powerSystem protection_compact_part1

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

© ABB Group April 13, 2015 | Slide 4

Medium Voltage Products

Transformers

Offerings in ABB Power Systems

© ABB Group April 13, 2015 | Slide 5

Substations

Grid Systems

Power Generation

Network Management

Protection & Control 

© ABB Group 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 

© ABB Group April 13, 2015 | Slide 14

Install series capacitor

Direction of rotation and mechanical and electrical torques for a generator rotor

Tm Te

© ABB Group April 13, 2015 | Slide 15

Synchronous stability : Equal area method Angular change If transferred power during fault is not zero

© ABB Group 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

© ABB Group April 13, 2015 | Slide 18

The shunt reactor absorbs the capacitive power generated in long lines and limits over voltages

© ABB Group 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

© ABB Group 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





© ABB Group 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



© ABB Group 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

© ABB Group 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

© ABB Group April 13, 2015 | Slide 45

Remote back-up protection with time grading

© ABB Group April 13, 2015 | Slide 46

Principle of breaker failure protection

© ABB Group 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 64S

CTRL

F 81 CTRL

0->I 79

I> 51

CTRL

I TH 49 SYNC

25 Logics

e.g. Z