The North American Electric Reliability Corp. (NERC) must be given flexibility for any revisions made to an existing reliability standard to address reliability concerns related to transmission system planning for extreme heat and cold weather events impacting the reliable operations of the bulk electric system, the American Public Power Association (APPA) and several other trade groups said in recent comments submitted to the Federal Energy Regulatory Commission (FERC).
The Aug. 26 comments were filed in response to a pending FERC notice of proposed rulemaking (NOPR) proposing to direct NERC to revise mandatory reliability standard TPL-001-5.1 (Transmission System Planning Performance Requirements) to address reliability concerns related to transmission planning for extreme heat and cold weather events.
APPA was joined in the comments by the Edison Electric Institute, Large Public Power Council, National Rural Electric Cooperative Association, and Transmission Access Policy Study Group.
While the groups support addressing the planning for extreme heat and cold weather events in NERC reliability standards, “the variation in extreme weather events between regions and the highly varied system topologies of registered entities call for the Commission to vest NERC and the standard drafting team with flexibility in determining how to address the issues identified by the Commission, including potential corrective actions,” APPA and the others said.
The groups noted that they share the Commission’s desire to better address and respond to extreme heat and cold weather events and therefore support efforts to improve system planning specifically for these extreme heat and cold weather events.
“The manner and process required to achieve these goals is complex, requiring flexibility and multiple tools, if this effort is to be fully effective,” they said.
APPA and the other groups said that the purpose of the TPL standard is to establish transmission system planning performance requirements over a broad spectrum of system conditions, including extreme events, based upon operating experience that may result in wide-area disturbances and following a wide range of probable contingencies.
“Including extreme heat and cold weather as described by the Commission potentially could require adding numerous elements and specifics to a planning analysis,” they told FERC.
Given the wide set of issues and corresponding circumstances that a new or modified standard must entail, the groups recommended that the Commission “defer to the technical competence of the subject matter experts on a standard drafting team in order to develop a risk-based approach to the myriad issues raised in the NOPR.”
The groups also said that addressing challenges to electric system reliability posed by extreme heat and cold weather should be informed by the highly varied nature of risks and potential consequences to the electric system posed by these events.
“Different parts of the country face different risks, in terms of both type and severity of weather events. The risks faced by, and appropriate measures for, an entity in Florida may look very different from those of an entity in Texas, Wisconsin, or California; the risks may, moreover, change over time,” APPA and the other groups pointed out.
“Entities also vary in terms of the scope of their facilities. For example, some NERC-registered transmission owners own only one or two bulk electric system transmission lines, while others own extensive transmission systems covering a wide range of varying topography. The flexible approach proposed by the NOPR is thus imperative to help ensure that threats are assessed accurately and that selected corrective actions are suited to the region, system topography, and affected entities.”
Further emphasizing the need for flexibility in the approach to new or modified standards, many of the associations’ members currently assess risk to their systems due to extreme heat and cold weather effects in varying ways.
“Some already have developed studies and implemented plans to maintain system performance in light of extreme weather. Electric utilities constantly evaluate and update these risks depending on their particular location and system topology,” the groups said.
Moreover, NERC registered entities have obligations under TPL-001-4 to include events that are expected to produce more severe system impacts on the bulk electric system in planning assessments.
“While NERC develops reliability standards that apply on a continent-wide basis, in some instances a regional variance may be developed if a standard cannot be met or complied with because of a physical difference in the Bulk-Power System or because of an operational difference,” APPA and the other groups said.
In the case of extreme heat and cold weather, “regional differences require some flexibility or customization because systems vary widely in their topology and electrical characteristics, as well as in the weather impacts they face.”
The standard drafting team “should determine the best possible approach for addressing a continent-wide extreme heat and cold weather planning standard that accounts for geographic, system topology, and other variations, as well as the best approach to accommodating such variations or determining if regional variances are necessary.”