ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F1 of 30
Protection in Transmission Networks
ABB
Protection
in
Transmission Networks

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F2 of 30
Protection in Transmission Networks
ABB
List of content Course C02EN, Part Application
of Line- and Transformer Protection
Introduction
Principles suitable for network protection
Short discussion of preferred principles depending on application
Current abbreviations
Line Protection
Kind of faults
Protection Schemes (redundancy, back-up)
Basic principle of distance protection
Autoreclosing
Transformer Protection
Kinds of faults
Protection Schemes (redundancy, back-up)
Basic principle of transformer differential protection
Example of distance protection setting

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F3 of 30
Protection in Transmission Networks
ABB
The data-flow
Data
Input
Data
Preparation
Data
Processing
Data
Evaluation
Data
Output
Data
Storage
Data Transfer (local and remote)
PROCESS
G
G
L
L
L
L
L
PROCESS
PROTECTION/CONTROL -
UNIT/SYSTEM
MMC

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F4 of 30
Protection in Transmission Networks
ABB
From the
problem to
the solution
Data
Input
Data
Preparation
Data
Processing
Data
Evaluation
Data
Output
Data
Storage
Data Transfer (local and remote)
PROCESS
G
G
L
L
L
L
L
PROCESS
PROTECTION/CONTROL - UNIT/SYSTEM
Problems Implications
- 3-phase faults
- 2-phase faults
- Earth-faults
- high impedance faults
- lightning
- evolving faults
- power swings
- power reversals
- swich-onto-faults
- load impedances
- CT saturation
- VT failure
- long lines
- short lines
- parallel lines
- intermediate infeeds
- week infeeds
- heavily loaded lines
- different grounding systems
- overheadlines and cables
etc.
- damage to living beings and material
- fire
- explosions
- overvoltages and overcurrents
- influence on neighbouring devices
- voltage increase during earthfaults
- high step and touch voltages
- loss of energy and black-outs
- semaphor effect
- influence of the zero-sequence impedance
- influence of the mutual zero-sequence impedance
etc.
MMC
Requirements
- Availability
- Simplicity
- Flexibility
- Reliability (Dependability, Security, Consistency)
- Selectivity
- Stability
- Speed
- Accuracy
- Sensitivity
Solutions
- Prot. functions (I, IN, Id, E/F, DEF, >U, TH, etc.)
- Control functions (AR, SYN, Interlocking, etc.)
- Monitoring functions (Selfsup., Trip circuit sup., etc.)
- Evaluation functions (Disturbance rec., Eventrec., etc.)
- Communication (Bay comm., Station comm., etc.)
- Calculations (Short circuit, Load flow, Setting calc., etc.)
- Engineering and Testing
- Filtering, galvanic separation
etc.

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F5 of 30
Protection in Transmission Networks
ABB
Measuring quantities and Measuring principles
Used for auxiliary functions,
such as stabilising features
Current
Phase quantities
Symmetrical
component
quantities
Phase
quantities
Symmetrical
component-
quantities
Mixed
phase-
quantities
Transient components Fundamental frequency components Higher harmonics
Voltage and current Voltage and current
Phase quantities
Distance prot.
Directional overcurrent prot.
Directional comparison prot. Line differential- or
Phase comparison prot.
Time-/
distance-
graded
Overcurrent prot.
Unit prot.

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F6 of 30
Protection in Transmission Networks
ABB
Types of protection, some definitions and abbreviations
¾ Overcurrent
¾ with current independent time delay (definite time)
¾ with current dependent time delay IDMTL
(Inverse time, with Definitive Minimum Time Lag)
0.1
1
10
100
1 10 30
20
8
6
4
2 3
Tripping
time
in seconds
1
I
I
β
k
t[s]
set
α
set
−






⋅
=
Several inverse-time characteristics are
available, most of them follow the term:
I / Iset

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F7 of 30
Protection in Transmission Networks
ABB
Types of protection, some definitions and abbreviations
¾ Directional comparison functioning in POTT (tripping) or BLOCKING mode
¾ Phase comparison Phase-angles of the currents of both line ends are compared
¾ Differential Full currents, amplitudes and phase-angles compared
¾ Biased differential Diff. circuit with low impedance
Biased = restrained = pick-up value is current dependent
¾ High-impedance Diff. circuit with high impedance
differential Matched CT‘s required, exclusively for this protection
¾ REF Restricted Earth Fault
High-impedance differential earth fault function protects
one transformer winding (restricted to one winding)

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F8 of 30
Protection in Transmission Networks
ABB
Types of protection, some definitions and abbreviations
¾ Distance protection = Directional multi-zone impedance protection
Non-switched: 6 loops per zone and min. 3 zones simultaneously measured,
one or several time delayed zones (= state of the art)
Switched: 1 loop measured, zone switching by timer (= older conventional types)
Mho type: directional circular measuring characteristic
Offset Mho type: directional circular „open“ characteristic, healthy voltage and/or
memory voltage polarised for enhanced directionality
Polygon type: polygonal characteristic with healthy voltage and/or memory
voltage polarised directional function

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F9 of 30
Protection in Transmission Networks
ABB
Types of protection, some definitions and abbreviations
¾ Communication between line ends, by carrier (PLC), fibre optics or microwave
PUTT Permissive underreaching transfer trip
POTT Permissive overreaching transfer trip
with add. logic's to cover cases with one weak infeed end
ECHO: in case of weak infeed, a received signal is “echo-ed” back, and the
strong end will trip
WIE Trip: Trip of weak infeed-end by received comm. signal + add. logic’s
UNBLOCK: simulates „signal receive“ in case of a carrier fail during a fault on the line
(useful for overhead lines with PLC communication)
BLOCKING: Overreaching blocking
¾ Phase selector = used for single-pole autoreclosure and for events / alarms

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F10 of 30
Protection in Transmission Networks
ABB
Types of protection, some definitions and abbreviations
¾ DEF = Directional earth fault prot.
Zero-sequence directional prot., often functioning in a communication scheme
¾ AR = Autoreclosing
Single- or three-pole high speed AR and/or one- or multishot three-pole
delayed AR
¾ Distance to fault locator = displays the distance to the fault
Mutual compensation: compensated by 3I0 of the parallel overhead line
Load compensation: corrects the influence of load in case of resistive faults

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F11 of 30
Protection in Transmission Networks
ABB
Line Protection

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F12 of 30
Protection in Transmission Networks
ABB
Line fault types
< 230 kV >230 kV
Type of fault: Single Phase 60 % 85 %
Two Phase 30 % 10 %
Three Phase 10 % 5 %
---------- ----------
100 % 100 %

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F13 of 30
Protection in Transmission Networks
ABB
Typical line protection schemes
A. Distance function with communication scheme to the opposite line end
and time delayed overreaching back-up zones
B. Line differential function combined with a distance function for back-up
1. Non-redundant
schemes
Main 1 Main 2
C. Distance function Same as Main 1
with communication
and back-up zones
(same as A)
D. ditto Line differential function
combined with distance for back-up.
E. ditto Directional comparison prot.
F. ditto Phase comparison prot.
G. ditto Rate of change function in
directional comparison
2. Redundant
schemes
To detect high resistive ground faults, above protection schemes are often combined with a zero
sequence overcurrent protection with inverse time delay or by a directional comparison DEF scheme

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F14 of 30
Protection in Transmission Networks
ABB
Line Protection, Basic Versions
Protection 1 Protection 2 Control
(Main 1) (Main 2 / Back-up) (Option)
Medium Voltage High Voltage
<= 36kV <=72.5kV <=145kV <=245 kV <=765 kV
I> + IN AR/SYN
Dir I> + IN AR/SYN
Id I>+IN AR/SYN
Id Z< AR/SYN
Z< AR/SYN
Z< I>+IN AR/SYN
Z< Z<+IN AR/SYN
Z< + DEF Z<+IN AR/SYN
Z< + DEF+IN Z< +DEF+IN AR/SYN
DirComp+DEF Z<+IN AR/SYN
DirComp+DEF+IN Z<+DEF+IN AR/SYN

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F15 of 30
Protection in Transmission Networks
ABB
Line Protection

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F16 of 30
Protection in Transmission Networks
ABB
Line Protection
DEF
2- or 1 ½ - CB
arrangements
Single CB scheme in
single- or multi-busbar
arrangements

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F17 of 30
Protection in Transmission Networks
ABB
Selective line protection scheme with single end infeed
1,4s
0,8s
1,4s
1,4s
1,1s
1,1s
0s
0,5s
0s
0s
0,3s
1,1s
= Time overcurrent relays
= Time overcurrent relays and directional relays, which only permit
tripping, if the fault is in the direction of the line.
0,3s
0s
0,8s 0,5s

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F18 of 30
Protection in Transmission Networks
ABB
The stepped time / distance characteristic of a distance relay
T = Protected line length
t1...t4 = Time steps
t = Operating time
I = Distance from relay
= Distance relay
A, B = Stations
A
t1
t3
t4
t
t2
T
B I
0,85...0,9 T

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F19 of 30
Protection in Transmission Networks
ABB
Distance relay grading diagram
t
A
B C D
= Distance relay
t = Operating time

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F20 of 30
Protection in Transmission Networks
ABB
Principle of the distance function (simplified)
≈
I Relay
ZS ZL
UG U
k0
3I0
I
U
Z
ph
ground
ph
L
⋅
+
=
−
L
S
G
Z
Z
U
I
+
=
S
R
ph
ph
L
I
I
U
Z
−
=
−
for 2- and 3-phase faults for single-phase to
ground faults
Operation will take place, if:
I > Iset AND ZL < Zset AND Fault forward

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F21 of 30
Protection in Transmission Networks
ABB
Distance characteristic
Polygon - type
ZONE 3
ZONE 2
ZONE 1
OVERREACHING-
ZONE
REVERSE DIRECTED
ZONE
R1
UNDERIMPEDANCE-
CHARACTERISTC
jX1

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F22 of 30
Protection in Transmission Networks
ABB
Line data, required for protection setting
Bundle
conductor
with 2, 3, 4
conductors
Zm0
= mutual zero sequence impedance
Ground-conductor
Positive sequence impedance = Z1 = R1+j·X1
Negative sequence impedance = Z2 = Z1
Zero sequence impedance of a single line Z0 = R0+j·X0
For parallel overhead lines on common towers additionally:
Mutual zero sequence impedance Zm0 = Rm0+j·X0
or
Zero sequence impedance of a double circuit line
Z0’’ = Z0 + Zm0

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F23 of 30
Protection in Transmission Networks
ABB
Impedance - grading
Z3 < 0.85 (a+k·b2)
1.2 a < Z2 < 0.85 (a+k·b1)
Z1 ≈ 0.85·a
ZOR ≈ 1,2·a
a b
A B C
b2
b1

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F24 of 30
Protection in Transmission Networks
ABB
Infeed factor k
≈
Impedance measured by
overreaching zones of relay A
la
d·Zc
Ia + Ib
Ib
A Za
≈
Ia
Z = Za +
d·Zc (la + Ib)
la
Z = Za + k ·d·Zc
where k = 1 +
Ib

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F25 of 30
Protection in Transmission Networks
ABB
Due to load-flow, the fault resistance RF appears as an
enlarged and complex impedance (so called „Semaphor- effect“)
≈ ≈
IphA UF
B
ZL IphB
RF
UA UB
UF = RF (IphA+ IphB)
Z as „seen“ by the distance protection =
With load-flow from A Æ B
With load-flow from B Æ A
RF as for single end infeed
jX
R
ZL
phA
phB
phA
I
I
I
RF
+
⋅
( )
phA
phB
phA
I
I
I
RF
ZL
Z
+
⋅
+
=

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F26 of 30
Protection in Transmission Networks
ABB
Permissive Underreaching Transfer Tripping (PUTT)
Tripping criterion in B Zone 1 of the distance function AND phase-selector
Tripping time in B no intentional delay
Tripping criterion in C Receive of signal from B AND overreaching zone AND phase-selector
Tripping time in C Zone 1 in B plus signal transmission time
This mode is widely used, since unequal characteristics of relays in A and B do not
harm the protection system performance
Tone Rx/Tx = NSD
Relay B
NSD (Tone)
Relay C
Protected line
Zone 1 of relay in B
Zone 1 of relay in C
B C
PLC
PLC = power line carrier

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F27 of 30
Protection in Transmission Networks
ABB
Permissive Overreaching Transfer Tripping (POTT)
Protected line
B C
Tripping criteria = {Zone 1 OR [receive_of_signal AND overreaching_zone]} AND (phase-selector)
Tripping time = No intentional delay for fault in zone 1
Measuring time of overreaching zone in opposite relay plus signal transmission time.
Additional logic's to cover weak infeed conditions :
• “Echo”-Logic allows fast tripping of the end with strong infeed
• Weak-infeed logic allows tripping of the end with weak infeed
Preferred mode for cable lines, short overhead lines and for series compensated lines.
Overreaching zone of relay B
Relay B
Overreaching zone of relay C
Relay C
NSD
NSD
PLC
PLC

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F28 of 30
Protection in Transmission Networks
ABB
Line differential protection
with fibre-optical communication 800/1A
1000/1A
E
O
E
O A
D
DIFF
A
D
E
O
E
O
DIFF
F.O.
< 28 km
With FOX (MUX) up to approx. 120 km
REL 316 REL 316
A/D = analogue / digital converter
E/O = electrical / optical converter

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F29 of 30
Protection in Transmission Networks
ABB
Autoreclosing on overhead lines (AR)
HSAR, single pole DAR, always three pole
Start 1-phase
Trip 3-pole 3-pole discriminating time
DAR open time
Start
Trip 3-pole
High speed HSAR Delayed DAR
Start 1-phase
Trip 1-pole
1-pole discriminating time
Close pulse, interrupted by new trip
Single-pole open time
Q0 Phase R
Q0 Phase S
Q0 Phase T

ABB Power Automation Ltd
T2313 / C02e_2001.ppt / F30 of 30
Protection in Transmission Networks
ABB
Zone 1 used as underreaching PLC-independent trip
X (Zone 1) = 37.1Ω ·0.8 = 29.7 Ω primary ⇒ 12.9 Ω secondary; k0 = 0.74; t1 = 0.0 s
set to 80% of full line instead of the usual 85%, since CVT’s (capacitive voltage transformers) are used
R (Zone 1) = 30 Ω primary ⇒ 13.0 Ω secondary
Zone OR used for the PUTT-scheme
X (Zone OR) >37.1 Ω ·1.5 = 55.6 Ω primary ⇒ 24.2 Ω secondary; k0 = 0.74; tOR = 0.0 s
R (Zone OR) = 40 Ω primary ⇒ 17.4 Ω secondary
this zone shall cover the full line A- B with a good safety margin
Note: To simplify we assume X ≈ Z.