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David Thorne

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Pepco Holdings Inc.

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Carl Kinsley

1) Subsequent to a review performed by NERC staff, the SDT has reformatted and modified certain requirements of the draft PRC-006-RFC-01 standard. Do you agree with the reformatted structure and modified requirements of the standard?

No

1) If not, please provide specific suggestions.

1)  From a Transmission Owner and Distribution Provider point of view, restricting UFLS program parameters to ranges that are consistent with RFC Legacy Region programs is both desirable and expeditious.  It makes implementation much simpler.   
However, NERC PRC-006-1 (R3) requires the Planning Coordinator to develop a UFLS program that meets very specific performance characteristics.  Simulations must be performed to demonstrate that the program is effective in maintaining frequency within the Under / Over frequency Performance Characteristic curves in PRC-006-1 Attachment 1, and that specific Volts per Hz performance criteria is not exceeded.  Until the Planning Coordinator has completed a NERC PRC-006-01 adequacy assessment of these legacy UFLS programs one cannot be assured that a UFLS program designed within the parameters identified by PRC-006-RFC-01 (R1 and R2) will be adequate to satisfy the newly established NERC frequency stabilization performance criteria in NERC PRC-006-1 (R3).  This could pose a potential conflict for the Planning Coordinator in trying to design a UFLS program that satisfies both sets of requirements.  As such, it is the Planning Coordinator who ultimately must determine if restricting the UFLS program parameters to legacy ranges is acceptable.
2)  Additionally, Sec 1.2.4 sets an arbitrary and non technically justified limitation on the frequency sets points (steps) of between .2 and .4hz.  This limitation is not consistent with the legacy programs.  Not only may this create limitations to the PC as described in #1 above, but will also result in companies having to reset over 50% of the UF relays.  The legacy MAAC criteria (B8, Sec 3.1) B allows load to be shed in .1hz steps as long as 10% is shed by 59.9hz and 58.5hz. That is how PHI and possibly others have implemented.   The requirement can be reworded such that the PC can take the existing steps into account in the studies.  There is no need to set artificial limits that have no technical merit.  If the requirement does not allow flexibility, additional time will be needed to implement, since a large number of relays will have to be reset.
2.   R3 through R7 add specificity and scope to the NERC PRC-006-1 standard requirements pertaining to identification and mitigation of islands as noted below.  Do you agree with the added specificity and scope pertaining to how islands are identified and addressed?  If not, please provide specific suggestions.

2) R3 through R7 add specificity and scope to the NERC PRC-006-1 standard requirements pertaining to identification and mitigation of islands as noted below.   


a. The Planning Coordinator needs to include additional items in their island identification criteria (R3).


b. The Planning Coordinator shall supply their island identification criteria (R4) and respond (R5) to any comments received on the island identification criteria from affected entities.


c. The Planning Coordinator shall identify and document islands by: applying the island identification criteria at least every 60 months (R6), supplying the results of applying the island identification criteria to affected entities (R6, Part 6.1), inviting, in writing, the participation of applicable entities, in the establishment of the mitigation plan (R6, Part 6.2) and establishing a mitigation plan to balance generation and Load and restore frequency in each area of islanding should the area of islanding become separated from the interconnection (R6, Part 6.3).


d. .Affected Distribution Providers, Transmission Owners and Generator Owners shall implement their portion of any mitigation plan (for the island(s)) as determined by the Planning Coordinator (R7).


Do you agree with the added specificity and scope pertaining to how islands are identified and addressed?

Yes

2) If not, please provide specific suggestions.

 

3) R8 and R9 extend the scope of the NERC PRC-006-1 standard to apply to Generator Owners’ underfrequency trip characteristics in planning UFLS programs as noted below. 

  
a. The premature tripping of a generating unit may have a very negative effect on the Bulk Electric System during a frequency excursion, and thus it is important to include a Generator Owner requirement within a standard dealing with UFLS. Generator Owners are required to either: 1) Set underfrequency protection in accordance with PRC-006-RFC-01 Attachment 1 (Time vs. Frequency curve) for generators that have automatic underfrequency protection installed, 2) establish and follow procedures for underfrequency operation in accordance with PRC-006-RFC-01 Attachment 1, for generators that do not have automatic underfrequency protection installed, or 3) arrange for Load shedding to be installed by mutual agreement with Distribution Providers, in addition to that required by the Planning Coordinator in Requirement R1 or Requirement R2, for generators that cannot meet the specifications in PRC-006-RFC-01 Attachment 1. (R8) (Note: the Time vs. Frequency curve in Attachment 1 is consistent with the curves in the NERC PRC-006-1 and draft PRC-024-1 standards (R11)).


b. Generator Owners (which are required to comply with R8) are required to supply underfrequency trip setting data to populate the Planning Coordinator’s UFLS data base (R9).  It is important for the Planning Coordinators to have such generator data in order to perform an accurate UFLS assessment (R10).  (This requirement may be removed once the NERC PRC-024-1 standard is completed and approved.)


Do you agree with the extended scope to include Generator Owners?

Yes

3) If not, please provide specific suggestions.

 

4) R10 and R11 extend the scope of NERC PRC-006-1 standard by including requirements to assess UFLS program implementation (in addition to UFLS program design required in the NERC PRC-006-1 standard) as noted below. 

  
a. The Planning Coordinator is to perform, document and make available an assessment of the effectiveness of the “implementation” of the UFLS programs.  The NERC PRC-006-1 standard only requires an assessment of the “design” of the UFLS programs.  This assessment will assess the effectiveness of the implemented UFLS programs using the information contained in the Planning Coordinator’s database which, while satisfying the design requirements, may exceed the design specifications (R10).


b. Applicable Distribution Providers, Transmission Owners and Generator Owners are to complete any required changes to the implementation of the UFLS program based on any implementation deficiencies noted in the Planning Coordinator’s assessment.  The NERC PRC-006-1 standard only requires the applicable entities to provide automatic tripping of Load in accordance with the UFLS program design and does not account for any changes which may be found necessary based on the Planning Coordinator’s assessment of implementation.  Such changes may be necessary for the overall effectiveness of the UFLS program when arresting frequency excursions.  The three calendar year completion interval was chosen to give applicable entities a reasonable amount of time for making changes in the field (R11).


Do you agree with the need to assess UFLS program implementation as well as design?

Yes

4) If not, please provide specific suggestions.

However, we believe “implementation” of the UFLS program by UFLS entities is already addressed in NERC PRC-006-01.  Requirement R9 states: “Each UFLS entity shall provide automatic tripping of Load in accordance with the UFLS program design and schedule for application determined by its Planning Coordinator…”.   
Per NERC PRC-006-01 Requirement R4, the Planning Coordinator must conduct an assessment to determine if the program meets the performance characteristics in Requirement R3 for each island identified in Requirement R2.  If it doesn’t then the program design needs to be revised, otherwise Requirement R3 would be violated.   
The phrase “schedule for application” in Requirement R9 requires the entity to make whatever UFLS program changes are dictated by the Planning Coordinator by the scheduled date set by the Planning Coordinator.  The three year completion interval proposed by Requirement R11 in the RFC standard may be appropriate and desirable; however, in its present form it does not appear to relieve the entity from meeting the “schedule for application” as established by the Planning Coordinator.

5) The Standard Drafting Team believes the standard is ready for Category Ballot. Do you agree?

No

5) If not, please provide specific suggestions that would make it acceptable to you.

Requirements R1.4 and R2.3 should be re-written to state “Set undervoltage inhibit, when enabled, no greater than 75 percent of nominal primary voltage.”  The phrase “as low as practical” should be removed.  This term is much too subjective to be used in an auditable standard.  What evidence / criteria would be required to demonstrate that the setting was “as low as practical”?  Besides, the “bright line” 75% voltage threshold itself is more than sufficient to ensure dependable operation during any recoverable system disturbances.   PRC-023 only requires transmission line relay loadability criteria be maintained for system voltages down to 85% on nominal. 
Also, see comments on Question 1.

Created at 9/7/2012 10:09 AM by System Account
Last modified at 9/7/2012 10:09 AM by System Account