Labels

Tuesday, January 25, 2011

electrical engineering projects ( iit kanpur )


Static Convertor for Railway
ACKNOWLEDGEMENT
Like great books, no project is created entirely by an individual. There are many people involved in this project too and have helped a lot right from the beginning till the completion of our project. Any bouquets for the merits in this project should go to our door. Any brickbats we are ready to catch ourselves.
It is with a great sincerity, we convey our heartfull gratitude to our guide Mohd.Israr, Supervisior, Electric Loco Shed, Kanpur, for his excellent guidance, valuable advice and ample co-operation throughout the training. It is a proud privilege to have availed of the opportunity of guidance.
We are thankful to Mr.A.K.Mishra too, for their excellent cooperation during our training for the proper response of the machine. We are grateful to all the railway employees,

ELECTRIC LOCO SHED, KANPUR
The
Electric loco shed, Kanpur was established during the year 1965 for homing 11 locomotives. This shed was commissioned primarily to meet the requirement of passenger and goods traffic over Indian railways. At present the shed has been expended suitably to home 176 loco motives for hauling, passenger and goods traffic.

The shed is responsible for carrying out monthly inspection schedule viz. IA, IB, IC, I0 & ICO in addition to annual and intermediate overhauling schedules.

Further the unscheduled repairs to electric locos of CNB shed & other sheds are being done as per requirements of RDSO organization & HQ’s instructions. All modification & special maintenance instructions, approved by RDSO & N.Rly. Hd.Qtr., are also carried out as per the guide lines being issued from time to time.

ELECTRIC LOCO MAINTENANCE SHED

Electric Loco Shed maintains locomotive for utilization in freight and passenger train. All the miner and major inspection are carried out in the shed on a regular schedule specified by RDSO (Research Design Standard Organization). Monthly schedule are done at an interval of 45 days and major schedule are carried out after 18 months.

QUALITY MANAGEMENT

Through this quality manual, ELS intents to provide a transparent quality system to assure its customer of ELS’s the capability in maintaining in electric locomotives to highest standard.

This quality manual has been written and develop in accordance with international quality system. Standard ISO-9001:2000. The manual is used as a refreshed document by:
• Employees of ELS to practice the quality system.

• Customers to have confidence in the capability of ELS to meet quality requirements on regular basis.

• Internal as well as external auditors for verification of compliance of the quality system.

OPERATION OF LOCOMOTIVE

The electric locomotive basically works at 25 KV, 50Hz supply. The 25KV AC supply is drawn from overhead catenaries wires. The supply from overhead wires are drawn through a pantograph inside the loco transformer. This transformer is an autotransformer from which regulated voltage is taken to a rectifier block for conversion from AC to DC .It may be worth mentioning that the final tractive effort is through DC traction motor hence AC is required to be converted to DC. The DC current from rectifier block is then filtered to pure DC and then fed to traction motor.

There are 6 traction motors which works parallel to provide the attractive effort for hauling the train.

All the operations are controlled through control circuit which works at 110 volt DC. Various power equipments during operation gets heated up and hence to cool the same, it is done by various blowers.


Different Equipments in an Electrical Locomotive


1) Pantograph

It is pneumatically operated equipment mounted on the roof for collection of current from overhead wire.

2) Main Transformer

It is an autotransformer which is utilized for drawing various grades of voltage required for operation of locomotive.

3) Rectifier

This unit consists of rectifier diodes connected in bridge for conversion of AC current to DC current.





4) Traction Motor

The traction motor is one of the most important equipment in the locomotive which transmits power to wheels for moving the trains.

5) Auxiliary Circuit

This Circuit is three phase 415 volts which supplies current to various three phase induction motors used for driving blowers for forced air cooling of major equipments like transformer, rectifier, smoothing reactor and traction motor. This 3 phase line voltage is supplied by either static converter or Rotary ARNO Converter.

6) ARNO Converter

Arno converter , is specific-duty machine for conversion of a single-phase supply into a three-phase supply. While the electric traction supply is standardized as single-phase A.C. supply, a three-phase supply is needed on locomotives for driving certain auxiliary equipments. The function of the Arno converter is to convert the incoming single-phase supply in to a three-phase supply for the auxiliaries.

ARNO Converter is of vertical construction and has a flexible mounting .The machine is of robust mechanical construction to withstand the several vibrations encountered on locomotives.

TECHNICAL DATA

Single-phase input Three-phase output
KVA 150 KVA 120
Volts 380 Volts 380
Amps 395 Amps 190
Frame VA-330

Class ’F’

Connection: Star RPM 1490 Cycle 50



OPERATIONAL PRINCIPLE

The single-phase supply of 380 volts AC is fed ‘direct’ to the ‘U’ & ‘V’ phases of the Arno converter. Since the ARNO Converter is connected to single-phase supply, no starting torque is developed. For starting the ‘ARNO’ split phase starting method has been employed. The W phase winding is connected to the supply phase U through a starting resistor R-118 and starting contactor C-118 for a short duration to start the Arno. Thus unbalanced three-phase voltage is impressed to each phase winding of Arno converter and the starting torque is developed .the Arno Converter picks up speed within five seconds. After the Arno has gained sufficient speed, the phase W is opened from the starting circuit by starting contactor C-118.

The Arno converts the single phase input into 3 phase output as 380 volt ± 22.5%. The three-phase output of the Arno converter is connected to the auxiliary motors.

7) Control Circuit

The control circuit is purely 110 volt DC and the most important network for handling various operational feature of the locomotive. All the power equipment and auxiliary circuit equipment are controlled through various switches in 110 volt circuit provided in the driving cab. All the circuit and equipment in the high voltage power side & auxiliary circuit equipment and the control circuit is protected against overloading, short circuiting and earth fault. For this purpose various relays have been used as protection device so as to protect the circuit from any mal functioning.

8) Asynchronous Motor
Modern traction motor type using three phase AC electrical supply and now the favoured design for modern train traction systems. Can be used on DC and AC electrified railways with suitable control electronics and on diesel-electric locomotives.
9) Axle Brush
The means by which the power supply circuit is completed with the substation once power has been drawn on the locomotive. Current collected from the overhead line or third rail is returned via the axle brush and one of the running rails.
10) Battery
All trains are provided with a battery to provide start up current and for supplying essential circuits, such as emergency lighting, when the line supply fails. The battery is usually connected across the DC control supply circuit.
11) Bucholz Relay
A device inserted in the oil cooling circuits of electric locomotive transformers to detect low oil pressure. In this event the relay trips out the power system. Often a source of spurious circuit breaker trips if not carefully calibrated.
12) Camshaft
Most DC electric traction power circuits use a camshaft to open or close the contactors controlling the resistances of the traction motor power circuit. The camshaft is driven by an electric motor or pneumatic cylinder. The cams on the shaft are arranged to ensure that the contactors open and close in the correct sequence. It is controlled by commands from the driver's cab and regulated by the fall of current in the motor circuit as each section of resistance is cut out in steps. The sound of this camshaft stepping can be heard under many older (pre electronics) trains as they accelerates.
13) Cannon Box
Sleeve used to mount a traction motor on axle in electric power bogies and sometimes including an axle brush.
14) Chopper Control
A development in electric traction control which eliminates the need for power resistors by causing the voltage to the traction motors to be switched on and off (chopped) very rapidly during acceleration. It is accomplished by the use of thyristors and will give up to 20% improvement in efficiency over conventional resistance control.

15) Circuit Breaker
An electric train is almost always provided with some sort of circuit breaker to isolate the power supply when there is a fault, or for maintenance. On AC systems they are usually on the roof near the pantograph. There are of two types - the air blast circuit breaker and the vacuum circuit breaker or VCB. The air or vacuum part is used to extinguish the arc which occurs as the two tips of the circuit breaker are opened. The VCB is popular in the UK and the air blast circuit breaker is more often seen on the continent of Europe.
16) Contactor
Similar to a relay in that it is a remotely operated switch used to control a higher power local circuit. The difference is that contactors normally latch or lock closed and have to be opened by a separate action. A lighting contactor will have two, low voltage operating coils, one to "set" the contactor closed to switch on the lights; the other to "trip" off the lights.
17) Converter
Generic term for any solid state electronic system for converting alternating current to direct current or vice versa. Where an AC supply has to be converted to DC it is called a rectifier and where DC is converted to AC it is called an inverter. The word originated in the US but is now common elsewhere.
18) Cooling Fans
To keep the thyristors and other electronic power systems cool, the interior of a modern locomotive is equipped with an air management system, electronically controlled to keep all systems operating at the correct temperature. The fans are powered by an auxiliary inverter producing 3-phase AC at about 400 volts.
19) Creep Control
A form of electronically monitored acceleration control used very effectively on some modern drive systems which permits a certain degree of wheel slip to develop under maximum power application. The GM Class 59 diesel-electric locomotive built for the UK has this system. A locomotive can develop maximum slow speed tractive effort if its wheels are turning between 5% and 15% faster than actually required by the train speed.
20) DC Link Filter
Used on modern electronic power systems between the single phase rectifier and the 3-phase inverter. It is easier to convert the single phase AC from the overhead line to the 3-phase required for the motors by rectifying it to DC and then inverting the DC to 3-phase AC.
21) Dynamic Braking
A train braking system using the traction motors of the power vehicle(s) to act as generators which provide the braking effort.
The power generated during braking is dissipated either as heat through on-board resistors (rheostatic braking) or by return to the traction supply line (regenerative braking). Most regenerative systems include on board resistors to allow rheostatic braking if the traction supply system is not receptive.
The choice is automatically selected by the traction control system. .
22) Grid
Train or locomotive mounted expanded steel resistor used to absorb excess electrical energy during motor or braking power control. Often seen on the roofs of diesel electric locomotives where they are used to dissipate heat during dynamic braking.
23) Ground Relay
An electrical relay provided in diesel and electric traction systems to protect the equipment against damage from earths and so-called "grounds".
The result of such a relay operating is usually a shut-down of the electrical drive. Also sometimes called an Earth Fault Relay.
24) GTO Thyristor
Gate Turn Off thyristor, a thyristor which does not require a commutation (reverse flow circuit) circuit to switch it off .

25) IGBT(Insulated Gate Bipolar Transistor)
Most recent power electronics development. It is replacing the GTO thyristor as it is smaller and requires less current to operate the switching sequences.
26) Inverter
Electronic power device mounted on trains to provide alternating current from direct current. Popular nowadays for DC railways to allow three phase drive or for auxiliary supplies which need an AC supply.
27) Jerk Limit
A means by which starting is smoothed by adjusting the rate of acceleration of a train by limiting the initial acceleration rate upon starting. It could be described as limiting the initial rate of change of acceleration. Also used in dynamic braking.
28) Line Breaker
Electro-mechanical switch in a traction motor power circuit used to activate or disable the circuit. It is normally closed to start the train and remains closed all the time power is required. It is opened by a command from the driving controller, no-volts detected, overload detected and (were required) wheel spin or slide detected. It is linked to the overload and no-volt control circuits so that it actually functions as a protective circuit breaker.
29) Master Controller
Driver's power control device located in the cab. The driver moves the handle of the master controller to apply or reduce power to the locomotive or train.
30) Motor Blowers
Traction motors on electric locomotives get very hot and, to keep their temperature at a reasonable level for long periods of hard work, they are usually fitted with electric fans called motor blowers. On a modern locomotive, they are powered by an auxiliary 3-phase AC supply of around 400 volts supplied by an auxiliary inverter.

31) Notching Relay
A DC motor power circuit relay which detects the rise and fall of current in the circuit and inhibits the operation of the resistance contactors during the acceleration sequence of automatically controlled motors. The relay operates a contactor stepping circuit so that, during acceleration of the motor, when the current falls, the relay detects the fall and calls for the next step of resistance to be switched out of the circuit.
32) No-Volt Relay
A power circuit relay which detected if power was lost for any reason and made sure that the control sequence was returned to the starting point before power could be re-applied.
33) Overload Relay
A power circuit relay which detected excessive current in the circuit and switched off the power to avoid damage to the motors.
34) Rectifier
A converter consisting of thyristors and diodes which is used to convert AC to DC. A modern locomotive will usually have at least two, one for the power circuits and one or more for the auxiliary circuits.
35) Relay
A remotely controlled switch which uses a low voltage control circuit. It will close (or open) a switch in a local circuit, usually of higher power.
36) Resistance Control
Method of traction motor control formerly almost universal on DC electric railways whereby the power to the motors was gradually increased from start up by removing resistances from the power circuit in steps Originally this step control was done manually but it was later automatic, a relay in the circuit monitoring the rise and fall of current as the steps were removed. Many examples of this system still exist but new builds now use solid state control with power electronics.
37) SEPEX
Short form of SEParate EXcitement of traction motors where the armature and field coils of an electric motor are fed with independently controlled current. This has been made much more useful since the introduction of thyristor control where motor control can be much more precise. SEPEX control also allows a degree of automatic wheel slip control during acceleration.
38) Shoegear
Equipment carried by a train and used for current collection on track mounted (third rail) power supply systems. Shoegear is usually mounted on the bogies close to the third rail. It is often equipped with devices to enable it to be retracted if required to isolate the car or on-board system which it supplies.
39) Synchronous Motor
Traction motor where the field coils are mounted on the drive shaft and the armature coils in the housing, the inverse of normal practice. Favoured by the French and used on the high speed TGV Atlantique trains, this is a single-phase machine controlled by simple inverter. Now superseded by the asynchronous motor.
40) Tap Changer
Camshaft operated set of switches used on AC electric locomotives to control the voltage taken off the main transformer for traction motor power. Superseded by thyristor control.
41) Thyristor
A type of diode with a controlling gate which allows current to pass through it when the gate is energised. The gate is closed by the current being applied to the thyristor in the reverse direction. Thyristors (also referred to as choppers) are used for traction power control in place of resistance control systems. A GTO (Gate Turn Off) thyristor is a development in which current is turned off is by applying a pulse of current to the gate.


42) Transformer
A set of windings with a magnetic core used to step down or step up a voltage from one level to another. The voltage differences are determined by the proportion of windings on the input side compared with the proportion on the output side. An essential requirement for locomotives and trains using AC power, where the line voltage has to be stepped down before use on the train.
43) Transistor
The original electronic solid state device capable of controlling the amount of current flowing as well as switching it on and off.
In the last few years, a powerful version has been applied to railway traction in the form of the Insulated Gate Bipolar Transistor (IGBT). Its principle advantage over the GTO Thyristor is its speed of switching and that its controls require much smaller current levels.
44) Wheel Spin
On a steam locomotive, the driver must reduce the steam admission to the cylinders by easing closed (or partially closed) the throttle/regulator when he hears the wheels start to spin.
On diesel or electric locomotives, the current drawn by individual or groups of traction motors are compared - the motor (or group) which draws proportionally less amps than the others is deemed to be in a state of slip - and the power is reduced.
Some systems - EMD Super Series for one - measure known wheel speed against ground speed as registered on a Doppler Radar. Many locomotives additionally use sand, which is applied to the wheel/rail contact point to improve adhesion - this is either controlled automatically, or manually by the driver.
45)Wheel Spin Relay (WSR)
A relay in older traction motor control circuits used to detect wheel spin or slide by measuring the current levels in a pair of motors on a bogie and comparing them.
The idea is to prevent motor damage by preventing an over-speeding motor causing an unacceptable rise in current in the other motor of the pair.
If detected, the imbalance causes the control circuits to open the line breakers and reset the power control to the start position like a "no-volt" relay.

The Block Diagram of Modern AC Electric Locomotive describing the various parts, can be given as:


180kVA Static Converter

Introduction of Static Converter in Indian Railway

The first Static converter was used in WCAM – 3 locomotives jointly developed by RDSO and BHEL in 1997. The Static Converter converters the DC / AC voltage into 3 phase 415 volts for running auxillary machines.

This converter was supplied by ACEC. In late 19s, SIEMENS provided 8 nos 180 KVA Static Converter in conventional Locomotive at ELS / NCR / CNB.

Presently CLW manufactures only Static Converter fitted locomotive and till date, the total population of Static Converters fitted locos are more than 750.

Advantages of Static Converter

i. Very steady output voltage with maximum regulation of ± 5%.
ii. All the three phases output voltages are balanced resulting in balanced supply to the loads.
iii. Very high system efficiency.
iv. Soft starting of loads possible resulting in reduced system over loading.
v. In-built fault management system with storage of faults and traces.
vi. Various problems of auxiliary machines are reduced due to regulated and balanced supply voltage.


Working Principal

The converter generates 415V, 3 phase, 50Hz output from 760V / 830V, 1 phase, 50Hz
input which is available from the main locomotive transformer.

The static converter is made using a half controlled single phase bridge rectifier at the input, a DC link filter and a three phase IGBT based PWM inverter.

All functions of the converter are controlled through 32 bits Digital signal processor (DSP) together with an EPLD & host of digital gates and analog amplifiers.






Fig. 180kVA Static Converter


The converter consists of following sub-modules:

A. Input Section

The input section consists of input fuse (MF), Metal oxide varistors and input bus bar. Input fuse is used to protect the converter and for ensuring safe operation of the converter under worst input conditions. Metal oxide varistors (MOV) are used to protect the converter from surges.

B. Rectifier Section



The rectifier section is made using a half controlled single phase bridge rectifier. This consists of a half controlled bridge rectifier, made up of 2 thyristors and 2 diodes.

When the input AC voltage is positive, one of the thyristors is fired with a predetermined delay. It starts conducting and the voltage of the DC link rises.



Fig. Rectified Waveform


The current continues to flow due to the DC link reactor, until the input voltage changes polarity and the other thyristor is fired.

Now, the other thyristor with the corresponding diode takes over the current.

The rectifier circuit converts single-phase AC input voltage into DC voltage of desired level (760 volts).




The main controller maintains the DC link voltage at a preset value by controlling the firing angle of the thyristors.

A PI(proportional integral) controller is used to determine the firing angle. If the DC link voltage is lower than desired voltage, the firing angle will be small and if the DC link voltage is higher than the desired voltage, the firing angle will be increased.

RC snubber circuits are provided across each thyristors and Diode’s to protect against high “dv / dt”(rate of change of voltage with time) experience by devices.

C. DC Link Filter & Over Voltage Chopper

The DC link filter consist of DC link Choke (FL) and DC link Capacitors (FC). DC link Choke and Capacitors provided at the output of the rectifier to reduce the ripples in the DC link voltage that is fed to the inverter.

The over voltage chopper is made-up of an IGBT switch with a resistor and an anti-parallel diode. The IGBT switches the resistor on and off in the DC circuit if the DC voltage exceeds a preset value.

The chopper dissipates the extra energy and protects the system from over voltage, especially during transients at start-up.

D. Inverter Circuit

The Inverter consists of six IGBT modules. IGBT modules are configured as a 3-phase bridge circuits. The bridge is made up of three identical phase branches and each branch consists of two IGBTs.

The DC link voltage is converted into PWM sinusoidal waves by switching IGBTs at a high frequency. The width of the individual pulses in the PWM wave determines the amplitude of the output voltage and the width of the pulse block determines the output frequency.

As the system is a constant voltage, constant frequency system, the output frequency is maintained at 50Hz and the PI controller receives an output voltage feedback in order to keep the voltage constant, too. The final stage is responsible for generation of switching signals utilizing Space Vector Pulse Width Modulation (SVPWM) technology.

State-of-the-art space vector PWM technique has been adopted in the design of inverter software as this technology is more flexible & adapts to wider variations in the input DC link voltages. For better regulation of the output voltage, proportional integrated control has been used.

E. Output LC Filter

The Inverter output voltage is PWM, which is converter into sine wave by using output filter. It consists of 3 phases AC Choke (ACL) and 3 phases Capacitor (ACC).




Brief Technical Specification

Input

i. Nominal voltage : AC single phase, 760V or 830V.
(corresponding to catenary voltage of 22.5KV)

ii. Min. voltage continuous : 642V AC.

iii. Max. Voltage continuous : 1014V AC.

iv. Min. voltage at which converter
trips on under voltage : < 591V AC.

v. Max. Voltage beyond which
converter trips on over voltage : 1150V AC.

vi. Input voltage range for which
guaranteed converter performance : 642V to 1014V AC.
is available

vii. Input voltage range for which
guaranteed converter performance : 591V to 642V on lower side.
is not available but converter will : 1014V to 1150V on higher side.
not trip on either under voltage
or over voltage

viii. Power factor : 0.8 (At rated conditions).

ix. Input frequency : 50±3Hz.


Output

i. Output power : 180kVA, 0.8pf (at nominal operation).

ii. Overload : 200% for 5sec. (360KVA & current
Limit of 600A).

iii. Voltage 1 : AC 415V±5%, 3 phase system
between 642 - 1014V.

iv. Frequency : 50 Hz ±1% .

v. Waveform : Sine wave.

vi. THD in voltage : 10% (up to 20th harmonic).

vii. Efficiency : 92% (At nominal input voltage
And at rated load).

viii. Voltage 2 : DC 110V±5%,
[±5% ripple (rms) at full load and at nominal continuous rated input voltage of 642 - 1014V].

Mechanical

i. Size (approx.) : Cubicle 1- 670mm(L)×1805mm(W)×1650mm(H).
: Cubicle 2 -850mm(L)×670mm(W)×390mm(H).

ii. Weight : Approx. 1440 kg (1320 kg + 120 kg).

iii. Cooling : Forced air cooling for Cubicle-1.


General

i. Ambient temperature : 0ºC to 70ºC (max. 55ºC inside loco).

ii. Humidity : 100% in rainy season (90% at 55ºC).

iii. Altitude : 160m above mean sea level.

iv. Dust : 1.6mg/cubic m, max. Ph 8.5.

v. Audible noise : 80dB (A) at 1m distance from
Cubicle as per IEC-1287-1.

vi. Display & communication : Vacuum fluorescent display and RS-232
Port for data logging.

vii. Control voltage : DC 110

As an effort towards continuous improvement, the present stage of the static converter incorporates :

a) Modular control electronics.
b) SMPS battery charger.



Fig. Modular Type Control Unit



Fig. Battery Charger Input / Output
Description of Static Converter
The static converter is made using a half controlled single phase bridge rectifier at the input, a DC link filter and a three phase IGBT based PWM inverter. All functions of the converter are controlled through 32 bits. Digital signal processor (DSP) together with a EPLD & host of digital gates and analog amplifiers.




A. Input Module

The input section consist of input fuse ( MF ) , Metal oxide varistors and input bus bar. Input fuse is used to protect the converter and for ensuring safe operation of the converter under worst input conditions. Metal oxide varistors ( MOV ) are used to protect the converter from surges.


Fig. Input Section


B. Rectifier Section

The input stage of the static converter consists of the main switch, input fuse and rectifier circuit. The input fuse protects the circuit against input over current. The rectifier circuit converts AC input voltage into DC voltage of desired level.

The configuration of the rectifier circuit is a semi-controlled rectifier bridge. When the input voltage is positive, one of the thyristors is fired with a predetermined delay. It starts conducting and the voltage of the DC link rises. The current continues to flow due to the DC link reactor, until the input voltage changes polarity and the other thyristor is fired. Now, this other thyristor with the corresponding diode takes over the current. The main controller maintains the DC link voltage at a preset value by controlling the firing angle of the thyristors. A PI controller is used to determine the firing angle .

If the DC link voltage is lower than desired voltage, the firing angle will be small and if the DC link voltage is higher than desired value, the firing angle will be increased.


Fig. Block Diagram of Rectifier Control





Fig. Rectifier Section



Fig. Thyristor GDU Card


C. DC link filter & Chopper Module

The DC link filter consist of DC link Choke ( FL ) and DC link Capacitors ( FC ). DC link Choke and Capacitors provided at the output of the rectifier to reduces the ripples in the DC link voltage which is fed to the inverter.

The over voltage chopper is made up of an IGBT switch with a resistor and an anti-parallel diode. The IGBT switches the resistor on and off in the DC circuit if the DC voltage exceeds a preset value. The chopper dissipates the extra energy and protects the system from over voltage, especially during transients at start-up.

D. SMPS battery charger

It is made up of uncontrolled rectifier, single phase IGBT inverter and filtering circuit for providing boost and float mode charging.

E. Inverter Section

The inverter consists of six IGBT modules. IGBT are configured as a 3-phase bridge circuits. The bridge is made up of three identical phase branches and each branch consists of two IGBTs.

The dc link voltage is converted into PWM sinusoidal waves by switching IGBTs at a high frequency.

The width of individual pulses in the PWM wave determines the amplitude of the O/P voltage and the width of the pulse block determines the O/P frequency.

As the system is a constant voltage, constant frequency system, the O/P frequency is maintain at 50 Hz and the PI controller receives an O/P voltage feedback in order to keep the voltage constant too.

The final stage is responsible for generation of switching signals utilizing space vector pulse width modulation (SVPWM) technology.





Fig. Inverter Module

F. Output LC Filter

The Inverter output voltage is PWM , which is converter into sine wave by using output filter. It consist of 3 phase AC Choke(ACL) and 3 phase Capacitor(ACC ).


G. Main Controller Unit ( MCU )

The main controller card consists of 32 bits digital signal processor (DSP) together with a EPLD, host of digital gates and analog amplifiers, controlled the function of the converter. It generates switching pulses to drive the IGBTs and thyristors.

It also monitors sensor signals to detect faults and abnormal operation of the static converter. Status of various parameters are monitored and compared with the reference levels. Desired preventive and corrective actions are initiated through the respective controllers in the event of abnormal conditions.

Faults, if any are identified, stored in the fault memory and also can be displayed through display panel. A communication port with RS-232 interface is provided on the front panel for control gain setting, fault information and real time monitoring through a Notebook PC.

A keyboard and Vacuum Fluorescent Display (VFD) is provided on the front panel for selection of operation mode & text display of monitoring status, voltage, current level & fault messages.

Main Control Card ( MCU ):
KIT-2 Main Control Card ( MCU ):
KIT- 3

H. Thyristor Gate Drive Card ( TGDU)

The gate driver circuit receives switching pulses from the MCU card. The opto-coupler in the gate driver provides the perfect isolation between the power circuit and the control circuit for these pulses.



After further amplification, these switching pulses are sent to the Thyristors.

I. Chopper Gate Drive Card

The gate driver circuit receives switching pulses from the MCU card. The opto-coupler in the gate driver provides the perfect isolation between the power circuit and the control circuit for these pulses.


After further amplification, these switching pulses are sent to the Chopper IGBT. In case of over-current of the chopper, the gate driver blocks the gate pulses to protect the IGBT and feeds the information back to the main control card.

J. Inverter Gate Driver Card

The gate driver circuit receives switching pulses from the MCU card. The opto-coupler in the gate driver provides the perfect isolation between the power circuit and the control circuit for these pulses.



After further amplification, these switching pulses are sent to the Inverter IGBTs. In case of over-current of the inverter, the gate driver blocks the gate pulses to protect the IGBTs and feeds the information back to the main control card.

K. Display card ( DCU )

A Vacuum Fluorescent Display ( VFD) is provided for display parameters and fault data along with its associated keys / push buttons.

Display is provided on the front panel for selection of operation mode & text display of monitoring status, voltage, current level & fault messages.

The display card also provide LED indications of various faults.





A communication port with RS-232 interface is provided on the front panel for fault information and real time monitoring through a Notebook PC.


L. Power Supply Card


M. Input Current Transformer ( ACCT )


The Input Current Transformer (ACCT ) is use to measure the input current. It is located near to input section / Fuse.

Its ratio is 800 / 1 Amp. A burden resistor of 6 ? is always connected across its terminal.

N. Input Potential Transformer ( ACPT 1 )


The Input Potential Transformer ( ACPT 1 ) is use to measure the input voltage. It is located at RFU section area. Its ratio is 1300/7.22 volts.

O.DC Link Current Transducer ( DCCT )

The DC Link Current Transducer ( DCCT ) is use to measure the DC link current.

P. DC Link Voltage Transducer ( DCPT )

The DC Link Voltage Transducer ( DCPT ) is use to measure the DC link voltage. It is located at RFU section area.
Q. Chopper Current Transducer ( CHCT )

The Chopper Current Transducer ( CHCT ) is use to measure the Chopper current.


R. Output Current Transformer

The Output Current Transformer ( ACCT1 / ACCT2 / ACCT3 ) are use to measure the output current. It is located output section.

Its ratio is 800 / 1 Amp. A burden resistor of 6 ? is always connected across its terminals.

S. Output Potential Transformer

The Output Potential Transformer ( ACPT 2) is use to measure the output voltage. It is located at RFU section area. Its ratio is 600/7.22 volts.

T. Zero Current Transformer

The Zero Current Transformers are use to measure the Input leakage current
( ZCT 1) and Output leakage current ( ZCT 2 ).

They are located near Input section and Output section respectively.

Protection & Settings

The Static converter is equipped with circuits to protect itself and its load from all disturbances. Its operation is stopped by all fault conditions.

1. Open Circuit in Auxiliary Winding

This circuit detects that input voltage is too low or completely absent. It is practically the protection from input under voltage.

2. Fuse Failure in Converter

This circuit monitors the signals from the fuse contacts and if a fuse blows the converter is tripped.



3. Thermal Overloading

Temperature sensors are mounted on the heat sinks of the rectifier unit and the inverter unit. If the temperature of the heat sink exceeds a predetermined level, a fault signal is sent to the main controller.

The operation of inverter is stopped. The circuit resumes operation automatically when the temperature returns to normal.

4. High/Low Voltage in DC Link

A voltage sensor monitors the DC link voltage. If DC link voltage is too high or too low, the main controller shuts down the converter.

5. Failure of Power Supply to Control Electronics

The main controller monitors the power supply. If a failure is detected, the main controller blocks the gate signals of IGBTs and thyristors.

6. Transient & Surge Protection

Voltage surge suppressor is provided at the input.

7. Input Over/Under Voltage

The main controller monitors input voltage continuously. The sensor is located at the input of the rectifier circuit.

In case the input voltage exceeds the predetermined value of under voltage or over voltage, an alarm signal is given to the main controller, which initiates adequate protective operation. When the input voltage returns to normal, the inverter resumes normal operation.

8. Input Over Current

The current sensors are also installed at the input of the rectifier circuit. Whenever the input current exceeds the predetermined value, a fault signal is sent to the main controller to initiate required protection.

9. Output Over/Under Voltage

The voltage exceeds the predetermined value of over voltage or under voltage, a fault signal is sent to the main controller to initiate the protective operation. The main controller immediately switches off the inverter.

10. Output Over Current

The output of the inverter is protected against overload. Whenever the output current exceeds the predetermined value, a fault signal is sent to the main controller to initiate required protection.

11. Short Circuit at Output

The output of the inverter is protected against short circuit. Whenever the output current exceeds the predetermined value, the main controller initiate required protection. Under short circuit conditions, a fast current limit protects the power semi-conductors in the 3-phase Inverter Bridge.

12. Earth Leakage

In case the earth leakage detector has detected an earth leakage current, an earth fault is initiated and the inverter trips.

13. Single Phasing

The single phasing protection is automatically available in the inverter through the over current protection. If the output current of the inverter exceeds the predetermined limit due to single phasing, then the inverter will trip.
















Low cost wind power plant

Energy is an important part of any country’s economy. Today major energy need in a
country is achieved by using conventional sources of energy. It includes coal, natural gas, nuclear fuel, etc. But
these sources are limited on earth .
Looking towards the environment effect as thermal plant releases smoke and ash which causes air pollution
Nuclear power plant releases radioactive waste which are hazardous and cause air and land pollution.
Due to these factor we concern our idea toward non conventional sources of energy.
Non –conventional sources of energy are environmental friendly, easily available
on earth .

Wind energy has evolved as one of the non conventional sources of energy . It is an indirect form of solar
energy. Wind power plant extract energy from wind and convert it into mechanical energy which is used by
turbine to convert it into electrical energy.

Cause of wind flow-

Due to non uniform heating of land and water by solar energy, air nearer to equator heats
up quickly , these hot air tend to move upward because of less density ,The air vacancy created is filled by
cold air coming from poles .
Air carrying momentum is known as wind. Turbine blades as barrier which extract power from wind.

Advantages of wind energy

• Wind energy is available in the country situated on bank of the sea.

• Wind power plant does not require any additional source of energy for power generation.

• It is pollution free and eco-friendly.

• Both type of plant large scale and small scale can be constructed.

Wind in India
Studies shows that wind in India is varying in nature. Wind direction changes with season .
Some state like Tamilnadu, Gujrat has large potential of wind energy.


Parts of wind power plant

Rotor blade
Blade extract power from the wind. When wind forces the blade it transfers some energy to rotar.

Betz’s coefficient -
• Theoretical studies show that ideal wind turbine extract 60 % of total wind energy.
• That is maximum fraction of power that can be extracted by wind turbine is 60%.Therefore shape and size of blade will determine turbine performance.

Shaft
Wind turbine shaft is connected to centre of rotor .when the rotor spins the shaft spins as well and rotor
transfers rotational energy to shaft .
Generator
Generator is a device which converts mechanical energy into electrical energy . Generator is based on the
principle of electromagnetic induction.
Gearbox
Gear box contains gear which are mechanically coupled to each other. Gear convert high speed-low torque
to low speed- high torque.
Turbine efficiency
Turbine efficiency = Na * Ng * Nc * Ngen

Where Na = aero turbine efficiency
Ng= gearing efficiency
Nc = mechanical coupling
Ngen = generator efficiency


Our wind power plan
Our wind plant is horizontal axis wind plant as in India wind blows much higher than our rooftops.
We use variable pitch gear as coupling device with variable speed controller using lever and crank-shaft
mechanism.
Type of material for blade – Wood (pine & spruce)
• Easy to carve
• Resistance to fatigue
Diameter of blade-5 meter
Number of blade –when the number of blade increases turbine will stops more wind energy i.e lift force on
Blade increases but axial thrust(drag)also increases which is counterbalanced by mechanical design .we use
three blades which are so adjusted on hub so as when speed increases there will be increase in drift and decrease
in drag.
Gear system and speed controller-we use variable pitch gear as coupling device which is mounted on
generator. Wind turbine rotator shaft is connected with a gear which is coupled through variable pitch gear by
chain which passes over a secondary gear .secondary gear is pivoted with crank shaft mechanism by a lever other
side of secondary gear is connected with spring for it’s sidewise movement.

Crank is attached with a motor which is connected with coil inside which there is a U –shaped permanent
Magnet.
Generator -we use three phase generator as it extract more power from rotor (three times more than
single phase). If more power is extracted there will less desipition of wind energy as vibrational energy.

Rectifier-we use six diodes to make rectifying circuit to convert AC into DC . diodes are provided with better
heat sink
Voltage regulator-voltage regulator circuit is drawn in figure.
Regulating operation
1. If the output voltage decreases , the increased base emitter voltage causes transistor to conduct more .
Thereby raising the output voltage –maintaining the output constant.
2. If the output voltage increases ,the decreased base emitter voltage causes the transistor to conduct less
Thereby reducing the output voltage –maintaining the output constant.

Battery storage
We use 12 V lead acid rechargeable battery as it’s energy/price ratio is more . it has long life
High charge\ discharge cycle. Easily available in market.





















1.2.3--- Ball bearing system
4------- blade
5 - variable pitch gear
6 - generator
13 - diode
14 - crank shaft
11 - U shaped magnet
10 - coil
8 - chain




Working - whole system is set up in low wind speed with chain on the upper most variable pitch gear
When wind increases it generates current in coil on free end of rotor which pull secondary
gear and draws the chain in second pitch on variable gear hence maintaining speed.

when wind speed decreases spring pull back chain to large diameter of variable pitch gear
hence maintaining speed of generator by increasing speed of variable pitch gear.







Power quality and its consequences..


Introduction:
The power quality problem is defined as any problem manifested in voltage, current or frequency deviations that results in mal-operation of customer equipment. The power quality problem causes the deterioration of performance of various sensitive electronic and electric equipments. The good quality of power can be specified as
The supply voltage should be within guaranteed tolerance of declared value.
The waveshape should be pure sine wave within allowable limits for distortion.
The voltage should be balanced in all three phases.
Supply should be reliable i.e continuous availability without interruption
Modern industrial machinery and commercial computer networks are prone to many different failure modes. When the assembly line stops, or the computer network crashes for no apparent reason, very often the electric power quality is suspected. It is a convenient culprit, as it is invisible and not easy to defend. Power quality problems may be very difficult to troubleshoot, and often the electric power may not have any relation to the actual problem. For example, in an industrial plant the faults of an automated assembly machine may ultimately be traced to fluctuations in the compressed air supply or a faulty hydraulic valve. Or in an office building, the problems on a local area network may be find their root cause with coaxial cable tee locations that are too close together, causing reflections and signal loss.

Why power quality is so important?
Power quality is an increasingly important issue for all businesses. Problems with powering and grounding can cause data and processing errors that affect production and service quality.
1 Lost production: Each time production is interrupted, your business loses the margin on the product that is not manufactured and sold.
2 Damaged product: Interruptions can damage a partially complete product, cause the items to be rerun or scrapped.
3 Maintenance: Reacting to a voltage disruption can involve restoring production, diagnosing and correcting the problem, clean up and repair, disposing of damaged products and, in some cases, environment costs.
4 Hidden costs: If the impact of voltage sag is a control error, a product defect may be discovered after customer delivery. The costs of losing repeat sales, product recalls and negative public relations can be significant and hard to quantify.
A recent study by IBM showed that power quality problems cost U.S. businesses more than $15 billion a year. That’s an average of $79,000 for each company!
The good quality of power can be specified as: -
1 The supply voltage should be with in guaranteed tolerance of declared value.in India the specifications related to power quality are _+10% variation in voltage and _+2%of frequency
2 The wave should be a pure sine wave within allowable limits for distortion.
3 Voltage should be balanced in all 3 phases.
4 Supply should be reliable
5 The earthing system should serve its purpose properly

Causes of poor power quality:
The causes of poor quality can be attributed to :
1 Variations in voltage, magnitude and frequency
2 Variations in magnitude can be due to sudden rise or fall of load, outages, repetitive varying loading pattern in rolling mills, power electronic converters, lightning etc.
3 Variations in frequency can rise of out of system dynamics or harmonics injection.

Consequently the voltage or current waveforms of a power system ceases to be purely sinusoidal in nature but consist of harmonics and other noises.

Impact of poor power quality:
The effect of these aforesaid poor power quality problems has serious implication on the utilities and customers. Utility side impacts higher losses in transformers, cables etc. In conductors the neutral wires can burn due to the presence of third harmonics generated by non-linear loads. The power factor correction capacitors may puncture due to resonant conditions at resonant frequencies near lower order harmonics. The energy-meters, which are calibrated to operate under pure sinusoidal conditions, may give erroneous readings. The solid-state protective relays can maloperate due to poor power quality. There can be increased losses in cables, transformers and conductors.
The customer side of the power network also experience adverse effects of poor power quality. The automatic processes employing adjustable speed drives may shut down because of nuisance tripping due to even short voltage sags.. The induction synchronous motors can have increased copper and core loses, pulsating torques and overheating with derating effect.

The non-sinusoidal power supply thus reduces torque and efficiency of the motors. The computers and telecommunication equipment encounter loss of data and maloperation due to poor power supply quality. The domestic electronic gadgets such as digital clocks, VCRs and TVs are also affected by voltage distortions.
Causes and consequences: -
The causes and consequences of power quality problems can be traced to a specific type of electrical disturbance. By analyzing the waveform of the disturbance, power quality engineers can determine what problems your facility has and what the optimal solution is.
For comparison purposes, a normal voltage waveform is 50 cycles per second - at most plus or minus ten percent of nominal voltage.
Power disturbances can be classified into five categories, each varying in effect, duration and intensity.

Voltage fluctuations:
Voltage fluctuations are changes or swings in the steady-state voltage above or below the designated input range for a piece of equipment. Fluctuations include both sags and swells.
1 Causes: Large equipment start-up or shutdown; sudden change in load; improper wiring; or grounding; utility protection devices
2 Vulnerable equipment: Computers; fax machines; variable frequency drives; CNC machines; extruders; motors
3 Effects: Data errors; memory loss; equipment shutdown; flickering lights; motors stalling/stopping; reduced motor life
Solutions: Verify proper electrical connections and wiring; relocate equipment; reduce voltage motor starters; uninterruptible power supply; voltage ride-through equipment.


Transients
Transients, commonly called "surges," are sub-cycle disturbances of very short duration that vary greatly in magnitude.
When transient occur, thousands of voltage can be generated into the electrical system, causing problems for equipment down the line.
1 Causes: Lighting; normal operation of utility equipment; equipment start-up and shutdown; welding equipment.
2 Vulnerable equipment: Phone systems; computers; fax machines; digital scales; gas pump controls; fire/security systems; variable frequency drives; CNC machines; PLCs.
3 Effects: Processing errors; computer lock-up; burned circuit boards; degradation of electrical insulation; equipment damage.
4 Solutions: Transient voltage surge suppression; uninterruptible power supply; isolation transformer; proper grounding
Harmonics:
A sinusoidal component of a periodic wave of quality having a frequency that is an integral multiple of the fundamental frequency. It is a mathematical model, which is used to analyse distorted waveforms and the current drawn by computers, electronic ballasts; variable frequency drives and other equipment, which have modern “transformer-less” power supplies.

The dynamic power system loads produce a time varying amplitude in current waveforms depending on the load characteristics which consists of the fundamental and harmonics components. These harmonic components distort the voltage or current waveforms thereby deteriorating the power quality. The non-linear loads such as inverter fed adjustable speed drives. UPS (uninterrupted power supply system), rectifiers and furnaces, cyclo-converters etc., which form the major chunk of industrial loads, contribute to the severe fluctuations in power quality

The industrial load also consist of large percentage of power factor improvement capacitors which often create resonance conditions at particular harmonic frequencies generated by non-linear loads fed from the load bus, producing high oscillating currents at resonant frequency and there by induces harmonic voltages distorting the pure sinusoidal voltage waveform..

For assessing power quality it is important to know the total harmonic distortion i.e. the voltage and current distortion factors
V THD = & I THD =
Vk = Voltage of Kth harmonic, Ik = Current of Kth harmonic
Where V1 and I1 are the r.m.s values of fundamental components of voltage and current waveforms. The power quality deteriorates if the source has significant impedance causing the distortion of voltage of the load bus supplying combination of linear and non-linear loads.

Harmonics problems often can be corrected by filtering or resizing power system components like:

Sources of harmonics:
Harmonics of different orders generated when connected power system network by different sources as below:
1. The non linear loads such as inverter fed adjustable speed drive.
2. The use of powerfactor correction capacitor creates parallel or series resonance problems increasing the harmonic distortion.
3. Process control and solid state power conversion equipments.
4. Energy efficient compact flourescent lamps.
5. Use of AC and DC adjustable speed drives
6. Static VAR compensators.
7. Transformers produces very high levels of harmonics when they are initially energized, the so called in rush current will generate harmonics of several orders.
8. Cycloconverters,Lift control system,Traction,AC voltage regulators, UPS, Battery chargers.
The following are the undesirable effects of harmonic on the operation of different equipment connected to power system network. The effect of harmonic depends on harmonic voltages and currents are the integral multiples of the fundamental frequency.

Effects of Hormonics:
?? The duration presence of long duration harmonic cause more serious effects on the various equipments connected to the power system .
Amplitude of harmonics :Large amplitude harmonics of short duration under resonance condition cause dielectric breakdown due to over voltages.
Now a days various devices and equipment being measured applications are more sensitive compared to the past.
? The capacitor used for power factor correction and in different filters decreases resulting in increasing in current drawn by capacitor beyond permissible limits. The capacitor acts as sink for harmonic currents resultant effect of harmonics is overloading , hence over heating increases dielectric stress and increase the power lost. The thermal failure of capacitor may take place because of higher temperature.
?????Non sinusoidal power supplies results in reduction of torque of induction motor
?????It will increase interference with telephone , communication and logic circuits.
? Error in reading of induction type energy meters which are calibrated for pure sinusoidal A.C power.
?????Higher order harmonics causes voltage stress and carona .
? Presence of harmonics in power system network can cause additional losses in power system netwooverheating of transmission lines, transformers and generators etc.,
? Malfunction or even failure of electronic or computer controls.
Hence it is clear that day by day the increase in harmonic contents will impose new problems on operations of electronic equipment . The energy efficient electronic equipment that will be produced in future trends result in poor performance due to the voltage distortion. Hence it is essential to have the proper coordination between the supply authorities and consumers regarding the power quality problem, their causes and results and solutions available to eliminate them.

Importance of Hormonic measurement:

? Meaurement provides the real time information about the power system network to utilities, consumer and designer .Filters designed after harmonic measurements are technically better and economical.
? Measurement provide information to analyze the combined effect of harmonic generated by different loads on power quality.
Different types of instruments available for harmonic measurement are :
? Power profiler BME 303A: It can measure and print in addition to various electric quantities voltage and current total harmonic distortion and frequency.
? Power network analyzer DIP8000: It is portable three phase network analyzer designed for power surveys in which the measured data are transformed to PC for evaluation and documentation.
? Measurement setup: The measurement is done via high quality probe. The computer loads the waveforms of graph sheets.
? Memory hicorder 8840(Hioki make) :It is used to measure three line currents and there line to voltage.
? Dynamic signal analyzer model Hp3561: The parameters such as fundamental frequency of A.C. current, line or phase voltage across potential transformer.

Hormonic elimination techniques:
To avoid the ill effects of harmonics on the operation of sensitive equipments, it is necessary to keep harmonic contents below safe limit by installing filter at load end. The simplest way of eliminating harmonics of different orders is to install filters at the location generated by different loads are connected in two ways in power system network.
1.Series connected filter:
Such type of filters are connected in series with power system network and offer high impedance at turning frequencies high impedance offered by filters allow very little harmonics are passed. The drawback of series filters are high cost, because the rating of filter component required is rated full load current.
2.Shunt connected filter:
It is most commonly used filters in A.C. power system network and offers very low impedance path to harmonics. Shunt type of filters are cheaper than series type because the shunt connected filters are designed for graded insulation levels which makes the components cheaper than the series filter components.
Following are the different techniques used to eliminate harmonics of different orders to keep harmonic distortion within permissible limit.
3.Passive filters:
These are LC resonating or parallel resonating circuits which offer very high or low impedance at tuning frequency. These filters are resistive at tuned frequency, capacitive at below tuned frequencies and inductive beyond tuned frequency.
Advantages of Passive filters:
1.Simple in construction, less costly and efficient
2.Serves dual purpose harmonic filtration and power factor correction of load.
Disdvantages of Passive filters:
1. Cannot function under saturated condition.
2.Number of passive filters installed must be equal to the number of harmonic levels to be compensated.
3. Connection of passive filters necessities a specific analysis of each installation.
4.Non adaptability to system variations .
5.Bulky in size.
6.Tendency to resonate with the other load.
Active filters:
When the number of harmonics to be filtered, large no of branches of passive filters will be required . The large no of branches of passive filters will be required. The actual number of branches will depend upon no of harmonic level of branches will depend upon no of harmonic level to be compensated. Hence, because of passive filter use for filtration of large no of harmonics results in large size &more cost. Introduction of self commutated devices e.g. MOSFETS, IGBT etc. Accelerated the research in design of active filter & resulted low cost, high performance active filter suitable to eliminate the harmonics of different orders to overcome the drawbacks of passive filters.
Active filters compensates voltage of current harmonic signal measured. The injected voltage or current harmonic signal measured. The injected voltage or current harmonic signals in to the power system network is of same magnitude and opposite in phase of the measured harmonic signal . It comprises power converter and control loop which controls the harmonics injection of the filter as the function of harmonic signal measure.


Electrical noise:
Electrical noise is high-frequency interference caused by a number of factors, including arc welding or the operation of some electric motors.
1 Causes: Lighting; normal operation of utility equipment; equipment start-up and shutdown; welding equipment.
2 Vulnerable equipment: Phone systems; computers; fax machines; digital scales; gas pump controls; fire/security systems; variable frequency drives; CNC machines; PLCs.
3 Effects: Processing errors; computer lock-up; burned circuit boards; degradation of electrical insulation; equipment damage.
4 Solutions: Transient voltage surge suppression; uninterruptible power supply; isolation transformer; proper grounding

Power outages:
Power outages are total interruptions of electrical supply. Utilities have installed protection equipment that briefly interrupts power to allow time for a disturbance to dissipate.
For example, if lightning strikes a power line, a large voltage is instantly induced into the lines. The protection equipment momentarily interrupts power, allowing time for the surge to dissipate.
1 Causes: Ice storms; lightning; wind; utility equipment failure.
2 Vulnerable equipment: All electrical equipment.
3 Effects: Complete disruption of operation.
4 Solutions: Transient voltage surge suppression; uninterruptible power supply.

SOLUTIONS: -
Surge suppressors:
These are small plug-in devices designed to protect equipment from moderate surges and spikes. Surge suppressors should be considered the minimum level of protection from internal and external transients on electrical, telephone and data lines. Installing surge suppression at the main service panel and following through to each electronic device is strongly recommended
Isolation transformers:
These devices electrically separate the electronic equipment from the incoming power system, reducing unwanted electrical noise.

CONCLUSION:
Harmonic distortion is increasing day by day at a faster rate and is a matter of concern to the utility, customer and manufacturers of different equipment. To keep the harmonic distortion to low value, following actions are necessary.
? In India it is necessary first to create awareness regarding harmonic problems, their effects and elimination techniques among the utility, consumers and manufacturers of different equipments to make power system less polluted.
? The harmonic standards should be imposed on the equipment and should be made mandatory to the manufactures and consumers. The equipment should strictly comply to the harmonic standards before selling it in open market.
? The utility should monitor the installation of high tension consumers periodically, regarding the harmonic distortion and penalties should be imposed on customers using equipments crossing specified limits.
? Filters should made compulsory to H.T. consumers.






3 comments:

  1. My cousin recommended this blog and she was totally right keep up the fantastic work!

    L&T Air Circuit Breaker

    ReplyDelete
  2. My cousin recommended this blog and she was totally right keep up the fantastic work!


    Electrical Project

    ReplyDelete