It can be easy to forget that there were no mandatory NERC reliability standards for anyone in the North American electric utility industry prior to June of 2007. There were policies, guidelines, and good utility practices, but no enforceable standards. The August 14, 2003 blackout resulted in the 2005 Energy Policy Act that, for the first time, authorized mandatory reliability standards in the United States (and the Canadian Provinces provided similar authorization). FERC certified NERC as the Electric Reliability Organization (ERO) in 2006 and approved 83 NERC Reliability Standards in March 2007, the first set of legally enforceable standards for the North American bulk power grid. Today there are 114 enforceable standards, but they are constantly being refined and extended.
Standards compliance is now a major consideration in the design and operation of all power plants, especially wind and solar. Compliance is especially difficult because the NERC standards are still developing, both because renewable generation technologies are still evolving and because the NERC standards themselves are also evolving. This gives some reason to hope that standards and compliance issues will get clearer in the future, but things will likely remain in flux for the next few years.
Wind and solar generation technologies are also maturing, as is the utility industry understanding of these technologies. In the 1980s, utilities required wind turbines to immediately trip if power system voltage or frequency deviated from the norm, so the unfamiliar technology would not make stressed conditions worse. As wind penetration increased, the industry realized that tripping additional generation during a disturbance might not always be a good idea. Interestingly, FERC’s solution was Order 661 (2005) which requires wind plants, and only wind plants, to ride through faults. So far, NERC has not imposed mandatory ride-through requirements on conventional generators.
While the basic concepts for improving reliability are evolving with a reasonable degree of consensus, the detailed implementations are more problematic. The definition of the Bulk Electric System (BES) provides a good example. The concept is straightforward; we agree that the BES should include all of the significant transmission and generation facilities, but it does not include the distribution system. Specific details get more difficult. Conventional generators greater than 20 MVA and plants greater than 75 MVA interconnected at 100 kV or above are included from the generator terminals through the step-up transformer. This is fairly straightforward for conventional generator technologies.
The BES definition for more dispersed energy resources composed of many smaller generation units (like wind and solar power plants) is more problematic. The 100 kV and 75 MVA limits are the same, but the applicability to equipment within the plant is not so clear. The generators themselves are included, as is the collector system, but only from the point at which generation aggregates to 75 MVA or greater. So there appears to be a hole in the defined BES between the generators themselves and the point where the collector system aggregates 75 MVA. Do NERC standards apply to the equipment between these points? Exactly what equipment does PRC-005 (the “Protection System Maintenance and Testing” standard) apply to?
A tax analogy may be helpful. In some ways mandatory compliance is similar to the shift in the focus between a discussion of tax policy with your congressman versus being audited by the IRS. Both are important. The former can result in fundamental changes in tax law. But the latter can result in fines and jail time. Both are important, but they are very different. In drafting NERC standards or setting policy, we care about intentions and goals. Will this requirement improve reliability? Is the added expense justified by the increased societal benefit? When complying with standards, we care about exactly how the auditor interprets each specific requirement. Unfortunately, in the immediate sense, record keeping may seem to become more important than reliability, but that is the nature of mandatory compliance.
New standards of potential concern for wind and solar plant owners and operators include:
- FAC-008-3: Facility Ratings
- MOD-025-2: Verification and Data Reporting of Generator Real and Reactive Power Capability and Synchronous Condenser Reactive Power Capability
- MOD-026-1: Verification of Models and Data for Generator Excitation Control System or Plant Volt/Var Control Functions
- PRC-019-2: Coordination of Generating Unit or Plant Capabilities, Voltage
- PRC-024-2: Generator Frequency and Voltage Protective Relay Settings
- PRC-025-1: Generator Relay Loadability
Cyber security is a major concern throughout the electric utility industry and standards requirements are in flux. The physically dispersed nature of wind and solar plants can complicate standards compliance. FERC’s January 2016 Order 822 approved revisions to seven critical infrastructure protection (CIP) standards:
- CIP-004-6: Personnel and Training
- CIP-006-6: Physical Security of BES Cyber Systems
- CIP-007-6: Systems Security Management
- CIP-009-6: Recovery Plans for BES Cyber Systems
- CIP-010-2: Configuration Change Management and Vulnerability Assessments
- CIP-011-2: Information Protection
Order 822 also directed NERC to address protection of transient electronic devices used at low impact Bulk Electric System cyber systems, protection of communication links and sensitive bulk electric system data communicated between Bulk Electric System Control Centers, and refinement of the definition for Low Impact External Routable Connectivity (LERC). NERC also intends to address cyber asset and BES Cyber asset definitions, network and externally accessible devices, transmission owner (TO) control centers performing transmission operator (TOP) obligations, and virtualization. All of these issues have the potential to change compliance requirements for wind and solar plants.
There is help. UVIG’s Wind Turbine Operations & Maintenance User Group is increasing coordination with the North American Generation Forum’s Dispersed Generation Resources Working Group (NAGF DGR). DGR’s mission is to “share information and best practices on how to implement new and existing NERC Reliability Standards.” Information flows both ways with the DGR. Plant owners and operators discuss standards requirements and successful methods for meeting requirements, but they also identify flaws in the standards themselves and pass these on to NREC for correction and improvement.
NERC’s Generating Availability Data System (GADS) is imposing new data collection requirements on renewable generators. NERC registered entities of 75 MW or greater, commissioned after 2004, must report plant data, group data, sub-group data, and performance data. Component data is optional. Voluntary reporting will be allowed in 2017 with mandatory reporting phased in over the following three years.
We should expect increasing standards requirements in the future. Ride-through requirements may evolve into “grid-support-capability” requirements, especially for frequency. NERC’s Essential Reliability Services Working Group (ERSWG) is working on clearer, technology-neutral definitions of fast frequency response metrics and requirements for the power system. ERCOT already recognizes the ability of demand response to provide very fast frequency response to replace conventional generation governor response and inertia. Some new storage technologies can also operate in this fast time frame, as can synthetic inertia from wind and fast response from PV. Careful attention to stability analysis, and equally careful drafting of standards, can result in increased power system reliability while allowing the power grid to operate efficiently and incorporate new technologies.
Brendan Kirby with thanks to Darnez Gresham and Terry Harbour of MidAmerican Energy Company.