1. Power System Restoration Kevin Schneider, Chen-Ching Liu University of Washington Department of Electrical Engineering

2. Overview Voltage, Current, Power Limit Checking Status Data and Analog Measurements All Operating Constraints Satisfied Operating Constraint's) Violated Emergency Control / Load Management Security Assessment System Restoration Loss of Load

3. Restoration Constraints Main power converter startup time Communications start up time Maximum dv/dt Node voltage limits

4. Main Power Converter Startup Time 10-15 second startup delay from when power is applied to the backbone During this time: o Startup supply capacitor charges to 48V o SCRs begin to fire at 45V o Startup power supply energized o Main power converter control circuits energized

5. Communications Startup Time Approximately ½ to 1 minute for the communications system to power up

6. Maximum DV/DT PN junctions in solid state components are sensitive to high values of DV/DT DI/DT will not be a concern for the NEPTUNE systems backbone solid state components

7. Node Voltage Limits If node voltage drops below≈ 5600V the control circuit will drop out and the converter will turn off Voltage cannot exceed certain levels or there could be arc over There will be an acceptable band of operation that must be adhered to

8. Security Analysis

9. Security Analysis Cont. Switching Action- For a restorative action there may be several possible ways to restore the system. Feasibility- A portion of these actions will place the system in insecure configuration for some period of time. Only switch actions which do not violate any constraint can be allowed. Note: a system may meet all 4 constrains but be operating in an insecure condition

10. Contingency Selection Before a switching action is performed the effect of the following must be considered for the new topology  Loss of shore station  Loss of shallow water links or deep water links  Significant load increase  Node failures  Others

11. Black Start Example Only the shore stations have power After a node is fully energized, 4 kW of scientific load is applied to that node

12. Victoria Nedonna Beach System Start-up From Black Start Ensuring Voltage Limits 942 185V 72V 18V

13. Summary Before every switching action  Ensure all 4 constraints are meet  Ensure transition is to a secure situation