Shri Vishnu Engineering College for Women :: Bhimavaram

Transcription

1 Shri Vishnu Engineering College for Women :: Bhimavaram A REPORT ON INTRODUCTION TO INDUSTRIAL ELECTRICAL SYSTEMS (IIES) SUBMITTED BY: 11B01A B01A B01A B01A B05A B05A0209 K.Tejaswi M.Lohitha P.Nikhita R.Sri Manvitha K.Sravani M.Majusha. DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

2 INTRODUCTION TO INDUSTRIAL ELECTRICAL SYSTEMS (IIES) Switchgear Training In L&T, Pune 1/9/14 3/9/14 Larsen & Tourbo Limited, also known as L&T,is an Indian multinational conglomerate head Quartered in Mumbai, India. L&T is an international manufacturer of a wide range of electrical and electronic products and systems. L&T also manufactures custom-engineered switchboards for industrial sectors like power, refineries, petrochemicals and cement. In the electronic segment, L&T offers a range of meters and provides control and automation systems for industries. Medical Equipment. As a group of 31 members along with our faculty reached the venue Central Institute Of Road Transport (CIRT) by 2:30am. After that we attended the class at 9am.We were lectured by the Training industrial Engineer, Onkar Tate and a technician, Swapnali. It was a three day programme. we trained regarding the Switch Gear Protection & its products.the hospitality given by the Training centre was delightful. The areas which we were to be trained were scheduled in three days.it covers a range of Low Voltage Switch Gear,Causes for the failure of motor & its protection,drives & circuit Breakers.This workshop not only made us technically strong but also made us confident in person.

3 DAY 1 Basics of electricity. Introduction to low voltage switch gear. Contactors construction, operation, application, demonstration. Various causes of motor failure. Thermal over load relay. BASICS OF ELECTRICITY: What is electricity?? o Electricity is one of the form of energy. o Energy can neither be created nor be destroyed. Generation of electricity: It is nothing but transfer of energy. Electricity is produced when electrons leave their atom. SOME BASICS: VOLTAGE: electro motive force(emf) Unit: volts(v) CURRENT: flow of free electrons per second Unit: ampere(a) POTENTIAL DIFFERENCE (PD): difference between the voltage level at two points Unit: volts (V) SOME BASICS LAWS: 1. OHM S LAW: Keeping all physical conditions constant current is directly proportional to voltage V=IR, R=resistance 2. KIRCHOFF S LAW: CURRENT LAW: Vector sum of current at any node in the circuit is zero.

4 VOLTAGE LAW: Vector sum of voltage drop in a loop is equal to the vector sum of voltage source connected in loop. 3. FARADAY S LAW OF INDUCTION: 1. Whenever current carrying conductor placed in magnetic field experiences chane in magnetic field causes induced emf in conductor. 2. Magnitude of induced EMF is directly proportional to rate of change of magnetic field. 4. LENZ S LAW: Induced emf opposes the cause of production of motion of conductor in magnetic field and change in magnetic field. 5. FLEMMINGS RIGHT HAND RULE: For generator: Input: 1. motion. 2. magnetic field Output: 1. induced current.

5 6. FLEMMINGS LEFT HAND RULE: For motors: Input: 1. Current. 2. Magnetic field. Output: 1. Motion. SINUSOIDAL WAVE:

6 LOW VOLTAGE SWITCH GEAR: VOLTAGE SYSTEM LV MV HV EHV UHV NOMINAL VOLTAGE (Vr)KV Vr 1 1<Vr 35 35<Vr <Vr <Vr SWITCH GEAR SWITCHING PROTECTION CONTACTOR Y N RELAY N Y STARTER Y Y SWITCH/SD N N HRC FUSE Y Y SFU/FSU/SDF Y Y ACB Y y MCCB Y Y MPCB Y y LV SWITCH GEAR S/C BREAKING CAPACITY: CONTACTOR 9 to 550A on/off Relay 0.6 to 450A o/l + single phasing Fuse 2 to 800A s/c 100KA ACB 400to6300A on/off+o/l+s/c 100KA. MCCB 16 to 1600A on/off+o/l+s/c-50/65ka MPCB 0.16 to 63A -on/off+o/l+s/c+single phasing -50KA MCB 0.5 to 100A-on/off+o/l+s/c-10KA RCCB/ELCB 25 to 100A-earth leakage/earthing RCBO 6 to 32A-on/off+o/l+s/c+earthing 6KA EL+MCB 6 to 63A on/off+o/l+s/c+earthing 6KA

7 MOTOR FEEDER COMBINATIONS: COMB I: Switch disconnector Fuse+fuse base Contactor Bmr/mp relay Isolator scpd switching device o/l+sp M COMB II: SDF Contactor Bmr/mp relay Scpd+isolator Switching device O/l+sp COMB III: M mccb contactor Bmr/mp relay Scpd+isolator Switching device o/l+sp m

8 COMB IV: mpcb contactor o/l+sp+scpd+iso switching device m COMB V: mpcb Switching+o/l+sp+scpd+isolator m CONTACTORS: A electro mechanical switching device capable of making,carrying and breaking currents under normal circuit condition including operating over load condition. CIRCUITS: Power circuit Control circuit Auxiliary circuit No electrical connection between them All can have different supply POWER CIRCUIT: Make, carry and break load current Consists of main contacts CONTROL CIRCUIT: For operating the contactor Consists of coil if the contactor

9 AUXILARY CIRCUIT: Accessory part Consists of n/o or/& n/c contacts Does not affect the contactor operation Gets affected by contactor operation Used for indication,inter locking etc CONTACTOR -LIMITS OF OPERATION: Pick up voltage 85% to 100% of uc Drop off voltage 75% to 20% of uc (for ac) 75% to 10% of uc (for dc) APPLICATIONS: Switching of Motor Capacitor Lightning loads Heating loads Dc loads Automatic operation CAUSES OF MOTOR FAILURE: Overload Heavy starting Locked rotor Supply variation Unbalance in supply Number of starts Single phasing Mechanical problem High ambient Problems in cooling

10 THERMAL OVERLOAD RELAY: Two metals with different temperature coefficient of expansion are fused together With heating one of them expands more and another expands less This action results in bending of bimetal Because of this mechanism this is also called as BIMETALLIC RELAY BIMETALLIC RELAY: Single slide mechanism o/l protection Double slide mechanism o/l protection single phasing double slide is advantageous than single slide mechanism SELECTION OF THERMAL O/L RELAYS: type of mechanism relay range it characteristics trip clss auxiliary contacts mounting ADVANTAGES: thermal memory compact accurate protection long life ambient protection low cost

11 I-T CHARACTERISTICS AND MOTOR DAMAGE CURVE: Day-2: The topics covered in day-2 are: AC motor starter HRC fuses Switches MCCB AC motor starter: Need of starter: ON/OFF operation To limit the inrush / starting current Over load and single phasing protection CONTROL CIRCUIT Start N/O N/C STOP

12 DIRECT ONLINE STARTING: Electrical impact of large starting current: Large voltage dip, operation of other equipment can effect Reduces life of switching device, increase line losses Mechanical impact: Excessive wear and tear on belts and pulleys STAR-DELTA STARTING METHOD: Star connection : phase voltage=1.732 times of line voltage When motor speed reaches greater than or equal to 80% of its rated speed change over action is initiated HRC FUSES: A device that by the fusing of one or more of its specifically design and proportioned components, opens the circuit in which it is inserted by breaking the current when this exceeds a given value for a sufficient time The fuse comprises all the parts that from the complete device. Main applications: Production of lighting & heating circuits Production of transformers Production of cables LET- THROUGH ENERGY: Reflects the quality of short circuit protection Reflects the current limiting capability of S.C.P.D Co-ordination: there are two types of co-ordinations Type-1:cheaper at the time of installation Type-2: costlier at the time of installation

13 SWITCH: A manual switching device It can make&brake, carry currents under normal&specified overload conditions SWITCH-SWITCHING CAPABILITIES: MAKE CARRY BRAKE NORMAL can can can OVER LOAD can can specified time can SHORT CIRCUIT can can specified time can t SWITCH DISCONNECTOR: It works like a switch but only the difference is switch has electrical output where as disconnector has mechanical output Positive opening of main contacts MCCB :( MOULDED CASE CIRCUIT BREAKER) lower down time reduced running cost low inventory by using MCCB we can protect the over load &short circuit faults some design can be provide current limiting feature it can interrupt within 19msec TYPES: 1. Conventional type: Operating time: 15to 20msec Higher let through energy 2. Current limiting MCCB: Lower Let through Energy

14 Day 3: Air Circuit Breakers (ACB) Over view of MCB and RCCB Power factor improvement Overview of bus bar trunking Air Circuit Breaker: An Air Circuit breaker is an electrical device that opens and closes a set of electrical contacts of an electrical circuit in air, at atmospheric temperature. The major parts of ACB are: Contacts: Circuit Breaker consists of 2 contacts out of which one is fixed and the other is moving, the contacts are operated to close or open the circuit breaker. Spring: The spring will provide a necessary restraining force for the movement of contacts. Latching Mechanism: Initially the circuit breaker contacts are closed by the latch. If the latch is moved, spring gets discharged and opens the contacts called as tripping of breaker. Type of mechanism: The following flow chart shows the operating mechanism of circuit breaker. ACB Manually operated Electrically operated fixed Draw out fixed Draw out

15 Accessories : 1. Shunt Release: The latching mechanism is operatd electrically by means of a device called shunt trip. The shunt release is connected to the control panel in times of emergency the circuit breaker is operated directly from the panel. 2.Under Voltage Release: This release gives the trip command to the circuit breaker when it detects a under voltage(voltage less than the rated voltage)according to which the circuit breaker operates. 3.Earth Fault Release: This release is generally required for giving earth fault protection. It is also necessary to specify7 the percentage of earth fault setting. Depending on the setting the earth fault release gives the tripping command to the circuit breaker. 4.Over Voltage Release: his release gives the trip command to the circuit breaker when it detects a over voltage(voltage greater than the rated voltage)according to which the circuit breaker operates. Selection Criteria of ACB: 1. Current Rating: It is decided based on the application of protection (either in source or load) 2.Rated Ultimate Short Circuit Breaking Capacity: Value of the prospective breaking current in KA.According to specified test sequence do not include the capability of the circuit breaking to carry its rated current continuously 3. Making Capacity: When the breaker is closed on a fault the current rises from zero to fault level i.e,a switching source takes place,putting the ACB to a more severe duty.it depends on power factor &instant of switching.

16 MCB :( miniature circuit breaker): A MCB perform the similar operation as ACB but it differs in size. it is used for low voltage applications like switches for ac s, Advantages: Can be use by both skilled and unskilled workers Overload and short circuit settings cannot be tempered. Mechanism of MCB is trip free. It can b used as a functional switch. It is used as an isolator. It is a fully enclosed unit and hence no ageing problems. MCB is a cost effective device Functions of MCB: Magnetic trip thermal strip For isolation For making & breaking current Solenoid Bimetal strip Short circuit overload RCCB (residual current circuit breaker): It is also called as earth leakage circuit breaker. When earth faults happens some value of current starts flowing to the earth which reduces the value of current in neutral. This results in reducing magnetic forces created by neutral In the core, subsequently causes the flow of current in the secondary of CT.This current induces magnetic force in the core of PMR which quashes the magnetic forces of permanent magnets resulting I opening of circuit to avoid further consequences this complete mechanism of RCCB operates and disconnects the circuit with in 30ms under earth fault.

17 Power factor correction: Power factor is the cosine of angle between phase voltage and phase current. Power factor correction Reduction in KVAR demand Reduction in switch gear rating Reduction in KVA demand Reduction in transformer ratings Reduction in cable size Reduction in line current Reduction in power loss

18 Necessity: Power factor correction is necessary to reduce the PF penalty by electricity board. And Maximum demand control is concern. Reduction Techniques: Capacitor Banks. Synchronous Machines. Capacitor Banks: Ia=8 10A,0.8PF G I=10A L 8A,PF=1 Ir=6A Effect of Capacitor: Upstream Current Reduces Upstream Pf Improves No change in the downstream current & PF PF can be improved to Remove Penalty Reduce Demand(KVA) Reduce Transformer Current Improve Voltage

19 BUSBAR TRUNKING SYSTEM: bus bar trunking system is a prefabricated electrical distribution system consisting of busbars in a protected enclosure including straight lengths fittings devices and accessories TYPES: 1. Air insulated 2. Sandwiched It was a very good experience we learnt a lot about the switch gear products, construction, and operation.this program really helped us to gain a good knowledge by interacting with highly professionalized people. We thank our management & department of EEE for giving us a very good opportunity.

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