This document provides an overview of machine protection for generators and motors. It discusses the types of faults that can occur internally and externally and the corresponding protection functions used. Some key protection functions discussed include differential protection, overcurrent protection, impedance protection, stator and rotor earth fault protection, unbalanced load protection, reverse power protection, over/under voltage protection, over/under frequency protection, and others. It also discusses considerations for the selection of protection functions based on the rated power of the generator. Finally, it covers redundancy concepts for protection including full redundancy and partial redundancy.

1. Copyright © Siemens AG 2008. All rights reserved.
Copyright © Siemens AG 2008. All rights reserved.
Siemens Power Academy TD
SIPROTEC 4 - Application and exercises of generator/motor protection
SIPROTEC 4 -
Application and
exercises of
generator/motor
protection

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Copyright
©
Siemens
AG
2008.
All
rights
reserved.
Siemens Power Academy TD
01 Introduction into Machine Protection
Using numerical machine and motor protection
Version: C 3_Page 2
Presenter: Bernd Sommer
PTD EA12
Phone 0911-433-8222
Fax 0911-433-7396
email Bernd.Sommer@siemens.com
Training: Generator Protection
Introduction into Machine Protection

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2008.
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Siemens Power Academy TD
01 Introduction into Machine Protection
Using numerical machine and motor protection
Version: C 3_Page 3
Rotating Machines:
 Generators (asynchronous and synchronous)
 Motors (asynchronous and synchronous)
Stand still Machines:
 Transformers (variable design and vector groups)
The machine protection includes all numerical devices which are able to de
detect faults and abnormal operating conditions on machines and react
according the situation. It protects the objects against inadmissible stress
and it’s indirect also a human protection.
The protection devices must fulfil the following 3S criteria:
 Selectivity (switch off of the faulty system)
 Speed (fast as necessary)
 Security (high security and reliability)
What are Machines and what is Machine Protection?

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Siemens
AG
2008.
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Siemens Power Academy TD
01 Introduction into Machine Protection
Using numerical machine and motor protection
Version: C 3_Page 4
Internal Faults:
Stator:
 Earth Faults
 Short Circuits
(two and three phase)
 Inter-turn Faults
(at separate stator windings)
 Overload
Rotor, Excitation Circuit:
 Earth Faults
(single, double)
 Failure in the Excitation
(partly or loss of excitation)
 Voltage Rise
 Over-excitation (U/f)
Faults in Synchronous Generators (1)

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AG
2008.
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Siemens Power Academy TD
01 Introduction into Machine Protection
Using numerical machine and motor protection
Version: C 3_Page 5
Grid/Transformer:
 Earth Faults
 Short Circuits
 Overload
 Unbalanced Load
 Asynchronous Condition
(cap.load, long short circuit duration)
 Torsion Stress
 Under-frequency (PG < PL)
In Turbine, Regulation:
 Loss of Prime Mover
(Reverse power)
 Over- and Under-voltage
 Over- and Under-frequency
 Over-excitation (U/f)
(Wrong regulation)
Faults in Synchronous Generators (2)
External Faults:

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©
Siemens
AG
2008.
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Siemens Power Academy TD
01 Introduction into Machine Protection
Using numerical machine and motor protection
Version: C 3_Page 6
 Generator - Differential Protection; 87G
 Transformer - Differential Protection; 87T
 Overcurrent Time Protection; 50, 51V
 Impedance Protection; 21
 Stator Earth Fault Protection for:
Generators directly connected to the busbar; 67N
Generators connected to the busbar via unit transformer
Protection Range 90 % ; 64
Protection Range 100 %; 64 100%
 Rotor Earth Fault Protection; 64R
 Unbalanced Load
(Negative Sequence) Protection; 46
 Reverse Power Protection; 32R
Main Components of Machine Protection (Part 1)

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AG
2008.
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Siemens Power Academy TD
01 Introduction into Machine Protection
Using numerical machine and motor protection
Version: C 3_Page 7
 Overvoltage Protection (Undervoltage); 59, (27)
 Over and Under-frequency Protection; 81
 Underexcitation (Loss of field) Protection; 40
 Stator Overload Protection; 49
 Over-excitation (U/f) Protection; 24
 Out of Step Protection; 78
 Breaker Failure Protection; 50BF
 Rotor Overload Protection; 49R
(Overcurrent at excitation transformer)
 Interturn Fault Protection
(separate Stator windings - hydro generators)
 Tripping matrix (Software matrix)
Main Components of Machine Protection (Part 2)

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AG
2008.
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Siemens Power Academy TD
01 Introduction into Machine Protection
Using numerical machine and motor protection
Version: C 3_Page 8
Protection ANSI Generator – Rated Power (MVA)
< 5 5 - 50 50 - 200 > 200
Stator earth fault 90 % 64, 59N, 67N X X X X
Stator earth fault 100 % 64(100%) X X
Differential 87G, 87T o X X X
Overcurrent time 50, 51V X X o o
Impedance 21 X X
Interturn fault X
Rotor earth fault 64R o X X X
Unbalanced load 46 X X X
Underexcitation 40 o X X X
Out of step 78 X
Stator overload 49 X X X X
Rotor overload 49R X
Overvoltage 59 X X X X
Frequency f > 81 X X X X
Frequency f < 81 X X X
Reverse power 32 X X X X
Undervoltage 27 Y Y Y Y
Overexcitation (U/f) 24 o X X
Y: Pump storage stations (motor /phase shift operation
o option
Proposal for Selection of Protection Functions

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Siemens
AG
2008.
All
rights
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Siemens Power Academy TD
01 Introduction into Machine Protection
Using numerical machine and motor protection
Version: C 3_Page 9
At the unit protection more than one trips and breakers are to handle.
It depends on the fault type, the plant design and plant operation,
generator operation and general operation philosophy.
 Generator Breaker
 Excitation Breaker
 Turbine Rapid Shut Down
 HV Network Breaker
 Auxiliary Supply Breaker 1
 Auxiliary Supply Breaker 2
 Aux. Supply Changeover
 SEE/SFC, Unit-trafo
 SEE/SFC, Aux.-trafo
 Reserve
 Special Trips at Hydro
Stations (e.g. braking)
Breakers
Protection
Functions
Tripping Concept

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©
Siemens
AG
2008.
All
rights
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Siemens Power Academy TD
01 Introduction into Machine Protection
Using numerical machine and motor protection
Version: C 3_Page 10
7UM6
Protection Group B
G
7UM6
Protection Group A
Redundancy Concepts (Large Units)
Each Object Protected by 2 Devices

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Siemens
AG
2008.
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rights
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Siemens Power Academy TD
01 Introduction into Machine Protection
Using numerical machine and motor protection
Version: C 3_Page 11
G
7UM62
Without Redundancy
Invest cost optimisation
G
7UM62
Partly Redundancy
(also limitations at the CTs and VTs
and trip circuits)
System/-cost optimisation
7UM61
Alternatives to the Full Redundancy