Background
While the current Standard Drafting Team (SDT) of Project 2022-02 is
working on the project, a new SAR related to TPL-001-5.1 was approved for
posting by the Standards Committee (SC). The SC asked the current SDT to
include this SAR as part of the project rather than creating a new project. The
new SAR will address Footnote 13d issue in Standard TPL-001-5.1.
Many areas of the North American bulk power system (BPS) continue to experience an increase in BPS-connected inverter-based resources (e.g., wind, solar photovoltaic (PV), battery energy storage systems (BESS), and hybrid power plants). NERC Reliability Standard TPL-001-5.1 is a foundational standard used for “establishing transmission system performance requirements within the planning horizon to develop a bulk electric system (BES) that will operate reliably over a broad spectrum of system conditions and following a wide range of probable contingencies." Transmission Planners (TPs) and Planning Coordinators (PCs) develop and use models of the electrical grid to perform planning assessments (e.g., steady-state, dynamic, and short-circuit) to develop corrective action plans for future reliability issues identified. Ensuring that the TPL-001 standard is reflective of the evolving nature of the BPS and its resource mix is paramount to ensuring reliable operation and resilience of the BPS moving forward.
The NERC Inverter-Based Resource Performance Task Force (IRPTF)[1] undertook a complete review of the NERC Reliability Standards in the context of increasing levels of BPS-connected inverter-based resources and published a white paper on the outcomes and recommendations of this review in March 2020.[2]
Based on the outcome of the review, it was determined that the TPL-001-4/5[3] needed clarifications “to address terminology throughout the standard that is unclear with regards to inverter-based resources" the next time the standard is revised.
Considering current trends, the NERC SPIDERWG undertook a review of the TPL-001 standard considering the potential impact of distributed energy resources (DERs). This review is captured in the following RSTC-approved white paper and serves as the technical justification for the revisions suggested in this SAR:
- SPIDERWG: Assessment of DER impacts on NERC Reliability Standard TPL-001 (here)
This SAR proposes to update TPL-001-5.1 to address some of the issues identified in the white paper.
TPL-001-5.1 does not currently require Planning Coordinators and Transmission Planners to complete Planning Assessments with adequate representation of the dynamic behavior of DERs. As the penetration of DERs increases, and based on the DER data and models available, Planning Assessments should include DERs that can potentially impact Transmission System performance assessment. NERC's “Lesson Learned: Single Phase Fault Precipitates Loss of Generation and Load", evaluating a 2019 frequency event in Southern England exacerbated by the unexpected reduction of 725 MW of IBR output and the unexpected loss of 350 MW of DER, highlights the critical importance of accurate Transmission System Planning Assessments. In July 2020, a significant quantity of solar PV facilities across a large geographic area in Southern CA reduced about 1000 MW output due to a disturbance on the bulk power system. Subsequent event analysis revealed that it was the consequence of momentary cessation and slow recovery of power. Standards enhancement has been one of the recommendations after the event analysis to ensure reliable operation of the bulk power system.
As the penetration of DERs continues to increase across the North American bulk power system (BPS), it is necessary to account for the potential impacts of DERs on reliability in the planning, operation, and design of the BES. The NERC System Planning Impacts of Distributed Energy Resources Working Group (SPIDERWG) has identified the need for improved modeling of aggregate DER for planning studies (including both utility-scale and retail-scale DER) conducted by Transmission Planners (TPs) and Planning Coordinators (PCs). MOD-032-1 addresses the gathering of modeling data to perform planning assessments but the standard currently has no specific reference to DER data. This SAR proposes to update MOD-032-1 to: (1) include “data requirements and reporting procedures"[4] for DER that are necessary to support the development of accurate interconnection-wide models, (2) replace Load-Serving Entity (LSE) with Distribution Provider (DP) because of the removal of LSEs from the NERC registry criteria, and (3) enable the SDT to review any additional gaps in DER data collection with the de-registration of LSE.
Standard(s) Affected: TPL-001-5.1 and MOD-032-1
Purpose/Industry Need
The NERC TPL-001-4 Reliability Standard was revised to TPL-001-5.1 (subject to Enforcement July 1, 2023), which expanded Footnote 13 from specific Protection System relays to include communication systems, station DC supply, and control circuitry. More specifically, Footnote 13.d now applies to control circuitry from the DC supply through and including the circuit breaker trip coil. However, the footnote only provides an exclusion for a single (non-redundant) monitored and reported trip coil, but not the control circuit itself.
By only excluding the trip coil and not permitting the control circuitry to be excluded, it implies that the remainder of the Protection System control circuitry is not excluded, even if it is monitored and reported. For example, it is very common to install trip circuit monitoring which monitors the control circuitry and the trip coil, but the trip coil is the only component that qualifies for the TPL-001-5.1 exclusion.
Modifying the Footnote 13.d exception to apply to any monitored and reported components of the control circuitry to be consistent with Protection System design and operational functionality will allow the DP, GO, and TO to achieve the required transmission performance mandated by TPL-001-5.1 in a much more efficient manner.
The original TPL-001-5 SAR revises requirements within the TPL-001-5 standard to provide clarity and consistency for how BPS-connected inverter-based resources are considered, modeled, and studied in planning assessments. The proposed revisions to TPL-001-5 will ensure industry is effectively and efficiently conducting planning assessments and that the requirements are equally suitable for inverter-based resources as they are for synchronous generation.
The purpose of this SAR is to revise requirements to provide clarity, or in some cases, expand the scope of requirements when considering the performance of DERs to ensure the accuracy of Transmission System Planning Assessments.
This SAR proposes to revise MOD-032-1 to address gaps in data collection for the purposes of modeling aggregate levels of DERs in planning assessments. The goal is to provide clarity and consistency for data collection across PCs and TPs when coordinating with the DP to gather aggregate load and aggregate DER data.
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1 The IRPTF has subsequently become the IRPWG under the NERC Reliability and Security Technical Committee (RSTC).
2 NERC IRPTF, “IRPTF Review of NERC Reliability Standards," March 2020: https://www.nerc.com/comm/PC/InverterBased%20Resource%20Performance%20Task%20Force%20IRPT/Review_of_NERC_Reliability_Standards_White_Paper.pdf
3 At the time of review, the TPL-001-5 standard had just recently been approved by FERC and was yet to be subject to enforcement.
4 See Requirement R1 of MOD-032-1, which requires each TP and PC to develop data requirements and reporting procedures for the collection of modeling data used for the development of models for each PC footprint.
