Bike to Basics: A Cargo Bicycle Design for Short-distance ...
Distance Basics
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Transcript of Distance Basics
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Power System Protection
Dr. Lionel R. Orama Exclusa, PE
Week 8
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Distance Relays
Mason
Chapter 4, pgs. 61-76
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Objectives
R-X Diagrams
Operating Principles of:
Impedance
Admittance (Mho) Reactance
Memory Action
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Distance Relays
Respond to phasor ratio of input voltage &
input current to relay (V/I)
They are directional
They have high speed Used to protect transmission lines
Usually induction cup design
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Construction
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R-X Diagram
Can use
impedance or R-Xdiagram to analyzerelay operation
1. Plot relaycharacteristic
2. Plot impedanceseen by the
relay (Z relay)
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Impedance Relay
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Admittance (Mho) Relay
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Offset Mho
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Offset Mho
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Angle Impedance Relay
Non-Directional
Not appropriate to work alone
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Reactance Relay
Non-Directional
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Distance Relays
Operating Time
Induction Cup: High
Speed Adjustments
Reach: TappedTransformer
Rises or lowers voltage onrestraining coil
Range of Z to cover downthe line
Offset: Tapped Reactor
For offset Mho, adjust ZT
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Application of Distance Relays to
Transmission Line Protection
Phase distance relays
Ground distance relays (will not becovered)
Step distance relays Usually 3 zones
Distance better than overcurrent
Faster Easier coordination
Permit higher line loading
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System Impedance on Relay Base
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System Impedance on Relay Base
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PT Connections-Phase Distance
Relays
600577115
4.66
10115
115 3
===
===
V
kV
V
VPTR
V
kV
V
VPTR
LGout
LGin
LG
LLout
LLin
LL
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CT Connection to Op Coils
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Impedances Detected by Phase
Relays
3 Phase Fault
Phase-Phase Fault
Relay settingbased on PositiveSequenceImpedance (Z1)
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Step Distance RelayingObjectives
Zones of protection
Effect of arc resistance
Effect of infeed Methods to reduce size of distance relay
characteristic
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Zones of Protection-3 Zones
3 zones (Primary & Backup)
Purpose: Provide high speed tripping for internal faults
Relay must be set to underreach
Does not cover entire line
Zone 1 settings: Reach:80-90%
Time: No time delay
Zone 1
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Zones of Protection
Purpose: Cover remaining 10-20% of AB segment Zone 2 must reach beyond B
Will detect faults on CD segment
Must have time delay
Zone 2 settings: Reach:120%
Time: 0.2-0.4 seconds
Zone 2
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Zones of
Protection
Purpose: Provides Backup protection for faults onadjacent line
Do not set such that load can cause a trip
Zone 3 settings: Reach:120% of ZAB+ZCD Time: 0.4-1.0 seconds
Zone 3
Equivalent Relays at B and D looking on the other direction
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Three Zones of Protection Using
Mho Relays
Advantage Lots of fault coverage
Disadvantage Characteristic gets
close to ZLOAD
GCY - GE Mho
R l Ch i i V A
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Relay Characteristic Vs Arc
Resistance
illustrates increase RF coverage with mho relay (GCY)& reactance relay (GCX)
O1 & M3 operate - Zone 1 O2 & M3 operate Zone 2 M3 operate Zone 3 M1 Zone1 using mho
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Zone 3 Setting with Infeed
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Zone 3 Setting with Infeed
danger
U f Bli d h I d
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Use of Blinders where Impedance
may cause incorrect tripping
Zone 3 so big
that ZLOAD getsinside of it
Angle Impedancerelays to blind
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Reverse Third ZoneZAB+ZCDIF/IA
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Reverse Third Zone
Load
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Admittance Relay Settings
Reach: Diameter of MhoCircle
Maximum Z that makesrelay operate
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Admittance Relay Settings
t varies from 0.10 to 1.00 (t higher, smaller circle)
k is called Basic Minimum Reach is adjustable
Angle of maximum torque is adjustable
Offset is adjustable
Impedances Detected by all Relays
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Impedances Detected by all Relays
During B-C FaultB-C Relay
A-B Relay
C-A Relay
Impedances Detected by all Relays
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Impedances Detected by all Relays
During B-C Fault
