IEEE 1283-2013

The scope of this guide is to describe the effects and impacts of high temperature operation on conductors, connectors, and conductor hardware. The guide will identify operating metrics which constitute elevated temperature operation based on present industry practices and its effects on overhead line components, and it will suggest potential mitigation options to manage or avoid identified adverse impacts.

The purpose of this guide is to provide general recommendations for consideration when evaluating existing overhead transmission lines or designing new overhead transmission lines which will be operated at high temperatures. Although this guide is intended for overhead transmission lines, most of the discussion will also be applicable to distribution lines. Recently within the industry a number of new and novel conductors have been designed using non-traditional materials specifically designed for high temperature operation. The collection of new and novel conductors is identified in the industry as high temperature low sag (HTLS) conductors. These new conductors are typically formulated with either standard aluminum strands, fully annealed aluminum or aluminum alloys which resist annealing at 200 °C or greater, exotic core materials which result in minimal sag changes with increasing conductor temperature, and extremely robust connectors. While the general concepts and cautions presented in this guide are appropriate for broad considerations when designing with the HTLS conductors, this guide does not specifically address the HTLS conductors as they are supported with other documents. Rathere, this guide is limited to conventional conductors and connectors typically formulated with cold worked aluminum or copper with reinforcement achieved using steel galvanized or steel aluminum clad core strands. One notable exception is steel supported aluminum conductors (SSAC) developed in the late 1970s (Reynolds Metal) utilizing a galvanized steel core or aluminum-clad steel core and fully annealed aluminum strands. Modern versions of the SSAC conductor are referenced as aluminum conductors steel supported (ACSS) and typically carry a steel core of either misch metal or aluminum-clad steel core and fully annealed aluminum strands. The trend in most utilities today is to increase the capacity of their transmission lines wherever practical. It has become increasingly difficult to build new lines because of increased costs to obtain rights-of-way, public intervention, and state licensing requirements. These obstacles have significantly increased the cost and lead times required to place new lines into service. The lost revenue opportunities from power purchase/sale agreements with other systems because of limited transmission facilities can be substantial. Therefore, utilities are attempting to find as much capacity as is practical from the addition of new high capacity lines or modifying existing lines for operation at higher temperatures than the existing facilities.

Revision Standard - Inactive-Reserved. Possible adverse impacts to an operating overhead transmission line which might occur when operating the line at high temperatures are discussed. Specifically, the transmission line's conductor, connectors, and attached accessories in terms of degradation in mechanical properties due to annealing elastic and in-elastic elongation, and accelerated aging are explored along with limited mitigation recommendations. Additionally, predictor equations for accelerated creep and conductor loss of strength are detailed in annexes with limited example calculations.