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Electrical Electrical Department Dep artment
Electrical Electrical Department Dep artment
Contents Page 1. Switch Yard
9. Power Transformer
10. OLTC, NGR
Electrical Electrical Depar Department:tment: Electrical Electrical department department is concerned concerned with the receiving, receiving, controlling controlling & distribution of electrical supply in the plant also the correct functioning, repair & maintenance of electrical equipments under their control. This department caters to the entire plant related electrical needs, as it has elect electri rical cal works workshop hopss scatt scatter ered ed in all all the the plant plant.. Incomi Incoming ng suppl supplyy of elec electr tric icit ityy is of 132K 132KV V has has to be step step down down to 6.6K 6.6KV V & 415V 415V for for distribution in the plant, residential colony, offices & for other purposes. This This dept. dept. also also helps helps the the produ product ction ion dept. dept. to produc producee the ceme cement nt by supplying supplying uninterrupted uninterrupted stable power. This dept. also takes up maintenance jobs for the smooth functioning of the plant. Here there is set a big electric power switch yard station where there are 2 transformers (28/32MVA each) for stepping down the electric supply to 6.6KV. In the electric electric workshops the motors which are not working working properly are over hauled, repaired & checked before taking them again in service. There are around 22 DC Motors& 1250 AC Motors in the plant. After this there is HT Motors 24 in NO. in the plant.
Cement manufacturing is a heavy industry. The plant here runs on full load approx 32MW.For the plant HPSEB gives a 3 phase, 50 Hz, 132KV dedicated line from Cham kauri substation. In the switchyard switchyard it is stepped stepped down to 6.6KV & further further to 415V supplied supplied to the plant plant auxilia auxiliary ry system. system. The The outp output ut power power of the the trans transfo form rmer er is trans transfe ferre rred d outg outgoi oing ng cables into the MPSS. Here all the controls of the transformers are kept.
This is a main power sub station for control , monitoring & distribution of power is carried out. The power is fed through a SF6 CB, having a rating of 630A & 3150A. MPSS also coordinates with the STATE LOAD DISPATCH CENTRE HPSEB which manages the power consumption. MPSS also has a very important job that is of safety. In case of overload, frequent start stops some times power is cut before the motor cause’s damage. The power also cut off during repair, regular maintenance or replacement so as to ensure safety for men working on it .The CB is taken out service. The MPSS also has capacitors for better power factor. They have a rating of 1590KVar each. These are kept second floor above the main floor in which HT panels are kept. The main incoming supply comes from the HPSEB i.e. 132KV. Then it step down up to 6.6KV by the 2 power transformer capacity 28/32MVA each. Further this supply is used for HT motors & auxiliaries equipment with the help of our distribution transformers (6.6KV/415v). Substation:-
A Substation may be defined as an assembly of apparatus which is installed for protection & control, transmission & distribution of electric power. The electric power is generated at the power station handled at several substations & then delivered to the consumers of electricity. The incoming supply comes from the HPSEB then after the output supply comes in breakers further this supply is used for our HT motors & also for auxiliaries with the help of our distribution transformer (6.6KV/415V). We are feeding power supply to cement plant through the HT cables (6.6KV grade).
Unit substation has been used for Stepping down supply i.e. 415V for using in auxiliaries equipment. We have following unit substations..
1. USS-1 2. USS-2 3. USS-3 4. USS-4
We have one distribution transformer (capacity 1250KVA, 6.6KV/433V) through which we are feeding power supply to USS-1(For Mining section). Further USS-1 is divided into two parts. 1. PCC-Power Control Centre 2. MCC- Motor Control Centre. USS-2:-
We have one distribution transformer (capacity 1250KVA, 6.6KV/433V) through which we are feeding power supply to USS-2(For Stacker & Reclaimer section). Further USS-2 is divided into two parts. 1. PCC-Power Control Centre 2. MCC- Motor Control Centre. USS-3:-
We have six distribution transformer (capacity 6×2000KVA, 6.6KV/433V) through which we are feeding power supply to USS-3(For Raw mill, Coal mill& Kiln section). Further USS-3 is divided into two parts. 1. PCC-Power Control Centre. (PCC-31, 32, 33, 34, 35/1, 35/2) 2. MCC- Motor Control Centre. (MCC-311, 312, 313, MCC-321, 322, 323, MCC-331,332,333, MCC-341,342,343, MCC-35/1, 35/2) USS-4:-
We have 3 distribution transformers (capacity 2×1250KVA&1×2000KVA 6.6KV/433V) through which we are feeding power supply to USS-4(For Cement mill section). Further USS-4 is divided into two parts.
1. PCC-Power Control Centre. (PCC-(PCC-41, 42, 43) 2. MCC- Motor Control Centre. (MCC-411,412,413, MCC-421,422,423, MCC-431,432,433).
Switch Yard comprises of following equipments & their specifications & functions:-
1. Transmission lines. 2. Poles & Towers. 3. Lightning Arrester. 4. PT. 5. Ckt Breakers. 6. Power Transformers. 7. Bus coupler 8. Isolators. 9. Earth switches. 10.CT. 11.PT. 12.Ckt Breakers. 13.Power Transformers. 14.Bus coupler. 15.NGR. 16.Earthing. Lighting arrestor:-
It is a device used to discharge excessive or high voltage build upon the lines ground due to lightning. These are used to provide safety to the line to the instrument connected at line when lightning occurs. Phase – Single. Voltage rating-120 KV Current rating- 10 KA Basic insulation level (BIL) – 650KV Type – Gapless (Zno) Metal Oxide.
Isolator (Air Break Disconnector): (89.1, 89.5, 89.8, 89.3):This is an off load switch which isolate one part of system from the other part. The isolators are generally provided on both sides of the CB but at switchyard. Here the isolators are provided on one side of the CB i.e. on the industry we are consuming electrical power and in case of any shutdown there is no chance of reverse power flow which may be the case of interconnected power system. The induction motors have been provided for operating the isolator. Type- RD300. Voltage (KV)- 145 BIL (KVp)-650 STC (KA/sec)-31.5/3 Motor Volt (AC)- 415V Type of Drive- MGB Freq. - 50Hz Current (A) - 800 Control Volt. (DC)- 220V Make -Switchgear Ltd. (Madras)
Earthing switch is connected between the line conductor & earth. Normally it is open. When the line is disconnected, the earthing switch is closed so as to discharge the voltage trapped on the line, capacitance to the earth. Normally the earthing switches are mounted on the frame of isolator. Make - Switchgear Ltd. Type- VLE Volt (KV)-145 BIL (KVp)- 650 STC (KA/sec)-31.5/3 Motor Volt (DC)-415V Type of Drive- MGB Freq. - 50Hz Control Volt. (DC)- 220V Isolator (Air Break Disconnector): (89.7, 89.9)
PT is basically step down transformer. The primary of a PT has many no. of turns as compare to its secondary and is connected across high voltage system whose voltage is to be measured. The secondary way is usually rated for 110v irrespective of the primary voltage rating if a voltage of 132kv is to be measured the PT will have a turn ratio 13200/110v i.e.1200:1. To insure safety to the operator the secondary of a PT should always be earth. Phase- Single. Freq. – 50 Hz Voltage – 145KV. BIL – 650KV. S1: 132KV/√3, 50VA/ph, CL. 0.5(HPSEB TVM) S2: 110KV/√3, 50VA/ph, CL. 0.5(HAC TVM) S3: 110KV/√3, 100VA/ph, CL. 1(To CRP metering ckt) S4: 110KV/√3, 100VA/ph, CL. 3P(To CRP relays ckt)
Current transformer (5-Core CT):-
CT is a basically step up transformer. These are used to measure very high current. The primary winding of CT consist of few turns and is connected in series with line whose current is to be measured the secondary has comparatively more no. of turns. A low range ammeter generally of rating 0-5A is connected in the secondary ckt. To insure safety to the operator the secondary of CT is always earth all type of protection relay are CT operated. Phase- Single. BIL- 650KV. Voltage- 145KV Current – 20KA. Core1 (C1): 200-400/1A, 30VA, CL. 0.5(To HPSEB TVM) Core2 (C2): 200-400/1, 30VA, CL. 0.5(To CRP HAC TVM ckt) Core3 (C3): 200-400/1, 30VA, CL. 1(To CRP metering ckt) Core4 (C4): 200-400/1, 30VA, CL. 0.5 P20 (To CRP Protection ckt) Core5 (C5): 200-400/0.557A, 30VA, CL. PS (To CRP Diff. Protection ckt) Bus Bars:-
Bus Bar is a conductor to which a number of incoming and outgoing circuits are connected. Voltage and frequency of the bus bars are constant. Power cables:-
To provide supply path to various auxiliary equipment and machines the power cables are used. Various sizes of the power cables for the LT and HT equipments and drives are 3×200mm2,3×300mm2,3×300mm2,3×600mm2. Post Type Insulator:-
These are used for supplying the Bus Bar and disconnecting switches in substation. A Post type Insulator is similar to a Pin type Insulator but has a metal base and frequently a metal cap so that more than one unit can be mounted in series.
In EHV substation (400KV & above) polycon post insulator are used. Also known as multicone insulator. In this Insulator protection elements are in form of cones. Bus coupler:-
Which system through the one transmission line to another transmission line is connected is called as bus coupler. They are made ACSR conductor. They have high strength. Breakers:-
These are used to make or break the power supply under no load , on load condition& abnormal conditions. We have different types of breakers like. 1. SF6 CB 2. VCB 3. ACB We are using SF6 breakers & VCB for the voltage level 132KV & 6.6KV. And for low voltage system we have ACB. SF6 Gas Ckt Breaker (52-A, 52-C,52-D):-
SF6 CB is a ckt breaker employing sulpher hexafluoride gas for arc extinction. In this CB when moving contacts separates from the fixed contacts the gas filled in the cylinder chamber is pressed and comes out through a narrow opening and extinguishes the arc. Type-20-SFM-32A Rated Lightning Impulse withstand Voltage- 650KVp Rated Short ckt Breaking Current-31.5KA Rated Operating Pressure- 15kg/cm2-g First pole to clear factor-1.5 Rated duration of S.C. current-31.5KA, 3sec Rated line charging current-50A Gas Wt.-9kg Rated Voltage-145KV Rated freq-50Hz Rated Normal Current-1600A
Rated closing Volt.-220V DC Rated opening Volt.-220V DC Rated gas pressure-5kg/cm2-g(at20deg.) Rated Volt. & freq for Aux. Ckt-415VAC &50Hz Rated operating sequence-0-0.3-co-3min-co Make-Crompton Greaves ltd Air Ckt breaker:-
In this ckt breaker Air is the medium which is extinguished the arc. Voltage- 415V Freq.-50Hz Utilization cat.-B Coil volt.-220VDC Make- L&T Fault current-75KA Rating-3200A At incomer feeder- 3200a(C&S make) At Tie- 2000A At MCC-1250A Vacuum Ckt Breaker :-
A Vacuum system is one in which the pressure maintained at a value below the atmospheric pressure & is measured in term of mm of mercury. In the VCB the arc extinguish on first current zero automatically due to vacuum i.e. the vacuum regains the dielectric property very quickly. Rated Volt. (Un)- 12KV SCC (Isc)- 44KA R.L.I.W. (Up)-75KV Normal current (ir) 1250A Operating time- 3 sec Mass-135Kg Freq.-50Hz Coil Volt. - 220VDC Motor Volt.-220VDC Make-Siemens
SF6 CKT BREAKER
Power Transformer 1:
The transformers having rating higher than the 2000KVA are used on the generation & are connected with each of transmission line to decrease or increase the voltage are called Power transformer. These transformers are usually on full load because they have high efficiency on full load. Type of cooling- ONAN/ONAF KVA Rating-28/32MVA Primary Volt (HV)-132KV Secondary Volt (LV)-6.6KV Phases- HV-3-star LV-3-star Ter.- 3-delta Vector group- YNynod11 Make - Kirlosker Company Power Transformer 2:
Type of cooling- ONAN/ONAF KVA Rating-28/32MVA Volt at No Load (HV)-132KV (LV)-6.6KV (Tertiary)- 11KV Amps (HV)- 122.5/140 (LV)- 2454/2500 (ter.)- 490/560 Phases- HV-3-star LV-3-star Ter. - 3-delta Vector group- YNynod11 Make – BBL Insulation levels P.F./Impulse HV 275KV/650KVp LV 28KV/75KVp Ter. 25KV/75KVp,
OLTC (On Load Tap Changer):-
For the required output we can keep on changing the tap of the transformer by OLTC on the on load condition. The lower level of range of 5.8kv & upper level is 6.8kv thus it gives us sufficient range to operate on. Type- FR-20 Normal working current -181A Step Volt-1145V Phase-3 Freq-50Hz Steps- 20 Make- Manufacturing Industries Ltd (Poona) NGR (Neural Grounding Resister):-
A resistance is connected with the neutral & then it is grounded. It is done so that if any one of the phase is grounded then a very large current should not flow in the ckt & thus it provided more safety. Make-Kores (pune) Resistance- 1.36Ohms Current-2800A Temp. Rise-350 deg. Volt.-6.6KV Protection-IP-32 Rating-10sec
POWER TRANSFORMER Capacitor Bank:-
We know that Capacitor bank is used to improve the power factor & we also know that current leads voltage by 90 deg. in the pure capacitor. In this plant 13 no. of capacitor bank is used for HT panels & equipment. Rated output:- 1590kvar Connection- Star U.Temp.Cat.-50deg Insulation level- 28/75KV Type of diel-pp Rated voltage-6.996KV Rated Freq.-50Hz No. of Phases-3 Type of IMPR.-NPCB Make- Shreem capacitors pvt. Ltd. Each Capacitor Rating:-
Make- Shreem capacitors pvt. Ltd. Rated output:- 106 kvar Amps-26.24 U.Temp.Cat.-50deg Insulation level- 28/75KV Type of diel-pp Rated voltage-4.04KV Rated Freq.-50Hz No. of Phases-1 Type of IMPR.-NPCB Total Weight-26Kg
A Reactor connected in series with the equipment to limit the flow of fault current, Harmonic current or for reactive power compensation. The series reactor can in different cases save a lot of investments in other fault current is limited to an acceptable level. Make- PS Electrical Pvt Ltd Insulation level- 28/75 Kvp Rated cont. current-131A Rated Voltage- 6600V Rated Freq.-50Hz Measured impedance at rated cont. current – 175 ohms Temp. Rise in oil over an ambient of 45deg. Phases -3 Type of cooling- ONAN Total wt.-1225Kg Choke volt/phase-229V Kvar rating- 90 Oil wt.-400Kg Wt.of coil assembaly-275Kg
Residual Voltage Transformer:-
RVT is a step down transformer which is used to supply the metering ckt & LCS (Local Control Switch). Phase-3 Connection of Prim./Sec./Ters.-Y/Y/D Ratio- 6.6 KV/110-190V Burden-50VA Freq.-50c/s Class-I/5PR Insulation Level-28/75KV Make-Automatic Elet.Ltd. Bombay
Battery room in MPSS :-
The Battery room is used in the MPSS for the DC power supply. DC supply is used for the trip circuit & control circuits in the power stations & sub stations; emergency lighting supply. Total no. of Battery-110, Rating-300AH, 220V, 2V each, Led Acid cell
Total no. of Capacitor Bank used in MPSS:-13 Total no. of DC Motors
Total no. of AC Motors
Total no. of HT Motors
Total no. of Transformers
Total no. of HT Breakers
Total no. of SF6 Breakers
DGPP (Diesel Generator Power Plant): Introduction: -
Diesel electric power plant is a power plant in which diesel engine is used as a prime mover for the generation of the electric energy. The diesel engine obtains energy from the liquid fuel usually called the diesel oil & converts it into the mechanical energy. An alternator or DC generator mechanically coupled to the diesel engine convert the mechanical energy into the electrical energy. Need of DGPP: -
The diesel generator power plant is used as a backup plant for the Ambuja Cement plant. The DG is run during the peak hours, or when the electrical demand of the plant rises than the electrical energy supplied by the electricity board. They are also run in the bad weather condition when there is a possibility of voltage dip. Voltage dip is a sudden decrease in the supply voltage. This low voltage remains only for few seconds or milliseconds. No. of DG set :-4 (2 Alternators are ABB make& remains 2 are BHEL make) Capacity of each unit : - 6 MW Total capacity of the plant : - 24MW
Specifications of Alternator:-
KVA rating-7500,KW rating- 6000,Speed-750 rpm P.F.-0.8 lag Stator volt-6600 Stator amp-65.6 Insulation class-F Make -BHEL,3-phaes, 50 Hz Connection-star Ambient temp-50deg Excitation V-225 Excitation A-350 Duty- Continuous Various Motors used in the Plant:-
1. Slip Ring Induction Motor 2. Squirrel Cage Induction Motor 3. D.C. Motor 1. Squirrel Cage Induction Motor: -
We are using Squirrel cage Induction Motor as a LT motors (415V operated) in cement plant. These motors are having good efficiency & maintenance cost of these motors comparatively less than other motors. We have these motors in range from 0.37 to 225KW at 415 voltage level. 2. Slip Ring Induction Motor:-
We are using Slip Ring Induction Motors as a HT motors (6.6KVoperated) because at the time of starting, high starting torque is required. This high starting torque can be achieved only by adding more resistance in rotor ckt. And with the help of Liquid Rotor Resistance we can add resistance in the rotor ckt. 1. D.C. Motor: -
We are using dc motors for the fine speed control of equipments. Basically DC motors are famous for the variable output speed. But now a days AC drives have overcome the area of DC motors.
The maintenance of DC motors is not easy because of its typical armature winding & internal accessories like commutator, carbon brushes (which required weekly inspection). We have these motors in the range of 1.5KW to 900KW.These motors used in a classifier, weigh feeder, belt conveyor, cooler & kiln main drive. 900KW DC Motor is used in the Kiln drive. Starters Employed For Starting the Motors:-
Starters may be defined as a device that used for the starting of various electrical motors without having a bad impact on the power systems performance. Thus the function of a starter is to limit the initial inrush of current to a predetermined level so that voltage drop in the distribution line can be could be minimized & the stoppage of the other motors connected to the same system could be avoided. The various starters used in the industries are:-
1. 2. 3. 4.
DOL Starter LRS GRR Star Delta Starter.
1. DOL Starter:-
This is Direct on Line Starters used in induction motor directly to the line. It is generally used for the motors below 45KW but in the industry DOL have been used up to 100KW.This type of DOL starters is called HDOL (Heavy Direct on Line Starter) starter i.e. used for high rpm motor .The RDOL (Reverse Direct on Line Starter) is also used for starting the motor i.e. starts in the opposite direction.
This is Liquid rotor Starters. In the LRS water & caustic soda is made as a resistance medium. The fixed & the moving contacts are placed in this solution. Firstly the both contacts are another in the solution (solution
offer the required starting resistance) & at the end when motor pick up the required speed then they are shorted. 3.GRR:-
This is Grid rotor starter. It is used to regulate motor speed & remains continuously in the ckt. It is used only during motor starting of slip ring induction motor. 4.Star Delta starter:-
This type of starting method is uses to reduced voltage at starting by connecting the phase in star for starting & in delta for normal running. This method is used up to 75KW Induction motors.
Transformers: Power Transformers
Distribution Transformers : - 2×2000KVA (6.6KV/660V)
Rating-2000KW, Speed- 992 rpm Stator volt-6600V, Stator current-125A Rotor volt-1875V, Rotor current-655A Type -Slip ring I. M., Insulation Class-F 3-phase, 50 Hz, Temp. rise -75 deg.
Reference: To CRP (Control & Relay Panel) Protective relays in Incomer side:-
1. 2. 3. 4. 5. 6.
Over current relay. Earth fault relay. Tripping relay. Sensitive Earth fault relay. Directional Over current relay. Under Frequency Relay.
Protective relays in Transformer Feeders:-
1. Tripping relay. 2. Over Current relay 3. Earth fault relay. 4. Instantaneous Earth fault relay. 5. Auxiliary relay. 6. Neutral Displacement relay. 7. Over Voltage relay. 8. Over fluxing relay. 9. Buchholz relay. 10.Differential relay. 11. Definite time Reverse power relay. Protective relays in Motor Feeders:-
1. 2. 3. 4.
Definite time over current relay. Auxiliary relay. Tripping relay. MOTPRO relay.
Protective relays in Capacitor Feeders:1. Tripping relay.
2. 3. 4. 5.
Over current relay. Instantaneous earth fault relay. Neutral Displacement relay. Auxiliary relay.
Protective relays in Bus PT Panel:1. Tripping relay.
2. Over Voltage relay. 3. Under Voltage relay. 4. Neutral Displacement relay. Protective relays in DG System:1. Tripping relay.
2. 3. 4. 5. 6.
Over Voltage relay. Under Voltage relay. Under Frequency Relay. Over Frequency Relay. Definite time relay.
CONTROL AND RELAY PANEL Tripping relay: -
Tripping relay is fast instantaneous relays & is generally attracted armature type. They are either hand or electrically reset type. Their operating time is of the order of 10ms. Tripping relays have a few pairs of robust contacts. Tripping relays are used for high speed tripping duties where a no. of simultaneous switching operation is desired.
Frequency relay: -
The freq. of induced emf of synchronous generator is maintained constant by constant speed. In case of under speeding due to increase in load etc. The freq. varies from normal value. Freq. relays are used in generator protection. This relays are generally connected to the secondary of Voltage transformer. The freq. relay monitors the freq. continuously. This relay is a over freq. or under freq type. Auxiliary relay:-
A protective relay only closes its contacts & it is relieved of other duties such as time lag tripping (carrying current for longer time, breaking trip ckt ) etc. These duties are performed by auxiliary relays. Repeat operations are also performed by repeats contactors/auxiliary relays. Differential relay: -
A protective system which responds to vector difference (phase/magnitude) between 2 or more similar electrical quantities are known as Differential relay. To achieve balance in pilot wires, ratio adjusting (current balancing) transformers etc. are used in some schemes. The relay unit used in such protection has 3 restraining coil & 1 operating coil.
Buchholz Relay: -
Buchholz Relay provides the protection of the internal side of the transformer. The faults are large internal faults, phase to phase fault, phase to ground fault, below oil level, resulting in decomposition of oil etc. Only faults below oil levels are detected by this relay. This relay used up to 500KVA & above.
Restricted Earth fault relay:-
A Relay which senses the earth fault is called earth fault relay. Earth fault relays give protection against earth faults on the delta or unearthed star connected winding of transformer. This protection may than be used for high speed tripping for faults on star connect earthed secondary winding of power transformer. Directional Over current Relay:-
A Relays which responds to increase in current. Directional protection responds to flow of power in a definite direction with reference to the location of CT’s & PT’s .Directional relays respond to the magnitude & sign (direction) of power applied to their terminals. This relays are used in protective system as elements which judge the direction of power flow. Under healthy system conditions or under fault conditions where the current flow is in the normal directional eddy currents induced in the sector produce a torque the direction of which restrains relay operation. Over fluxing Relay: -
This relay operates the condition of heating of core; core bolts, core bolt insulation etc. The magnetic flux density (B) in the transformer core is a function of V/F. Hence the relay senses magnetic flux condition over fluxing relay is provided with enough time lags.
Instantaneous Earth fault relay: -
A fast relay which senses the earth fault having relay time of less than 0.2 second and having no intentional time lag is called Instantaneous Earth fault relay.
Reverse Power relay:-
Reverse Power protection operates when the power direction is reversed in relation to the normal power flow. Reverse power relay is different in construction than directional over current relay. The reverse power occurs in case of prime mover fails; the generator continues to run as a motor & takes power from bus bars. Neutral Displacement relay:-
We know that the neutral current is the sum of the all 3 phase currents. If the fault occurs in any phase the current is flowing to the neutral than the neutral point is displacing of the original position than this relay is operate. MOTPRO Relay:-
The most effective device used for the motor protection in the plant is called MOTPRO Relay. This is an Electronic relay. This relay provides comprehensive protection for AC induction motors. This relay has following protection features & the flexibility to select any required combination of these for a particular application: 1. Thermal over load 2. Short ckt. 3. Stalling 4. Negative phase sequence 5. Reverse phase sequence 6. Earth fault 7. Prolonged start 8. Loss of load 9. Too many starts etc...
This training has been of more importance for us. We have correlated our theoretical knowledge to what is practical. Some new industrial concepts came to know, how do
we manage our department, team work. Really industrial environment is challenging to build up our career. Through this training we have get overview about our Ambuja Parivaar. We will try to do our best for our company