Smart Grid Protection in China

1. Smart Grid Protection in China Wu Guopei Guangzhou Power Supply Bureau Guangdong Power Grid, China

2. Contents • Smart grid in China and the challenge for protection • Change from relay protection to grid protection • Concept of grid protection system • Reach of grid protection • Case study

3. Smart Grid in China • China is speeding up the infrastructure of smart grid • Main characteristics of Smart grid • self-healing and adaptive • safe, stable and reliable • fine compatibility • high quality and efficiency • coordinated and economic • friendly interaction with the users WU– CHN – RT 3b

4. New Challenges for Smart Grid Protection • Adaptive • Flexible topology structure • Connection with distributed generators • Self-healing • Preventive control under normal operation condition • Automatically recover to normal state with minimum manual intervention WU– CHN – RT 3b

5. Change from relay protection to grid protection • Three-defense line for the safety of power system • First defense line ：Conventional relay protection To safeguard power system stable operation by fast and selective tripping of fault elements.

6. Change from relay protection to grid protection • Second defense line：Power stability control system To avoid system out-of-step by applying load shedding and generator shutdown according to pre-set control tactic.

7. Change from relay protection to grid protection • Third defense line：emergency control Designed to prevent from system collapse and large area blackout using out-of-step islanding and frequency & voltage control.

8. Concept of grid protection • Possibility grid protection: • Development of information and storage technology eliminates the information isolated island in power system. • Safe and realtime information exchange • Extension from substation domain information interaction to power grid wide area information interaction.

9. Concept of grid protection • Goal： • Realize integrated and optimized protection and control tactic instead of isolated three-defense line protection system

10. Research of grid protection • Optimized protection performance • Limit of conventional protective relay: The selectivity of protective relays, especially back up protective relays, are dependent on the current, impedance and time settings, which may cause operation time delay and loss of selectivity. • Accurate fault locate and precise fault isolation can be achieved by using wide area fault distinguishing information at each node.

11. Research of grid protection • Fast power recovery in regional power grid • When the substation is loss of power due to power supplies out-of-service, the power supply in other substations will be connected according to system operation mode and topology state.

12. Research of grid protection • Improve the safety and reliability of distribution network after power recovery • Overload caused by power recovery may affect the power grid reliable operation • Load shedding shall be adopted to ensure the power supply to important consumers. • Acquire pre-fault static load information through the wide area information interaction with EMS, and optimize load shedding strategy to maximally protect reliable power supply.

13. Research of grid protection • Improve the safety and reliability of distribution network with distributed power supply • When distributed power supplies are connected to distribution network, the conventional relay setting regulations can not meet the requirements of system selectivity. • The electrical character are varying according to the type of distributed power supplies during system fault and grid interconnection. • Fast and precise fault locate and fault tripping using wide area measurement data • Check if the distributed power supply can restored to interconnection or isolated island state after fault is cleared, and ensure the safe and reliable operation of distribution network by applying grid interconnection control and load shedding.

14. Case study – Grid protection distribution network in China Southern Grid • Located in financial high-tech service area of Guangdong • Includes 2 substations, 65 kilometers distribution lines, 58 switch room ring main • Build distributed Intelligent Self-Healing Control System Based on Multi-Agent • The goals: average fault outage time 5.2min/year WU– CHN – RT 3b

15. Implementation of Grid protection Taking into account the real-time performance of feeder automation devices (FA) and information completeness of distribution automation system (DMS), to raise the smart level of real-time control. Distribution terminals with enhanced functions will be used as agents of grid protection and control system, to realize local signal acquisition pre-treatment, logic determination and implementation of remote commands. WU– CHN – RT 3b

16. Implementation of Grid protection Embedded central control stations with rapid information processing ability will be set up, for fault criteria logic calculation based on wide-area information, to realize rapid fault location. System configuration tool shall be provided with graphic interface to realize system configuration for IEDs of smart distribution network protection. WU– CHN – RT 3b

17. Implementation of Grid protection Wide-area information protection logics such as improved directional pilot protection suitable for distribution grid will be used, to effectively determine distribution grid fault zone connected with distributed power source at load terminals. WU– CHN – RT 3b

18. Implementation of Grid protection Realize power restoration path selection function based on grid topology, assisted with load control technologies such as LF load disconnection, to realize rapid load restoration and load optimization and re-distribution. Micro-grid frequency and load control technology with multi-DG access will be tried, for distribution grid multi-DG coordination control in island operation. WU– CHN – RT 3b

19. Thank you for your attention ! WU– CHN – RT 3b