Upload
dangthu
View
216
Download
0
Embed Size (px)
Citation preview
Relion. Thinking beyond the box.Designed to seamlessly consolidate functions, Relion relays are
smarter, more flexible and more adaptable. Easy to integrate and
with an extensive function library, the Relion family of protection
and control delivers advanced functionality and improved
performance.
This webinar brought to you by the Relion® product family Advanced protection and control IEDs from ABB
October 7, 2014 l Slide 1
© ABB Group
ABB is pleased to provide you with technical information regarding protective
relays. The material included is not intended to be a complete presentation of
all potential problems and solutions related to this topic. The content is
generic and may not be applicable for circumstances or equipment at any
specific facility. By participating in ABB's web-based Protective Relay School,
you agree that ABB is providing this information to you on an informational
basis only and makes no warranties, representations or guarantees as to the
efficacy or commercial utility of the information for any specific application or
purpose, and ABB is not responsible for any action taken in reliance on the
information contained herein. ABB consultants and service representatives
are available to study specific operations and make recommendations on
improving safety, efficiency and profitability. Contact an ABB sales
representative for further information.
ABB Protective Relay School Webinar SeriesDisclaimer
October 7, 2014 l Slide 2
© ABB Group
Line distance protection fundamentalsElmo PriceOctober 7, 2014
ABB Protective Relay School Webinar Series
Presenter
Elmo Price received his BSEE from Lamar State College of Technology in Beaumont, Texas and his MSEE degree in Power Systems Engineering from the University of Pittsburgh.
He began his career with Westinghouse in 1970 and worked in many engineering positions. He also worked as a district engineer located in New Orleans providing engineering support for Westinghouse power system products in the South-central U.S.
With the consolidation of Westinghouse into ABB in 1988, Elmo assumed regional responsibility for product application for the Protective Relay Division. From 1992 to 2002 he worked in various technical management positions responsible for product management, product design, application support and relay schools. From 2002 to 2008 Elmo was a regional technical manager providing product sales and application support in the southeastern U.S.
Elmo is currently senior consultant for ABB, a registered professional engineer and a Life Senior member of the IEEE. He is a member of the IEEE Power System Relay Committee and the Line Protection Subcommittee, serving as a contributing member to many working groups. He has two patents and has authored and presented numerous industry papers.
October 7, 2014 | Slide 4
© ABB Group
Elmo Price
Learning objectives
Line distance measurement methods and characteristics
Apparent impedance of fault loops and differences in
phase and ground measurements
The importance of faulted phase selection
Step distance line protection
Zone acceleration schemes (non-pilot)
Basics of communications assisted schemes
(optional – time permitting)
October 7, 2014 | Slide 5
© ABB Group
Distance and impedance relays
Uses both voltage and current to determine if a fault is within the relay’s set zone of protection
Settings based on positive and zero sequence transmission line impedance
Measures phase and ground fault loops
October 7, 2014 | Slide 6
© ABB Group
ZLIR
ZS
~VR
Distance and impedance relays
1921 – Voltage restrained time overcurrent was first form of impedance relaying
• 1929 – Balance beam impedance relay improved operating speed performance, but was non-directional
• 1950 – Induction cup phase comparator providing mho distance characteristic
• 1965 – Solid-state implementations
• 1984 – Microprocessor implementations
Brief History
October 7, 2014 | Slide 7
© ABB Group
ZLIR
ZS
~VR
Impedance relaySimple balance beam
October 7, 2014 | Slide 8
© ABB Group
ZRIR
ZS
~VR
Restraint
Torque
Operate
Torque
VR
Reach to balance point = VR/IR = ZR
IR*ZR
X
R
ZR
Distance relays
Need
Fault levels are higher on high voltage transmission lines
Faults need to be cleared rapidly to avoid instability, and extensive damage
Advantages
The impedance zone has a fixed impedance reach
Greater Instantaneous trip coverage with security
Greater sensitivity
Easier setting calculations and coordination
Fixed zone of protection that are relatively independent of system changes
Higher independence of load
October 7, 2014 | Slide 9
© ABB Group
Distance relay application
October 7, 2014 | Slide 10
© ABB Group
Relay
ZG
G H
Relay
ZHZL
ZR
X
ZL
ZG
ZH
RG
HImpedance
PlaneZR
Operating Characteristic
Distance relay characteristicsImpedance
October 7, 2014 | Slide 11
© ABB Group
ZR
X
RMTA
No operation region
ZL
ZH
G
H
32 (Directional unit)
Operate
Distance relay characteristicsMho distance, self (fault voltage) polarized
October 7, 2014 | Slide 12
© ABB Group
ZR
X
RMTA
ZH
G
H
ZL
No Operation Region
Operate
Distance relay characteristicsMho distance, (healthy) voltage polarized
October 7, 2014 | Slide 13
© ABB Group
ZR
X
R
ZH
G
H
Operate
ZL
ZG
No Operation Region
• Typical polarizing Quantities
• Cross
• Positive Sequence
• Memory
Distance relay characteristicsOffset mho distance
October 7, 2014 | Slide 14
© ABB Group
ZR
X
RMTA
32 (Directional unit)
ZL
ZH
G
H
Close-in faults
Operate
No operation region
Distance relay characteristicsReactance
October 7, 2014 | Slide 15
© ABB Group
XR
X
R
MTA
32 (Directional unit)
OperateZL
ZH
G
HZR
Load
supervision
- XR
No operation region
R
Distance relay characteristicsQuadrilateral
October 7, 2014 | Slide 16
© ABB Group
XR
X
RMTA
ZL
ZH
G
H
Operate
ZR
RR
32 (Directional unit)
MTA
Good resistance coverage
No operation region
Distance relay characteristicsSwitched zone quadrilateral
October 7, 2014 | Slide 17
© ABB Group
X
Operate
R
Zone-3
Zone-2
Zone-1
No operation region
Distance relay characteristicsMho distance with switched reactance
October 7, 2014 | Slide 18
© ABB Group
X
ROperate
Zone-3
Zone-2
Zone-1
No operation region
Distance relay characteristicsLenticular
October 7, 2014 | Slide 19
© ABB Group
X
RMTA
ZH
G
HMulti-phase
faultsNo operation region
Phase comparators
October 7, 2014 | Slide 20
© ABB Group
PHASE
COMPARATOR
S1
S2
1 / 0
Compares the phase
angle of two phasor
quantities to determine
operation
S2S1
OPERATE
Apply
operating
torque
RESTRAIN
Apply
opening
torque
Distance relay characteristicsKD-10 cylinder unit (comparator) and compensator
October 7, 2014 | Slide 21
© ABB Group
Phase-to-phase unit
X
Y
Z
XZY
FXY
FZY
VA
VB
VC
IB
IC
IA
COMPENSATOR
CYLINDER
UNIT
S2
S1
ZR
ZR
Distance relay characteristicsKD-10 cylinder unit
October 7, 2014 | Slide 22
© ABB Group
Trips when
VXY leads VZY
XZY
sequence
X
Y
Z
VAG
VCG
VBG
IA - I B
IC - IB
Cylinder unit
CompensatorVXY = VAB - (IA - IB)ZR
VZY = VCB - (IC - IB)ZR
VXY
VCB VZY
(IA - IB)ZR
(IC - IB)ZR
FZY
FXY
Distance relay characteristicsMho distance phase comparator principle
October 7, 2014 | Slide 23
© ABB Group
IZC
IZC - IZ
IZ
(a) Self (faulted phase) Polarized
V
IR
IX
IZC
IZ
(b) Internal and External Fault
V
IR
IXIZC – IZ
ßß > 90°
ß < 90°
IZIZVIZS
IZVS
CfC
f
2
1
ZC = impedance reach setting
Z = fault impedance
Vf = fault voltage at relay
I = fault current
Generic single phase self polarized without zero sequence compensation
Trip b < 90O
S2S1
Distance relay characteristicsMho distance phase comparator – cross polarized
October 7, 2014 | Slide 24
© ABB Group
IZS
IZC
IZ
I(Z+ZS)V
VS
IR
IX
IZC - IZ
IZIZS
VVVZZIS
C
MemBCS
2
11 ,,);(
Z+ZS = fault impedance from source
VS = source voltage
Generic single phase (healthy) voltage
polarized without zero sequence
compensation
Distance relay characteristicsMho distance phase comparators
October 7, 2014 | Slide 25
© ABB Group
VOP VPOL Comments
Zc*IXY - VXY jVXY XY = AB, BC, CA Zc = setting
Three units required for phase-to-phase and three-phase
Self Polarizing No expansion Requires directional unit supervision
Requires memory for zero voltage faults
VOP leads VPOL
Zc*IXY - VXY VZ XY = AB, BC, CA Z = C, A, B Zc = setting
Three units required for phase-to-phase and three-phase
Cross Polarizing Source Impedance expansion Requires directional unit supervision Requires memory for zero voltage faults
VOP leads VPOL
VAB – (IA – IB)Zc
VCB – (IC – IB)Zc
Zc = setting Single unit required for phase-to-phase (AB, BC, CA)
Separate unit required for three-phase faults
Source Impedance expansion
VOP leads VPOL
Positive Sequence Polarizing, VPOL == sub jVZY with VX1
Distance relay characteristicsMho distance phase comparators
October 7, 2014 | Slide 26
© ABB Group
VOP VPOL Comments
VXG – Zc*(IX + K0I0)
VZY X = A, B, C
YZ = BC, CA, AB I0 = 1/3(IA+IB+IC)
K0=(Z0 - Z1)/Z1
Three units required for phase-to-ground (A, B, C)
zero sequence (I0)compensation Cross Polarizing Source Impedance expansion
Requires directional unit supervision
VOP leads VPOL
VXG – Zc*(IX + KNIR)
jVZY X = A, B, C
YZ = BC, CA, AB IR = IA+IB+IC
KN = (Z0 - Z1)/3Z1
Three units required for phase-to-ground (A, B, C)
Residual ground (Ir=3I0) compensation
Cross Polarizing Source Impedance expansion Requires directional unit
supervision
VOP leads VPOL
Positive sequence polarizing, VPOL == sub jVZY with VX1
Quadrilateral characteristicsReactance Lines (current polarization)
October 7, 2014 | Slide 27
© ABB Group
X
R
ZC
S1 = IZC - V = (XC - Z)I
S2 = VPOL = XCI
Z
XC - Zq
S2S1
q
XC
-XC
Z
q
RC
Operate q < ± 90O
RF
Only the forward reach line can be defined, therefore, it must be directionally supervised
I2 used for load compensation
Quadrilateral characteristicsResistance (current polarized)
October 7, 2014 | Slide 28
© ABB Group
X
R
S1 = IRCF - V = (RCF - Z)I
S2 = VPOL = RCFI ZRCF - Z
Operate q < ± 90O
q
S2S1 q
RCF
Z
RCF
Distance relay characteristics
E. Price, T. Einarsson, “Complementary Approach for
Reliable High Speed Transmission Line Protection,” 62nd
Annual Georgia Tech Protective Relaying Conference,
Atlanta, Georgia, 2008.
Reference
October 7, 2014 | Slide 29
© ABB Group
Apparent impedance of fault loops
October 7, 2014 | Slide 30
© ABB Group
6 fault loops measured for
each zone
Fault Types
• Phase-to-ground
• Phase-to-phase
• Two phase-to-ground
• Three phase
AG
CG
BG
CA
BC
AB
Apparent impedance of fault loopsThree phase
October 7, 2014 | Slide 31
© ABB Group
ZR1
MTA R
X
Relay Phase Impedance
Characteristic
Apparent impedance (per
phase)
VA= IA ZL1
Z3P = ZL1 =VA/IA
IN = 0
Fault applied on line at ZL1
ZL1
ZL1
ZL1
ZLN
Phase reach is set in terms of
positive sequence impedance, ZL1
Apparent impedance of fault loopsPhase-to-phase
October 7, 2014 | Slide 32
© ABB Group
ZL1
MTAP
R
X
Relay Phase-to-phase
impedance characteristic
Apparent impedance, ZPP
VAB = (IA - IB ) ZL1 = 2IA ZL1
ZPP =ZL1 = VAB/(IA - IB ) = (VA - VB )/(IA - IB )
ZL1
ZL1
ZL1
ZLN
Phase reach is set in terms of positive sequence impedance, ZL1
Apparent impedance of fault loopsPhase-to-ground
October 7, 2014 | Slide 33
© ABB Group
MTAP
Apparent impedance (no load IA = 3I0 )
VA = IA ZL1 + 3I0ZLN = IA (ZL1 + ZLN)
ZG = VA /IA = (ZL1 + ZLN)
MTAG = Argument ( ZL1 + ZLN )
ZG = ZL1 + ZLN
R
X
Relay Phase-to-ground
impedance characteristic
MTAG
ZL1ZL1
ZL1
ZL1
ZLN
Apparent impedance of fault loopsPhase-to-ground
October 7, 2014 | Slide 34
© ABB Group
Apparent impedance
ZG = (ZL1 + ZLN)
ZLN = (ZL0 - ZL1) / 3
ZG = (2ZL1 + ZL0) / 3 (ground loop)
ZL1 with residual 3I0 compensation
ZG = ZL1 ( 2 + ZL0 / ZL1) / 3
ZG = ZL1 ( 2 + 1 + ZL0 / ZL1 - 1 ) / 3
ZG = ZL1(1 + KN); KN = (ZL0 - ZL1)/3ZL1
MTAG = Arg( ZG)
Relay Phase-to-ground
impedance characteristic
MTAP
R
X
MTAG
ZL1
Arg(1+KN)
Apparent impedance of fault loopsPhase-to-ground
October 7, 2014 | Slide 35
© ABB Group
Residual [neutral] current compensation
KN compensates for 3I0
Zero sequence current compensation
K0 compensates for I01 -
Z
ZK
1 -Z
ZIIZV
3Z
Z-ZK
3Z
Z-Z3IIZV
L1
L0
0
L1
L00AL1A
L1
L1L0
N
L1
L1L00AL1A
Ground reach is set in terms of ZL1 and KN: ZG = ZL1(1 + KN)
Two Factors used by different relays and manufacturers
Faulted phase selection
October 7, 2014 | Slide 36
© ABB Group
Release or identify correct
impedance loop
Single pole trip
Event recording
Fault location
A-B B-C C-A
A-G B-G C-G
6 fault loops measured in each
zone
Faulted phase selectionIssues
October 7, 2014 | Slide 37
© ABB Group
Multiple impedance loop operations for a fault event
• Common phases of a fault loop
• Magnitude of fault quantities
• Load
• Fault resistance
A-B B-C C-A
A-G B-G C-G
Faulted phase selection
The FF unit may operate for close-in reverse FF, FFG, orFG faults
The FF unit may operate for close-in forward FG faults
The FG units may operate for close-in reverse FG faults
The FF unit of a non-faulted loop may operate for FFG faults with high fault resistance
e.g. CA unit for a BCG fault
The CA operation will occur with the expected BC operation giving the appearance of a three phase fault.
Issues
October 7, 2014 | Slide 38
© ABB Group
These issues are resolved with directional and/or sequence current supervision.
Faulted phase selection
The FG unit of the leading phase will overreach for forward external FFG faults with any measurable fault resistance
e.g. BG unit for a BCG fault
The FG unit of the lagging phase will underreach for forward internal FFG faults near the reach setting with any measurable fault resistance
e.g. CG unit for a BCG fault
This is generally of no consequence
Issues
October 7, 2014 | Slide 39
© ABB Group
These issues are the result of FFG faults and must be resolved by accurate phase
selection.
Faulted phase selection
0
0.5
1
1.5
2
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1
Fau
lt L
oca
tio
n i
n P
U o
f Z
on
e R
each
Set
tin
g,
Zc
Per Unit Fault Resistance, Rg
3
5
1
0.5
0.5
1
3
5
SIRz
Overreaching BG Units
Underreaching CG Units
CG is operated
BG is operated
A
B
BC Unit
Operates for all parameters at 1.0
Error Zone of FG
units for FFG faults
Response of BG, CG and BC units to BCG fault
October 7, 2014 | Slide 40
© ABB Group
Faulted phase selection
E. Price, T. Einarsson, “The Performance of Faulted phase
Selectors used in Transmission Line Applications,” 62nd
Annual Georgia Tech Protective Relaying Conference,
Atlanta, Georgia, 2008.
Reference
October 7, 2014 | Slide 41
© ABB Group
Application
Reach of a distance relay is measured from the
location of the voltage transformer
Directional sensing occurs from the location of the
current transformer
In most applications vts and cts are usually at same
location (no measurable impedance between them)
Their location should always be considered
especially for applications with transmission lines
terminated with transformers
Location of cts and vts
October 7, 2014 | Slide 42
© ABB Group
Application
Zone 1 set for 80 - 90 % of line impedance
Zone 2 set for 100% of line plus 25 - 50% of shortest adjacent line from remote bus
Zone 3 set for 100% of both lines plus 25% of adjacent line off remote bus
Step distance protection
October 7, 2014 | Slide 43
© ABB Group
G H
Z3Z2
Z1
T3
T2
T1
Z3Z2
Z1T1
T2
T3
Step distance protection
Do not want Zone 1 to reach beyond remote bus
10 to 20% is safety factor
Inaccuracies
Relays
Current and potential transformers
Line impedances
Zone 1
October 7, 2014 | Slide 44
© ABB Group
G H
Z3Z2
Z1
T3
T2
T1
Z3Z2
Z1T1
T2
T3
Step distance protection
Operates through a timer (T2)
Timer set for Coordination Time Interval (CTI) that allows remote relay zone 1 [Z1] and breaker [at H] to operate with margin before zone 2 [Z2] relay
Z2 at G must overreach the remote bus H, but should not overreach the closest far bus at R
Z2 at G is remote backup to Z1 at H
Zone 2
October 7, 2014 | Slide 45
© ABB Group
G H
Z3Z2
Z1
T3
T2
T1
Z3Z2
Z1T1
T2
T3
HZ1 R
Step distance protection
Operates through a timer (T3)
Timer set for Coordination Time Interval (CTI) that allows remote relay zone 2 [Z2] and breakers [at H and R] to operate with margin before the zone 3 [Z3] relay
Z3 at G is also remote backup to Z1 and Z2 at H
Zone 3
October 7, 2014 | Slide 46
© ABB Group
G H
Z3Z2
Z1
T3
T2
T1
Z3Z2
Z1T1
T2
T3
H Z1Z2
R
Step distance protection
Zone 3 relay [Z3] may be applied looking reverse for pilot system logic with no timer
Zone 3 relay [Z3] may be applied looking reverse for reverse [backup] bus protection
Timer set to allows reverse zone 1 [Z1] relay and breaker [at G] to operate with margin before zone 3 [Z3] relay
Zone 3
October 7, 2014 | Slide 47
© ABB Group
G H
Z3 Z2Z1
T2
T1
T3Z2
Z1T1
T2
RZ1
T3
Step distance protectionOperating time profile
October 7, 2014 | Slide 48
© ABB Group
Z1
Z2 T3
Z3
Z1
Z2
Z1
Z2
T2
21/67 (Impedance controlled directional TOC)
Step distance protection
Reduces the apparent reach measured by distance relays
Depends on the ratio between current going through relay (IG) and current from infeed (IIN)
Usually not a factor on Zone 1 [Z1] relay unless tapped line [or appreciable fault resistance for ground faults]
Zone 2 may underreach remote bus
Infeed [from remote bus]
October 7, 2014 | Slide 49
© ABB Group
G
Z2
Z1
IG
IIN
Step distance protection
With Zero voltage fault and Z2 = ZG + ZH
VG = IGZG + ( IG + IIN ) ZH
ZA (Apparent) = VG / IG
ZA = ZG + (1 + IIN/IG) ZH
ZA = ZG + ZH + (IIN/IG)ZH (Increase in Apparent Impedance)
Z2 must be set to overreach bus H for infeed at bus H
and not overreach bus K for no infeed at bus H
Infeed [from remote bus]
October 7, 2014 | Slide 50
© ABB Group
G
Z2
ZG
IG
IIN
ZH
IG+ IIN
VG
G
H
K
Step distance protection
Usually associated with three terminal line applications and paralleling of line segment
Example: VG = 2(1) + 2(1 ) = 4
ZG (Apparent) = VG / IG
ZG = 4/2 = 2 W
Z1 will overreach and see the fault
Outfeed
October 7, 2014 | Slide 51
© ABB Group
G
1 W 2 W
2 a
1 W1 W
1 a 1 a
1 a
Z1 = 2.5 W
Step distance protection
VG = IGmZL + ( IG + IH ) ZT
ZG (Apparent) = VG / IG
ZG = mZL + (1 + IH/IG) ZT
ZG = mZL + ZT + IH/IGZT (Increase in apparent impedance)
Apparent impedance will always be larger than impedance to fault
Tapped transformers and loads
October 7, 2014 | Slide 52
© ABB Group
G
mZL
m
(1-m)ZL
IHIGIG + IH
ZT
Step distance protection
IH and VH preferred to provide line protection
Use of VL and/or IL affects measured impedance and requires ct and/or vt ratio adjustment
Transformer should always be protected separately
Lines terminated into transformers
October 7, 2014 | Slide 53
© ABB Group
IL IH
VLVH
ZT ZL
Reference
E. Price, R. Hedding, “Protecting Transmission Lines Terminated into
Transformers,” 63nd Annual Georgia Tech Protective Relaying
Conference, Atlanta, Georgia, 2009.
Source impedance ratio
Ratio of source impedance to the line impedance
SIR to the relay is the ratio of source impedance to the zone impedance setting
The higher the SIR the more complex the line protection with zone 1
Measurement errors are more pronounced
Current and or voltage transformer error
CVT transients
Zone-1 may not be recommended in many applications
Current differential protection preferred
October 7, 2014 | Slide 54
© ABB Group
Source impedance ratio
Short Line SIR > 4.0
Current Differential
Phase Comparison
Pilot (POTT, DCB)
Medium Line 4.0 > SIR > 0.5
Above
Step Distance
Long Line 0.5 > SIR
Above
Step Distance
Recommended applications
October 7, 2014 | Slide 55
© ABB Group
IEEE Guide for Protective Relay Applications to
Transmission Lines - IEEE Std C37.113-1999
Non-pilot applications
Z1 reach is initially set to overreach remote bus
Circuit breakers controlled by relays A, C, & D trip for a fault at F
Z1 reach is reduced to not overreach remote bus
High-speed reclose
Zone 1 extension
October 7, 2014 | Slide 56
© ABB Group
BF
Z1
C DA
Z1
Z1 Z1
Non-pilot applications
After high-speed reclose
Circuit breaker controlled by relay C trips instantaneously
Circuit breaker controlled by relay D trips time-delayed
Circuit breaker controlled by relay A does not trip
Zone 1 extension
October 7, 2014 | Slide 57
© ABB Group
BF
Z1
C DA
Z1
Z1
Z1
Z2
Non-pilot applications
Unbalanced fault occurs at F Breaker controlled by relay B trips instantaneously by Z1 Balanced load current, IL, is interrupted LLT Logic at A
Detects loss of balanced (load) current and bypasses Z2 timer to trip
Does not operate for three-phase fault
Load loss trip
October 7, 2014 | Slide 58
© ABB Group
F
Z1
BA
Z1
Z2Z2
IL
Switch onto fault logic
Logic determines breaker has been open awhile and sets SOTF logic (aka: CIFT, SOFT) Breaker position
Dead line logic
When breaker controlled by relay A closes SOTF asserts when: I and Not V, and/or
ZSOTF operates Set ZSOTF offset, overreaching line and below minimum load impedance
October 7, 2014 | Slide 59
© ABB Group
BA
I
V
OPENCLOSING
ZSOTF
Pilot relaying schemes Communication assisted schemes
October 7, 2014 | Slide 61
© ABB Group
Goal - High speed simultaneous tripping of all line
terminals for internal line faults
A B
STATION C STATION D
X
STATION E
CP & C
P & C
P & C
Pilot relaying schemes Communication assisted schemes
October 7, 2014 | Slide 62
© ABB Group
Goal - High speed simultaneous tripping of all line
terminals for internal line faults
COMMUNICATIONS
A B
STATION C STATION D
X
STATION E
CP & C
P & C
P & C
Requires reliable high-speed communications between line terminals.
Pilot Communications
Power Line Carrier (PLC)
The communication signal is coupled to the transmission line being protected requiring additional substation equipment
Line traps
Line tuners
Coupling capacitors
On/Off Keying, Frequency Shift Keying (FSK)
Generally more available and economical than other forms of pilot communications
Communication issues tend to occur when reliable communications is need most – during the fault
DCB (On/Off) and DCUB (FSK) developed specifically for PLC
63
Pilot Communications
Non Power Line Carrier
The communication signal is routed separately from
the transmission line conductor
Audio tone – FSK over voice (telephone, microwave)
Digital – most reliable, particularly with fiber optics,
direct connected or multiplexed
64
Directional Comparison
Directional Comparison relaying determines the fault direction at each line
terminal and compares the results to determine the fault to be internal or
external to the protected line.
65
A B
FWD Element (FP-A)à
ßFWD Element (FP-B)
FINT
STATION C STATION D
A B
FWD Element (FP-A)à
FEXT
STATION C
STATION D
INTERNAL
FAULT
EXTERNAL
FAULT
REV Element (RP-B)à
Distance Protection Directional Comparison Schemes
Non PLC Channels
DUTT* – Direct-underreaching transfer trip
POTT – permissive-overreaching transfer trip
PUTT – permissive-underreaching transfer trip
PLC
DCB – directional comparison blocking
DCUB – directional comparison unblocking
* Although there is no directional comparison between terminals this scheme is usually considered with directional comparison schemes.
66
DUTT – Direct-underreaching Transfer Trip
Also known as an “Intertrip” scheme
67
A B
FINT
STATION C STATION D
21-1
21-1
Rx [f1 from B]
21-1 (A)
Tx [f1 to TRIP B]
TRIP A
Must Overlap
Underreaching
Distance Relay
CommTx
RxComm
Tx
Rx
f1
Rx [f1 from A]
21-1 (B)
Tx [f1 to TRIP A]
TRIP BOR OR
DUTT – Direct-underreaching Transfer Trip
Advantages
Fast method for clearing end zone faults
Single communications channel
Disadvantages
Cannot protect full line if one terminal is open or has weak infeed
Requires ground distance relays for accurate reach on ground faults (no overcurrent)
Subject to 21-1 overreaching issues (e.g. ccvttransients)
Spurious communication channel noise may cause undesired trip (secure channel desired – FSK, digital)
68
PUTT – Permissive-underreaching Transfer Trip
69
A B
FINT
STATION C STATION D
21-1
21-1
Rx [f1 from B]
Tx [to B]
TRIP A
Must Overlap
Underreaching
Distance Relay
21-2
21-2
Overreaching
Distance Relay
21-2 (A)
CommTx
RxComm
Tx
Rx
f1
Rx [f1 from A]
Tx [f1 to A]
TRIP B21-2 (B)AND AND
21-1 (A) 21-1 (B)
Rx signal should have a minimum receive time to allow operation of 21-2.
PUTT – Permissive-underreaching Transfer Trip
Advantages
More secure than DUTT requiring a 21-2 operation for
permission to trip
Single communications channel
Disadvantages
Cannot protect full line if one terminal is open or has
weak infeed
Requires ground distance relays for accurate reach on
ground faults (no overcurrent)
70
POTT – Permissive-overreaching Transfer Trip
71
A B
FINT
STATION C STATION D
FP-A
Rx [f2 from B]
Tx [f1 to B]
TRIP A
Overreaching Distance
and OC Relays:
21-2, 21N-2, 67N
FP-A
FP-B
CommTx
RxComm
Tx
Rx
f1 f2
Rx [f1 from A]
Tx [f2 to A]
TRIP BFP-B ANDAND
Rx signal should have a minimum receive time to allow operation of 21-2.
POTT – Permissive-overreaching Transfer Trip
Advantages
More dependable than PUTT because it sees all line faults.
Open terminal and weak-end infeed logic can be applied.
Forward and reverse ground directional overcurrent relays may be applied for greater sensitivity to high resistance ground faults
Disadvantages
Requires a duplex communications channel (separate frequency/signal for each direction)
Will not trip for internal fault with loss of channel (but usually applied with a zone-1/2 step-distance relay)
72
Directional Comparison Blocking (DCB) and Unblocking (DCUB)
DCB and DCUB schemes are specifically intended to be used with systems where
communications is less secure (likely to be lost) during line fault conditions
Power-line carrier – signal communications is on same
conductor that you are protecting
73
A B
Power Line
Carrier
Channel
STATION C STATION D
Transmission Line
Relay Relay
Signal Path
The PLC Channel
H
Coupling Capacitor
Voltage
Transformer (ccvt)
Drain
Coil
Line
Tuner
Coaxial Cable
Line Trap
Station A Bus
Fault2 1
Protective
Relay
System
T
R
Control
House
Switchyard
Relay PT
inputs
Signal:
30 to 500 kHz
1 to 100 Watts
(7 to 70 V rms)
DCUB – Directional Comparison Unblocking
75
fB1 and fB2 are continuous block signals until a fault is detected and
the frequency is shifted to the unblock (trip) f1 and/or f2.
DCUB – Directional Comparison Unblocking
Advantages
Very secure at it requires receipt of Unblock signal for tripping.
Has logic to handle loss of channel during faults.
Open terminal and weak-end infeed logic can be applied.
Forward and reverse ground directional overcurrent relays may be applied for greater sensitivity to high resistance ground faults
Security logic for loss of channel (carrier holes) only delays trip during loss of channel
Disadvantages
Requires a duplex communications channel (separate trip and guard frequencies for each direction)
76
DCB – Directional Comparison Blocking
Advantages
Very dependable – does not depend on channel for tripping for internal
faults
Open terminal and weak-end infeed are handled by scheme
Forward and reverse ground directional overcurrent relays may be applied
for greater sensitivity to high resistance ground faults
Low cost communications channel – single frequency channel On/Off PLC
Disadvantages
Not as secure – tends to overtrip for slow channel or loss of channel
Security logic for carrier holes may be required – slows tripping.
Channel is normally off so periodic checking is required
78
References
1. IEEE Guide for protective Relay Applications to
Transmission Lines, IEEE Std. C37-113, 1999.
2. W. A. Elmore, Protective Relaying: Theory and
Application, Marcel Decker, Inc., New York,1994.
October 7, 2014 | Slide 79
© ABB Group
REL650The best choice for sub-transmission applications
REL670Optimized for transmission applications
Relion® REL650/670 Advancing Line Distance ProtectionFor maximum reliability of your power system
Achieve significant savings in configuration and commissioning with efficient system integration and optimum “off-the-shelf” solutions and settings
Do more with less - the advanced logic and multipurpose functionality allow you to customize protection schemes for multiple objects with a single IED
Protect your investment with unrivalled sensitivity, speed and the best possible protection for power transformer winding turn-to-turn faults
Maximize flexibility and performance with powerful application and communication capabilities that allow you to integrate these IEDs into new or retrofit substation automation systems or use them as stand-alone multifunctional units
• Relion Series Relays – Advanced flexible platform for protection and control
• RTU 500 Series – Proven, powerful and open architecture
• MicroSCADA - Advanced control and applications
• Tropos – Secure, robust, high speed wireless solutions
This webinar brought to you by:ABB Power Systems Automation and Communication
We combine innovative, flexible and open products with
engineering and project services to help our customers
address their challenges.
Thank you for your participation
Shortly, you will receive a link to an archive of this presentation.
To view a schedule of remaining webinars in this series, or for more
information on ABB’s protection and control solutions, visit:
www.abb.com/relion
October 7, 2014 | Slide 82
© ABB Group