Bapuji S Palki, INCRC/PowerTechnologies, 15-11-2009
Protection Application – An Overview
Part 1a
© ABB Group
April 13, 2015 | Slide 1
© ABB Group
April 13, 2015 | Slide 2
Electric Power Systems
Generation
Transmission
© ABB Group
April 13, 2015 | Slide 3
Consumption
M
G
Generation
Distribution
Transmission
Distribution
Load
Offerings in ABB Power Products
High Voltage Products
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April 13, 2015 | Slide 4
Medium Voltage Products
Transformers
Offerings in ABB Power Systems
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April 13, 2015 | Slide 5
Substations
Grid Systems
Power Generation
Network Management
Protection & Control

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April 13, 2015 | Slide 6
© ABB Group
April 13, 2015 | Slide 7
Power Transmission & Distribution Network
400 / 220 kV
Transmission
substation
Transformer
110 / 132 kV
132/66/11 kV
Main substation
400 V
Secondary
substation
11/22 kV
© ABB Group
April 13, 2015 | Slide 8
Distribution
substation
POWER
MAP
OF INDIA
Power
Grid India
Transmission
Network
POWERGRID LINES
Power System
Transmission Lines: Electrical Characteristics
Representation of short lines < 50kM
Voltage Stability

A feeder circuit will have a voltage drop related to the
impedance of the line and the power factor

Adding capacitance will actually cause a voltage rise by
supplying reactive current to the bus
(less current = less voltage drop)
© ABB Group
April 13, 2015 | Slide 12
Voltage drop compensation with series capacitor
Load_1_comp
Load_1_no_comp
EA
Load_2_comp
Load_2_no_comp
distance
A
B
ZSA1
EA
Power line
~
Load
Series
capacitor
VisioDocument
© ABB Group
April 13, 2015 | Slide 13
Actions to reduce voltage drop

Keep service voltage high

Decrease reactive power flow in line by
producing reactive power


Install shunt capacitors
Reduce inductive reactance of line

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April 13, 2015 | Slide 14
Install series capacitor
Direction of rotation and mechanical
and electrical torques for a generator rotor
Tm
Te
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April 13, 2015 | Slide 15
Synchronous stability : Equal area method
Angular change If transferred power during fault is not zero
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April 13, 2015 | Slide 16
Actions to improve stability

More than one conductor per phase

Series capacitor

Short fault clearing time

Single phase autoreclosing

Increase inertia constant in the generator
© ABB Group
April 13, 2015 | Slide 17
Representation of long lines 50 - 200 kM
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April 13, 2015 | Slide 18
The shunt reactor absorbs the capacitive power
generated in long lines and limits over voltages
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April 13, 2015 | Slide 19
Fixed Four-reactor Scheme
ABC
ABC
L
R
Lp Lp Lp
Ln
© ABB Group
April 13, 2015 | Slide 20
Neutral reactor

Capacitive coupling between phases help maintain arc
at fault point making I ph auto reclosing difficult

For longer lines necessary to provide reactors on both
ends and neutral reactor

Inductance of neutral reactor ~ 26%
© ABB Group
April 13, 2015 | Slide 21
© ABB Group
April 13, 2015 | Slide 22
Lightning
stroke
UR
US
Relay time 0,02 seconds
Breaker time 0,06 seconds
Voltage interruption 0,5 seconds
UT
IR
IS
IT
© ABB Group
April 13, 2015 | Slide 23
Need for fault calculations

Load and short circuit ratings for high voltage equipment

Breaking capacity of CBs

Application and design of control & protection equipment

Investigation of unsatisfactory performances of the equipment
© ABB Group
April 13, 2015 | Slide 24
Types of short-circuits
IF1
IF1
IF2
IF1
IF1
IF2
IF1
F1
Single-phase-toearth fault
F2
Two-phase-to-earth
fault
Detected by distance
protection
F3
F4
Cross-country earth
fault and evolving fault
Open phase with
one end to earth
Detected by
distance protection
(e.g. broken cable
and on the other
side falling to
ground)
Critical detection due
to geographically
coincident or at some
other point in the
system.
Balanced fault calculations
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April 13, 2015 | Slide 26
Unbalanced fault calculation
© ABB Group
April 13, 2015 | Slide 27
Symmetrical Components

Used for unbalanced fault calculations

Introduced by Fortescue in 1916

Developed in a book by Wagner and Evans


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April 13, 2015 | Slide 28
Very efficient for hand-calculations
Forms the base for computer programs

Power System Consulting
Power
System studies for
industries & utilities

Transmission & Distribution
system studies
 Industrial power system
studies
Power
evacuation studies
NEPLAN®
software - sale &
support
DPR

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April 13, 2015 | Slide 29
Preparation
© ABB Group
April 13, 2015 | Slide 30
Earthing

Protective earthing


Protects people from dangerous voltages
System earthing

Deliberate measures that connect normally live system to
earth
Why use system earthing

Fix network to earth potential to prevent dangerous voltages
due to capacitive couplings

Reduction of fault current at earth fault in unearthed network
(with neutral point impedance)

Reduce over voltage

For transient earth faults

Increase in neutral point over voltage

Coupling and lightning over voltage
Different types of system earthing

Systems with isolated neutral point

Coil earthed systems

Earthed systems

Effectively earthed systems

Not effectively earthed systems
Different system- groundings in distribution networks
Neutrals isolated
CE
Networks 3kV - 24kV
- small rural networks
- city networks
- industry
Neutrals of infeed
transformers with
Current limiting
resistors
Petersen coil
compensated
networks
CE
Networks 8kV - 24kV
- rural networks
- big city networks
RN
5 ....300A
Networks 3kV - 33kV
- Generators
- Industry
- small networks
Neutrals of infeed
transformers with current
limiting reactors
XN
Neutrals of infeed
transformers
directly grounded
1500A
Networks 33kV - 132kV
Limited step- and touchvoltages.
Networks
33 kV - 800 kV
Practices of earthing


Germany , Sweden , Netherlands

Limit earth fault current to low value

Protect telephone network and people
USA , Canada , UK, India

Accept high earthfault current

Prevent overvoltage in power system

Simplify fault clearance
Practices of earthing



Voltages over 100kV

Direct earthing all over world

Transformers and insulators can be of lower test voltage
Voltages between 25-100kV and 1-25kV

Directly earthed in India

High resistance grounding for Generators

Practices vary in other parts
Voltages < 1 kV

Normally direct earthed

Industries with motors unearthed
Step and touch voltages in direct earthed
networks
Limiting the fault current helps reducing
step and touch voltage
© ABB Group
April 13, 2015 | Slide 37
Bapuji S Palki, INCRC/PowerTechnologies, 15-11-2009
Protection Application – An Overview
Part 1b
© ABB Group
April 13, 2015 | Slide 38
© ABB Group
April 13, 2015 | Slide 39
Electric Power Systems
Generation
Transmission
© ABB Group
April 13, 2015 | Slide 40
Consumption
M
G
Generation
Distribution
Transmission
Distribution
Load
Protection & Control

© ABB Group
April 13, 2015 | Slide 41
The main task for Relay Protection
U
I
C
E
• Protect people and property
around the power system
• Protect equipment, lines etc..
in the power system
• Separate the faulty part from
the rest of the power system
© ABB Group
April 13, 2015 | Slide 42
K
MAIN REQUIREMENTS OF
PROTECTION ARE:
•
•
•
•
•
© ABB Group
April 13, 2015 | Slide 43
SPEED
SENSITIVITY
SELECTIVITY
DEPENDABILITY
SECURITY
Different fault types in a power system
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April 13, 2015 | Slide 44
Primary and backup protection zones
Remote back-up with time selectivity is most common
at Medium and low voltage functions
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April 13, 2015 | Slide 45
Remote back-up protection with time
grading
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April 13, 2015 | Slide 46
Principle of breaker failure protection
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April 13, 2015 | Slide 47
Y
Y
Y
A
A
A
A
CT, VT ARRANGEMENTS
© ABB Group
April 13, 2015 | Slide 48
Y
BUS PROTN.
Y
CIRCUIT
PROTN.
Y
F2
Y
F1
© ABB Group
April 13, 2015 | Slide 49
Chronology of Protection

Technology history

Electromechanical

Solid state

Numerical

Distributed numerical
Electromechanical
Numerical
Solid-state
1960
1970
1980
1990
2000
Technology history
Electromechanical 1900 - 1965
- All types of protection
- High impedance busbar
protection
- Very short tripping times
if sufficient torque
- Good reliability in case of
adequate maintenance
Technology history
Solid state 1965 -1980
- No moving parts
- Reduced CT - burden
- Short tripping times
over wide ranges
- More algorithms possible
- Low impedance busbar
protection
- EMC
Technology history
Numerical 1980 - …
- All types of protection
- Optimized numerical algorithms
at increased long time stability
- Multifunctional units with less HW
- New availability concept
using benefit of self monitoring
- Communication / interaction with
Station- & Network control
Adaptive Protection
Technology history
SW Flexibility
Protection Library
CPU Capacity
I>
51
I>>
50
I>U<
51-27
U
60
I
87G
I
87T
I2
46
I TH
49
U>
59
U<
27
F<>
81
U/f
24
Z<
21
X<
40
Ucos
78
P<32
U0>
64S
CTRL
F<>
81
CTRL
0->I
79
I>
51
CTRL
I TH
49
SYNC
25
Logics
e.g. Z<3ph. needs 17%
Timer
Counter
Technology history
Combined Applications
Control (FunctionPlan)
Monitoring
U, I, f, P, Q
Protection
(Library)
87G
Id
21
Z<
32
P<-
59
U>
40
X<
Technology history
Distributed Numerical 1995 - …
- Numerical busbar protection
- Communication within the system
itself (Central / Bay level)
- New distributed algorithms to
come with adaptive protection
(e.g. load shedding with
measurement of power)
- New hierarchical self-supervision
concept
- Open for new sensor technology
Technology history
Synergy
Between:
Fast Microprocessor technology
and
Communication via
optical fibres
Technology history
Innovations thanks to new technologies
U/I
Combisensor
Conventional CT
Total SA-Solution
Total SA-Solution from Process to Station Level based on the IEC
61850 Standard
61850-9-2
61850-9-2
ABB
Wide Area Monitoring System
Global measurements provided by a WAMS
improve voltage stability assessment
GPS synchronised current and
voltage phasor measurement
Im
U1
I3
Time resolution: <10-6 s
GPS
Satellite
Re
U3
Wide Area
Monitoring
Center
I1
U2
I2
PMU
Transmission Network
PMU
PMU
Im
Im
U1
I3
U3
I1
Re
U2
I2
U3
Im
Im
U1
I3
PMU
PMU
I1
Re
U2
I2
U1
I3
U3
I1
Re
U2
I2
U1
I3
U3
I1
Re
U2
I2
Numerical technique - Advantages
•Less space
•Self supervision
•Less wiring
•Communication
•Less terminations
•Greater flexibility
•Less components
•Better functionality
•Less aging problems
•Adaptive functions
There are only advantages!
© ABB Group
April 13, 2015 | Slide 62
Fault Clearance System
Protection System
Circuit Breaker
CT
VT
Protection
Equipment
TE
DC-System
© ABB Group
April 13, 2015 | Slide 63
Trip
Coil
Circuit
Breaker
Mechanism
How to enhance dependability of fault
clearance system

The addition of a second main protection
increases the availability and dependability of
fault clearance system

In addition the provision of back-up protection
that operates independently of specified
devices in the main protection system
enhances this further.
© ABB Group
April 13, 2015 | Slide 64
Different parts of fault clearance system
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April 13, 2015 | Slide 65
Redundant protection system
Redundant system costs more but can give big savings in the primary
system due to short fault clearance time
© ABB Group
April 13, 2015 | Slide 66
© ABB Group
April 13, 2015 | Slide 67
Main functions of control

Control mode selection

Open/ Close

Position indication

Alarm Indication

Alarm system

Equipment supervision= Protection

HV equipment blocking

Anti pumping

Pole disagreement
© ABB Group
April 13, 2015 | Slide 68
Main functions of control

Interlocking

Voltage indication

Interposing (RTU)

Regulation

Synchronizing

Automation

Recording

Measuring

Metering

Logging

Network power control
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April 13, 2015 | Slide 69
Interlocking
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April 13, 2015 | Slide 70

CBs are not allowed to
operate if adjacent
disconnectors are in
intermediate position

Isolators are not permitted
to break power current
nor to interconnect
different voltage system.

Earthing switches may
only be operated if the
isolators on both sides
are open. Only an open
CB is not enough
Operation modes - Synchronising

Manual via instruments

Manual via synchronising check relay

Automatic closing via synchronising or synchronising check relay

For energising function the VT Fuses / MCBs should be
supervised
© ABB Group
April 13, 2015 | Slide 71
Disturbance Recorder & Event Logger

DisturbanceRecorder provides better understanding of the
behavior of Power network after a disturbance

The Event Logger is used to record the state of switchyard
equipment and relays and occurrences of alarms
© ABB Group
April 13, 2015 | Slide 72
© ABB Group
April 13, 2015 | Slide 73
Introduction
I1
Main tasks of current transformer are
Measurement of Current
Measurement of Power
I2
Isolation between High voltage and Low Voltage
Inputs to Relays & Protection Systems
I1
N1
I2
N2
I1 = N2
I2 = N1
IEC 44-1 and IEC 44-6 covers instrument transformers
© ABB Group
April 13, 2015 | Slide 74
CTs and VTs
Current transformer

I1/I2 = N2/N1

Magnetizing current is
negligible
Voltage transformer
© ABB Group
April 13, 2015 | Slide 75

E1/E2 = N1/N2

Voltage drop by
magnetizing current is
negligible
P1
Nitrogen Gas
Oil Level Ind.
Expan. Tank
Conn. Head
Pri. Terminal
Pri. Conductor
Pri. Insulation
Insulator
Terminal Box
Bottom Tank
Sec. Cores
CT – Construction
© ABB Group
April 13, 2015 | Slide 76
P2
CT
Saturation due to DC-offset (Transient saturation)
current
CT primary current
CT secondary current
time
Current Transformer output

Metering and instrument
High accuracy for 25-100 % of rated burden

Protection and DR
Lower accuracy but high capability to transform high fault
current. Protection classes 5P and 10P are acc to IEC 44-1
and cores for transient behavior are acc to IEC 44-6
© ABB Group
April 13, 2015 | Slide 78
Metering
Types of current transformers
Metering Core
VA Burden, Accuracy, ISF
e.g. 15 VA, 0.5 Cl., ISF < 10
Protection
Protection Core
VA Burden, Accuracy, ALF
e.g. 15 VA, 5P20
PS Core
Vk, Io, Rct
e.g. Vk > 400 V, Io < 50 mA at Vk/2, Rct < 5 Ohms
© ABB Group
April 13, 2015 | Slide 79
© ABB Group
April 13, 2015 | Slide 80
Introduction
Main tasks of Voltage transformer
Measurement of Voltage
Isolation between High Voltage & Low Voltage.
Inputs to Relay/Protection systems
PLCC (Power line Carrier Communication)
Types of voltage transformer
Magnetic voltage transformer (VT)
Capacitive voltage transformer (CVT)
IEC 186 covers voltage transformers
© ABB Group
April 13, 2015 | Slide 81
CTs and VTs
Current transformer

I1/I2 = N2/N1

Magnetizing current is
negligible
Voltage transformer
© ABB Group
April 13, 2015 | Slide 82

E1/E2 = N1/N2

Voltage drop by
magnetizing current is
negligible
VT with two secondary windings
© ABB Group
April 13, 2015 | Slide 83
CVT – Construction
Pri. Terminal
Metal Bellow
Insulator
Cap. Stack
HF Bushing
20 kV Bushing
Terminal Box
Spark Gap
Epoxy PT
EMU
© ABB Group
April 13, 2015 | Slide 84
Accuracy classes for for metering and
protection & disturbance recording as per
IEC 186
© ABB Group
April 13, 2015 | Slide 85
© ABB Group
April 13, 2015 | Slide 86