ArrowheadWestonTransmission Line

Project

Dave Van HouseMinnesota Power

Description & Overview

220 mile 345,000 volt electric transmission line

Approved by the Minnesota and Wisconsin regulators in 2001

Construction Began in Minnesota February 2004

Construction to Begin in Wisconsin Fall 2004

Construction scheduled to be completed in 2008

Why was it proposed?

Reliability!!

Improves Regional System Security

Provides Maintenance & Operational Flexibility

Allows Customers Greater Access to Generation Sources

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www.powerupwisconsin.com

Minnesota

Minnesota’s electric network is tied to neighboring states.

If Wisconsin has a problem, Minnesota has a problem.

Minnesota Power customers have been knocked off line by electric system disturbances related to the weak Minnesota-Wisconsin connection.

Recent Regional Problems

June 11, 1997

June 25, 1998

June 10, 1999

IMPACT OF June 25, 1998 DISTURBANCE

IN MAPP■ 60+ TRANSMISSION LINES TRIPPED■ 4,000+ MW OF GENERATION LOST■ More Than 39,000+ CUSTOMERS

AFFECTED

IN NW ONTARIO■ BLACK OUT TO 113,000 CUSTOMERS■ 650 MW OF LOAD LOST ■ 270 MW OF Generation Lost

Wisconsin Actions

1997 events raise concerns about electric supply reliability in Wisconsin

Wisconsin utilities and regulators form Wisconsin Reliability Assessment Organization (WRAO)

WRAO forms engineering group to study alternatives - WIRES group

PERFORMANCE EVALUATION

DETAILED POWER FLOWS SIMULATION

GENERATOR RESPONSE

DYNAMIC STABILITY

VOLTAGE STABILITY

IMPACT ON MAPP

CONSTRUCTION COSTS

LOSS EVALUATION

Power Flow Analysis

Reactive Voltage Support Requirements

Steady State Maximum Transfer capability

Sensitivity to Modeling Assumptions

Transmission System Loss Analysis

Generator Response

Mechanical Stress on Weston Generator Shaft

■ Large Phase Angle Across MAPP MAIN Interface

■ Eau Claire Arpin Line Switching

■ Instanteous change in Power output

Dynamic Stability

Ability of Systems Generators to remain synchronized and recover from Major System Disturbance

MAPP WUMS Disturbances Loss of New Facilities Impact on Existing Limiting Conditions Dynamic Reactive Support Requirements

Voltage Stability

Ability of the System to Maintain Adequate Voltage Following a Disturbance

Without Adequate Voltage Support System can Experience■ Increased Current Demand (P = VI)■ Slowly Declining Voltage■ Loss of Voltage Sensitive Loads■ Voltage Collapse

Engineering to Support Permitting

Calculation of;■ AUDIBLE NOISE■ ELECTRIC FIELD■ MAGNETIC FIELD

Analysis of Potential Farm Impacts■ Stray Voltage■ Earth Currents

Magnetic Field Electric Field Spark Discharge

Multiple Routes Multiple Structures Multiple Circuits Multiple Flows Future Years

EMF Issues

Transmission Line Noise

Due to Corona Discharge■ Electric Field at surface of the conductor

exceeds the breakdown strength of air■ Generates light, audible noise radio noise

and energy losses

Mitigation■ Increase Conductor Surface area

• Larger Conductors• Multiple conductors

Substation Noise Monitoring

Long Term

Short Term

ExistingEquipment

Impact ofAdditions

Arrowhead Substation Noise

Other Engineering Issues

Differential GPS Interference (Precision Farming)

Electric & Magnetic Field

■ Impacts on Pacemakers and implantable Defibulators

■ Impacts on Railroad, Pipeline and AM Radio Transmitter sites

Opposition to the project:

Save Our Unique Lands Citizens Utility Board Wisconsin Environmental Decade North American Water Office Hillside Dairy World Organization of Landowner

Freedom

Common Utility Corridor

Visual Impact Of Crossing

Existing 161 kV H-Frame

954 ACSR 2-ConductorBundle with Shield Wire

Single 3M Composite Conductor

Post Permit Studies

Equipment Specification

Construction Support Analysis

Operating studies

Equipment Specifications Transient studies

■ Breaker Switching Duties• Shunt Reactor• Shunt Capacitor• 345 & 230 kV line breakers

■ Capacitor Bank Switching Issues• Voltage Magnification

■ Insulation Coordination• Surge Arrester rating & placement• Equipment BIL requirements• Line Insulation

Construction Impact Studies

Constructability■ Line outage concerns■ Maintenance issues■ Ownership Issues

Increased Cost Landowner Opposition

Operating Studies

Determination of Operating Limits■ Reactive Support Requirements

• Shunt Capacitor location optimization■ Line Loadability Issues

• System Intact and Post Contingency■ Phase Shifter Requirements

• Line load sharing optimization• Post Contingency requirements

■ New Flow-Gate Limits• System Intact and Post Contingency

Summary

Operating experience has shown there is a significant risk to electrical reliability in the upper Midwest and Wisconsin

Engineering study commissioned through Assembly Act 204

WRAO recommendation Arrowhead Weston 345 kV Line

Summary

The Arrowhead-Weston Project will substantially alleviate the reliability problems being experienced due to the weak electrical tie between the upper Midwest and Wisconsin.

It will also provide import capability for Wisconsin to meet its emergency power supply requirements.