Looking for a Tutor Near You?

Post Learning Requirement »
x

Choose Country Code

x

Direction

x

Ask a Question

x

x
x
For better view click here
x
Hire a Tutor
DISCOVER

Generator Protection

Loading...

Published in: Electrical
15,735 Views

Types of Faults in Generator.

Tatsam P / Agra

7 years of teaching experience

Qualification: B.Tech,GATE,UPSC,MBA

Teaches: Economics, Geography, History, KVPY Exam, Mathematics, Physics, Political Science, Sociology, Algebra, All Subjects, EVS, NTSE, Science, Social Studies, AIEEE, AMIE, BITSAT, CET, GATE Exam, IIT JAM, IIT JEE Mains, WBJEE, Electrical, Slow Learners

Contact this Tutor
  1. GENERATOR PROTECTION -TATSAM PRIYADARSHI
  2. INTROPIUCT\ON 2. It is imperative need to install some protective system to protect the expensive components of the protective system like generators, transformers, transmission lines etc. from different types of faults which OCCUrs in power system. In generating stations , continuous operation of generator is more necessary so the faulty part needs to be cleared very quickly for uninterruptable power supply
  3. (O) GENERATOR FAULTS AND PROTECTION TECHNIQUES *TYPES OF GENERATOR FAULTS: i. ii. iii. Stator Winding Fault Rotor Winding Fault Abnormal Operating Conditions 'DIFFERENT PROCESS OF PROTECTING THE GENERATOR: i. iii. V. Vie Stator Protection Overcurrent Protection Over voltage Protection Protection Rotor Fault Protection External Fault Backup Protection
  4. STATOR FAULTS AND ITS PROTECTION + Stator faults Include The following: Phase to earth faults ii. Phase to phase faults Inter-turn faults iii. (Phase to phase faults Inter-turn faults are less common, these generally developed into an earth fault. Inter-turn fault are more difficult to be detected Different (Protection Schemes_for Stator (Protection: Differential Qrotection (Biased Circulating Current (Protection (Balance Earth-fault (Protection Stator Overheating (Protection
  5. DIFFERENTIAL PROTECTION Two sets of identicalCTs, each mounted on either side of stator phase winding. The secondaries of these current transformers sets are connected in star. •3 At normal operating conditions, the currents at two ends of protected section remains same(11=12). So relay will not operate. When the faults occurs the balance condition gets disturbed and hence current(11-12)flows through the operating coil of the relay causing relay operation and the trip circuit gets closed The relays employed in this protection system are generally of electro-magnetic type are arranged for instantaneous operation as faults are expected to be clear as soon as possible
  6. CT 1 EARTH ING STANCE DIAGRAM GENERATOR CT 2 MAIN CIRCUIT BREAKER RELAY R TO TRIP CIRCUIT fig 2
  7. BALANCED EARTH FAULTS In case of small generators the neutral end of 3 phase winding is not available because it is made inside the generator and grounded through some low resistance then percentage differential relay for ground fault is provided U is frown as balanced earth fault This scheme can be used only for ground faults but not for phase faults CT Earthing resistance Alternator Relay To trip circuit Restricted or Balanced earth fault protection
  8. ROTOR FAULTS & ITS PROTECTION faults in the rotor circuit may be either earth faults or between the turns of the field winding. field circuits are normally operatedun-earthed So a single fault will not affect its operation. (But when a secondfault arises then field winding is short circuited U produce unsymmetrical field system which leads to unbalanced forces on rotor and results in excess pressure and bearing and shaft distortion •The Different (Protection Schemes for Rotor (Protection: 1. w. Rotor Earth fault (Protection Loss of Excitation (Protection (Rotor Temperature Alarm Automatic field Suppression Vse Of Neutral Circuit (Breaker
  9. Exciter Armature Generator Field Wtinding Current limiting reactor (in case Of DC) Capacitor (in case Of DC) Sensitive over Voltage relay TO auxiliary supply AC or DC Exciter Armature Rotor Earth Fault Protection Rotor Earth Fault Protection Circ Globe High Resistance Midpoint Sensitive Earth Fault Relay circuit ROTOR EARTH FAULT PROTECTION high resistance is connected across the rotor circuit and its mid point is grounded through a sensitive relay. The another method of rotor earth fault protection is done by DC injection method ii. AC injection method *The dc or ac voltage is impressed between the field circuit and ground through a sensitive over voltage relay and current limiting resistor or capacitor(in case of ac). A single earth fault in rotor circuit will complete the path and the fault is sensed by the relay. 'DC injection method is simple & has no problems of leakage current.
  10. LOSS OF EXCITATION PROTECTION When the excitation of generator is lost it operates as an Induction generator. It derives excitation from the system and supply power at leading power factor which may cause- i. A fallin voltage so loss of synchronism system instability. ii. Over heating of rotor due to induction current on it. The relay mostly used for this type of protection is Directional distance type relay. GENERATOR FIELD WINDING EXCITER SHUNT UNDER-CURRENT MOVING COIL RELAY Coss EGitation frotection
  11. (O) ROTOR TEMPERATURE This type of protection scheme is installed generally in large alternators. It indicates the level of temperature but not the actual hot spot temperature. The relay measures the temperature by measuring the resistance(as shown in fig). The relay measures the ratio of voltage current. GENEeATOR FIELD WINCING SLIP RINGS VOLTAGE COIL MOVING COIL RELAY
  12. In case of a fault in the generator and though the circuit breaker is tripped , the fault continues to fed as long as excitation will exist because emfis induced in the generator itself + Hence all protection system not only trip the generator circuit breaker but also trip the "automatic field discharge switch
  13. NEGATIVE PHASE SEQUENCE PROTECTION Unbalance may cause due to single phase fault or unbalanced loading and it gives rise to negative sequence current. This current in rotor causes rotor overheating and damage to the rotor. This can be protected by negative sequence current filter with over current relay. .•rdrq *use Re$•y
  14. CONCLUSION *Switchgears other protective devices are used in the electrical machines in the power system elements. i. To detect the abnormal faulty condition. ii. To notify this information to the maintenance officer of that factory or generation station. iii. To disconnect the faulty elements from the healthy system or shutdown the faulted apparatus for continuous operation of the machines, for safety of this expensive electrical devices as well as for the safety of the workers. The protective device does not prevent the cause of fault or occurrence of fault , it is used after the occurrence of fault for quic€action to remove those faulty section for further normal operation .

Need a Tutor or Coaching Class?

Post an enquiry and get instant responses from qualified and experienced tutors.

Post Requirement

Related PPTs

Upload PPTs

If you have your own PowerPoint Presentations which you think can benefit others, please upload on LearnPick. For each approved PPT you will get 100 Credit Points and 100 Activity Score which will increase your profile visibility.

Upload Now
Home > PowerPoint Slides > Generator Protection