TPL-007-4 – Transmission System Planned Performance for Geomagnetic Disturbance EventsJuly 2024
On January 1, 2024, North American Electric Reliability Corporation (NERC) Reliability Standard TPL-007- 4, Requirement 7 and Requirement 11 became effective. These were the last two requirements to become effective for this standard.
TPL-007-4 has been a challenging standard from its conception since it requires two Geomagnetic Disturbance (GMD) Vulnerability Assessment studies which have never been performed before. None of Archer’s clients have been audited yet for TPL-007- 4, so there is little evidence as to how auditors will approach this new standard.
Archer has heard that some regional entities are planning to audit this standard within the next year now that all of its requirements are in effect, so we recommend that our clients review their evidence to ensure that they are ready for any upcoming audits.
In recent mock audits, Archer has found that several of its clients were under the impression that no additional studies were required for Requirement 4 and Requirement 8 if no applicable transformers exceeded the current thresholds for Requirement 6 and Requirement 10. This is unfortunately not the case, since R4 and R8 require that GMD Vulnerability Assessment be performed to demonstrate acceptable system performance based on TPL-007-4, Table for the benchmark event (R4) and the supplemental event (R8).
As shown in the flow chart above, the GMD Vulnerability Assessments require AC power flow analysis to:
- Demonstrate the transformer Var losses that will result for the GMD event are modeled in the AC power flow cases to assess the impact on system voltage and to ensure that the voltage criteria identified pursuant to TPL-007-4, Requirement 3 was
- Demonstrate that the events listed in TPL-007-4, Table 1 have been simulated for loss of reactive compensation devices (e.g., Static Var Compensators) other Transmission Facilities (e.g., older electro-mechanical relays) that may trip during the GMD event.
- Demonstrate that voltage collapse, Cascading and uncontrolled islanding did not occur under Peak and Off-peak conditions in the base cases or in any of the contingency cases per TPL-007-4, Table
Archer recommends that its PC and TP clients have documented evidence that the following items were addressed prior to the effective date of each requirement:
- R1 – Role and responsibilities were assigned for the PC, TP, GO and TO entities for all
- R2 – GIC models were established and
- R3 – A voltage criteria was established for acceptable System steady state voltage performance for its System during the GMD events described in Attachment
- R4/R8 – A report that documents that an AC power flow study was performed to simulate contingencies developed in accordance with Table to ensure that the voltage criteria from R3 was met and that no voltage collapse, Cascading or uncontrolled separation was identified for the benchmark or supplemental
- R5/R9 – Distribution of GIC flow evidence to all GO and TO entities regardless of whether the R6/R10 thresholds were
- R6/R10 – If the threshold was exceeded, GO and TO entities must have evidence that a thermal impact assessment was performed for the facilities that exceeded the threshold.
- R7/R11 – If any voltage violations, voltage collapse, Cascading or uncontrolled separation were identified in the GMD Vulnerability Assessment for the benchmark or supplemental event, evidence that Corrective Action Plans were developed in accordance with R7/R11 must be
- R12/R13 – Written procedures must be available and implemented to demonstrate that the required data can be accessed.
The effective date for the requirements for most entities within the United States are as follows:
- October 1, 2020 – R1, R2, R5, R9
- July 1, 2021 – R12, R13
- January 1, 2022 – R6, R10
- January 1, 2023 – R3, R4, R8
- January 1, 2024 – R7, R11
Please feel free to ask Archer to assist you with any of the items above where you may need advice or assistance. We have a team of experts ready to customize your evidence and/or train your team on what is required and empower them to demonstrate compliance themselves.
Please contact Catrina Martin at c.martin@archerint.com or (801) 903-3102.