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1. GENERATOR PROTECTION

2. TURBO GENERATOR
DIESEL GENERATOR
HYDRO GENERATOR
WIND GENERATOR
GENERATOR PROTECTION
TYPES OF GENERATORS

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

4. PROTECTION OF GENERATOR
STATOR WINDING FAULTS
FIELD /ROTOR WINDING FAULTS
FAULTS DUE TO ABNORMAL OPERATING
CONDITIONS
FAULTS RELATED TO SUB SYSTEMS
PROTECTIONS FOR CONTROL
GENERATOR PROTECTION

5. OVER LOAD
OVER CURRENT
SHORT CIRCUIT
UNBALANCE LOADING
INTER TURN FAULT ( Ph to Ph)
INTER TURN FAULT(Ph to EARTH)
EARTH FAULT 90%
EARTH FAULT 100%
GENERATOR PROTECTION
STATOR FAULTS

6. ROTOR EARTH FAULT
ROTOR OVER VOLTAGE
UNDER EXCITATION
OVER EXCITATION
DIODE FAILURE
GENERATOR PROTECTION
ROTOR FAULTS

7. UNBALANCE LOAD
OVER FLUXING
REVERSE POWER
LOW FORWARD POWER
LOSS OF EXCITATION
OVER SPEED
OUT OF STEP
GENERATOR PROTECTION
FAULTS DUE ABNORMAL OPERATING CONDITIONS

8. FAULTS RELATED TO SUB-SYSTEMS
UNDER VOLTAGE
OVER VOLTAGE
UNDER FREQUENCY
OVER FREQUENCY
GENERATOR PROTECTION

9. CATEGORY OF PROTECTIONS
CLASS A
CLASS B
GENERATOR PROTECTION

10. CATEGORY OF PROTECTIONS- CLASS A
GENERATOR PROTECTION
GENERATOR BREAKER IS TRIPPED
TURBINE / PRIME MOVER is STOPPED
-DIFFERENTIAL FAULT
-EARTH FAULT
-SHORT CIRCUIT
-2
ND
ROTOR E/F
-HIGH BEARING TEMP

11. CATEGORY OF PROTECTIONS- CLASS B
GENERATOR PROTECTION
GENERATOR BREAKER IS TRIPPED
-REVERSE POWER
-OVER CURRENT
-THERMAL OVER LOAD
-UNBALANCE
-UNDER /OVER VOLTAGE
-UNDER /OVER FREQUENCY
-OVER FLUXING

12. GENERATOR PROTECTION
TYPES OF FAULTS (STATOR SIDE)
VOLTAGE RESTRAINED O/C
SHORT CIRCUIT
THERMAL OVER LOAD
CURRENT UNBALANCE
DIFFERENTIAL
EARTH FAULT (100%)
EARTH FAULT (95%)
OUT OF STEP
ROTOR EARTH FAULT
EXCITATION UNDER VOLTAGE
EXCITATION UNDER CURRENT
DIODE FAILURE
GENERATOR PROTECTION
OVER VOLTAGE
UNDER VOLTAGE
OVER FREQUENCY
UNDER FREQUENCY
LOSS OF FIELD
REVERSE POWER
UNDER POWER
INADVERTANT NERGISATION
OVER FLUXING (V/Hz)
CHECK SYNCHRONISING
AUTO SYNCHRONISING
LOAD SHARING
LOAD SHEDDING
TRIP CICUIT SUPERVISION
PT FUSE FAILURE

13. SINGLE LINE DIAGRAM
GENERATOR PROTECTION
G

49 4640
81
32
87G
51V 3764
5927
11 kV
6.6 MW
400/5
400/5
400/5
11000/110v
GENERATOR PROTECTION

14. PROTECTION PHILOSOPHY
TYPE OF GENERATOR
GENERATOR SIZE
NATURE OF GROUNDING
ECONOMY
TYPE OF CONNECTION
TYPE OF LOADS
GENERATOR PROTECTION

15. GENERATOR PROTECTION
ANOTOMY OF FAULTS

16. 1.01.0 OVER CURRENT PROTECTIONOVER CURRENT PROTECTION
STATOR FAULTS (EXTERNAL )
PLAIN OVER CURRENT
( SMALL MACHINES)
VOLTAGE DEPENDANT OVER CURRENT
(LARGE MACHINES)

17. 1.01.0 PLAIN OVER CURRENT PROTECTIONPLAIN OVER CURRENT PROTECTION
STATOR FAULTS (EXTERNAL )
RELAY ON BREAKER SIDE
RELAY ON NEUTRAL SIDE

18. 1.01.0 PLAIN OVER CURRENT PROTECTIONPLAIN OVER CURRENT PROTECTION
STATOR FAULTS (EXTERNAL )
FAULT AWAY FROM TERMINALS
(PLAIN O/C PROTECTION)
FAULT CLOSE TO TERMINALS
(VOLTAGE DEPENDENT O/C)

19. 1.01.0 FAULT CLOSE TO TERMINALSFAULT CLOSE TO TERMINALS
STATOR FAULTS (EXTERNAL )

20. VOLTAGE DEPENDENT OVER CURRENTVOLTAGE 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

21. VOLTAGE CONTROLLED OVER CURRENTVOLTAGE CONTROLLED OVER CURRENT
STATOR FAULTS
HAS TWO TRIP CHARACTERISTICS
THE TERMINAL VOLTAGE DECIDES
WHICH CHARCTERISTIC WILL BE
FOLLOWED BY THE RELAY WHEN
A FAULT OCCURS

22. VOLTAGE CONTROLLED OVER CURRENTVOLTAGE CONTROLLED OVER CURRENT
STATOR FAULTS
I >
kI >
Vs >
Voltage Level
Pick up level

23. VOLTAGE RESTRAINED OVER CURRENTVOLTAGE RESTRAINED OVER CURRENT
V/Vs
I*/ [I>]
0.2 0.8
0.2
1.0
GENERATOR PROTECTION

24. EARTH FAULTEARTH FAULT
STATOR FAULTS
DEPENDS ON HOW
THE GENERATOR IS EARTHED

25. GENERATOR PROTECTION
EARTHING OF GENERATORS
GENERATOR NEUTRAL IS EARTHED
-for stator protection
-for operator safety

26. GENERATOR PROTECTION
EARTHING OF GENERATORS – DIRECT EARTHING
Stator Windings
RELAY

27. 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)

28. GENERATOR PROTECTION
EARTHING OF GENERATORS –
RESISTANCE EARTHING
Stator Windings
CURRENT
RELAY

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

30. GENERATOR PROTECTION
EARTHING OF GENERATORS –
TRANSFORMER EARTHING (CURENT BASED)
Stator Windings
CURRENT
RELAY

31. GENERATOR PROTECTION
EARTHING OF GENERATORS –
TRANSFORMER EARTHING (OPEN DELTA)
Stator Windings
VOLTAGE
RELAY
OPEN
DELTA PT
VOLTAGE
RELAY

32. EARTH FAULTEARTH FAULT
STATOR FAULTS
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

33. STATOR EARTH FAULT
95% EARTH FAULT NORMAL RELAY
100% EARTH FAULT SPECIAL RELAY
SENSES ABSENCE
OF 3RD HARMONICS
GENERATOR PROTECTION

34. STATOR EARTH FAULT
0 %
95%
95 TO 100%
GENERATOR PROTECTION

35. GENERATOR PROTECTION
-Third harmonic Voltage is always present at neutral.
-When there is a fault close to neutral,
this comes down or disappears.
-First E/F near neutral, produces negligible current
as driving voltage is zero
-But, if there ia another E/F at the machine terminal,
fault current will be very high.
-Hence the first E/F ( close to neutral) has to be cleared fast.

36. GENERATOR PROTECTION
EARTHING OF GENERATORS –
(Close to neutral faults)
Stator Windings
CURRENT
RELAY
a If
V
If = aV / R

37. 100% STATOR EARTH FAULT
GENERATOR PROTECTION
Measurement of third harmonic voltage
across the earthing impedance
Use of low frequency voltage injection
between star point & earth

38. 100% STATOR EARTH FAULT – DC INJECTION METHOD
GENERATOR PROTECTION

39. GENERATOR PROTECTION
Differential Protection
This is to handle faults
inside the Generator

40. 87
64
Internal Faults
87Differential fault
64Restricted Earth Fault
GENERATOR PROTECTION

41. TRANSFORMER PROTECTION
COMBINED PROTECTIONS – DIFFERENTIAL

42. TRANSFORMER PROTECTION
COMBINED PROTECTIONS – DIFFERENTIAL
Should trip for an internal fault.
Trip time is always instantaneous.
Should not trip for an external fault.

43. GENERATOR PROTECTION
87
I
1
I
2
Id = Relay Pick up setting
Relay will trip if
I1 – I2 > Id
Differential Protection
Notes :
Under Normal conditions
(when machine is on load)
I1=I2 Id=0, Relay will not trip.

44. GENERATOR PROTECTION
87
I
1
I
2
Id = Relay Pick up setting
Relay will trip if
I1 – I2 > Id
Differential Protection
Notes :
Under External fault conditions
I1 = I2, Id= 0 ????????????
Relay will not trip.

45. GENERATOR PROTECTION
87
I
1
I
2
Id = Relay Pick up setting
Relay will trip if
I1 – I2 > Id
Differential Protection
Notes :
Under Internal fault conditions
I2=0, I1-I2 = I1, Id= IL
Relay will trip.

46. CT CORE CHARACTERISTIC

47. GENERATOR PROTECTION
B
H ( Proportional I1 or I2)
B1
B2
Notes :
For same H,
CT1 can be at B1
CT2 can be at B2

48. GENERATOR PROTECTION
Effect of CT Mis-match
Under an External fault ( through fault ),
even when the primary side currents of the CTs are same,
the secondary currents I1 & I2 of the CTs will not be same
since CT1 is at B1 and CT2 is at B2
This may result in an unwanted differential current Id
and the relay will trip for a through fault.

49. GENERATOR PROTECTION
Problems of a simple differential relay
Spurious trippings at :
Inrush
Tap change
Load throw off
Through fault

50. TRANSFORMER PROTECTION
Characteristics of a simple differential relay
Average Current I.
Id
0.15

51. GENERATOR PROTECTION
Average Current I.
BIASED DIFFERENTIAL
I1 - I2 RELAY OPERATING
CURRENT
(I1+I2)/2 RELAY RESTRAINING
CURRENT
TRIP SETTING = (I1- I2)
(I1 +I2)/2
(BIAS %)
NORMALLY BIAS % =
20%
RELAY WILL TRIP WHEN
Id > (2*(I1 - I2)/(I1+I2))*100

52. 1.PERCENTAGE BIASED
2.DUAL SLOPE
3.DISPLAYS OF Id
4.VECTOR/AMPLITUDE
COMPENSATION (W/O ICTs)
5.2ND HARMONIC RESTRAINT
6.5TH HARMONIC RESTRAINT
7.WAVE FORM CAPTURE
8. INBUILT REF
DIFFERENTIAL

53. Characteristics of a simple differential relay
Average Current I.
Id
0.15
P1 P2

54. Over Fluxing Protection
•Grid transformers
Usually only a problem during run-up or shut down, but
can be caused by loss of load / load shedding etc.
Flux   V/ f
•Generator transformers
•Effects of overfluxing :
–Increase in magnetising current
–Increase in winding temperature
–Increase in noise and vibration
–Overheating of laminations and metal parts (caused
by stray flux)

55. V/Hz PROTECTION
- INCORRECT VOLTAGE REGULATOR ACTION (High Voltage)
- LOAD THROW – OFF ( High Voltage)
-SUDDEN OVER VOLTAGE
-OVER LOAD ( LOW FREQUENCY)
RESULTS IN OVER FLUXING OF GENERATOR
AND OVER HEATING
GENERATOR PROTECTION

56. Over Fluxing Protection
m
Ie
m


57. Over Fluxing Protection
V/Hz 1.051.1 1.151.2 1.25
Damage
Time(min) Inf 20 6 1 0.2

58. VOLTAGE, FREQUENCY & NEUTRAL MONITORING
THREE PH O/V & U/V
THREE PH O/F & U/F
ZERO SEQUENCE VOLTAGE 2 LEVELS
OVER FLUXING 2 LEVELS
VOLTAGE UNBALANCE 2 LEVELS
VECTOR SURGE OPTION
NO NEED FOR OPEN DELTA PT

59. 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

60. Under-excitation or a total loss of excitation can result from
-a short circuit
-open circuit in the excitation circuit,
- a mal-operation of the automatic voltage regulator,
-incorrect control of generators and transformers, or
- in the event of a generator connected to a system
with capacitive load.
GENERATOR PROTECTION

61. LOSS OF FIELD IN GENERATORS
PHASE ANGLE BETWEEN
ANGLE  VOLTAGE & CURRENT
IMPEDANCE REPLICA OF
ANGLE  PHASE ANGLE
 = 360
O
- 
GENERATOR PROTECTION

62. LOSS OF FIELD IN GENERATORS
I


Z
GENERATOR PROTECTION

63. GENERATOR PROTECTION
The amount of power that
a generator can deliver is
defined by the
"generator capability curve".

64. GENERATOR PROTECTION
The capability curves of a synchronous
generator operating at rated voltage
give the maximum active- and reactive-
power loadings that can be suplied
without exceeding the KVA rating
(armature heating limit) or the field
heating limit.
 

65. GENERATOR PROTECTION

66. R
X
Z
LOSS OF
FIELD
NORMAL
LOSS OF FIELD
PROTECTION
GENERATOR PROTECTION

67. R
X
Z
LOSS OF
FIELD
NORMAL
K1
K2
LOSS OF FIELD
PROTECTION
GENERATOR PROTECTION

68. GENERATOR PROTECTION
Specifications of Generator 
Make: BHEL
MVA: 247
Connection: Three PhaseDouble
Star Connected.
Voltage: 15750 Volts
Current: 9050 Amp
Frequency: 50 Hz
Speed: 3000 RPM
No. of Poles: 2
Synchronous Impedance: 222%
Sub Transient Impedance: 30.5%
Transient Impedance: 21.4%
Cooling: water/ HydrogenCooled
Neutral Grounding: High lmpedance thro NGT

69. GENERATOR PROTECTION
Setting criteria
K1 = 0.5*Xd*CTR/PTR
 
Xd
 = 30.5% = 0.305 pu ……
(sub-transient reactance of generator)
 
Xd in ohms = Xd (pu)*kv
2
/MVA
= 0.305*15.75
2
/247=0.306311993
K1 = 2.139 ohm
K2 = Xs * CTR/PTR
 
Xd (ohmic) = Xd(pu)*kv
2
/MVA
K2 = 2.22(15.75
2
/247)(10000/5)(110/15750)=
 31.14 ohm

70. 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

71. INADVERTANT ENERGISATION
- APPLICATION OF FULL VOLTAGE AT
STANDSTILL
COASTING TO STOP
BEFORE SYNCHRONISM
- PRESENCE OF UNBALANCE VOLTAGE DUE TO
FLASH OVER AT ONE 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

72. GENERATOR PROTECTION
ROTOR EARTH FAULT
Detection Methods
-High resistance across rotor winding
-Low frequency ac injection

73. ROTOR EARTH FAULT – AC INJECTION METHOD
GENERATOR PROTECTION
based on injection of AC auxiliary voltage to field winding through a capacitor.
When any point of field winding is grounded, circuit will be complete and the
protection signalizes the rotor ground fault.

74. ROTOR EARTH FAULT – DC INJECTION METHOD
GENERATOR PROTECTION
The DC output of the rectifier is connected to the field circuit and the second output
is grounded. Every point of the field winding grounded closes circuit through
current relay

75. GENERATOR PROTECTION

76. GENERATOR PROTECTION
Diode failure relay

77. GENERATOR PROTECTION
Brushless Exciters

78. GENERATOR PROTECTION PACKAGESGENERATOR PROTECTION PACKAGES
CURRENT
MC11
MC61A
MC61C
IM30G
IM3G-V
VOLTAGE
MV11
MND11
MVP-01
DIFFERENTIAL
MD32-G
SC14S
ROTOR
UBO/CR
SYNCHRONISING
SCM21 / SPM21
ISLANDING
UFD34
UM30
MW33
LOAD SHEDDING
UFD34
MW33
MX7/5
REX-8
LOAD SHARING
RRS

79. SYNCHRONISATION
OF GENERATORS

80. 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

81. 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

82. PARAMETERS GOVERNING
SYNCHRONISATION :
VOLTAGE
FREQUENCY
PHASE ANGLE

83. B1 B2
G1
G2
PT1
PT2
COMMON BUS
SYNCHRONISING OF GENERATORS
SCM 21

84. 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

85. TYPES OF SYNCHRONISING RELAYS
CHECK SYNCHRONISING RELAY
AUTO SYNCHRONISING RELAY

86. 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
CHECK SYNCHRONISING RELAY

87. AUTO SYNCHRONISING RELAY 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

88.  
 
-
BC1
BC2
B1 B2 B3
G1 G2 G3
PT1
PT2
PT3
CT1
CT2
CT3
BUS-1 BUS-2 BUS-3
PULSES FOR
GOVERNOR &
EXCITER
PULSES FOR
GOVERNOR &
EXCITER
PULSES FOR
GOVERNOR &
EXCITER
LOAD SHARING OF GENERATORS
LSR = LOAD SHARING RELAY
Fig. -1
L
S
R
L
S
R
L
S
R
L
S
R
L
S
R
L
S
R

89. 
GRID ISLANDING SCHEME

REVERSE POWER RELAY
LOW FORWARD POWER RELAY
UNDER VOLTAGE RELAY
DIRECTIONAL O/C + E/F RELAY
dF/dT RELAY
UNDER FREQ. RELAY
OVER FREQ. RELAY
VECTOR SURGE RELAY
DG
GRID INCOMER
TRANSFORMER
PLANT
LOADS

Fig. -2

90. GENEATOR PROTECTION - BUILDING BLOCKS FROM L&T
PROTn.
RELAY
DIFF.
RELAY
SYNCH.
RELAY
LOAD
SHARE
RELAY
GRID
ISLAND
RELAY
SCHEME FOR :
AUTO START, SYNCH.& LOAD SHARING
GRID ISLANDING & LOAD SHEDDING
COMMUNICATION SOFTWARE FOR
CENTRALISED DAS AND CONTROL
Fig.-3
PC SYSTEM
WITH
SOFTWARE