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To detect the fault and initiate the
operation of the circuit breaker to isolate the defective element from the rest
of the system, thereby protecting the system from damages consequent to the
2. Give the consequences of short circuit.
Whenever a short-circuit occurs, the current
flowing through the coil increases to an enormous value. If protective relays
are present , a heavy current also flows through the relay coil, causing it to
operate by closing its contacts.The trip circuit is then closed , thecircuit
breaker opens and the fault is isolated from the rest of the system. Also, a
low voltage may be created which may damage systems connected to the supply.
3. Define protected zone.
Are those which are directly protected by a
protective system such as relays, fuses or switchgears.If a fault occurring in
a zone can be immediately detected and or isolated by a protection scheme
dedicated to that particular zone.
What are unit system and non unit system?
A unit protective system is one in which
only faults occurring within its protected zone are isolated.Faults occurring
elsewhere in the system have no influence on the operation of a unit system.A
non unit system is a protective system which is activated even when the faults
are external to its protected zone.
5. What is primary protection?
Is the protection in which the fault
occurring in a line will be cleared by its own relay and circuit breaker.It
serves as the first line of defence.
6. What is back up protection?
Is the second line of defence , which
operates if the primary protection fails to activate within a definite time
7. Name the different kinds of over current
Induction type non-directional over current
relay,Induction type directional over current relay & current differential
8. Define energizing quantity.
It refers to the current or voltage which is
used to activate the relay into operation.
9. Define operating time of a relay.
It is defined as the time period extendind
from the occurrence of the fault through the relay detecting the fault to the
operation of the relay.
10. Define resetting time of a relay.
It is defined as the time taken by the relay
from the instant of isolating the fault to the moment when the fault is removed
and the relay can be reset.
11. What are over and under current relays?
Overcurrent relays are those that operate
when the current in a line exceeds a predetermined value. (eg: Induction type
non-directional/directional overcurrent relay, differential overcurrent
relay)whereas undercurrent relays are those which operate whenever the current
in a circuit/line drops below a predetermined value.(eg: differential
12. Mention any two applications of
Protection of generator & generator
transformer unit; protection of large motors and busbars .
13. What is biased differential bus zone
The biased beam relay is designed to respond
to the differential current in terms of its fractional relation to the current
flowing through the protected zone. It is essentially an over-current balanced
beam relay type with an additional restraining coil. The restraining coil
produces a bias force in the opposite direction to the operating force.
16 Marks Questions
1. (a) What are the causes of over voltage
on a power system? (8)
(b) Why is it necessary to protect the lines
and other equipment of the power system
against over voltages? (8)
2. Describe the phenomenon of lightning.
3. What protective measures are taken
against lightning over voltages? (16)
4. (a) What is tower-footing resistance? (4)
(b) Why is it required to have this
resistance as low as economically possible? (4)
(c) What are the methods to reduce this
5. (a) What is necessity of protecting
electrical equipment against traveling waves?(6)
(b)Describe in brief the protective devices
used for protection of equipment against such
6. Describe the protection of stations and
sub-stations against direct lightning stroke. (16)
7. Describe the construction and principle
of operation of
(i) expulsion type lightning arrester, (8)
(ii) Value type lightning arrester. (8)
8. What is Peterson coil? What protective
functions are performed by this device? (16)
9. Write short notes on the following.
(i) klydonograph and magnetic link (4)
(ii) Rod gap (4)
(iii) Arcing horns (4)
(iv) Basic impulse insulation level (4)
10. What are the requirements of a ground
wire for protecting power conductors against direct lightning stroke? Explain how
they are achieved in practice. (16)
11. Determine the inductance of Peterson
coil to be connected between the neutral and ground to neutralize the charging
current of overhead line having the line to ground capacitive of 0.15μf. If the
supply frequency is 50Hz and the operating voltage is 132 KV, find the KVA
rating of the coil. (16)
12. (a) Explain the term insulation
(b) Describe the construction of volt-time
curve and the terminology associated with impulse-testing. (8)
13. Explain the operation of various types
of surge absorbers (16)
II OPERATING PRINCIPLES AND RELAY CHARACTERISTICS
14. What is the need of relay coordination?
The operation of a relay should be fast and
selective, ie, it should isolate the fault in the shortest possible time
causing minimum disturbance to the system. Also, if a relay fails to operate,
there should be sufficiently quick backup protection so that the rest of the
system is protected. By coordinating relays, faults can always be isolated
quickly without serious disturbance to the rest of the system.
15. Mention the short comings of Merz Price
scheme of protection applied to a power transformer.
In a power transformer, currents in the
primary and secondary are to be compared. As these two currents are usually
different, the use of identical transformers will give differential current,
and operate the relay under no-load condition. Also, there is usually a phase
difference between the primary and secondary currents of three phase transformers.
Even CT’s of proper turn-ratio are used, the differential current may flow
through the relay under normal condition.
16. What are the various faults to which a
turbo alternator is likely to be subjected?
Failure of steam supply; failure of speed;
overcurrent; over voltage; unbalanced loading; stator winding fault .
17. What is an under frequency relay?
An under frequency relay is one which
operates when the frequency of the system (usually an alternator or
transformer) falls below a certain value.
18. Define the term pilot with reference to
power line protection.
Pilot wires refers to the wires that connect
the CT’s placed at the ends of a power transmission line as part of its
protection scheme. The resistance of the pilot wires is usually less than 500
19. Mention any two disadvantage of carrier
current scheme for transmission line only.
The program time (ie, the time taken by the
carrier to reach the other end-upto .1% mile); the response time of band pass
filter; capacitance phase-shift of the transmission line
20. What are the features of directional
High speed operation; high sensitivity;
ability to operate at low voltages; adequate short-time thermal ratio; burden
must not be excessive.
21. What are the causes of over speed and
how alternators are protected from it?
Sudden loss of all or major part of the load
causes over-speeding in alternators. Modern alternators are provided with
mechanical centrifugal devices mounted on their
driving shafts to trip the main valve of the
prime mover when a dangerous over-speed occurs.
22. What are the main types of stator
Fault between phase and ground; fault
between phases and inter-turn fault involving turns of the same phase winding.
23. Give the limitations of Merz Price
Since neutral earthing resistances are often
used to protect circuit from earth-fault currents, it becomes impossible to
protect the whole of a star-connected alternator. If an earth-fault occurs near
the neutral point, the voltage may be insufficient to operate the relay. Also
it is extremely difficult to find two identical CT’s. In addition to this,
there always an inherent phase difference between the primary and the secondary
quantities and a possibility of current through the relay even when there is no
24. What are the uses of Buchholz’s relay?
Bucholz relay is used to give an alarm in
case of incipient( slow-developing) faults in the transformer and to connect
the transformer from the supply in the event of severe internal faults. It is
usually used in oil immersion transformers with a rating over 750KVA.
16 Marks Questions
1. What are the different types of
electromagnetic relays? Discuss their field of applications. (16)
2. What are the various types of over
current relays? Discuss their area of application. (16)
3. Describe the operating principle,
constructional features and area of applications of reverse power or
directional relay. (16)
4. Describe the construction and principle
of operation of an induction type directional over
current relay. (16)
5. Explain the working principle of distance
6. Write a detailed note on differential
7. Describe the realization of a directional
over current relay using a microprocessor. (16)
8. Derive a generalized mathematical model
of distance relays for digital protection. (16)
9. (a) How can digital distance relaying
algorithm be implemented on the 8086 Micro
(b) It is possible to implement these
algorithms on the 8085micro processor? (8)
10. Explain with sketches and their R-X
diagrams for the following distance relays.
(i) Impedance relay (5)
(ii) Mho relay (5)
(iii) Reactance relay (6)
11. (a) Explain the applications of
microprocessors in power system protection. (8)
(b) Explain microprocessor based inverse
time over current relay. (8)
III APPARATUS PROTECTION
25. What are the types of graded used in
line of radial relay feeder?
Definite time relay and inverse-definite
26. What are the various faults that would
affect an alternator?
(a) Stator faults 1, Phase to phase faults
2, Phase to earth faults 3, Inter turn faults
(b) 1, Earth faults 2, Fault between turns
3, Loss of excitation due to fuel failure
(c) 1, Over speed 2, Loss of drive 3, Vacuum
failure resulting in condenser pressure rise, resulting in shattering of the
turbine low pressure casing
(d) 1, Fault on lines 2, Fault on busbars
27. Why neutral resistor is added between
neutral and earth of an alternator?
In order to limit the flow of current
through neutral and earth a resistor is introduced between them.
28. What is the backup protection available
for an alternator?
Overcurrent and earth fault protection is
the backup protections.
29. What are faults associated with an
(a) External fault or through fault
(b) Internal fault 1, Short circuit in
transformer winding and connection 2, Incipient or slow developing faults
30. What are the main safety devices
available with transformer?
Oil level guage, sudden pressure delay, oil
temperature indicator, winding temperature indicator .
31. What are the limitations of Buchholz
(a) Only fault below the oil level are
(b) Mercury switch setting should be very
accurate, otherwise even for vibration, there can be a false operation.
(c) The relay is of slow operating type,
which is unsatisfactory.
32. What are the problems arising in
differential protection in power transformer and how are they overcome?
1. Difference in lengths of pilot wires on
either sides of the relay. This is overcome by connecting adjustable resistors
to pilot wires to get equipotential points on the pilot wires.
2. Difference in CT ratio error difference
at high values of short circuit currents that makes the relay to operate even
for external or through faults. This is overcome by introducing bias coil.
3. Tap changing alters the ratio of voltage
and currents between HV and LV sides and the relay will sense this and act.
Bias coil will solve this.
4. Magnetizing inrush current appears
wherever a transformer is energized on its primary side producing harmonics. No
current will be seen by the secondary.
CT’s as there is no load in the circuit.
This difference in current will actuate the differential relay. A harmonic
restraining unit is added to the relay which will block it when the transformer
33. What is REF relay?
It is restricted earth fault relay. When the
fault occurs very near to the neutral point of the transformer, the voltage
available to drive the earth circuit is very small, which may not be sufficient
to activate the relay, unless the relay is set for a very low current. Hence
the zone of protection in the winding of the transformer is restricted to cover
only around 85%. Hence the relay is called REF relay.
34. What is over fluxing protection in transformer?
If the turns ratio of the transformer is
more than 1:1, there will be higher core loss and the capability of the
transformer to withstand this is limited to a few minutes only. This phenomenon
is called over fluxing.
35. Why busbar protection is needed?
(a) Fault level at busbar is high
b) The stability of the system is affected
by the faults in the bus zone.
(c) A fault in the bus bar causes
interruption of supply to a large portion of the system network.
36. What are the merits of carrier current
Fast operation, auto re-closing possible,
easy discrimination of simultaneous faults .
37. What are the errors in CT?
(a) Ratio error
Percentage ratio error = [(Nominal ratio –
Actual ratio)/Actual ratio] x 100
The value of transformation ratio is not
equal to the turns ratio.
(b) Phase angle error:
Phase angle _ =180/_[(ImCos _-I1Sin _)/nIs]
38. What is field suppression?
When a fault occurs in an alternator winding
even though the generator circuit breaker is tripped, the fault continues to
fed because EMF is induced in the generator itself.Hence the field circuit
breaker is opened and stored energy in the field winding is discharged through
another resistor. This method is known as field suppression.
39. What are the causes of bus zone faults?
Failure of support insulator resulting in
earth fault _ Flashover across support insulator during over voltage _ Heavily
polluted insulator causing flashover _ Earthquake, mechanical damage etc.
40. What are the problems in bus zone
Large number of circuits, different current
levels for different circuits for external faults. _ Saturation of CT cores due
to dc component and ac component in short circuit currents. The saturation
introduces ratio error. _ Sectionalizing of the bus makes circuit complicated.
_ Setting of relays need a change with large load changes.
41. What is static relay?
It is a relay in which measurement or
comparison of electrical quantities is made in a static network which is
designed to give an output signal when a threshold condition is passed which
operates a tripping device.
42. What is power swing?
During switching of lines or wrong
synchronization surges of real and reactive power flowing in transmission line
causes severe oscillations in the voltage and current vectors. It is
represented by curves originating in load regions and traveling towards relay
43. What is a programmable relay?
A static relay may have one or more programmable
units such as microprocessors or microcomputers in its circuit.
44. What is CPMC?
It is combined protection, monitoring and
control system incorporated in the static system.
45. What are the advantages of static relay
over electromagnetic relay?
Low power consumption as low as 1mW
No moving contacts; hence associated
problems of arcing, contact bounce, erosion, replacement of contacts
No gravity effect on operation of static
relays. Hence can be used in vessels ie, ships, aircrafts etc.
A single relay can perform several functions
like over current, under voltage, single phasing protection by incorporating
respective functional blocks. This is not possible in electromagnetic relays
Static relay is compact
Superior operating characteristics and
Static relay can think , programmable
operation is possible with static relay
Effect of vibration is nil, hence can be
used in earthquake-prone areas
Simplified testing and servicing. Can
convert even non-electrical quantities to electrical in conjunction with
16 Marks Questions
1. Enumerate the relaying schemes which are
employed for the protection of a modern
2. (a) What is transverse or split phase
protection of an alternator? (4)
(b) What type of fault is this scheme of
protection employed? (4)
(c) With a neat sketch discuss the working
principle of this scheme. (8)
3. What type of a protective device is used
for the protection of an alternator against
overheating of its (i) stator (ii) rotor?
Discuss them in brief. (8+8)
4. What type of a protective scheme is
employed for the protection of the field winding of
the alternator against ground faults? (16)
5. Discuss the protection employed against
loss of excitation of an alternator. (16)
6. (a) What do you understand by field
suppression of an alternator? (8)
(b) How is it achieved? (8)
7. Briefly discuss the protection of an
(i) Vibration of distortion of motor (4)
(ii) Bearing overheating (4)
(iii) Auxiliary failure (4)
(iv) Voltage regulator failure (4)
8. What type of pilot protection is used for
EHV and UHV transmission lines. (16)
9. (a) What is carrier protection? (4)
(b) For what voltage range is it used for
the protection of transmission line? (4)
(c) What are its merits and demerits? (8)
10. (a) What is carrier aided distance
(b) What are its different types? (4)
(c) Discuss the permissive under-reach
transfer tripping scheme of protection. (8)
11. (a) Draw and explain the merz-price
protection of alternator stator winding. (10)
(b) A generator is protected by restricted
earth fault protection. The generator ratings
are 13.2kv, 10MVA. The percentage of winding
protected against phase to ground fault
is 85%. The relay setting is such that it
trips for 20% out of balance calculate the
resistance to be added in the neutral to
ground connection. (6)
IV THEORY OF CIRCUIT INTERRUPTION
46. What is resistance switching?
It is the method of connecting a resistance
in parallel with the contact space(arc). The resistance reduces the restriking
voltage frequency and it diverts part of the arc current. It assists the
circuit breaker in interrupting the magnetizing current and capacity current.
47. What do you mean by current chopping?
When interrupting low inductive currents
such as magnetizing currents of the transformer, shunt reactor, the rapid
deionization of the contact space and blast effect may cause the current to be
interrupted before the natural current zero. This phenomenon of interruption of
the current before its natural zero is called current chopping.
48. What are the methods of capacitive
• Opening of single capacitor bank
• Closing of one capacitor bank against
49. What is an arc?
Arc is a phenomenon occurring when the two
contacts of a circuit breaker separate under heavy load or fault or short
50. Give the two methods of arc
High resistance interruption:-the arc
resistance is increased by elongating, and splitting the arc so that the arc is
fully extinguished _ Current zero method:-The arc is interrupted at current
zero position that occurs100 times a second in case of 50Hz power system
frequency in ac.
51. What is restriking voltage?
It is the transient voltage appearing across
the breaker contacts at the instant of arc being extinguished.
52. What is meant by recovery voltage?
The power frequency rms voltage appearing
across the breaker contacts after the arc is extinguished and transient
oscillations die out is called recovery voltage.
53. What is RRRV?
It is the rate of rise of restriking
voltage, expressed in volts per microsecond. It is closely associated with
natural frequency of oscillation.
16 Marks Questions
1. (a) What is resistance switching? (4)
(b) Derive the expression for critical
2. (a) Explain the phenomenon of current
chopping in a circuit breaker. (12)
(b) What measures are taken to reduce it?
3. Discuss the problem associated with the interruption
(i) Low inductive current (5)
(ii) Capacitive current and (5)
(iii) Fault current if the fault is very
near the substation. (6)
4. Explain in detail about RRRV. (16)
V CIRCUIT BREAKERS
54. What is circuit breaker?
It is a piece of equipment used to break a
circuit automatically under fault conditions. It breaks a circuit either
manually or by remote control under normal conditions and under fault
55. Write the classification of circuit
breakers based on the medium used for arc
_ Air break circuit breaker
_ Oil circuit breaker
_ Minimum oil circuit breaker
_ Air blast circuit breaker
_ SF6 circuit breaker
_ Vacuum circuit breaker
56. What is the main problem of the circuit
When the contacts of the breaker are
separated, an arc is struck between them. This arc delays the current
interruption process and also generates enormous heat which may cause damage to
the system or to the breaker itself. This is the main problem.
57. What are demerits of MOCB?
_ Short contact life
_ Frequent maintenance
_ Possibility of explosion
_ Larger arcing time for small currents
_ Prone to restricts
58. What are the advantages of oil as arc
• It absorbs the arc energy to decompose the
oil into gases, which have excellent cooling properties
• It acts as an insulator and permits
smaller clearance between line conductors and earthed components
59. What are the hazards imposed by oil when
it is used as an arc quenching medium?
There is a risk of fire since it is
inflammable. It may form an explosive mixture with arc. So oil is preferred as
an arc quenching medium.
60. What are the advantages of MOCB over a
bulk oil circuit breaker?
• It requires lesser quantity of oil
• It requires smaller space
• There is a reduced risk of fire
• Maintenance problem are reduced
61. What are the disadvantages of MOCB over
a bulk oil circuit breaker?
The degree of carbonization is increased due
to smaller quantity of oil o There is difficulty of removing the gases from the
contact space in time o The dielectric strength of the oil deteriorates rapidly
due to high degree of carbonization.
62. What are the types of air blast circuit
_ Arial-blast type _ Cross blast _
63. What are the advantages of air blast
circuit breaker over oil circuit breaker?
The risk of fire is diminished o The arcing
time is very small due to rapid buildup of dielectric strength between contacts
o The arcing products are completely removed by the blast whereas oil
deteriorates with successive operations
64. What are the demerits of using oil as an
arc quenching medium?
• The air has relatively inferior arc
• The air blast circuit breakers are very
sensitive to variations in the rate of rise of restriking voltage
• Maintenance is required for the
compression plant which supplies the air blast
65. What is meant by electro negativity of
SF6 has high affinity for electrons. When a
free electron comes and collides with a neutral gas molecule, the electron is
absorbed by the neutral gas molecule and negative ion is formed. This is called
as electro negativity of SF6 gas.
66. What are the characteristic of SF6 gas?
It has good dielectric strength and
excellent arc quenching property. It is inert, non-toxic, noninflammable and
heavy. At atmospheric pressure, its dielectric strength is 2.5 times that of
air. At three times atmospheric pressure, its dielectric strength is equal to
that of the transformer oil.
67. Write the classifications of test
conducted on circuit breakers.
_ Type test
_ Routine test
_ Reliability test
_ Commissioning test
68. What are the indirect methods of circuit
o Unit test
o Synthetic test
o Substitution testing
o Compensation testing
o Capacitance testing
69. What are the advantages of synthetic
• The breaker can be tested for desired
transient recovery voltage and RRRV.
• Both test current and test voltage can be
independently varied. This gives flexibility to the test
• The method is simple
• With this method a breaker capacity (MVA)
of five time of that of the capacity of the test plant can be tested.
70. How does the over voltage surge affect
the power system?
The over voltage of the power system leads
to insulation breakdown of the equipment’s. It causes the line insulation to
flash over and may also damage the nearby transformer, generators and the other
equipment connected to the line.
71. What is pick up value?
It is the minimum current in the relay coil
at which the relay starts to operate.
72. Define target.
It is the indicator used for showing the
operation of the relay.
73. Define reach.
It is the distance upto which the relay will
cover for protection.
74. Define blocking.
It means preventing the relay from tripping
due to its own characteristics or due to additional relays.
75. Define a over current relay.
Relay which operates when the current ia a
line exceeds a predetermined value.
76. Define an under current relay?
Relays which operates whenever the current
in a circuit drops below a predetermined value.
77. Mention any 2 applications of
Protection of generator and
generator-transformer unit: protection of large motors and bus bars
78.Mention the various tests carried out in
a circuit breaker at HV labs.
Short circuit tests, Synthetic tests&
78. Mention the advantages of field tests.
The circuit breaker is tested under actual
conditions like those that occur in the network. Special occasions like
breaking of charging currents of long lines ,very short line faults
,interruption of small inductive currents etc… can be tested by direct testing
79. State the disadvantages of field tests.
The circuit breaker can be tested at only a
given rated voltage and network capacity. The necessity to interrupt the normal
services and to test only at light load conditions. Extra inconvenience and
expenses in installation of controlling and measuring equipment in the field.
80. Define composite testing of a circuit
In this method the breaker is first tested
for its rated breaking capacity at a reduced voltage and afterwards for rated
voltage at a low current. This method does not give a proper estimate of the
81. State the various types of earthing.
Solid earthing, resistance earthing ,
reactance Earthing , voltage transformer Earthing and zig-zag transformer
82. What are arcing grounds?
The presence of inductive and capacitive
currents in the isolated neutral system leads to formation of arcs called as
83. What is arc suppression coil?
A method of reactance grounding used to
suppress the arc due to arcing grounds.
84. State the significance of single line to
In single line to ground fault all the
sequence networks are connected in series. All the sequence currents are equal
and the fault current magnitude is three times its sequence currents.
85. What are symmetrical components?
It is a mathematical tool to resolve
unbalanced components into balanced components.
86. State the three sequence components.
Positive sequence components, negative
sequence components and zero sequence components.
87. Define positive sequence component.
has 3 vectors equal in magnitude and
displaced from each other by an angle 120 degrees and having the phase sequence
as original vectors.
88. Define zero sequence component.
They has 3 vectors having equal magnitudes
and displaced from each other by an angle zero degees.
89. State the significance of double line
It has no zero sequence component and the
positive and negative sequence networks are connected in parallel.
90. Define negative sequence component.
It has 3 vectors equal in magnitude and
displaced from each other by an angle 120 degrees and has the phase sequence in
opposite to its original phasors.
91. State the different types of faults.
Symmetrical faults and unsymmetrical faults
and open conductor faults.
92. State the various types of unsymmetrical
Line to ground ,line to line and double line
to ground faults
93. Mention the withstanding current in our
94. State the different types of circuit
Air ,oil,vacuum circuit breakers.
95. Define per unit value.
It is defined as the ratio of actual value
to its base value.
96. Mention the inductance value of the
97. Define single line diagram.
Representation of various power system
components in a single line is defined as single line diagram.
98. Differentiate between a fuse and a
Fuse is a low current interrupting device.
It is a copper or an aluminium wire.Circuit breaker is a high current
interrupting device and it act as a switch under normal operating conditions.
99. How direct tests are conducted in
Using a short circuit generator as the
source. Using the power utility system or network as the source.
100. What is dielectric test of a circuit
It consists of overvoltage withstand test of
power frequency lightning and impulse voltages.Testa are done for both internal
and external insulation with switch in both open and closed conditions.
16 Marks Questions
1. Discuss the recovery rate theory and
energy balance theory of arc interruption in a circuit breaker. (16)
2. Explain terms:
i) Restriking voltage (3)
ii) Recovery voltage (3)
iii) RRRV (3)
iv) Derive expressions for restriking
voltage and RRRV. (3)
v) What measures are taken to reduce them?
6. With neat sketch, describe the working
principle of an axial air blast type circuit breaker. (16)
7. (a) Discuss the operating principle of
SF6 circuit breaker. (10)
(b) What are its advantages over other types
of circuit breakers? (3)
(c) For what voltage range is it
8. Describe construction, operating
principle and application of vaccum circuit breaker. For what voltage range is
it recommended? (16)
9. (a) What are the various types of
operating mechanisms which are used for opening and closing of the contacts of
a circuit breaker? (10)
(b)Discuss their merits and demerits. (6)
10. (a) Enumerate various types of ratings
of a circuit breaker. (4)
(b) Discuss symmetrical and asymmetrical
breaking capacity, (4)
(c) Making capacity (4)
(d) Short-time current capacity. (4)
11. What are the different methods of
testing of circuit breakers? Discuss their merits and
12. What is the difficulty in the
development of HVDC circuit breaker? Describe its
construction and operating principle. (16)
13. (a) What are the physical chemical and
dielectric properties of SF6 Gas (8)
(b) Define switchgear. What are the
essential features of switchgear (8)
14. A 3-phase alternator has the line
voltage of 11kV. The generator is connected to a
circuit breaker. The inductive reactance
upto the circuit breaker is 5_/phase. the
distributed capacitance upto circuit breaker
between phase and neutral is 0.001 μF.
Determine peak restriking voltage across the
CB, frequency of restriking voltage,
average rate of restriking voltage upto peak
restriking voltage, maximum RRRV. (16)