Studies and Reports > 2009 MN Biennial Report > TC Planning Zone > Needs: 6.5.15 Glendale-Lake Marion Area

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6.5.15 Glendale-Lake Marion Area

Tracking Number: 2009-TC-N2

Utility: Great River Energy

Inadequacy: The Glendale-Lake Marion area is experiencing high growth resulting in significant deficiencies with the present lines and equipment. Each of the 115/69 kV transformers and nearly all of the 69 kV lines in this area would be overloaded during contingencies at long-range load levels projected by GRE. Several facilities would overload for system intact loads as well. An analysis of reliability indices shows that the transmission facilities serving this area have poor reliability due primarily to the high number of consumers in the area and the large load impacted by the outages.

The Glendale-Lake Marion area includes the 69 kV system that is supplied from the Glendale and Lake Marion 115/69 kV substations, but does not include the Glendale-Burnsville 69 kV line and the Lake Marion-Farmington 69 kV line.

The following table summarizes the facilities, the cause of the criteria violation, and the estimated year the planning criteria are exceeded.

A map of the area is shown following the discussion.

Alternatives: Two basic alternate options have been developed to resolve the deficiencies in this area.

Option 1. The first option utilizes load conversion to 115 kV and the addition of a 115/69 kV source at New Market to minimize the need for 69 kV facility upgrades.

Option 2. The second option includes the replacement of the Glendale 115/69 kV transformers to defer the need for load conversion to 115 kV.

Both options plan for development of 115 kV facilities and conversion of load to the 115 kV system, but one defers the load conversions. Both options require the Lake Marion 115/69 kV transformer to be replaced with a larger unit in conjunction with the Lake Marion 345/115 kV source. The Lake Marion source delays the loading problem of the Glendale transformers.

Option 3. Distributed generation was also considered.

Analysis: Each of the options has been analyzed.

Option 1: Convert Loads to 115 kV

This option minimizes investments on the 69 kV system by converting load to 115 kV. In 2010 and 2013, successive segments of the Credit River Tap-Cleary Lake-Credit River 69 kV line need to be upgraded. The plan is to rebuild this line to 115 kV, with continued operation at 69 kV. In 2014, in conjunction with the CapX 2020 installation of a 345/115 kV source at Lake Marion, the Lake Marion 115/69 kV transformer will be upgraded to 140MVA.

Load conversion to 115 kV will start in 2016 timeframe with the addition of a 115 kV line from Lake Marion to Helena. This option uses the route of the existing Lake Marion Tap-Elko-New Market 69 kV line for a single circuit 115 kV line requiring the Elko 69 kV distribution substation to be converted to 115 kV. This option also adds a 115/69 kV substation at New Market to supply the remaining load on the 69 kV circuit in the area. The Prior Lake and New Market 69 kV distribution subtations are recommended for 115 kV conversion in the 2018 and 2026 timeframes respectively.

Option 2: Upgrade Glendale 115-69kV Transformers

Similar to Option 1, this option also recommends rebuilding the Credit River Tap-Cleary Lake-Credit River 69 kV line and upgrading the Lake Marion 115/69 kV transformer. It also recommends building a 115 kV line from Lake Marion to Helena double circuiting the Lake Marion to Elko to New Market 69 kV line. This option in addition recommends replacing the Glendale 115/69 kV transformers and converting the Elko and New Market 69 kV subs to the 115 kV system.

The following table summarizes the estimated timeline and construction costs for the various facilities under Option 1 and Option 2:

Cost analyses showed that Option 1 is the least cost plan. Option 1 is best suited to accommodate future load growth in the area as more loads will be converted to 115 kV in this option than in Option 2. Option 2 was found to have higher losses than Option 1, i.e., Option 1 saves nearly two MW of power in the 2021 timeframe over Option 2. Thus Option 1 is the preferred option for this area.

Option 3. Distributed Generation

In comparison to the preferred option for this area, a distribution generation option is not desirable to address deficiencies in this area for the long term. A distributed generation option would have to be sufficient enough to serve the present loads that cause the deficiencies as well as the growing loads in the area. It would require several generating facilities at multiple locations to address transmission loading problems during contingencies. This would require a significant investment which wouldn’t be a least cost plan in comparison with the preferred plan. The preferred option, unlike the distributed generation option, helps to address the Carver County – Scott County – New Prague area deficiencies (Tracking Number 2009-TC-N5). Thus, distributed generation is not a desirable option for this area.

Schedule: Refer to the above tables

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