Review of Distribution Network Protection Lonnie Malek Oncor Electric Delivery Distribution Planning

Review of Distribution Network Protection Oncor’s Downtown Networks Contingency Considerations in Distribution Networks Protection Considerations for Distribution Networks Oncor’s Network Protection Review Lessons Learned

Review of Distribution Network Protection Oncor’s Downtown Networks Seven Total Networks Network Substation Design Three Transformers per Substation Double Synchronized Ring-bus 12 Distribution Feeders per Network Network Delivery Voltages 4 kV and 15 kV Single-customer Spot Network 277/480 volt Single-customer Spot Network 120/208 volt Grid-connected Vaults

Review of Distribution Network Protection Contingency Considerations for Downtown Networks Oncor’s Design is 2nd Contingency No outages under any 1st or 2nd contingency event Load modeling must account for every combination of 2nd contingency Loss of any 2 combinations of equipment Substation transformers Primary feeders Vault transformers Sister feeder consideration

Review of Distribution Network Protection Contingency Considerations for Downtown Networks (Cont.) X X

Review of Distribution Network Protection Protection Considerations for Distribution Networks Transmission Lines Substation Transformers Substation Ring Bus Distribution Primary Cable Vault Transformers Vault Secondary Bus Distribution Street Grid Network Substation Network Vault Designed to Self Clear

Review of Distribution Network Protection Protection Considerations for Distribution Networks (Cont.) Substation B 480 v Spot Network Customer Service V P B V P Network Protector B V P B V P

Review of Distribution Network Protection Protection Considerations for Distribution Networks (Cont.) Substation B 480 v Spot Network Customer Service V P B V P B V P B X X V F P

Review of Distribution Network Protection Oncor’s Network Protection Review Catalog existing settings and drawings Model fault scenarios Verify coordination Document findings / make revisions

Review of Distribution Network Protection Lessons Learned Street grid voltage can dip below 0.9 PU during certain fault conditions Relay power redundancy is important Verify coordination and reach with back-up device(s) during 1st contingency situations Systems with Y-Y vault transformer connections require additional considerations when modeling faults Do not let high reliability in your network mask the importance of network maintenance

Review of Distribution Network Protection Thank You!