Real Time Contingency Analysis Practice at the Ontario Grid

Control Centre

Yinhua Guo Jeff Penrice Vivian Cheuk

Ontario Grid Control Centre

Hydro One

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Hydro One Power System

• Major Transmission Company in Ontario

– 97% of Ontario transmission network, 29,000km high voltage circuits

– Interconnect with New York, Michigan, Minnesota, Manitoba, and Quebec (asynchronous)

• Largest Distribution Utility in Ontario

– 123,000km low voltage distribution network

– Serving 1.3 million rural customers

– Extensive distributed generation (wind & solar)

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Courtesy of WorldAtlas

Hydro One Real Time CA Sequence

• State Estimation (SE): every 30sec.

• Thermal Limit Calculation: limited time ratings

• SPS Basecase: arming status, tripped modules

• Contingency Analysis (CA): every 3min

– Contingency case redefinition (over 4100 ctgs)

– Extensive SPS simulation

– Contingency case screening (down to ~50 ctgs)

– Full processing for selected ctgs

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CA Redefinition

• Dynamically Expand CA Outages at CB Level

• Simulating Protective Relay Actions

– Interlock bypass switches considered

• Transfer Trip for LEO Protection

• SPS Remedial Actions Incorporated

• Cascading Outages: iterative simulations for interactions among SPS, LEO, overload, 59/27 voltage relays

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CA Redefinition

- Example of interlock bypassing & cascading

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SPS in Ontario Power System

• Rely Heavily on Special Protection Systems

– Stability concern, thermal limit, voltage violation

– ~400 modules, ~600 signals, ~3600 control actions

• SPS Remedial Action Examples

– Generation/load rejection

– Generation/HVDC runback

– Breaker (group) trip/close

– Equipment (group) rejection

– Capacitor/reactor switching

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SPS Simulation in CA

• SPS Contingency Detection Logic

– Status/topology based

– Analog value based

– Protective relay trip signals

• Arming and Conditional Arming

– Selection and blocking switches

– Trip supervision (voltage, status)

– Staged tripping

– Arming from OGCC and from IESO

– Selection from plant/station

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Transformer 2pu Protection

– Over current based: I > 2*I_rated

– Staged tripping of loads in 4.5”, 7.5”, 9.5”

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Line Backup Protection

– Not the classic zone 3 remote backup relay

– Loss of transfer trip communication on DESN

– Transformer back feeding

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CA Limits & Monitoring

• CA Branch Limit Violations

– Transformer/overhead line/cable thermal limits calculation in real time: IEEE standard based and expanded

– 15min or 2hr LTR used for CA monitoring

• CA Voltage Violations

• Transformer Back-feeding Condition

• CA Causing Islands

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Control Action Cancellation

• Manual Control Actions Developed

– Control action type CTG pre-defined for target CTG: with control actions reverted

– Enabled when target CTG cause violation

– Cancel control action when violations disappear for control action type CTG

• SPS Arming/Disarming Decision

– Target CTG cause violations -> arm SPS

– Control action type CTG with SPS disabled, when no more violations -> disarm SPS

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Detailed CA Post Flow

• CA Post Contingency Detailed Solution

– CA reports ctg violations/warnings only

– Postflow shows full CA solution for specified ctg

– Results shown on both tabular and one-lines

– Run in STNET, access from RTCA, STNET, STCA

• Different from Applying Ctg to Basecase

– Monitored limits: norm vs. emer, cont. vs. 15min

– Post ctg protective relay and SPS actions

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CA Solution Validation

• Verification of CA Solutions

– SE solution against SCADA measured values

– CA solution against SE/power flow solution

– Pre-outage CA solution against post-outage system state (real time or DTS Replay)

• CA Case Coverage

– Missing CA case definition? => monthly check

– Screen masking? =>periodical comparison of CA results with/without screening (off-line)

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CA Setup & Maintenance

• Solution Algorithms & Options

– Full Newton method (auto-enable)

– Fast Decoupled (default)

– MW only solution

– Separate control options for base and ctg cases

• Tuning & Trouble Shooting

– Model & solution must match system response

– Application parameters tuning

– Identifying ctg case causing crashing

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Performance Monitoring

• CA Solution Quality and Availability

– Invalid basecase

– Solution with extreme voltage (too high/low)

– Unsolved contingency cases

– Run every 3 minutes

• Monitoring Procedures and Tools

– Shift control engineer/officer (7x24), issuing tickets

– Application staff, 2nd level support

– Watchdog application, running in real time

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Questions?

Thank You !

contact: Yinhua.Guo@HydroOne.com

Ontario Grid Control Centre

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