PSC: GMD Voltage Criteria Proposal (20220719)

ITC Holdings Feedback on Proposed Voltage Criteria for NERC TPL-007-4 GMD Assessment

ITC appreciates the opportunity MISO has provided for stakeholder feedback in this important effort.  ITC provides the following comments for MISO’s consideration with regards to the Proposed Voltage Criteria for NERC TPL-007-4 GMD Assessment:

In reviewing MISO’s proposed criteria, ITC has identified an area of concern with the proposed Emergency Voltage parameters MISO has proposed when utilized exclusively with only monitoring voltages at 200 kV and above.  ITC believes that for an entity to see a true picture of how the system is responding to a GMD event, MISO should be monitoring facility voltages at 100 kV and above and providing this information to the TPs.  The TPs will then have a better understanding of how widespread potential issues are from a GMD event.  Providing only information at 200 kV and above, which means receiving information at 345 kV only for many systems, will not provide much granularity to TP.  TP may also need to adjust the criteria being proposed by MISO to identify if they will be getting the feedback they need to identify low voltages for loads in their respective areas thus causing a voltage collapse.

In order to be responsive to MISO, ITC also requests that MISO identify at its earliest convenience, its deadline for TP’s who might elect to modify their LPC to include Voltage Criteria for NERC TPL-007.

Muscatine Power and Water has reviewed MISO's GMD Voltage Criteria Proposal dated 07-19-2022.

We certainly appreciate the importance of understanding the impact of geomagnetic disturbances and their variations in the geomagnetic field upon power systems.

MPW would be very interested in the incidence/frequency rates and predicted intensities of these events. I think this would be potentially covered by the GMD Vulnerability Assessment.

As a Transmission Owner (TO), the provided steady state (+/- 5%) and emergency (+/- 10%) voltage thresholds are reasonable - I note they are applicable to monitored facilities 200 KV and above and for those facilities where LPC is absent.

MPW does not have 200 kV+ facilities and also provides our LPC, and would prefer to use our LPC in this assessment.

On Page 8,  for the note where MISO expects TPs to determine when voltage collapses in their system - is this GMD specific or related to contingency analysis?

Thank you very much,

Greg Slonka

Muscatine Power and Water

Feedback TPL-007-4 GMD Voltage Criteria Proposal.

Comment 1

General – there is a huge gap between Operating and Planning Standards addressing GMD events.    Standard EOP-010-1 — Geomagnetic Disturbance Operations has no requirement to perform assessment studies.   TPL-007-4 requires the assessment of a static field peak strength for both benchmark and supplemental assessment.      The Benchmark event is a 32-hour event with many oscillations between near peak levels in both the positive and negative directions.   Even though the direction changes, the extra reactive loss from the Geomagnetic Induced Current (GIC) in transformers is always positive.  When the field transitions from positive to a negative or vice versa, it transitions through zero, thus no GIC in transformers, no extra reactive loss and voltage returns to normal.   There are several of these transitions in the benchmark waveform and several that transition period less than 5 minutes.   Any actions to mitigate the GMD effects must be evaluated through these transitions to determine actions can be repeated throughout the GMD event without voltage collapse, see comments below.

Comment 2

Slide 8 - It is unclear when the emergency voltage limits are applied in the R4 and R8 assessments.   These assessments have two parts; Part 1 assessing the impact of the GMD event itself and Part 2 with the GMD field applied the impact of loss of BES elements from harmonics.

Clarity is needed on the limit applicability.   One view is normal limits to be used for Part 1 and Emergency limits for Part 2.   Another view using Emergency limits for part 1 and voltage collapse and cascading for Part 2.    This needs to clearly identified.

Comment 3

Slide 8 – there needs to be voltage change criteria.  This voltage change criteria needs to be associated with capacitor operation to avoid overvoltage tripping of capacitors.  Majority of BES capacitors have discharge timers that prevent a capacitor returning to service before any trapped charge can be discharged.   This timer is normally 5 minutes.

The scenario that the voltage change criteria needs to address is where capacitors are used to maintain the voltage limit and with the field transition through zero, the capacitors trip due to high voltage.  If this happen the capacitors will not be available to arrest the voltage reduction from the next near-peak condition.

Terry Volkmann, Volkmann Consulting on behalf of Glencoe Light and Power

Comments are based on experience in conducting GMD studies on the BES systems in Wisconsin and Maine.   Also experience gained from participating the Geomagnetic Disturbance Task Force (GMDTF) that lead to the basis of the TPL-007 standard.