enhanced multiple element contingency screening and ... · •generator low voltage (0.9 pu)...
TRANSCRIPT
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Enhanced Multiple Element Contingency Screening and Cascading
Analysis for NERC Compliance
Chengyue Guo
Chuck Lawrence
MIPSYCON
November 5th , 2014
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ATC - Who we are
• Founded in 2001
• Multi-state transmission-only utility
• Over 9,500 miles of transmission line and 530 substations
• Voltages from 69 kV to 345 kV
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Business Triggers
• Improve compliance support documentation
• Enhance ATC cascading methodology
• Simulate a larger number of multiple element contingencies
• Automate post-processing of simulation results
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Total Load At Risk
• Consequential load loss (NERC term)
• Subsequent cascading load loss
• Expected load shed
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• Used to classify “More Severe” contingencies
• Used to better define when NERC Cascading may occur (cascading versus Cascading)
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Total Load At Risk
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ATC Enhanced Cascading Tripping Criteria
• Overhead conductor loading
– 345kV (110%)
– 115kV ,138kV, 161kV, 230kV (105%)
– 69kV (100%)
• Transformer loading (30 min)
• Underground/Submarine cable loading (125%)
• Generator low voltage (0.9 pu)
• Load low voltage (0.8 pu)
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Study Methodology
Steady-state screening analysis – Screening analysis without mitigation
(Stage 1)
– Screening analysis with mitigation
(Stage 2)
Steady-state cascading analysis – (Stage 3)
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Screening Analysis – Stage 1
Identifies contingencies:
• Potential Voltage Instability
–> Stage 3
• Exceeding system tripping criteria
–> Stage 3
• Exceeding system normal limits
–> Stage 2
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Screening Analysis – Stage 2
Identifies contingencies :
• Exceeding emergency limits, but do not exceed tripping criteria
- Two step mitigation analysis
• Exceeding normal limits, but do not exceed emergency limits
- One step mitigation analysis
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Feasible Mitigations
• Capacitor and inductor switching
• Transformer LTC adjustment
• Phase shifter adjustment
• Generator voltage schedule
• System reconfiguration
• Generation redispatch
• Load curtailment
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Cascading Analysis – Stage 3
•Cascading Tier Analysis o Simulation stop criteria
No more tripping
Number of BES lines tripped threshold exceeded
Total load at Risk threshold exceeded
Unmitigated voltage instability
•Post Cascading Mitigation Analysis
o Same as Stage 2 process
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Working with V&R
• Screening and Cascading Analysis scripts
o POM/OPM
o Microsoft® VB.NET
o Tailored to ATC’s process
o Easy to use with different input options
o Results tabulated in spreadsheets
o Adaptable to various compliance studies
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Typical Running Time
• Screening Analysis - Stage 1 ~250,000 contingencies
~25 hours
• Screening Analysis - Stage 2 ~14,000 contingencies
~10 hours
• Cascading Analysis - Stage 3 ~800 contingencies
~2 hours
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Future Improvements
Add consideration of :
•Circuit terminal equipment tripping criteria
•Generator high voltage tripping criteria
•Special Protection Schemes
•Loadability relay actions
•Element tripping sequence
•Breaker-to-breaker tripping
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• Questions?