1. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT 1 Current Differential Relay Specification WECC TSS August 20,2014 Amos Ang

2. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT 2 Agenda  Purpose  Background  Relay Model Specification  Work Involved  Next Steps

3. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT Purpose  To get approval from TSS for model specification Model purpose  To model relay behavior in transient stability analysis  To satisfy the new TPL standards of modeling the actions of protection relays for compliance  Facilitate modeling interactions between RAS and Protection relays  To facilitate transfer of information from System Protection to Transmission Planner and to other entities (i.e. coordination with your neighbor)  Established a phased approach to implementing more functionality 3

4. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT Background  Identified current differential relay as one of the most used primary protection for 200 kV and above  MV&WG has approved the specifications on June 18,2014 4

5. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT Current Differential Relay Specification 5

6. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT Functional requirement of Relay  Model can be applied to branches i.e. lines and transformers and also apply to multi-segmented or multi sectional lines  Model can be applied to three terminal lines / three winding transformers  Model will open only the branch(es) within its zone of protection  Monitor only mode  Can be applied to a specific set of branches through the zone/kV/area/owner specifications  Can be applied to specific branches to override the general specifications stated above 6

7. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT Model Simplification 7  Details for detecting a fault within the zone of protection as done by the current differential relay is not necessary – Additional details does not add any more value – No known interactions from other system events so this is immune to power swings, etc.  In simulation, the fault is applied by the engineer and so the initiating event for the model is the application of the fault on the branch  After fault is applied, then associated breaker times, communication times, and relay delay times will open the appropriate branches

8. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT Modeling  2 Types of Current Differential Relay Model – A generic / general current differential model DIFFRLYG Applies to a set of branches by a priority list of kV range then a logical AND combination of Area / Zone / Owner Tripping and timings applies to all branches that meet the criteria and from bus to bus – A specific current differential model DIFFRLYS Applies to a specific branch or branch set Overrides the DIFFRLYG model Correctly defines the zone of protection that the DIFFRLYG cannot for such things as: –3 terminal lines –3 Winding Transformers –Multi-segmented and multi-sectional lines 8

9. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT Zone of Protection  Correctly defining the zone of protection is important for this relay so the following are illustrations of what is defined as the zone of protection 9

10. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT Zone of Protection (cont.) 10

11. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT DIFFRLYG ParameterTypeDescription AreaIntegerArea Number / -1 if not used ZoneIntegerZone Number / -1 if not used OwnerIntegerOwner Number / -1 if not used kV1FloatkV which the timings will be applied (for transformers high side) kV2FloatIf 0 then line else it is the low side of transformer kV3FloatTransformer (tertiary side), If not used = 0 MonitorInteger0 (alarm); 1 (trip) Tcb*FloatBreaker Time in Cycles TcC*FloatCommunication time and relay time delay (and lockout relay time) in Cycles 11 *Clearing time is the sum of Tcb and TcC

12. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT DIFFRLYS 12 ParameterTypeDescription Fb Integer1 st bus Sb Integer2 nd bus (for a three terminal line, this is the tap bus) Ckt1IntegerCircuit ID between 1 st bus and 2 nd bus or 3Winding XFMR ID Ckt2IntegerCircuit ID between Sb bus and Tb bus Ckt3IntegerCircuit ID between Sb bus and Ttb bus Tb Integer3 rd bus (far end of multi-segment line or three terminal line), 0 if not used TTb Integer3 rd bus (tertiary for XFMR or third bus of a three terminal line) MonitorInteger0 (alarm); 1 (trip) Tcb*FloatBreaker Time in Cycles TcC*FloatCommunication time and relay time delay (and lockout relay time) in Cycles *Clearing time is the sum of Tcb and TcC

13. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT Work Involved  If Protection has set the differential current relays the same for a certain voltage class then the work involved is: – One line in the master dyd for all 230 kV lines in area 24 Ex. diffrlyg: ‘area’24, ‘zone’-1, ‘owner’-1, ‘kV1’ 230, ‘kV2’ 0, ‘kV3’ 0, ‘monitor’ 1, ‘Tcb’ 4, ‘TcC’ 2  If the zone of protection is more complicated then the DIFFRLYS is used and that overrides the DIFFRLYG model 13

14. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT Next Steps  Phase 2 – Apply to bus differential protection – once node-breaker model is used in WECC base cases 14

15. TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT Any Questions? 15