Tree-trimming Standards and Practices

City Council Work Session

November 19, 2007

Introduction• Two General Categories

- Transmission - Distribution

• Work Performed by Outside Contractor - ANSI A300 (Tree Care Operations – Tree, Shrub, and other Woody Plant Maintenance – Standard Practices)- Interpretation and Implementation of A300- Line clearances to GP&L standards

• Line Clearances - Transmission Standard (GP&L OH-907)- Distribution Standard (GP&L OH-908)

Transmission Standards Overview

• Subject to NERC Standard FAC-003-1

• Lists ANSI A300 as industry “best practice” for vegetation management

• Transmission Vegetation Management Program (TVMP) per FAC-003-1

• Passed ERCOT/NERC audit this year

• Liable for ALL vegetation related outages

• Increased penalties under nodal market

GP&L Standard OH-907

Typical Transmission Standard

• Zones defined by the TVMP

- Border zone requires documented plan

- Wire zone requires immediate resolution

New Transmission Design

• New transmission design increases clearances

Transmission Standards Outlook

• Development along transmission corridors - Increase compliance effort- Increase in vegetation encroachments- Increase interaction with property owners

• Reduce this impact by providing information to property owners along transmission corridors.

• Improve corridor access to insure timely identification of potential encroachments.

Distribution Standards Overview

• Majority of annual trimming operations• Not currently subject to regulatory audits• Line clearances per GP&L OH-908• Contractor adheres to ANSI A300 for

vegetation management• Trimming format (V-out, side, notch, etc.)

chosen to provide desired clearances without killing tree.

• Trunk location typically dictates trim format

GP&L Standard OH-908

Distribution Standards

V-Out Format

Distribution Standards

Side Format

Distribution Standards

Notch Format

Distribution Standards Outlook• NERC regulatory voltage will continue to be

lowered – distribution may be subject to standards in the near future?

• Increased trimming in past 3-5 years – greatly reduced storm related outages

• System reliability directly affected by magnitude of trimming operation

• Enhance customer notification process• Provide information on clearance

requirements to property owners

QUESTIONS?

Balancing aesthetics & reliability!