HomeMy WebLinkAbout8 Electric System Master Plan Agenda Item # 8
gu UVC EE DONNER
Public Utility District
Memorandum
To: Board of Directors
From: Joe Horvath, District Electrical Engineer
Date: February 1, 2002
Subject: Proposed Capital Improvement Projects (Draft)
Electric System Master Plan - 2002
Attached is the proposed capital improvement program report for the District's electric
system. The capital improvements span a 15-year planning period and are summarized
in Table 1 and depicted on Exhibit 1. 1 intend to go over the report in detail and I
welcome your comments and suggestions for improvement. No formal Board action is
requested at this time.
DRAFT
Capital Improvement Projects
Electric System Master Plan
Introduction
Cost estimates have been prepared for the proposed capital improvements to the District's
electrical distribution system.The cost estimates include substation and distribution
system improvements over a 15-year period and are summarized in Table 1 and depicted
in Exhibit 1. The dollar amounts listed in Table I are based on unit costs prepared for
underground, overhead, and substation construction and include allowances for
construction, engineering services, overheads, and contingencies. All costs are in
2002 dollars.
Cost Estimates
Unit construction cost estimates were developed for different types of new overhead and
underground distribution lines on a per-mile basis, for the upgrade of Donner Lake
Substation, and for a new substation to serve District loads in the Glenshire area. Cost
estimates include allowances for construction, engineering services, overheads, and
contingencies. Construction costs include materials, labor, and other services, such as
outside contractors, necessary for each type of construction. Material and labor costs
reflect the Districts current standard construction costs updated with year 2002
overheads. The civil site work costs for trenching and excavation were based on actual
bid costs received from area contractors for similar District projects completed within the
last three years. An allowance of 20 percent of construction costs has been included to
cover construction contingences associated with each cost estimate. An additional
allowance of 20 percent of construction costs has been included to cover engineering,
legal, administrative costs. Unit construction costs are summarized by type of
construction in Table 2.
The costs of overhead distribution lines were estimated using 397MCM conductors with
160 foot spans between pole locations for a total of 34 poles per mile on average. Pole
size was assumed to be the District's standard 45 foot, class 2 Douglas Fir treated wood
pole. Variations to overhead construction included modifying the number of angles and
deadend poles per mile (heavy and light feeder construction), and performing a
reconductor project on an existing line where the conductors are replaced with a larger,
higher capacity conductor. In addition, an estimate was prepared for underbuilding a
distribution circuit on Sierra Pacific's existing 60kV transmission line.
02/01/2002 Preliminary Draft Page 1 of 3
The costs of underground distribution lines were estimated using 500MCM and 1/0
aluminum medium voltage cables, placed in 6-inch conduit for mainline circuits and
4-inch conduit for distribution loops. Cable runs were limiting to a maximum of 500 feet
between pulling locations in accordance with good installation practice. Variations to
underground construction included modifying the number of vaults, switches,junction
enclosures, road crossings, and transformers per mile (heavy, medium, light and express
feeder construction). In addition, an estimate was prepared for those locations were the
District has installed empty conduit for future use. In these areas, only the installation of
electrical equipment and vaults are required to complete the underground system (special
feeder construction).
The cost to upgrade Donner Lake Substation includes the installation of new
transformers, voltage regulators, high and low side distribution bus, and the removal of
old equipment. Site work costs such as a new entrance road, foundations, grounding
system are also included. It is proposed to increase the existing capacity of Donner Lake
substation from 3.75MVA to 15MVA, the same capacity as the District's other three
substations. This will increase the District's overall reliability by allowing load transfers
among substations upon the loss of any one substation during an emergency condition.
The District's electrical distribution system in the Glenshire area is presently served via a
primary meter from Sierra Pacific's Glenshire substation at a voltage of 14.4kV. It is
proposed that the District extend Truckee Circuit 1 along Glenshire Drive and install a
small substation to convert from 12.47kV to 14.4kV. The new Glenshire substation
would consist of a 2.5MVA, 12.47/14.4kV autotransformer, and associated switches,
disconnects, transformer foundation, grounding system, fence, and entrance road to be
constructed on property owned by the District and located along Glenshire Drive near
Berkshire Circe. This substation will reduce our dependence on Sierra Pacific and
increase our reliability for our Glenshire customers for those instances when outages
occur on Sierra's system. In the past, these outages have included transmission system,
distribution system, and substation outages upstream of our current primary metering
point, all outside of the District's control.
Project Justification
Table I includes a column where the justifications of individual projects are briefly
noted. These justifications include the following:
• Upgrade main line to 397MCM
• Provide a tie point to an adjacent circuit
• Provide loop capability
• Load growth /transfer capability
• Reduce dependence on SPPC
• Improve reliability and aesthetics
02/01/2002 Preliminary Draft Page 2 of 3
Upgrade main line to 397MCM: The District is currently using 397MCM conductor for
main or backbone feeder overhead circuit configuration.This conductor size allows
feeder loading to not exceed 50 percent of the conductor ampacity rating under normal
maximum operating conditions. This allows for up to 100 percent loading during
contingency or emergency operating conditions such as picking up the load from an
adjacent feeder.
Provide a tie point to an adjacent circuit: The District's distribution feeders should have
back-up ties to other feeders, including feeders from other substations. Providing
sufficient full capacity feeder ties to feeders from other substations is necessary to cover
the loss of any one substation during an emergency condition.
Provide loop capability: Currently, some of the District's main distribution feeders are a
radial only configuration. This means that for an outage on a feeder, all customers
downstream of the outage point will be without power. The construction, where possible,
of loops within individual feeders allows the District to backfeed areas and remove from
service the smallest possible line section, affecting the smallest number of customers
while repairs are made.
Load growth/transfer capability: Adequate reserve transformer capacity must be
provided to serve District loads with any one substation out of service. See also the
explanation under the Donner Lake Substation part of the Cost Estimates section above.
Reduce dependence on SPPC: See the explanation under the Glenshire Substation part of
the Cost Estimates section above.
Improve reliability and aesthetics: Feeders out of substations should be placed
underground allowing trees and shrubs to be planted around the substation perimeter
virtually camouflaging the station from the public's view. This will not only be
aesthetically pleasing but may also reduce vandalism. Station reliability will be improved
due to reduced exposure to outages associated with exposure to trees, animals, vehicles,
and weather related phenomena.
02/01/2002 Preliminary Draft Page 3 of 3
TABLE 2
COST DETAIL SUMMARY
Electric System Master Plan -2002
Type of Cost
Construction Configuration Description Code $/Mile $/Foot
Overhead Heavy Feeder 3 Phase, 397AAC, 45/2 poles, 160 ft. spans OH-HF $218,400 $41
8 tangent, 20 light angle, &6 deadend poles per mile
Light Feeder 3 Phase, 397AAC, 45/2 poles, 160 ft. spans OH-LF $199,800 $38
22 tangent, 8 light angle, &4 deadend poles per mile
Reconductor 3 Phase, 397AAC, 45/2 poles, 160 ft. spans OH-RC $147,400 $28
replace 25% of existing poles & all crossarms
Underbuild SPPC 3 Phase, 397AAC, 50/113 poles, 240 ft. spans OH-UB $227,000 $43
6 tangent, 12 light angle, &2 deadend poles per mile
Underground Heavy Feeder 3 Phase, 500MCM cable, 5 vaults, 5 switches, 5 JEs, UG-HF $1,087,700 $206
10 road crossings, 5- 3ph transformers with 10 services,
and 10 - 1ph transformers with 20 services per mile
Medium Feeder 3 Phase, 500MCM cable, 3 vaults, 8 switches, 3 JEs, UG-MF $854,400 $162
5 road crossings, 3 - 3ph transformers with 5 services,
and 5- 1 ph transformers with 10 services per mile
Light Feeder 3 Phase, 500MCM cable, 9 vaults, 1 switches, 2 JEs, UG-LF $611,800 $1:16
2 road crossings, 2 - 3ph transformers with 4 services,
and 2 - 1 ph transformers with 4 services per mile
Express Feeder 3 Phase, 500MCM cable, 9 vaults, 2 road crossings, UG-XF $500,200 $95
no transformers, switches, or junction enclosures
Special Feeder 3 Phase, 500MCM cable, 9 vaults, 2 road crossings, UG-SP $245,100 $46
no transformers, switches, or junction enclosures
Existing conduit, only vault installation required.
Substations Description Code Cost
Donner Lake Upgrade capacity to 15MVA Sub-DL $908,700
Glenshire Install 2.5MVA, 12.5/14.4kV transformer to serve Sub-Glen $152,600
Glenshire area from Truckee Circuit 1
Notes:
1. Costs are in 2002 dollars.
2. Costs include allowances for construction contingencies of 20 percent and allowances for engineering and
administration of an additional 20 percent.
02/01/2002 Preliminary Draft