TRC

Regulatory Update   |   Feb 24th, 2017 NERC Standard Governing Remedial Actions Schemes Poised for Approval

Transmission20 Lines 001 Jpg Feb2017

On January 19, 2017 FERC issued a Notice of Proposed Rulemaking (NOPR) to approve NERC’s PRC-012-2 reliability standard governing Remedial Action Schemes (RAS)1.

PRC-012-2 significantly changes how Remedial Actions Schemes will have to be managed. The standard streamlines and consolidates existing requirements; corrects the applicability of previously unapproved Reliability Standards and implements a uniform continent-wide RAS review program. It also modifies the obligations of generators and transmission utilities that are responsible for Remedial Action Schemes.  

While the proposal is to approve PRC-012-2, FERC also is seeking industry comments regarding the standard as it relates to “limited impact” RAS. Based on comments and information received, FERC says it may issue directives to modify the standard as appropriate in its final order.

Background

RAS2 are designed to detect predetermined system conditions and take automatic corrective actions to protect the reliability and integrity of the Bulk Electric System (BES). The PRC-012-2 standard aims to ensure that RAS do not introduce unintentional or unacceptable reliability risks.

NERC’s revised RAS/SPS-related standards address: 

  • Planning, coordination, and design of RAS; 
  • Review, assessment, and documentation for RAS;  
  • Analysis of RAS operation(s), consequences of failure(s) to operate; 
  • Requirements for corrective actions if RAS failures occur; and 
  • Testing of RAS and the maintenance of any non-protection system components used. 

Limited Impact RAS

The concept of a “limited impact” RAS is a key new feature contained in PRC-012-2.  According to NERC, a limited impact RAS cannot, by inadvertent operation or failure to operate, cause or contribute to BES cascading, uncontrolled separation, angular instability, voltage instability, voltage collapse, or unacceptably damped oscillations. Limited impact RAS are not subject to the RAS single component malfunction and failure tests of Parts 4.1.4 and 4.1.5 of PRC-012-23.

Requiring a limited impact RAS to meet these tests would add complexity to the design with minimal benefit to reliability. The addition of this concept will facilitate the efficient transition to the PRC-012-2 standard and allow regions which had multiple types and levels of sophistication within their existing special protection system programs to be better classified under the new PRC-012-2 scheme. A review of each special protection system will need to be undertaken to arrive at a conclusion as to whether it qualifies as a RAS, or limited impact RAS. 

FERC Seeks More Information

FERC has invited comment on NERC’s proposal to clarify that the proposed PRC-012-2 will not modify or supersede any system performance obligations under Reliability Standard TPL-001-4. FERC also seeks comment on the processes used to ensure the WECC Local Area Protection Schemes (LAPS) or NPCC Type III RAS will be compliant with TPL-001-4 prior to the effective date of PRC-012-2. FERC is also interested in comments on the potential interactions between the PRC-012-2 standard and the TPL-001-4 regarding whether load disconnected by a RAS installation is considered consequential or nonconsequential load. If such load is non-consequential and the load loss is 75 MW or greater this may bring into play certain provisions of the TPL-001-4 standard. Finally, FERC wants to hear from industry on whether the term “limited impact RAS” should be defined in the Glossary of Terms Used in NERC Reliability Standards.

How to Prepare

While the NOPR process runs its course, utilities which have SPS or RAS as part of their systems should begin their preparations by conducting a planning and engineering review of their designs. Functional performance verification and type classification will be required to determine the extent of changes to internal processes and procedures which may be required to meet the new standard in a way consistent with TPL-001-4. Protection engineering resources and experience will be needed to support assessment and compliance mitigation planning. Planning studies will also be required under the requirements of the NERC TPL-001-4 standard. TRC can provide independent review of functionality and classification in support of RAS compliance obligations in preparation for the required review by both a Planning Coordinator and Reliability Coordinator called for in the PRC-012-2 Standard.  

Resources

1TRC’s March 2016 Regulatory Update provides background on the development of the standard. In its NOPR, FERC has now proposed to approve that standard.

2A scheme designed to detect predetermined system conditions and automatically take corrective actions that may include, but are not limited to, adjusting or tripping generation (MW and Mvar), tripping load, or reconfiguring a System(s). RAS help:

  • Meet requirements identified in the NERC Reliability Standards;
  • Maintain Bulk Electric System (BES) stability; 
  • Maintain acceptable BES voltages; 
  • Maintain acceptable BES power flows; 
  • Limit the impact of Cascading or extreme events.

3Prior to development of PRC-012-2, the Northeast Power Coordinating Council (NPCC) and the Western Electric Coordinating Council (WECC), used individual classification regimes to identify RAS that would meet criteria similar to those described as “limited impact.” NERC in its petition stated that the standard drafting team identified the Local Area Protection Scheme (LAPS) classification in WECC and the Type III classification in NPCC as consistent with the “limited impact” designation.

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