CONCEPT OF SYMMETRICAL COMPONENT AS A TECHNIQUE FOR ANALYSIS OF FAULT AND IMPROVEMENT OF OVERCURRENT PROTECTION SCHEME
- 1. A SEMINAR PRESENTATION ON “CONCEPT OF SYMMETRICAL COMPONENT AS A TECHNIQUE FOR ANALYSIS OF FAULT AND IMPROVEMENT OF OVERCURRENT PROTECTION SCHEME” Submitted to: Submitted by: Mr. Ankush Tandon Saurabh Varshney Mrs. Deepti Arela (10ESKEE106) 1
- 2. CONTENT INTRODUCTION PROTECTION SYSTEM SYMMETRICAL COMPONENT FAULT OVERCURRENT RELAY ALGORITHM SIMULATION DISTRIBUTION SYSTEM RESULTS CONCLUSION 2
- 3. INTRODUCTION Aim of my seminar topic is better understanding the concept of symmetrical components for enhancing protection scheme by providing a practical technology for understanding and analyzing power system operation during unbalanced condition. 3
- 4. PROTECTION SYSTEM What is need of protective system ? In order to maintain steady state of power system by taking correct and quick remedial action during any faulty condition. Properties of a good protective system Automatic Quick Minimum amount of disruption 4
- 5. SYMMETRICAL COMPONENT Unbalanced systems are difficult to handle. It provide balanced analysis of an unbalanced system The unbalanced three phase system can be transformed into three balanced phasors Positive Sequence Negative Sequence Zero Sequence 5
- 6. POSITIVE PHASE SEQUENCE Each have the same magnitude. Each positive sequence voltage or current quantity is displaced 120 from one another. The positive sequence quantities have a-b-c, counter clock-wise, phase rotation. 6
- 7. NEGATIVE PHASE SEQUENCE Each have the same magnitude. Each negative sequence voltage or current quantity is displaced 120 from one another. The negative sequence quantities have a-c-b, counter clock-wise, phase rotation. 7
- 8. ZERO PHASE SEQUENCE Each zero sequence quantity has the same magnitude. All three phasor with no angular displacement between them, all in phase. 8
- 9. 9 FAULT o General Causes of fault Fault due to lightning Tree limbs falling on the line Wind damage Effects of fault Flow of excessive current Abnormal voltages Induces over voltages on neighbouring equipments. Hazards to human, equipment and animals
- 10. TYPES OF FAULTS • Balanced Faults : – Three-phase fault • Unbalanced Faults : – Single line to ground fault – Line to line fault – Double line to ground fault 10
- 12. SINGLE LINE TO GROUND FAULT The most common type of fault is the single line to ground fault: 12
- 13. 13 The SLG fault can be described by the following voltage and current relationship: Ib=0 & Ic=0 Va=IaZf The Sequence current can be given as:
- 14. LINE TO LINE FAULT It occurs when two conductors are short circuited. There is no zero sequence component due to absence of ground return path. The positive and negative sequence components are connected in parallel. 14
- 15. DOUBLE LINE TO GROUND FAULT In double line to ground fault two line conductors come in contact with each other and ground . The networks are connected in parallel. For the zero sequence component it requires to add an external impedance of Zf+3Zg 15
- 16. OVER CURRENT RELAY Short-circuit currents are generally several times (5 to 20) full load current. Hence fast fault clearance is always desirable on short circuits. A relay that operates or picks up when it’s current exceeds a predetermined value (setting value) is called Over current Relay. Over current includes short-circuit protection, and short circuits can be: Phase faults Earth faults Winding faults 16
- 17. TYPES OF OVER CURRENT RELAY I. Instantaneous Over current (Definite Current) Relay II. Definite Time Over current Relay III. Inverse Time Over current Relay (IDMT Relay) i. Moderately Inverse ii. Very Inverse Time iii. Extremely Inverse IV. Directional over current Relay 17
- 18. ALGORITHM The criterion function for discriminating fault from non fault switching is defined as follows : R= |I1|-|I2| / |I1|+|I2| 18
- 20. RESULTS Several non faults events are applied to this system along with some short circuit events a different time. The discrimination of fault from a non fault event could be done by representing two cases Transformer energizing Fault 20
- 21. TRANSFORMER ENERGIZING Various inrush current condition were simulated. Various parameters which have considerable effect on the characteristic of the current signal were changed and was analysed. FAULT In this case a single line to ground fault occurs. 21
- 22. 22 NON FAULT CONDITION WHEN VALUE OF R>=.35s FAULTY CONDITION WHEN VALUE OF R<.35s
- 23. 23 THREE PHASE CURRENT BEFORE FAULT THREE PHASE CURRENT AFTER FAULT
- 24. CONCLUSION Simple method of improving over current relays operation by algorithm, based on different behaviour of the current amplitudes. Based on the differences, a criterion function R is defined such that undesirable operation of the over current relays to the switching is prevented. 24