ECONOMIC FACTORS
Tables 3.10-1 and 3.10-2 summarize the major improve-ments in ampacity that may be realized by the various uprating and upgrading techniques described in this chapter. The specific costs for each depend largely on the unique aspects of each installation or project, but qualitative costs, along with many other factors, are listed in the tables for reference.
The case studies in Section 3.9 give an indication of spe-cific costs for one of the uprating projects.
Table 3.9-2 Comparison of Normal “Book” Rating to Real-Time and Dynamic Ratings
Rating Type Minimum Maximum
Normal Book (Previous Study) 743A
Real-Time Normal 621A 817A
Dynamic Normal (100% Loss Factor) 0A (722A) 877A Dynamic Normal (with Cyclic Rating
Factor) 0A (774A) 929A
Table 3.10-1 Summary of Uprating and Upgrading Techniques Applicable to All Cable Types
Evaluation Criteria
Measure Soil Rho, Heat Pipes,
Mitigate Hot Spots
Real Time Monitoring
Replace Conductors
Voltage Upgrading
Thermo-couples (Temp.)
Dist. Fiber Optic (Temp.)
Dynamic Ratings Rating Incremental Increasea
a. Incremental increase in ampacity over previous options.
20% N.A.b
b. Monitoring the cable circuit alone, does not provide for rating improvements. Real-time monitoring, with the monitored parameters fed into rating calculations provides for optimum ampacities.
10-20% 3-20% 66-80%
Reliability High High High High High High
Maintenance Low Low Low Low Low Increased, but
Low
Losses None None None Low Low Increased, but
Low Lead
Time
Installation 2 mos. 3 mos.c
c. If not done during the original installation of the cable system.
3 mos. 2 mos. 14 mos. 24 mos.
Operating None Real Time Real Time Real Time None None
Cost Installationd
d. Including material costs.
Low Low-Med Low-Med Low High High
Operating None Low Low Low Med.-High Med.-Highe
e. Generally, higher voltage equipment requires more extensive and expensive maintenance.
Table 3.10-2 Summary of Uprating Techniques Predominantly for Pipe-Type Cables Evaluation Criteria Fluid Filling Circulation Forced Cooling
Slow Rapid
Passive Heat Exchanger
Forced-Air Heat
Exchanger Refrigerated Cooling Rating Incremental
Increase 2% 21% 8% 16% 31% 16%
Reliability High Medium Medium Medium Low Low
Maintenance Medium Medium Medium Medium High High
Losses None Low Medium Medium High High
Lead Time
Installation 10 mos. 2 mos. 2 mos. 2 mos. 3 mos. 6 mos.
Operating N.A. Lowa
a. Typically less than 24 hours.
Lowa Lowa Lowa Lowa
Cost Installation High Low Low Medium High High
Operating Low Low Medium Medium Medium High
REFERENCES
The following references were used for this chapter and may be useful to the reader for additional background on the topics discussed.
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Bascom, III, E. C. and J. A. Williams. 2002. “Taking Your Cable’s Temperature.” Transactions of the T&D World Expo. 7-9 May. Indianapolis, Indiana.
Bascom, III, E. C. and J. A. Williams. 2002. Ampacity Evaluation and Distributed Fiber Optic Testing on Pipe-Type Cables Under Bridgeport Harbor. Electric Power Research Institute Publication 1007534. December.
Bascom, III, E. C. and J. H. Cooper. 2002. Condition and Power Transfer Assessment of CenterPoint Energy’s Polk-Garrott Pipe-Type Cable Circuit. Electric Power Research Institute Publication 1007539. December.
Bascom, III, E.C. 2003. “Underground Cable Uprating and Upgrading Tutorial.” Transactions of IEEE PES Transmission & Distribution Conference. Paper 03TD0362 (Panel Session). Dallas, Texas. 7-12 September.
Bascom, III, E. C., J. A. Williams, M. A. Pasha, S. M.
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APPENDIX 3.1 PIPE-TYPE AMPACITY