Hybrid circuit breaker


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Hybrid circuit breaker

  1. 1. L. E. College, Morbi GUJARAT TECHNOLOGICAL UNIVERSITY “HYBRID CIRCUIT BREAKER” A Product survey Report On SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF BACHELOR OF ENGINEERING Electrical Engineering SUBMITTED TO: L. E. COLLEGE, MORBI SUBMITTED BY Student Name Enrollment No. 1. Bhimani Vishal R. 100310109056 2. Patel Priyesh B. 100310109059 GUIDED BY:Prof. S. N. Purohit Assi. Prof. Electrical Department October 2013 1 L.E. COLLEGE - MORBI
  2. 2. Lukhdhirji Engineering College, Morbi Gujarat Technological University CERTIFICATE This is to certify that 1. Bhimani Vishal R. (100310109056) 2. Patel Priyesh B. (100310109059) of final year Electrical Engineering students have satisfactorily and accurately completed their project work entitled “Product survey on Hybrid Circuit Breaker” for the subject code 170001 Project I in the 7th semester of academic year 2013-14 for the partial fulfilment of the award of the Bachelor of Engineering in Electrical Engineering at Gujarat Technological University. DATE:- PROF. S. N. PUROHIT PROF. A. K. JOSHI PROJECT GUIDE HEAD OF DEPARTMENT 2 L.E. COLLEGE - MORBI
  3. 3. ACKNOWLEDGEMENT We owe a great many thanks to a great many people who helped and supported us during the writing of this report. Our deepest thanks to S.N.Purohit the Guide of the project for guiding and correcting various documents of ours with attention and care. He has taken pain to go through the project and make necessary correction as and when needed. We express our gratitude to our head of the Department Prof A.K.JOSHI for his invaluable support and encouragement at every stage. We also express our thanks to the Principal Prof. P. C. Vasani ,Lukhdhirji Engineering College, Morbi-2, for his constant support and encouragement. We would also thank our Institution and the faculty members without whom this project would have been a distant reality. Name Sign Bhimani Vishal R. Patel Priyesh B. 3 L.E. COLLEGE - MORBI
  4. 4. ABSTRACT: High Voltage Circuit Breaker (CB) is important electrical equipment used in the power system network to isolate the faulty section from the healthy network and thus ensure safe operation of the electrical system. Vacuum Circuit Breakers and SF6 Circuit Breakers are widely used depending upon the power rating of the transmission line. The merits and demerits of the two are reviewed and the need for hybrid model is analyzed. The hybrid circuit breaker has at least two series-connected arcing chambers, which are operated by a common drive via a transmissionconnected upstream from it. It is intended to be possible to assemble this transmission easily in the interior of the hybrid circuit breaker. This is achieved in that the transmission is formed from at least two transmission parts which can be plugged together, with a first transmission part being firmly connected to the at least one first arcing chamber and a second transmission part being firmly connected to the at least one second arcing chamber. The transmission also has means which allow the movements of the at least two arcing chambers to be technically suitably matched to one another and to be optimized with respect to the time sequence and switching speed thereof. A hybrid circuit breaker consists of a series-connected vacuum interrupter and sulfur hexafluoride interrupter wherein the contacts of each are simultaneously operated. The sulfur hexafluoride interrupter is of the type in which an arc is rapidly rotated through a relatively static volume of sulfur hexafluoride. In one embodiment of the invention, the vacuum interrupter is replaced by a second sulfur hexafluoride interrupter in which the arc gap between the electrodes receiving the final arc to be interrupted is relatively smaller than the corresponding arc gap in the other sulfur hexafluoride interrupter. 4 L.E. COLLEGE - MORBI
  7. 7. CHAPTER 1: INTRODUCTION For many years various investigators have explored different approaches to develop a high voltage direct current circuit breaker. Recently a joint effort by the Bonneville Power Administration (BPA), Electric Power Research Institute (EPRI) and BrownBoveri Corporation (BBC) resulted in the successful development and field testing of a practical, 500 kV, 2000A air - blast HVDC breaker. The primary focus of all HVDC breaker development has been overcoming the problem of dc systems having no natural currentzero. Inthe familiar high voltage ac circuit breaker, the interruption process depends on the naturally occurring cyclic instances of current zero. The breaker will typically arc through high current periods making no attempt to clear until or about the current zero point, whereupon it will then isolate the circuit. To obtain similar isolation in a dc circuit, it is necessary to create a current zero point. Most of these methods create a current zero by active or passive commutation of the direct current. Active commutation methods have a capacitor, typically pre-charged, inserted across the main interrupter element through some switching device. The surge current caused by the insertion of this capacitor quickly drives the direct current in the interrupter to zero. The present invention relates to a hybrid circuit breaker, comprising a first circuit that comprises: a main current path which comprises a mechanical switch element, and at least one commutation path arranged in parallel with the main current path and comprising a controllable semi-conductor switch element. The invention also relates to an electric power supply system comprising a hybrid circuit breaker according to the invention. The breaker is an electric current breaker. In particular, it may form part of an AC electric power system. In particular, it may form part of a medium or high voltage electric power system, medium or high voltage being referred to as a voltage of 400 V or above. However, lower voltage applications are not excluded. The mechanical switch element may comprise any type of mechanical switch comprising first and second contact elements that are movable in relation 7 L.E. COLLEGE - MORBI
  8. 8. to each other in connection to the switching operation thereof. Typically, the mechanical switch comprises a mechanical circuit breaker. Electric ships with Integrated Power Systems (IPS) can benefit from dc distribution architectures that allow bi-directional power flow. One drawback has been the lack of suitable dc circuit breakers that can operate at medium to high voltages and operate fast enough to limit peak fault currents to acceptable levels. General Atomics (GA) has developed a novel high voltage hybrid dc circuit breaker, Fig. that employs a fast mechanical interrupter in parallel with a solid-state commutation circuit to achieve short interrupt times for medium to high voltage systems. The controllable semi-conductor switch element may be any kind of solid-state breaker based on semi-conductor technology and of controllable character such as a controllable thyristor, an IGBT (Insulated Gate Bipolar Transistor), an IGCT (Insulated Gate-Commutated Thyristor) or a GTO, all well known within this field of technology. The expression "controllable" indicates that the element in question opens or closes as soon as an appropriate control is applied to it. Accordingly, in this regard, the controllable semi-conductor element is an active element, or at least not passive. 8 L.E. COLLEGE - MORBI
  9. 9. CHAPTER 2: HYBRID CIRCUIT BREAKER (AC) 2.1:-DESIGN: The interrupter is fundamentally a very high performance pneumo-electromechanical device. Aside from the initial magnetic impulsive force and the reclose/contact pressure operation, the interrupter is essentially a passive device. However, achieving the specified voltage breakdown recovery in the specified time depends on a complex set of coupled nonlinear actions including: The drive circuit energy store must have sufficient energy and the drive coil must magnetically couple to the piston in a manner that propels the piston to establish an adequate electric gap in the specified time. The gas specie and initial gas pressure must fill the electric gaps in the specified time with sufficient pressure to achieve the specified breakdown strength. The inner cylinder volume and check valve design must dissipate the kinetic energy of the piston to arrest and latch the piston open. And, the gas system must allow for piston reclose on command and the establishment of an adequate contact pressure to achieve low insertion loss. A thorough understanding of all these actions is essential to ensuring that the interrupter is properly designed and can meet the objective requirements. The design development was necessarily model & simulation driven, relied heavily on finite element analysis (FEA) and computational fluid dynamic (CFD) techniques and consisted of four key analytical efforts. 1. Piston Opening Dynamics 2. Electrostatic & Voltage Recovery Analysis 3. Piston Arrest & Latch Dynamics 4. Piston Structural & Friction Analysis 9 L.E. COLLEGE - MORBI
  10. 10. Fig. Hybrid Circuit Breaker (AC) 2.2:-METHOD OF OPERATION: When the interrupter receives a signal to “Open”, the interrupter controller sends a command to the drive circuit triggering an electric discharge into the drive coil. The electric pulse in the drive coil couples to the conducting face of the pistons which are accelerated away from the electrodes under the Lorentz forces at very high speeds. As the contactor piston moves away from the electrodes, the pressure builds in the inner cylinder until the check-valve opens venting gas from the inner cylinder to the outer cylinders. “close”, the interrupter controller signals the gas system to pump gas from the outer cylinder to the volume of the inner cylinder between the check-valve and piston. The piston is pushed toward the electrodes under gas pressure until seated. When the contactor pistons are seated against the electrodes, the interrupter controller signals the gas system to restore and maintain a specified pressure to ensure a good electrical contact between the pistons and the electrodes. The interrupter is now “closed” and ready to resume normal operations. The closing sequence is illustrated in Fig. 4 „Closing Sequence‟ a-e. 10 L.E. COLLEGE - MORBI
  11. 11. Fig. High-speed Interrupter Open/Close Sequence 11 L.E. COLLEGE - MORBI
  12. 12. 2.3:-CURRENT INTERRUPTION IN HYBRID MODEL: The minimum arc duration are shorter in a vacuum interrupter as compared to the SF6 interrupter by several milliseconds. Hence it is preferable to open the SF6 interrupter initially followed by the opening of vacuum interrupter with some delay of a few milliseconds. Since there are two interrupters connected together therefore the currents can be interrupted by each of the interrupters. Interruption Initially By Vacuum Interruption: In this case, current is first interrupted by the vacuum interrupter. This mode of operation is observed at the highest current. Vacuum interrupter first transmits initial recovery voltage peak value and the latter higher peak value is shared by SF6 interrupter as highlighted in fig. As can be seen in fig. ,the vacuum arc extinguishes at current zero while the SF6 arc continues to operate for the next 5usec and then after current zero 8 A post arc current flows in the vacuum interrupters. When the vacuum post arc current decays to zero then only the SF6 post arc current is forcibly chopped to zero. Due to this, the arc voltage and current do not cross zero simultaneously and the arc voltage is initially of opposite polarity. Interruption SimutaneouslyBy Vacuum And Sf6 Interrupter: In this case, current is simultaneously interrupted by both vacuum and SF6 interrupters. This mode of operation is typically observed in conditions in which current is less than maximum current. Here, the performance of SF6 circuit breaker is reduced deliberately but it is sufficient to do the job alone.SF6 post arc current is much smaller as compared to the vacuum CB, so the SF6 interrupter stops the flow of vacuum arc charge. The post arc vacuum charge remains trapped. This prevents the Transient Recovery Voltage (TRV) to build up in vacuum interrupter until all the charges disappear Therefore the complete TRV is carried by SF6 interrupter. The above operation can be easily seen in fig below. The performance of the hybrid circuit breaker in the first mode is better than that in second mode. 12 L.E. COLLEGE - MORBI
  13. 13. Fig. SF6 and vacuum interrupt simultaneously 2.4:-REQUIREMENTS AND OBJECTIVES: In 2011, GA proposed to the US Department of Energy’s Advanced Research Projects Agency (ARPA-e) and was awarded a contract to develop a high-speed, high voltage, low insertion loss hybrid circuit breaker. The objective of the project was to develop a circuit breaker that could achieve or exceed the technical performance measures listed in Table 1 and full circuit breaker open/latch/reclose functionality. Table 1: Interrupter Requirements Description Description Units Requirement Normal Current: A 500 Interrupt Current, Max: kA < 3.5 Interrupt Time: s < 250 Rated Voltage: kV 125 Insertion Loss: W 1,000 13 L.E. COLLEGE - MORBI
  14. 14. CHAPTER 3: HYBRID HVDC CIRCUIT BREAKER 3.1:-DESIGN OF HYBRID CIRCUIT BREAKER: Recent studies focus on designing a hybrid circuit breaker operation mechanism with strong controllability property and low dispersion degree. The former researchers have adopted an operation mechanism that connects the two interrupters with the help of a connection rod or a spring. This mechanism led to weak controllability property and low dispersion degree. Depicts a hybrid circuit breaker based on fiber control vacuum CB connected in series with SF6 CB. A synchronized coordinate operation control unit which adjusts the coordination movements of the two interrupters in microseconds is utilized in this scheme. The top bus terminal of vacuum circuit breaker is connected with the bus input, and the end bus terminal box is linked with top bus terminal of SF6 circuit breaker. The end bus terminal of SF6 circuit breaker is connected to bus output, its operation mechanism and synchronization unit are placed at low potential. The synchronization unit of hybrid circuit breaker receives system control signal and perform synchronized operation to operate the vacuum circuit breaker and SF6 circuit breaker respectively. 3.2;-CIRCUIT DIAGRAM OF HYBRID HVDC BREAKER: As presented in Figure, the hybrid HVDC breaker consists of an additional branch, a bypass formed by a semiconductor-based load commutation switch in series with a fast mechanical disconnector. The main semiconductor-based HVDC breaker is separated into several sections with individual arrester banks dimensioned for full voltage and current breaking capability, whereas the load commutation switch matches lower voltage and energy capability. After fault clearance, a disconnecting circuit breaker interrupts the residual current and isolates the faulty line from the HVDC grid to protect the arrester banks of the hybrid HVDC breaker from thermal overload. 14 L.E. COLLEGE - MORBI
  15. 15. Fig. hybrid HVDC circuit breaker During normal operation the current will only flow through the bypass, and the current in the main breaker is zero. When an HVDC fault occurs, the load commutation switch immediately commutates the current to the main HVDC breaker and the fast disconnector opens. With the mechanical switch in open position, the main HVDC breaker breaks the current. The mechanical switch isolates the load commutation switch from the primary voltage across the main HVDC breaker during current breaking. Thus, the required voltage rating of the load commutation switch is significantly reduced. A successful commutation of the line current into the main HVDC breaker path requires a voltage rating of the load commutation switch exceeding the on-state voltage of the main HVDC breaker, which is typically in the kV range for a 320 kV HVDC breaker. This result in typical on-state voltages of the load commutation switch is in the range of several volts only. The transfer losses of the hybrid HVDC breaker concept are thus significantly reduced to a percentage of the losses incurred by a pure semiconductor breaker, i.e. 0.01% of the transmitted power. The mechanical switch opens at zero current with low voltage stress, and can thus be realized as a disconnector with a lightweight contact system. The fast disconnector will be exposed to the maximum pole-to-pole voltage defined by the protective level of the arrester banks after 15 L.E. COLLEGE - MORBI
  16. 16. first being in open position while the main HVDC breaker opens. Thomson drives result in fast opening times and compact disconnector design using SF6 as insulating media. Proactive control of the hybrid HVDC breaker allows it to compensate for the time delay of the fast disconnector, if the opening time of the disconnector is less than the time required for selective protection. As shown in Figure, proactive current commutation is initiated by the hybrid HVDC breaker`s built-in overcurrent protection as soon as the HVDC line current exceeds a certain overcurrent level. The main HVDC breaker delays current breaking until a trip signal of the selected protection is received or the faulty line current is close to the maximum breaking current capability of the main HVDC breaker. To extend the time before the self-protection function of the main HVDC breaker trips the hybrid HVDC breaker, the main HVDC breaker may operate in current limitation mode prior to current breaking. The main HVDC breaker controls the voltage drop across the HVDC reactor to zero to prevent a further rise in the line current. Pulse mode operation of the main HVDC breaker or sectionalizing the main HVDC breaker as shown in Fig.will allow adapting the voltage across the main HVDC breaker to the instantaneous HVDC voltage level of the HVDC grid. The maximum duration of the current limiting mode depends on the energy dissipation capability of the arrester banks. On-line supervision allowing maintenance on demand is achieved by scheduled current transfer of the line current from the bypass into the main HVDC current breaker during normal operation, without disturbing or interrupting the power transfer in the HVDC grid. Fast backup protection similar to pure semiconductor breakers is possible for hybrid HVDC breakers applied to HVDC switchyards. Due to the proactive mode, over-currents in the line or superior switchyard protection will activate the current transfer from the bypass into the main HVDC breaker or possible backup breakers prior to the trip signal of the backup protection. In the case of a breaker failure, the backup breakers are activated almost instantaneously, typically within less than 0.2 ms. This will avoid major disturbances in the HVDC grid, and keep the required current-breaking capability of the backup breaker at 16 L.E. COLLEGE - MORBI
  17. 17. reasonable values. If not utilized for backup protection, the hybrid HVDC breakers automatically return to normal operation mode after the fault is cleared. 3.3:-PROTOTYPE DESIGN OF THE HYBRID HVDC BREAKER: The hybrid HVDC breaker is designed to achieve a current breaking capability of 9.0 kA in an HVDC grid with rated voltage of 320 kV and rated HVDC transmission current of 2 kA. The maximum current breaking capability is independent of the current rating and depends on the design of the mainHVDC breaker only. The fast disconnector and main HVDC breaker are designed for switching voltages exceeding 1.5 p.u. in consideration of fast voltage transients during current breaking. The main HVDC breaker consists of several HVDC breaker cells with individual arrester banks limiting the maximum voltage across each cell to a specific level during current breaking. Each HVDC breaker cell contains four HVDC breaker stacks as shown in Figure. Two stacks are required to break the current in either current direction. HVDC breaker cell FIG. DESIGN OF 80KV MAIN HVDC BREAKER CELL Each stack is composed of up to 20 series connected IGBT (insulated gate bipolar transistor) HVDC breaker positions. Due to the large di/dt stress during current breaking, a mechanical 17 L.E. COLLEGE - MORBI
  18. 18. design with low stray inductance is required. Application of press pack IGBTs with 4.5 kV voltage rating enables a compact stack design and ensures a stable short circuit failure mode in case of individual component failure. Individual RCD snubbers across each IGBT module ensure equal voltage distribution during current breaking. Optically powered gate units enable operation of the IGBT HVDC breaker independent of current and voltage conditions in the HVDC grid. A cooling system is not required for the IGBT stacks, since the main HVDC breaker cells are not exposed to the line current during normal operation. For the design of the load commutation switch, one IGBT HVDC breaker module for each current direction is sufficient to fulfill the requirements of the voltage rating. Parallel connection of IGBT modules increases the rated current of the hybrid HVDC breaker. Series connected, redundant IGBT HVDC breaker modules improve the reliability of the load commutation switch. A matrix of 3x3 IGBT positions for each current direction is chosen for the present design. Since the load commutation switch is continuously exposed to the line current, a cooling system is required. Besides water cooling, air-forced cooling can be applied, due to relatively low losses in the range of several tens of kW only. 18 L.E. COLLEGE - MORBI
  19. 19. CHAPTER 4: TESTING OF HYBRID CIRCUIT BERAKER 4.1:-TEST RESULTS MAIN BREAKER: During the design of the hybrid HVDC breaker prototype, different tests were performed in order to verify expected performance. The first test setup reported earlier focuses mainly on the control of semiconductor devices and their current breaking capability. The second test setup verifies both the voltage and current capability of one cell of the main HVDC breaker. The ongoing extension of this test setup will focus on the overall performance of the hybrid HVDC breaker. Due to big differences in voltage levels in the test setup, construction of the test circuits is quite different but the test procedure is similar. A scaled-down prototype of the main breaker cell with three series connected IGBT modules and a common arrester bank was used to verify the current-breaking capability of 4.5 kV StakPak IGBTs in the first test circuit as shown in Figure . A fourth IGBT module was connected in opposite primarycurrent direction to verify the functionality of the incorporated anti-parallel diode. Discharge of acapacitor bank by a thyristor switch, limited only by a minor DC reactor, represents pole-to-ground faults in the HVDC grid. The HVDC voltage level prior to the fault and after fault clearance is less critical, since the voltage stress across the IGBT HVDC breaker positions during current breaking depends on the applied arrester bank only. Fig. DC breaker Component test Circuit 19 L.E. COLLEGE - MORBI
  20. 20. As shown in Figure, the maximum current breaking capability of the IGBT HVDC breaker cell is determined by the saturation current of the applied IGBT modules rather than the safe operation area (SOA) as is typical in voltage source converter applications. The series connected HVDC breaker IGBT positions commutate the line current within 2  s (microseconds) into the RCD snubber circuits, which limits the rate of rise in voltage across the positions to 300 V/ Zero voltage switching reduces the instantaneous switching losses s. and ensures equal voltage distribution independent of the tolerances in the switching characteristics of the applied IGBT modules. The line current commutates from the RCD snubbed circuit into the arrester path after the common voltage across the IGBT HVDC breaker positions reaches the protective level of the arrester bank. The IGBT HVDC breaker positions passed the stress tests for breaking currents below 10 kA. For higher currents, the IGBT saturation current level is reached by the internal current limitation in thebreaker, causing an immediate voltage drop across the IGBT modules. During a purposely destructive test, the resulting internal heat dissipation within the IGBT module destroys the encapsulated IGBT chips. Due to the use of press pack IGBTs, a reliable short circuit without mechanical destruction of the failed IGBT module is enabled. Since only one of the IGBT modules failed during the test, the fault can still be cleared by the two other modules. The nominal HVDC voltage per IGBT HVDC breaker cell is 80 kV. Due to the high voltage level, the second test setup requires a significantly larger space. In Figure 7, the test circuit for the hybrid HVDC breaker concept is shown. A ±150 kV HVDC switchyard supplies the containerized test equipment to verify the functionality of the main IGBT HVDC breaker represented by two series connected IGBT HVDC breaker stacks and a common arrester bank. The desired HVDC voltage level is built up by charging the capacitor bank C1. The reactor L1 is selected to give the expected current derivative (di/dt) during a short-circuit fault. The short-circuit fault is initiated by the triggered spark gap Q5. 20 L.E. COLLEGE - MORBI
  21. 21. Fig. DC Breaker Test Circuit Figure, shows a typical test result. A maximum breaking current of over 9 kA is verified. The voltage across the HVDC breaker cell exceeds 120 kV during current commutation. The breaking capability of one 80 kV HVDC breaker cell thus exceeds 1 GVA. Furthermore, equal voltage distribution with a maximum voltage drop of 3.3 kV and a spread of less than 10 percent was only observed for the individual IGBT HVDC breaker positions in the HVDC breaker cell. 21 L.E. COLLEGE - MORBI
  22. 22. 4.2:-TEST RESULTS HYBRID HVDC BREAKER: The main breaker test setup described in Section 5 and reported earlier was expanded to verify the complete hybrid HVDC breaker concept. A second capacitor bank and large reactors were installed to limit the rate of line current rise to typical HVDC grid values. The ultra-fast disconnector and load commutation switch are included in the system configuration. Successful verification testing at device and component level has proven the performance of the components. The complete hybrid HVDC breaker has now been verified in a demonstrator setup at ABB facilities. The diagram in Figure 9 shows a breaking event with peak current 9 kA and 2 ms delay time for opening the ultra-fast disconnector in the branch parallel to the main breaker. The maximum rated fault current of 9 kA is the limit for the existing generation of semiconductors. The next generation of semiconductor devices will allow breaking performance of up to 16 kA. The purpose of the tests was to verify switching performance of the power electronic parts, and the opening speed of the mechanical ultra-fast disconnector. The test object consisted of one 80 Kv unidirectional main breaker cell, along with the ultra-fast disconnector and load commutation switch. The higher voltage rating is accomplished by connecting in series, several main breaker cells, but the switching stress per cell is the same as in the demonstrator. This series connection approach is also used to test conventional HVDC Light and HVDC Classic valves. Tests have not only been carried out for normal breaking events, but also for situations with failed components in the breaker, in order to verify reliable detection and safe operation in such cases. 22 L.E. COLLEGE - MORBI
  23. 23. Fig, Verification of the hybrid HVDC breaker system 23 L.E. COLLEGE - MORBI
  24. 24. CHAPTER 5: NEED OF HYBRID CIRCUIT BREAKER AND SPECIFICATION 5.1:-NEEDS OF HYBRID CIRCUIT BREAKER The ongoing research in the field of High Voltage Engineering focuses on the modeling of Hybrid circuit breakers, which in the future have the potential to take over SF6 circuit breakers. The vacuum interrupters have the ability to recover the dielectric strength across the interrupting gap at the time of current zero. In case of vacuum arc mode, the dielectric recovery is the fastest. Figure 1 indicates the comparison of dielectric strength recovery speed between SF6 interrupter and vacuum interrupter when the gap is 6.35mm breaking current 1600A, 180A vapor pressure. The rate of rise of vacuum recovery voltage is 20kV/us which is faster than SF6. This type of CB has the following shortcomings: Random dielectric breakdown across the open contacts of the CB can occur under continuous voltage stress which can lead to energizing the system to be isolated. This breakdown occurs for about one cycle of the system frequency. The butt contacts of the CBs, may bounce or close. Due to the multiple make and break operations occurring in the circuit, the voltage produced may reach above the insulation level of the system and the equipment. Vacuum interrupters have the tendency to chop the current as it reaches zero during circuit interruption .High voltages comparable to the system voltage but less than the insulation level are generated due to chopping . The interrupting gap in SF6 CBs has high dielectric recovery capability along with thermal recovery and high dielectrics withstand capability under continuous voltage stress. This characteristic helps to prevent the random breakdown of the gap by isolating the vacuum CB from the system. SF6 has wiping contacts of tulip and 24 L.E. COLLEGE - MORBI
  25. 25. bayonet type. SF6 arc resistance is higher than that of vacuum arc resistance. Thus in the hybrid model SF6 CB bears the main voltage drop and works in conjunction with vacuum CB to complete current interruption. These contacts make the circuit without any bounce and thus no multiple system energisations will occur. The hybrid circuit breaker has the following advantages over SF6 and vacuum CBs: This type of breaker has the capability of switching short line faults at high voltage. High operating force is not required and the size and the cost of the breaker reduces Various standard design of this type are available which can be applied to free standing breakers and compact substation breakers. It has an excellent capability to deal with the steep-rising transient recovery voltage (TRV). A basic interrupting module can be formed which is rated at 145kV or more. Fig. the comparison of dielectric recovery speed between SF6 interrupter and vacuum interrupter 25 L.E. COLLEGE - MORBI
  26. 26. 5.2:-SPECIFICATION Table 3: Specification of hybrid circuit breaker System Voltage Interrupter Opening Time Breaker Interrupt Time 325 Kv 240 s 340 s 125 130 230 50 85 185 7 65 165 26 L.E. COLLEGE - MORBI
  27. 27. CHAPTER 6: ABOUT OF THE INVENTION 6.1:-OBJECT OF THE INVENSION It is an object of the present invention to present a hybrid circuit breaker which works on the principle of keeping the voltage across a mechanical switch thereof sufficiently low to prevent arcing between the contacts of the mechanical switch in connection to its switching operation. A hybrid circuit breaker which can be used in an electrical high-voltage network. This hybrid circuit breaker has two series-connected arcing chambers, a first of which is filled with sulfahexafluoride gas as a quenching and insulating medium, and a second of which is in the form of a vacuum interrupter chamber. The second arcing chamber is surrounded by sulfahexafluoride gas on the outside. The main contacts of the two arcing chambers are operated simultaneously by a common drive via a simple lever transmission. Both arcing chambers have a power current path, in each of which the erosion-resistant main contacts are located and, in parallel with this, a rated current path, with this rated current path having only a single interruption point. During disconnection, the rated current path is always interrupted first of all, after which the current to be disconnected commutates onto the power current path. The power current path then continues to carry the current until it is definitively disconnected. Simple lever transmissions such as these are comparatively difficult to match to the movement profiles required in hybrid circuit breakers. Furthermore, the bearing points are subject to mechanically very severe stresses, which results in the bearing points having a complex and expensive design, as a result of which the hybrid circuit breaker price is increased. If this configuration of the bearing points is dispensed with, then the time penalty for the maintenance work which is then required more frequently restricts the availability of the hybrid circuit breaker in a disadvantageous manner. Furthermore, the complexity for 27 L.E. COLLEGE - MORBI
  28. 28. installing the lever transmission in the interior of the hybrid circuit breaker is comparatively great, owing to the restricted accessibility in this area. 6.2:-SUMMARY OF THE INVENTION The invention, as it is characterized in the independent claims, achieves the object of providing a hybrid circuit breaker having a transmission, which can be joined together easily in the interior of the hybrid circuit breaker. The hybrid circuit breaker has at least two series-connected arcing chambers, which are operated by a common drive. These arcing chambers are preceded by a common transmission. This transmission has at least two transmission parts, which are designed such that they can be plugged together, with the first transmission part being firmly connected to the at least one first arcing chamber, and the second transmission part being firmly connected to the at least one second arcing chamber. The transmission has means which allow the movements of the at least two arcing chambers to be technically sensibly matched to one another and to be optimized with respect to the time sequence and switching speed thereof. It has been found to be particularly advantageous for the transmission to be designed such that it is self-locking both in the connected position and in the disconnected position since this means that there is no need for any additional locking apparatus or catches. Furthermore, the drive does not need to apply any particular holding forces in the two limit positions, so that a simple and particularly low-cost drive can be used here. The longitudinal axes of the two arcing chambers in one preferred embodiment of the hybrid circuit breaker lie in one plane and are inclined at an angle α to one another, with the angle α being less than 90°, and preferably being in the range between 68° and 800°. This arrangement of the arcing chambers makes it possible to produce a hybrid circuit breaker which has a comparatively short extent in the axial direction, so the space required for this hybrid circuit breaker is particularly small. The further refinements of the invention are the subject matter of the dependent claims. 28 L.E. COLLEGE - MORBI
  29. 29. The invention, its development and the advantages which can be achieved by it are explained in more detail in the following text with reference to the drawing, which illustrates only one possible embodiment approach. CHAPTER 7: ADVANTAGES, DISADVANTAGES, AND COST OF HYBRID BREAKER 7.1:-ADAVANTAGES 1. Arc-less interruption 2. Required fault current handling capability of the mechanical contacts can be reduced. 3. Turn-on at lower fault current compared with the conventional hybrid breaker 4. Lower turn-off current. 5. The solid-state device must handle (dissipate) comparably lower energy. 6. Compact solution, the solid-state device is not as bulky as in the case of the conventional hybrid breaker. 7. Lower temperature rise in the solid-state device due to lower peak current. 8. Current limiting ability 9. Can be used in both AC and DC current interruptions. 10. Lower varistor rating is required. 11. Overall turn-off process completes earlier. 12. Comparably lower commutation time possible. 13. Possible reduction of the conduction time of the solid-state breaker. 14. The connected network components don't need to be rated with respect to shorttime very high fault current-handling capability. 29 L.E. COLLEGE - MORBI
  30. 30. 7.2:-DISADVANTAES High cost Complex design Construction under process 7.3:-COST OF HYBRID CIRCUIT BREAKER No. Capacity rating Prize(Rs) 1 Up to 11 kv 2000 2 Up to 121 11,000 3 Up to 500 kv 22,000 4 Up to 2000 A 50,000 (around) 30 L.E. COLLEGE - MORBI
  31. 31. CHAPTER 8: PHOTO OF HYBRID CIRCUIT BREAKER LIST OF DESIGNATIONS: 1 First longitudinal axis 2 Second longitudinal axis 3 Drive linkage 4 Bolt 5 Contact rod 6 Enclosure 7 Slot 8 Roller 9 Bolt 10 Rotation axis 11 Surface 31 L.E. COLLEGE - MORBI
  32. 32. 12 Slotted guide disk 13 Bolt 14 Guide enclosure 15 Slot 16 Rotation axis 17, 18 Insulating enclosure 19 Bolt 20 Double lever 21 Bolt 22 Drive rod 23 Flange 24 Stop part 24a, 24b Shoulder 25 Collar 26 Cup spring pack 27 Step 28 Arrow 29 Transmission 30, 31, 32 Arrow 33 Curved surface 34 Planar surface 35 Guide tube 36 Slot 37 Collar 38 Slotted guide part 39 Slot 40 Guide slot 41 Bolt 42 Dashed line of action 42a, 42b Section 43 Holder 32 L.E. COLLEGE - MORBI
  33. 33. 44 Union nut a Angle b Angle R Radius of curvature CONCLUSION From the testing it is observed that the initial peak of the transient recovery voltage falls across the vacuum interrupter and the later much higher peaks are taken by the SF6 interrupter. In this way both the SF6 interrupter and the vacuum interrupter assist each other. The vacuum interrupter capability to withstand the steep rate of rise of recovery voltage reduces the pressure of SF6 gas in SF6 interrupter. Hence it can be concluded that the breaking capacity of the hybrid circuit breaker is more than that of the SF6 circuit breaker. In the future, it can be seen as a great alternative of SF6 circuit breaker in high voltage applications. 33 L.E. COLLEGE - MORBI
  34. 34. REFERANCE: [1] E. Koldby, M. Hyttinen “Challenges on the Road to an Offshore HVDC Grid,” (Nordic Wind Power Conference, Bornholm, Sept. 2009) [2] Å. Ekström, H. Härtel, H.P. Lips, W. Schultz “Design and testing of an HVDC circuit breaker,” (Cigré session 1976, paper 13-06) [3] C.M. Franck “HVDC Circuit Breakers: A Review Identifying Future Research Needs,” (IEEE Trans. on Power Delivery, vol. 26, pp. 998-1007, April 2011) [4] J. Magnusson, O. Hammar, G. Engdahl “Modelling and Experimental Assessment of Thomson Coil Actuator System for Ultra Fast Mechanical Switches for Commutation of Load Currents,” (International Conference on New Actuators and Drive Systems, Bremen, 14-16 Juni 2010) [5] G. Asplund “HVDC switch for current limitation in a HVDC transmission with voltage source converters,” (European Patent EP0867998B1) [6] S. Eicher, M. Rahimo, E. Tsyplakov, D. Schneider, A. Kopta, U. Schlapbach, E. Caroll “4.5kV Press Pack IGBT Designed for Ruggedness and Reliability,” (IAS, Seattle, October 2004) [7] M. Rahimo, A. Kopta, U. Schlapbach, J. Vobecky, R. Schnell, S. Klaka “The Bi-mode Insulated Gate Transistor (BiGT) A potential technology for higher power applications,” (Proc. ISPSD09, p. 283, 2009) [8] J. Häfner, B. Jacobson, ” Proactive Hybrid HVDC Breakers - A key innovation for reliable HVDC grids,” (Cigré Bologna, Paper 0264, 2011) 34 L.E. COLLEGE - MORBI
  35. 35. [9] J .J . V i t h a y a t h il , "HVdc Breaker and i t sApplication", Proceedings o fthe I n t e r n a t i o n a l Symposium on HVdc Technology, Rio de Janeiro, B r a z i l , March 20-25, 1983 [10] B. Bachmann, G. Mauthe, E. Ruoss, H.P. Lips, J.W. Porter and J.J. V i t h a y a t h il , "Development o f a 500 kV A i r b l a s t HVdc C i r c u i t Breaker", IEEE Transactions on Power Apparatus and Systems, Vol. 104, No. 9, September 1985, pp. 2460-2466. [11] J.J. V i t h a y a t h il , A.L. Courts, W.G. Peterson, N.G. Hingorani, S . Nilson and J.W. Porter, "HVdcC i r c u i t Breaker Development and F i e l d Tests", IEEE Transactions on Power Apparatus and Systems, Vol. 104, No. 10, October 1985, pp, 2693-2705. [12] A, Lee, P.G. Slade, K.H. Yoon, J. Porter and J. V i t h a y a t h i l , "The Development o f a HVdc sF6 Breaker", IEEE Transactions on Power Apparatus and Systems, Vol. 104, No. 10, October 1985, pp. 2721-2729. [13] D. Goldsworthy and J.J. V it h a y a t h il , "EMTP Model o f an HVdc Transmission System", Proceedings of the IEEE Montech '86 Conference on HVdc Power Transmission, September 29 - October 1, 1986, pp. 39-46. [14] J.D. Cobine, "Gaseous Conductors, Theory and Engineering Applications", Dover Pub1 i c a t i o n s ,Inc. New York. pp. 344-348. [15] K. Ragaller, A. Plessl, W. Hermann, W. Egli, "Calculation Methods f o r ,;he Arc Quenching System o f Gas Circuit-Breakers , CIGRE Report 13-03, 1984. [16] E. Bross, H. Schubert, "The DLF Range o fHigh Voltage A i r b l a s t C i r c u it Breakers; Design Performance, Applications", Brown Boveri Review 65,1978 WEBSITE: www.sumobrain.com/patents/wipo/Hybrid-circuit-breaker/WO2011044928.html www.freepatentsonline.com/6727453.html www.siemens.com/energy 35 L.E. COLLEGE - MORBI