transmission & interconnection planning t&d business unit 1 current differential relay...
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TRANSMISSION & INTERCONNECTION PLANNINGT&D BUSINESS UNIT 1
Current Differential Relay Specification
WECC TSS
August 20,2014
Amos Ang
TRANSMISSION & INTERCONNECTION PLANNINGT&D BUSINESS UNIT 2
Agenda Purpose
Background
Relay Model Specification
Work Involved
Next Steps
TRANSMISSION & INTERCONNECTION PLANNINGT&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
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TRANSMISSION & INTERCONNECTION PLANNINGT&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
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TRANSMISSION & INTERCONNECTION PLANNINGT&D BUSINESS UNIT
Current Differential Relay Specification
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Current Differential
Relay Model
Is there a fault applied in zone of
protection?
Communication Channel in service?
Monitor only?
Trip Branch
TRANSMISSION & INTERCONNECTION PLANNINGT&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
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TRANSMISSION & INTERCONNECTION PLANNINGT&D BUSINESS UNIT
Model Simplification
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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
TRANSMISSION & INTERCONNECTION PLANNINGT&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
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TRANSMISSION & INTERCONNECTION PLANNINGT&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
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Fb SbTransmission Line
Fb SbTwo Winding Transformer
Fb SbThree Winding Transformer
Tb
TRANSMISSION & INTERCONNECTION PLANNINGT&D BUSINESS UNIT
Zone of Protection (cont.)
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TRANSMISSION & INTERCONNECTION PLANNINGT&D BUSINESS UNIT
DIFFRLYGParameter Type Description
Area Integer Area Number / -1 if not used
Zone Integer Zone Number / -1 if not used
Owner Integer Owner Number / -1 if not used
kV1 Float kV which the timings will be applied (for transformers high side)
kV2 Float If 0 then line else it is the low side of transformer
kV3 Float Transformer (tertiary side), If not used = 0
Monitor Integer 0 (alarm); 1 (trip)
Tcb* Float Breaker Time in Cycles
TcC* Float Communication time and relay time delay (and lockout relay time) in Cycles
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*Clearing time is the sum of Tcb and TcC
TRANSMISSION & INTERCONNECTION PLANNINGT&D BUSINESS UNIT
DIFFRLYS
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Parameter Type DescriptionFb Integer 1st bus
Sb Integer 2nd bus (for a three terminal line, this is the tap bus)
Ckt1 Integer Circuit ID between 1st bus and 2nd bus or 3Winding XFMR ID
Ckt2 Integer Circuit ID between Sb bus and Tb bus
Ckt3 Integer Circuit ID between Sb bus and Ttb bus
Tb Integer 3rd bus (far end of multi-segment line or three terminal line), 0 if not used
TTb Integer 3rd bus (tertiary for XFMR or third bus of a three terminal line)
Monitor Integer 0 (alarm); 1 (trip)
Tcb* Float Breaker Time in Cycles
TcC* Float Communication time and relay time delay (and lockout relay time) in Cycles
*Clearing time is the sum of Tcb and TcC
TRANSMISSION & INTERCONNECTION PLANNINGT&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
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TRANSMISSION & INTERCONNECTION PLANNINGT&D BUSINESS UNIT
Next Steps Phase 2
– Apply to bus differential protection – once node-breaker model is used in WECC base cases
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TRANSMISSION & INTERCONNECTION PLANNINGT&D BUSINESS UNIT
Any Questions?
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