GENERATOR PROTECTION

GENERATOR PROTECTION

TYPES OF GENERATORS

 TURBO GENERATOR
 DIESEL GENERATOR
 HYDRO GENERATOR
 WIND GENERATOR
 GENERATOR PROTECTION

GENERATOR MAIN-SYSTEMS
SUB SYSTEMS OF GENERATORS

• STATOR
• ROTOR
• TRANSFORMER
 GENERATOR PROTECTION

GENERATOR SUB-SYSTEMS
SUB SYSTEMS OF GENERATORS
• STATOR
• ROTOR
• PRIME MOVER
• EXCITATION SYSTEM
• VOLTAGE REGULATOR
• GOVERNOR
• COOLING SYSTEM
 GENERATOR PROTECTION

FAULTS IN GENERATOR

EXTERNAL FAULTS
 INTERNAL FAULTS
 ROTOR EARTH FAULT
 FAULTS RELATED TO SUB SYSTEMS
 GENERATOR PROTECTION

EXTERNAL FAULTS

OVER LOADING
UNBALANCE LOADING
SHORT CIRCUIT
EARTH FAULT
 GENERATOR PROTECTION

INTERNAL FAULTS

• PHASE TO PHASE FAULTS

IN WINDINGS
• PHASE TO EARTH FAULTS
 GENERATOR PROTECTION
FAULTS RELATED TO SUB-SYSTEMS

 UNDER VOLTAGE
 OVER VOLTAGE
 UNDER FREQUENCY
 OVER FREQUENCY
 REVERSE POWER
 LOSS OF EXCITATION
 LOW-FORWARD POWER
 GENERATOR PROTECTION
TYPES OF FAULTS (STATOR SIDE)
GENERATOR PROTECTION
VOLTAGE RESTRAINED OVER CURRENT
THERMAL OVER LOAD
CURRENT UNBALANCE
OVER VOLTAGE
UNDER VOLTAGE
OVER FREQUENCY
UNDER FREQUENCY
LOSS OF FIELD
REVERSE POWER
UNDER POWER

OUT OF STEP
INADVERTANT ENERGISATION
EARTH FAULT (100%)
EARTH FAULT (95%)

GENERATOR DIFFERENTIAL

OVER EXCITATION (V/Hz)

 GENERATOR PROTECTION

TYPES OF FAULTS (ROTOR SIDE)

ROTOR EARTH FAULT

EXCITATION UNDER VOLTAGE
EXCITATION UNDER CURRENT
DIODE FAILURE
 GENERATOR PROTECTION
SINGLE LINE DIAGRAM
11 kV GENERATOR PROTECTION

11000/110v

 27 59 81

400/5 49 51V 46 40 32 37 64

400/5

87G
6.6 MW
G

400/5
 GENERATOR PROTECTION

PROTECTION PHILOSOPHY

TYPE OF GENERATOR
GENERATOR SIZE
NATURE OF GROUNDING
ECONOMY
TYPE OF CONNECTION
TYPE OF LOADS
 GENERATOR PROTECTION

ANOTOMY OF FAULTS
 STATOR FAULTS (EXTERNAL )

1.0 OVER CURRENT PROTECTION

PLAIN OVER CURRENT

( SMALL MACHINES)

VOLTAGE DEPENDANT OVER CURRENT

(LARGE MACHINES)
 STATOR FAULTS (EXTERNAL )

1.0 PLAIN OVER CURRENT PROTECTION

RELAY ON BREAKER SIDE

RELAY ON NEUTRAL SIDE

 STATOR FAULTS (EXTERNAL )

1.0 PLAIN OVER CURRENT PROTECTION

FAULT AWAY FROM TERMINALS

(PLAIN O/C PROTECTION)

FAULT CLOSE TO TERMINALS

(VOLTAGE DEPENDENT O/C)
 STATOR FAULTS

VOLTAGE DEPENDENT OVER CURRENT

- WHEN O/C FAULT, TERMINAL VOLTAGE REDUCES.

- RELAY MAY NOT TRIP, SINCE FAULT CURRENT
THROUGH RELAY MAY BE LESS THAN SET POINT

NECESSARY TO VARY THE O/C PICK UP SETTING

WITH RESPECT TO VOLTAGE
 STATOR FAULTS
VOLTAGE CONTROLLED OVER CURRENT

HAS TWO TRIP CHARACTERISTICS

THE TERMINAL VOLTAGE DECIDES

WHICH CHARCTERISTIC WILL BE
FOLLOWED BY THE RELAY WHEN
A FAULT OCCURS
 STATOR FAULTS
VOLTAGE CONTROLLED OVER CURRENT

Pick up level

I>

kI >

Voltage Level
Vs >
 GENERATOR PROTECTION

VOLTAGE RESTRAINED OVER CURRENT

I*/ [I>]

1.0

0.2

0.2 0.8 V/Vs

 STATOR FAULTS

EARTH FAULT

DEPENDS ON HOW
THE GENERATOR IS EARTHED
 GENERATOR PROTECTION

EARTHING OF GENERATORS

GENERATOR NEUTRAL IS EARTHED

- for stator protection

- for operator safety
 GENERATOR PROTECTION

EARTHING OF GENERATORS – DIRECT EARTHING

Stator Windings

RELAY
 GENERATOR PROTECTION

EARTHING OF GENERATORS –
IMPEDANCE EARTHING
Stator Windings

TYPES OF IMPEDANCES

• RESISTOR
(CURRENT BASED PROTECTION)
B) TRANSFORMER
(VOLTAGE BASED PROTECTION)
C) TRANSFORMER
D) (CURRENT BASED PROTECTION)
 GENERATOR PROTECTION
EARTHING OF GENERATORS –
RESISTANCE EARTHING
Stator Windings

CURRENT
RELAY
 GENERATOR PROTECTION
EARTHING OF GENERATORS –
TRANSFORMER EARTHING (VOLTAGE BASED)
Stator Windings

VOLTAGE
RELAY
 GENERATOR PROTECTION
EARTHING OF GENERATORS –
TRANSFORMER EARTHING (CURENT BASED)
Stator Windings

CURRENT
RELAY
 GENERATOR PROTECTION
EARTHING OF GENERATORS –
TRANSFORMER EARTHING (OPEN DELTA)
Stator Windings

OPEN
DELTA PT

VOLTAGE
RELAY
VOLTAGE
RELAY
 STATOR FAULTS

EARTH FAULT

WHEN A FAULT OCCURES CLOSE TO NEUTRAL,

WITH IMPEDANCE GROUNDING, THE
E/F CURRENT MAY BE LESS THAN THE
PICK UP THRESHOLD OF THE NORMAL
E/F RELAY OR DIFFERENTIAL RELAY
 GENERATOR PROTECTION

STATOR EARTH FAULT

95% EARTH FAULT NORMAL RELAY

100% EARTH FAULT SPECIAL RELAY

SENSES ABSENCE
OF 3RD HARMONICS
 GENERATOR PROTECTION

STATOR EARTH FAULT

0%

95 TO 100%
95%
 GENERATOR PROTECTION
EARTHING OF GENERATORS –
(Close to neutral faults)
Stator Windings
V

a If

CURRENT If = aV / R
RELAY
 GENERATOR PROTECTION

100% STATOR EARTH FAULT

Measurement of third harmonic voltage

across the earthing impedance

Use of low frequency voltage injection

between star point & earth
 GENERATOR PROTECTION

LOSS OF FIELD IN GENERATORS

GENERATOR WILL OVER SPEED &

OPERATE AS AN INDUCTION GENERATOR
(OVER SPEEDS OF THE ORDER OF 2 TO 5% )

GENERATOR WILL CONTINUE TO DELIVER POWER

WILL DERIVE EXCITATION FROM THE SYSTEM

STATOR CURRENT WILL BE 200%

THERE WILL BE HEAVY ROTOR CURRENT
RESULTS IN OVER HEATING
 GENERATOR PROTECTION

LOSS OF FIELD IN GENERATORS

PHASE ANGLE BETWEEN

ANGLE  VOLTAGE & CURRENT

IMPEDANCE REPLICA OF
ANGLE  PHASE ANGLE

 = 360O - 
 GENERATOR PROTECTION
LOSS OF FIELD IN GENERATORS




Z
 GENERATOR PROTECTION

 = 0o (360O) FORWARD RESISTIVE

 = +30o FORWARD RESISTIVE + FORWARD CAPACITIVE
= +60o FORWARD RESISTIVE + FORWARD CAPACITIVE

= +90o FORWARD CAPACITIVE (LOSS OF FIELD)

 = +120o REVERSE RESISTIVE + FORWADRD CAPACITIVE

 = +150o REVERSE RESISTIVE + FORWARD CAPACITIVE
 = +180o REVERSE RESISTIVE

 = +210o (-150O) REVERSE RESISTIVE + FORWARD INDUCTIVE

 = +240o (-120O) REVERSE RESISTIVE + FORWARD INDUCTIVE

 = +270o (-90O) FORWARD INDUCTIVE

 = +300o (-60O) FORWARD INDUCTIVE + FORWARD RESISTIVE

 = +330o (-30O) FORWARD INDUCTIVE + FORWARD RESISTIVE
 GENERATOR PROTECTION

LOSS OF FIELD X
PROTECTION

Z
NORMAL
R

LOSS OF
FIELD
 GENERATOR PROTECTION

LOSS OF FIELD X
PROTECTION

Z
NORMAL
R
K1

LOSS OF
FIELD K2
 GENERATOR PROTECTION

REVERSE POWER GENERATORS

GENERATOR WILL BECOME MOTOR

HARMFUL TO THE PRIME MOVER

( STEAM TURBINE WILL OVER HEAT)

(DIESEL ENGINE WILL EXPLODE DUE
TO UNBURNT FUEL)
(HYDRAULIC TUBINE WILL HAVE CAVITATION)
 GENERATOR PROTECTION

INADVERTANT ENERGISATION

- APPLICATION OF FULL VOLTAGE AT

STANDSTILL
COASTING TO STOP
BEFORE SYNCHRONISM

- PRESENCE OF UNBALANCE VOLTAGE DUE TO

FLASH OVER AT IONE OR TWO POLES OF BREAKER

GENERATOR FORCED TO START AS

INDUCTION MOTOR RESULTING IN MECHANICAL
DAMAGES TO PRIME MOVER AND EXCESSIVE
HEATING IN THE ROTOR
 GENERATOR PROTECTION

V/Hz PROTECTION

- INCORRECT VOLTAGE REGULATOR ACTION

- LOAD THROW - OFF
- SUDDEN OVER VOLTAGE / OVER FREQUENCY

RESULTS IN OVER FLUXING OF GENERATOR

AND OVER HEATING
 GENERATOR PROTECTION PACKAGES

CURRENT VOLTAGE SYNCHRONISING

MC11 MV11 SCM21 / SPM21
MC61A MND11
MC61C MVP-01
ISLANDING
IM30G UFD34
DIFFERENTIAL UM30
IM3G-V
MD32-G MW33
SC14S
LOAD SHEDDING
ROTOR UFD34
LOAD SHARING MW33
UBO/CR
RRS MX7/5
REX-8
 LOAD SHARING OF GENERATORS

BC1 BC2
BUS-1 BUS-2 BUS-3
 
 B1  B2  B3
PT2 PT3
PT1
L L L L
L L S S S S
S S - R R R R
R R CT3
CT1 CT2

G1 PULSES FOR G2 PULSES FOR G3 PULSES FOR

GOVERNOR & GOVERNOR &
GOVERNOR & EXCITER EXCITER
EXCITER

LSR = LOAD SHARING RELAY

Fig. -1
 GRID ISLANDING SCHEME

GRID INCOMER
TRANSFORMER

REVERSE POWER RELAY

LOW FORWARD POWER RELAY
UNDER VOLTAGE RELAY
DIRECTIONAL O/C + E/F RELAY


   

dF/dT RELAY
UNDER FREQ. RELAY
DG
OVER FREQ. RELAY PLANT
VECTOR SURGE RELAY LOADS
Fig. -2
SYNCHRONISATION
OF GENERATORS
SYNCHRONISING IS THE PROCESS OF
ELECTRICALLY CONNECTING
TWO AC POWER SOURCES WITH
ROTATING MACHINES

WITHOUT ANY DISTURBANCE TO

EXISTING SYSTEM AND

WITHOUT ANY DAMAGE TO THE

EXISTING SYSTEM
 SYNCHRONISATION

SINGLE GENERATOR TO A BUS

(DEAD BUS / LIVE BUS SYNCH.)

MULTIPLE GENERATORS TO A BUS

(SIZE, VINTAGE, RESPONSE TIMES)

AUTO CHANGEOVER IN BUS CONNECTIONS

MANUAL & AUTO SYNCHRONISATION

REVERSE SYNCHRONISATION
PARAMETERS GOVERNING
SYNCHRONISATION :

VOLTAGE

FREQUENCY

PHASE ANGLE
 SYNCHRONISING OF GENERATORS

COMMON BUS

 B1  B2
PT1 PT2

SCM 21

G1 G2
 RESULTS OF INCORRECT SYNCHRONISATION

FREQUENCY ACTIVE POWER FLOW

HIGH FREQ. TO LOW FREQ.

PHASE ANGLE JOLT TO THE SYSTEM

FATIGUE TO SHAFT
DAMAGE TO BEARINGS
OVER HEATING OF STATOR

VOLTAGE REACIVE POWER FLOW

HIGH VOLTAGE TO LOW VOLTAGE
TYPES OF SYNCHRONISING RELAYS

CHECK SYNCHRONISING RELAY

AUTO SYNCHRONISING RELAY

 CHECK SYNCHRONISING RELAY

ADJUSTABLE SETTINGS FOR F, V, 

MINIMUM V,F FOR CB CLOSURE
DEAD BUS / DEAD LINE SELECTION
CB CLOSURE ONLY IF  IS DECREASING
BREAKER OPERATING TIME
MINIMUM RECLOSING TIME
2LINE + 1 BUS CONFIGURATION
U/V + O/V PROTECTION

SYNCHRONISING TROLLEY
AUTO SYNCHRONISING RELAY

IN ADDITION TO SCM21 FEATURES:

INC / DEC PULSES FOR GOVERNOR

INC / DEC PULSES FOR AVR
ADJUSTABLE PULSE WIDTH
PULSES PROPORTIONAL TO F, V
KICKER PULSE CONTROL
ANTI MOTORING CONTROL