respect to the transmission system. Policies regarding T&D systems are varied and imposed by many entities; there is significant public resistance to siting new transmission lines; and the business cases for utilities to invest in modern grid processes and technologies are often incomplete, as societal costs and benefits are not typically internalized in companies’ decision making. For example, the cost of not having power when it is needed is far greater to the user than the lost revenues to the utility that cannot provide it. Recognizing the value of a reliable, efficient, and flexible grid, and supporting the investments to make that possible, may require a national-level strategy.

As discussed below in this chapter, expanding and modernizing distribution systems will require considerably more investment than for transmission systems. Much of the expansion will be noncontroversial because it will be required to meet growing loads and can be done without much impact on people who do not directly benefit from it. In addition, modernization of distribution can be achieved on a more limited basis than for transmission, which will require coordination across many systems. Therefore, the emphasis in this chapter will be on transmission.


A modern T&D system should have capabilities beyond the reach of current systems through their incorporation of new technologies (hardware and software). They must also be expanded to meet future needs. New technologies such as power electronics, real-time thermal rating of transmission lines, and composite conductors can allow an increase in power flow on the existing T&D system, but new lines also will be needed.

Modern T&D systems are intended to provide effective operation, asset optimization, and systems planning capabilities under routine conditions and emergency response and fast restoration after a system failure. The characteristics required to achieve these performance standards are as follows:10


Adapted from characteristics defined by the National Energy Technology Laboratory (NETL, 2007c,d) and discussed in more detail in the annex.

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