ERCOT Update on UFLS Annual Survey with TSP/DSP

September 2014

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• ERCOT coordinated and conducted an annual survey on May 13, 2014 with the TSPs and DSPs to ensure that the required automatic under-frequency load shed circuits were configured to provide the appropriate load relief in an under-frequency event as required by table below from Operating Guides 2.6.1(1) Requirements for Under-Frequency Load Shedding:

Background on UFLS Survey Requirement

Frequency Threshold Load Relief

59.3 Hz 5% of the ERCOT System Load (Total 5%)

58.9 Hz An additional 10% of the ERCOT System Load (Total 15%)

58.5 Hz An additional 10% of the ERCOT System Load (Total 25%)

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Below is a list of dates and activities reflecting the timeline and coordination of this survey:

•04/23/2014 - ERCOT announcement of survey timeline and effort to OWG

•04/10/2014 -  ERCOT email notification sent by Client Services to TSP/DSP Authorized Representatives

•05/13/2014 -  Survey test day

•06/13/2014 -  Survey results due back to ERCOT

•September/October-  Results compiled and being reported to OWG/ROS/TAC

Results of UFLS Survey Requirement

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The results of the requirement were successful and are reflected below:

Execution of UFLS Survey Requirement

Frequency response block Minimum

Requirement Survey

measurement

Block 1 response at 59.3 5% 6.7%

Block 2 response at 58.9  10% 11.3%

Block 3 response at 58.5  10% 11.8%

Total 25% 29.8%

ERCOT Reliability and Compliance contacted several participants to request that the 5%, 10%, 10% breakdown be adhered to, if possible. Some participants met the 25% total but had more load in the 5% or one of the 10% brackets and not quite 10% in the other bracket

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Execution of UFLS Survey Requirement

The survey submitted by the participants indicated that they all could meet the 25% minimum requirement.

Some participants met the cumulative 25% total by having more load in one bracket but not the minimum amount in another bracket. The load was reallocated to different relays to meet this minimal requirement of at least 5%, 10%, 10% in each bracket.