.: Home  .: Products  .: Services  .: News & Annoucements .: About Us   .: Contact Us 

.:Advantage  .: History & Future  .: Successful Installations  .:Technical & Specifics 

Sagging Line Mitigator (SLiM)

Problem Statement:

Line-to-ground clearance dictates line loading levels in many key situations. Excessive sag from high conductor temperature operations, caused by ambient conditions and line loading, is often the limiting condition. Previously, expensive line reconstruction or reconductoring were the only true solution to this problem.

Our Solution:

PTS current product is the Sagging Line Mitigator (SLiM), a new class of transmission line hardware that fixes the problem of excessive transmission line sag at just the right time.  Using state-of-the-art materials and a tested and proven concept, SLiM reacts to increasing conductor temperature by decreasing the effective length of conductor in the span. 

How SLiM Works:

SLiM is activated by the same temperature changes that cause a transmission line conductor to sag too much. The device is passive, which means there are no motors or electronic controls.  As high temperature increases conductor length and hence its sag, SLiM changes its geometry to decrease line length.  As conductor temperature returns to normal, SLiM returns to its original shape.  It is always ready to respond to the next conductor temperature excursion.  In addition, the conductor always remains within acceptable sag and tension limits. 

Line w/o SLiM

Line with SLiM


SLiM’s Value Proposition

  1. Solves an age-old utility challenge of transmission line sag by a simple, elegant, fail-safe and passive design

    a. More economical than traditional alternatives
    b. Quicker and easier than traditional alternatives

  2. Increase asset utilization by increasing transmission line through-put (payback in < 1-year):  Line re-rating à increase in electricity sales à increase industry’s profits
  3. Increase ability to integrate renewable resources

SLiM Characteristics

SLiM is passive, rugged, strong, fail-safe, virtually maintenance-free and designed to have a very long life.  It is composed of high quality materials and is designed for easy installation (similar to splicing) by linemen using live-line (hot) or dead-line (cold) procedures.  Industry standard connectors are used to attach SLiM to the line.  Its operation is adjustable to match specific line and configuration requirements.  SLiM has no negative effects on line electrical or mechanical performance.

SLiM is presently configured with one basic design that can be custom made to various applications and sizes.  It targets mid-voltage transmission market (69 – 345kV, which eas established based on a market survey that determined majority of sag problems occur on lines operating at 115-230kV).  The SLiM device can be applied to lower voltages without any modifications.  For higher voltages, if such is desired by utilities, SLiM device can still be used once it is modified to address corona.

Some Possible Applications

Many older lines were constructed to 120°F/130°F maximum conductor temperature operation.  However, most these conductors can safely operate at much higher temperature (200°F and above) without degradation thus allowing much higher current to pass through them.  However, uprating such lines may lead to clearance problems due to additional line sag.  SLiM enables operation of such lines at a conductor temperature exceeding 200°F without compromise of line clearances or tensions. This can represent a multi-fold increase of rated line capacity.

A system contingency situation (one or more line out) increases line loading on nearby lines causing some of them to exceed their thermal limits – usually established to maintain conductor-to-ground clearances. The action of SLiM, which mitigates the excess sag caused by high temperature operation, can allow for safe line and system operation during the contingency situation since line capacity is increased by allowing operation beyond conventional thermal limits. This eliminates the need for costly line modification projects.

System planning projects that certain lines will become overloaded as a result of local load growth. In this instance SLiM can delay the need for either a new line or considerable line modifications while the anticipated load materializes.

Line routing or line modifications near airports quite often require structures to be as low-profile as possible. SLiM can be employed in a cost effective fashion to minimize line height for such installations while maintaining required ground clearances.





Site by: ESwebworks.com