ComEd 2006 Annual Report Download - page 58

(e) Base-load units are plants that normally operate to take all or part of the minimum continuous load of a system, and
consequently, produce electricity at an essentially constant rate. Intermediate units are plants that normally operate to take
load of a system during the daytime higher load hours, and consequently, produce electricity by cycling on and off daily.
Peaking units consist of low-efficiency, quick response steam units, gas turbines, diesels and pumped-storage hydroelectric
equipment normally used during the maximum load periods.
The net generation capability available for operation at any time may be less due to regulatory
restrictions, fuel restrictions, efficiency of cooling facilities and generating units being temporarily out of
service for inspection, maintenance, refueling, repairs or modifications required by regulatory authorities.
Generation maintains property insurance against loss or damage to its principal plants and
properties by fire or other perils, subject to certain exceptions. For additional information regarding
nuclear insurance of generating facilities, see ITEM 1. Business - Generation. For its insured losses,
Generation is self-insured to the extent that any losses are within the property deductible or exceed the
amount of insurance maintained. Any such losses could have a material adverse effect on
Generation’s consolidated financial condition or results of operations.
ComEd and PECO
The electric substations and a portion of the transmission rights of way are located on property
owned by ComEd and PECO. A significant portion of the electric transmission and distribution facilities
is located over or under highways, streets, other public places or property owned by others, for which
permits, grants, easements or licenses, deemed satisfactory by ComEd and PECO but without
examination of underlying land titles, have been obtained.
Transmission and Distribution
ComEd’s and PECO’s higher voltage electric transmission lines owned and in service at
December 31, 2006 were as follows:
Voltage (Volts) Circuit Miles
ComEd ....................................... 765,000 90
345,000 2,621
138,000 2,867
69,000 149
PECO ........................................ 500,000 188(a)
220,000 541
132,000 156
66,000 153
(a) In addition, PECO has a 22.00% ownership interest in 127 miles of 500,000 voltage lines located in Pennsylvania and a
42.55% ownership interest in 131 miles of 500,000 voltage lines located in Delaware and New Jersey.
ComEd’s electric distribution system includes 43,197 circuit miles of overhead lines and 34,917
cable miles of underground lines. PECO’s electric distribution system includes 12,811 circuit miles of
overhead lines and 15,224 cable miles of underground lines.
Gas
The following table sets forth PECO’s gas pipeline miles at December 31, 2006:
Pipeline Miles
Transmission ...................................................... 31
Distribution ........................................................ 6,623
Service piping ..................................................... 5,398
Total ............................................................. 12,052
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