TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT 1 Current Differential Relay Specification...

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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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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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


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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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


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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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


Zone of Protection (cont.)

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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


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


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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Next Steps Phase 2

– Apply to bus differential protection – once node-breaker model is used in WECC base cases

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Any Questions?

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TRANSMISSION & INTERCONNECTION PLANNING T&D BUSINESS UNIT 1 Current Differential Relay Specification...

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