Transmission

A transmission right-of-way is made up of one or many contiguous parcels of land with the actual corridor dimensions described within an easement document. Easement(s) allow a right-of-way to be established for the purpose of construction, operation, and maintenance of transmission electrical facilities and contain information regarding how each of these activities may be completed.

Transmission facilities transmit power from generating stations to substations, often covering many miles before the electricity is distributed to customers. A transmission power line can carry voltages of 34 thousand volts (kV), 69kV, 115kV, 230 kV, or greater. A single transmission line can travel 1 to 50 miles and provide power to thousands of customers. These lines occupy right-of-way corridors that ordinarily range in width from 50 feet to 100 feet and up to 350 feet when paralleling adjacent rights-of-way.

Transmission poles can be identified by their unique numbering system. Typically, each pole will have a black, 6-digit number with a yellow background called a TEFIS number that is aligned vertically on the face of the pole. This number is used to reference information such as pole location, line name, and pole type within the TEFIS (Transmission Electrical Facility Information System) software application. Since no two poles will have the same number, it is important when providing this number that it is communicated as it appears on the pole so the correct information can be obtained. Landowners that have transmission lines traversing their property are asked to have this number available when questions arise about our normal operations & maintenance as well as any emergency situations.

Distribution

A distribution right-of-way is a corridor of land that is dedicated to the construction, operation, and maintenance of distribution electrical facilities. Distribution facilities distribute power from substations to industrial, commercial, and residential customers. A distribution power line can carry voltages of 7.5 thousand volts (kV), 12 kV, or 34kV. Distribution lines often travel for miles across rural stretches of land, but they typically follow urban and suburban streets. A distribution feeder might serve several to several thousand customers. These lines occupy right-of-way corridors that range in width from 10 to 40 feet, with 20 feet being most common.

Secondary and service lines are the lines that carry your power from the primary distribution system to your home or business. The power that you use is reduced in voltage by a transformer that converts the higher voltage to a level that is appropriate, usually 110 volts or 220 volts. Santee Cooper distribution poles can be identified by an oval plate that is positioned about 5 feet above ground on the pole. The plate bears the name of the SC Public Service Authority (Santee Cooper), and has a 4-6 digit number embossed on the plate.

IVM is an approach to vegetation maintenance that employs a variety of management tools to control troublesome vegetation in a way that is safe, efficient, and environmentally responsible. Large trees that conflict with the power lines are controlled by directional pruning and/or removal, which is performed by qualified line clearance tree trimmers. Closer to the ground, troublesome brush is controlled by manual or mechanical cutting, as well as the selective application of herbicides in low, regulated volumes. Tree growth regulators (TGR's) are sometimes used to reduce the growth rates of fast-growing trees. Santee Cooper's vegetation managers integrate these management tools to achieve the desired results, while maintaining a strong commitment to environmental stewardship. Whether the lines belong to distribution or transmission power systems, our goals are the same.

When trees and vines grow into the power lines, or when tree limbs fall onto the lines, they create the potential for power outages. Also, when a tree is too close to an energized conductor, a potentially hazardous situation exists for people who work or play near the trees. Santee Cooper regularly trims trees in order to provide adequate clearance to help prevent power outages and to protect public safety. Our commitment is to provide reliable electric service at the lowest possible cost. Controlling trees that will interfere with the power lines is one of the many things Santee Cooper does to meet these goals.

The most prominent written pruning standard in the entire arboriculture industry is published by the American National Safety Institute (ANSI). The standard is commonly referred to as A-300, but is entitled, American National Standard for Tree Care Operations - Tree, Shrub and Other Woody Plant Maintenance - Standard Practices. ANSI A-300 is not only relevant to the utility industry, but is widely used and supported by organizations such as, The International Society of Arboriculture, National Arbor Day Foundation, and American Forests. Santee Cooper relies on the ANSI A-300 standard as a tree pruning guideline for its line clearance contractors. Variation from the standard is only applied when special conditions require alternate methods.

In utility arboriculture, the most common method of pruning is called directional pruning. Directional pruning seeks to eliminate branches that will grow toward the power lines, while leaving behind select branches that will grow away from the lines. This is done to reduce the need for future pruning. Pruning cuts are made in a way that is best for the long-term health of the tree. Branch collars are left intact, and flush cuts and stubs are avoided.

For a more detailed description on the proper pruning, please refer to the web site for the International Society of Arboriculture.

Transmission and Distribution share the same goal, which is to provide reliable electrical service as well as a safe environment for property owners and line personnel within the right-of-way. Both use accepted arboriculture tree maintenance standards such as directional pruning and/or removal when dealing with trees in urban and rural areas. The exception to this is when a species of tree does not have the necessary structure that allows directional pruning and when the goal is to reduce the threat of tree related outages from felled trees. In these cases, the tree(s) will be topped appropriately to conserve the remaining portion of the tree and ensure that upon falling it does not make contact with electrical conductors. Tree species, age, and site quality are taken into consideration before a tree is topped. Only those species that have shown a positive response in the past to this type of maintenance practice are topped. All other species are removed if directional pruning is not an option.

Because an outage to a transmission line can literally impact thousands of customers, it is important to remove or decrease the heights of trees growing along the edge of a transmission right-of-way as a normal maintenance practice. The byproduct of such a practice is good electrical reliability for customers who rely on electrical service for their home and businesses.