index
• MAIFI Momentary Average Interruption Frequency
  Index
• Less Common
• ASAI Average Service Availability Index
• (8,760-SAIDI)/8,760 x 100
• CEMI Customers Experiencing Multiple
  Interruptions

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Typical U.S. Utility Values of

• SAIDI 110 minutes each year
• SAIFI 1.4 interruptions per year
• CAIDI 79 minutes per year
• ASAI 99.98

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A well sectionalized system with good
coordination should decrease the SAIFI, SAIDI and
CAIDI, but may increase the MAIFI
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A well sectionalized system with good
coordination should also decrease your OM costs.
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How much are you spending on a per outage basis?
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When designing an economical coordination scheme,
outage data is an invaluable tool.
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Linemen/Operations staff are the best resource
for determining the locations that could use a
protective device.
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So, how often should you update your system
coordination?
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Summary of Results, Conclusions and
Recommendations from Conductor Break Tests
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Equipment Used

• Line truck with winch and tested high tension
  capacity spring scales.
• Conductors were attached using a dead-end shoe.

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introduction
A total of 20 conductor break tests were
preformed, 18 on 4 ACSR and two on 8 CWC. All
conductors were pulled to the point that the
conductor either broke or tension was released
from the wire stretching. All of the damaged
conductors tested were from lines with stretched
conductor which the Engineer recommended to for
either total line replacement or the replacement
of the conductor but were included only for
re-sagging by the FEMA Project Officer.
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SUMMARY OF TEST RESULTS
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NOTE All 4 ACSR conductors which were not
previously stretched in the storm, which were
conductors that broke above their rated breaking
strength, would stretch significantly before
breaking and then break at about 1600 pounds.
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conclusions

• New and undamaged 4 ACSR conductors take a
  permanent stretch of a few feet between 2500 and
  2600 pounds and then drop in breaking strength to
  about 1600 pounds.

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• It is nearly impossible to detect conductor
  damage either from the ground or even up close to
  the conductor. However, some of the best
  indications of conductor damage are
• Excessive sag. This probably indicates the
  conductor has taken a permanent stretch and has
  lost 30-35 percent of its strength. The damaged
  (stretched) segment will likely be 10-15 feet in
  length.

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• Splices. It was found that many of the
  conductors broke at or near a splice. The splice
  did not appear to have failed. It is likely that
  the entire damage segment of the conductor, up to
  ten feet on each side of a break, was not
  replaced after the conductor broke and while
  splicing new a segment. It appeared that the
  aluminum strands broke outside the splice then
  the steel strand pulled out of the splice. This
  was true for both the automatic and compression
  splices tested.
• Locations were short circuit contacts frayed or
  nicked the conductor. The arc which occurs
  during short circuit conditions burns the
  conductor and may also anneal the steel strand.
  Usually this type of damage is localized to a
  short length.

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• The test indicated that when excessive sagging
  occurred, it is likely that the conductor was
  damaged only is short segments, not the entire
  span.

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• The armor rod near the support seems to protect
  the conductor from damage due to excessive
  tension.
• A span of stretched conductor is most likely to
  be weakened just beyond the armor rod at the
  supports.

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• Short circuit and the resulting pitting on CWC
  conductors deduces the strength of the conductor.
• Automatic splices, when properly installed, have
  as much or more strength as the conductor.

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recommendations

• If a conductor breakers due to tension loading
  (i.e., breakers not due to burning from current
  at electrical short circuits), a minimum of 5.0
  feet on each side of the break should be cut out
  before repairing the conductor.

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• Conductors which incurred increase sag due to ice
  loading should be replaced as the results of
  these tests indicate that there is a high
  probability that there was a significant loss of
  conductor strength.

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Questions?