Download McCamey Area Limits

Current Operational Challenges
• Computing the West –
North Limits
• Potential IROLs
• Local Voltage & Thermal
issue (OOME)
• High Voltage
• Outages
Computing the W-N Limits
• Power Flow Analysis
– Build base case
• Determine next day’s peak hour using load forecast
• Use peak hour load and generation plan
• Include scheduled outages for peak hour
– Must clear any base case violations where Normal Rating ≥
100%.
– Save as STNET case:
x_basecase_mmddyy_initials
Computing the W-N Limits
• West – North thermal SOL
– Increase West – North transfer
• Increasing generation at West and Far West zones
• Scaling load up in the North Central zone and scaling
load down in the West and Far West zones if more
transfer is need
– The sum of the flow on Graham-Parker and
Graham-Benbrook 345 kV DBL Ckt is W-N
thermal SOL
West-North CSC
W
N
W-N Transient Stability Limit
• 6 lines
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345 kV Graham SES – Long Creek Switch
345 kV Graham SES – Bowman Switch
345 kV Graham SES – Tonkawa Switch
345 kV Graham SES – Sweetwater Generation Plant
345 kV Bowman Switch – Jacksboro Switch
345 kV San Angelo Red Creek – Comanche Switch
Number of units on-line at each plant site
Status of Power System Stabilizers
West and Far West plants
Outages
Transient Limit
Several conditions that are controlled by ERCOT operators
W-N Stability Limit
Objectives for SOLs and IROLs
• Know the definitions and the differences
between an SOL and an IROL
• Understand the steps in determining an
IROL.
What is an SOL?
• System Operating Limit (SOL) – The value (such as MW, MVAR,
Amperes, Frequency, or Volts) that satisfies the most limiting of the
prescribed operating criteria for a specified system configuration to
ensure operation within acceptable reliability criteria.
• SOLs are based upon certain operating criteria. These include but
are not limited to:
– Facility Ratings (Applicable pre- and post- Contingency equipment on
facility ratings)
– Transient Stability Limits (Applicable pre- and post- Contingency
Stability Limits)
– Voltage Stability Limits (Applicable pre- and post- Contingency
Voltage Stability)
– System Voltage Limits (Applicable pre- and post- Contingency
Voltage Limits)
What is an IROL?
• Interconnected Reliability Operating Limit (IROL) – System
Operating Limit that, if violated, could lead to instability,
uncontrolled separation, or Cascading Outages that adversely
impact the reliability of the Bulk Electric System.
• IROLs are a subset of SOLs.
• If a limit is violated for more than 30 minutes then we are in
violation of NERC Operating Criteria.
How do you Identify an IROL?
Use the following criteria to disqualify exceeded limits.
– Magnitude and Time over Limit: SOLs which are not exceeded
by 100% of the calculated value, using the emergency rating,
for over 30 continuous minutes are considered controllable and
not IROL violations.
– Double Circuit Contingencies: Post Contingency Overloads as
a result of the outages of multiple elements that are considered
as feasible due to proximity of each other (i.e. shared structure
or right-of-way) and not due to the absence of circuit breakers
between elements.
– System Impact: SOLs exceeded that would not expose a
widespread portion of ERCOT even under worst-case
scenarios. Some contingencies may cause overloads to
equipment that if lost would not credibly result in cascading
outages, instability, or uncontrolled separation.
How do you Identify an IROL?
If an IROL is identified, must report to NERC within 72 hrs of the
event:
– Determine which form(s) needs to be filled out.
• Interconnected Reliability Limit violation non-compliance
report
• NERC Operating Security Limit and Preliminary
Disturbance Report
• DOE Form EIA- 417 Emergency Incident and Disturbance
Report
– Email report to NERC within the appropriate time frame. (If
report cannot be sent within the time frame, call NERC and/or
DOE and report a brief summary. Then fill out report and send
in As Soon As Possible).
Active Constraints vs.
Congestion Management
• Challenges with current Market Operator Interface
(MOI) Congestion Management tools
– Monitor Actual Zonal Flows vs. calculated CSC Limits
– MOI Utilizes Calculated Flows
• Operator must enter new projected constraint limit in MOI prior
to the execution of the Real Time Balancing Market (RTB)
– Entered into the MOI 30 – 40 minutes before the interval
is completed
– Monitor Real Time Contingency Analysis (RTCA)
– Must not violate NERC Operating Criteria
MOI Constraint Management
Wind QSE Low & High
Frequency Excursions
High Voltage
High Voltage
Zonal Transfers
W
N
S
Outages affecting Wind
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345 kV Graham SES – Sweetwater Generation Plant
345 kV Graham SES – Long Creek Switch
345 kV Long Creek Switch– Abilene Mulberry Creek
138 kV Putnam – Leon Switch
138 kV Adamsville – Evant
60% due to maintenance to improve reliability during
light load season
• 40% due to W-N transfer
Questions?