Are all genereators serve energy for consumers throughout the year?

The number of generators connected in parallel serve the energy for consumers.According season(or time),the load varies.In winter,half of the load will be eliminated.At this half of load ,the running of all generators is uneconomical.So,optimum condition should be obtained.This will be achieved by eliminating unnecessary generators from bus-bar(or load) during that period.Frequent connection and disconnection of generators should must be done in-order to achieve optimum operation.

MEASUREMENT OF UNKNOWN RESISTANCE BY DC CROMPTON'S POTENTIOMETER

i.                    Make the connection as per above figure in which R is an unknown resistance and S is known resistance.

ii.                  The current through a circuit is controlled with the help of a rheostat.

iii.                A two pole double throw switch is use. The switch, when put in position 1, 1’ connects the unknown resistance to the potentiometer. Therefore voltage across R is determined by D.C. Crompton’s potentiometer. V_r be the voltage across R.

iv.                When switch is thrown to position 2-2’, potentiometer measures voltage across known S. let V_s be the voltage across S.

v.                  Therefore resistance is measured by using below formula.

vi.                R = (V_R.S)/V_s

 

1-phase Power transmission through fiber optics

CHAPTER 1

INTRODUCTION

Optical  fiber  has  long  been  used  to  provide  illumination,  communication  links,  and  a  sensing platform,  but  has  been  little  utilized  as  a  means  for  providing  electrical  power  through conversion of light into a usable voltage and current. Fiber-provided electrical power has the advantage of providing total immunity from electrical noise and complete isolation of the source and system. Applications exist in a number of areas including powering sensors in areas of high electromagnetic fields, providing an isolated power and data link to sensors in high  voltage  areas  such  as  substations,  allowing  for  all-optical  networks  containing  active components without  the  need  for  a  separate  electrical  connection,  and providing  power  to  areas  of  high  sensitivity  to  RF  emissions. Devices operating on fiber- provided power have the additional advantage of using the same fiber for high bandwidth data transmissions. Although  many  applications  do  not  require  high  levels  of  electrical  power, other applications, such as powering motors or actuators, require watts or more of power. One limitation lies in the optical power handling capabilities of a fiber. This area has been studied, especially with regard to the need for higher power in long communications links  and in the area  of  laser  to  fiber  coupling  ,  but  the  application  to  power  Transmission has  not.  Other limiting factors in optical power transmission include the coupling efficiency of the laser and the efficiency of the op to-electronic converter. Optical fibers have several limitations in their power transmitting capabilities. The first of these is absorption that results in heating above the melting point of the material. Silica, commonly used in optical fiber, can theoretically handle up to 100 kW of optical power in a 100-micron diameter fiber or 10 kW in a 10-micron diameter fiber. However, other factors produce more stringent limitations. These are fiber fusing, end point damage, and bending failures. Fiber fusing is an effect whereby the local power density in a fiber is greatly increased due to contaminants, end point reflections, self focusing, or some other means. At this location, the fiber actually melts and forms a trigger for a second fusing event and so forth, producing a chain reaction that can propagate along the length of a fiber. Fiber fuses of as much as 1.5km have been observed. End point damage is the most common form of fiber failure. This  is  most  likely  to  occur  at connectors  where  an  epoxy  is  commonly  used.  The  epoxy  heats  rapidly  when  illuminated  by high  powers  (due  to  its  higher  optical  absorption)  and  can  result  in  melting  of  the  end point. End point damage is less likely with non-connectorized fibers, but can still occur due to scratches or contaminants on the end point that form a point of localized heating. Bending failures can occur when a fiber is bent to a small radius of curvature. As the radius decreases, more light is coupled into the cladding of the fiber and reaches the outer plastic coating. The coating is much more absorptive and thereby heats more readily under high power. 

1.1    CONDITIONS FAVORING THIS LIGHT TECHNOLOGY

Optical power transmission is an elegant way to replace copper wiring with fiber optic cable for applications where conventional power supply is challenging or even impossible due to:

i.                    The risk of short circuits and sparks

ii.                  The need for lightning protection

iii.                 Electromagnetic interference

iv.                 The need for galvanic isolation

v.                   High magnetic fields

vi.                 Heavy weight of long distance cabling

vii.              Susceptibility to corrosion and moisture

BLOCK DIAGRAM:

                                                                  

CHAPTER 2

CONVERSION OF ELECTRICITY INTO LIGHT

The electricity generated in the power station is AC in nature. This AC is converted to DC through three stages i.e. rectification, filtering, regulating. This high voltage DC is applied to laser LED. In this way electricity is converted into light.

2.1 CONVERSION OF AC TO DC:

2.1.1CONVERSION AC TO PULSATIVE DC:

 

                   

                                    

                                                                    

During positive half cycle, current direction is as follows:

Voltage source-SCR4-LOAD SCR2-volatage source

During negative half cycle:

Voltage source-SCR3-LOAD-SCR1-voltage source

2.1.2 CONVERSION OF PULSATIVE DC TO UNREGULATED DC:

                              

In this type inductor L is in series and capacitor C is in shunt with load. The choke (L) allows the dc component to pass through easily because its dc resistance R is very small. The capacitive reactance XC is very high for dc and it acts as open circuit. All dc current passes through across which dc output voltage is obtained.

The inductive reactance XL = 2πfL is high for ac components. Therefore the ripples are reduced. Even if any ac current passes through L, it flows through the capacitor because of its low capacitive reactance.

2.1.3 CONVERSION OF FILTERED DC TO REGULATED DC:

In this stage, filtered DC is converted into constant DC.

All the thyristors, capacitors, inductors and resistors are designed to withstand rated capacity.

2.2 TRANSMISSION OF DC ELECTRICITY INTO LIGHT:

A light-emitting diode (LED) is a two-lead semiconductor light source. It is a p–n junction diode, which emits light when activated. when a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence, and the color of the light (corresponding to the energy of the photon) is determined by the energy band gap of the semiconductor.

An LED is often small in area (less than 1 mm²) and integrated optical components may be used to shape its radiation pattern.

Appearing as practical electronic components in 1962, the earliest LEDs emitted low-intensity infrared light. Infrared LEDs are still frequently used as transmitting elements in remote-control circuits, such as those in remote controls for a wide variety of consumer electronics. The first visible-light LEDs were also of low intensity, and limited to red. Modern LEDs are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.

Early LEDs were often used as indicator lamps for electronic devices, replacing small incandescent bulbs. They were soon packaged into numeric readouts in the form of seven-segment displays, and were commonly seen in digital clocks.

Recent developments in LEDs permit them to be used in environmental and task lighting. LEDs have many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching. Light-emitting diodes are now used in applications as diverse as aviation lighting, automotive headlamps, advertising, general lighting, traffic signals, and camera flashes and lighted wallpaper. As of 2015, LEDs powerful enough for room lighting remain somewhat more expensive, and require more precise current and heat management, than compact fluorescent lamp sources of comparable output.

LEDs to be used to convert electricity into light are designed to withstand rated capacity.

CHAPTER-3

FIBER-OPTIC CABLES

An optical fiber cable is a cable containing one or more optical fibers that are used to carry light. The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube suitable for the environment where the cable will be deployed. Different types of cable are used for different applications, for example long distance telecommunication, or providing a high-speed data connection between different parts of a building.

3.1 CONSTRUCTION:

Optical fiber consists of a core and a cladding layer, selected for total internal reflection due to the difference in the refractive index between the two. In practical fibers, the cladding is usually coated with a layer of acrylate polymer or polyimide. This coating protects the fiber from damage but does not contribute to its optical waveguide properties. Individual coated fibers (or fibers formed into ribbons or bundles) then have a tough resin buffer layer and/or core tube(s) extruded around them to form the cable core. Several layers of protective sheathing, depending on the application, are added to form the cable. Rigid fiber assemblies sometimes put light-absorbing ("dark") glass between the fibers, to prevent light that leaks out of one fiber from entering another. This reduces cross-talk between the fibers, or reduces flare in fiber bundle imaging applications. For indoor applications, the jacketed fiber is generally enclosed, with a bundle of flexible fibrous polymer strength members like aramid (e.g. Twaron or Kevlar), in a lightweight plastic cover to form a simple cable. Each end of the cable may be terminated with a specialized optical fiber connector to allow it to be easily connected and disconnected from transmitting and receiving equipment. For use in more strenuous environments, a much more robust cable construction is required. In loose-tube construction the fiber is laid helically into semi-rigid tubes, allowing the cable to stretch without stretching the fiber itself. This protects the fiber from tension during laying and due to temperature changes. Loose-tube fiber may be "dry block" or gel-filled. Dry block offers less protection to the fibers than gel-filled, but costs considerably less. Instead of a loose tube, the fiber may be embedded in a heavy polymer jacket, commonly called "tight buffer" construction. Tight buffer cables are offered for a variety of applications, but the two most common are "Breakout" and "Distribution". Breakout cables normally contain a ripcord, two non-conductive dielectric strengthening members (normally a glass rod epoxy), an aramid yarn, and 3 mm buffer tubing with an additional layer of Kevlar surrounding each fiber. The ripcord is a parallel cord of strong yarn that is situated under the jacket(s) of the cable for jacket removal. Distribution cables have an overall Kevlar wrapping, a ripcord, and a 900 micrometer buffer coating surrounding each fiber. These fiber units are commonly bundled with additional steel strength members, again with a helical twist to allow for stretching. A critical concern in outdoor cabling is to protect the fiber from contamination by water. This is accomplished by use of solid barriers such as copper tubes, and water-repellent jelly or water-absorbing powder surrounding the fiber. Finally, the cable may be armored to protect it from environmental hazards, such as construction work or gnawing animals. Undersea cables are more heavily armored in their near-shore portions to protect them from boat anchors, fishing gear, and even sharks, which may be attracted to the electrical power that is carried to power amplifiers or repeaters in the cable. Modern cables come in a wide variety of sheathings and armor, designed for applications such as direct burial in trenches, dual use as power lines, and installation in conduit, lashing to aerial telephone poles, submarine installation, and insertion in paved streets.

                                   

                                                              

3.2 RELIABILITY AND QUALITY:

Optical fibers are very strong, but the strength is drastically reduced by unavoidable microscopic surface flaws inherent in the manufacturing process. The initial fiber strength, as well as its change with time, must be considered relative to the stress imposed on the fiber during handling, cabling, and installation for a given set of environmental conditions. There are three basic scenarios that can lead to strength degradation and failure by inducing flaw growth: dynamic fatigue, static fatigues, and zero-stress aging.

3.2.1 LOSSES:

Typical modern multimode graded-index fibers have 3 dB/km of attenuation loss (50% loss per km) at 850 nm and 1 dB/km at 1300 nm. 9/125 single mode loses 0.4/0.25 dB/km at 1310/1550 nm. POF (plastic optical fiber) loses much more: 1 dB/m at 650 nm. Plastic optical fiber is large core (about 1mm) fiber suitable only for short, low speed networks such as within cars.

Each connection made adds about 0.6 dB of average loss and each joint (splice) adds about 0.1 dB. Depending on the transmitter power and the sensitivity of the receiver, if the total loss is too large the link will not function reliably.

Invisible IR light is used in commercial glass fiber communications because it has lower attenuation in such materials than visible light. However, the glass fibers will transmit visible light somewhat, which is convenient for simple testing of the fibers without requiring expensive equipment. Splices can be inspected visually, and adjusted for minimal light leakage at the joint, which maximizes light transmission between the ends of the fibers being joined.

The charts at "Understanding wavelengths In fiber optics" and "Optical power loss (attenuation) in fiber" illustrate the relationship of visible light to the IR frequencies used, and show the absorption water bands between 850, 1300 and 1550 nm.

3.2.2 SAFETY:

The infrared light used in telecommunications cannot be seen, so there is a potential laser safety hazard to technicians. The eye's natural defense against sudden exposure to bright light is the blink reflex, which is not triggered by infrared sources. In some cases the power levels are high enough to damage eyes, particularly when lenses or microscopes are used to inspect fibers that are emitting invisible infrared light. Inspection microscopes with optical safety filters are available to guard against this. More recently indirect viewing aids are used, which can comprise a camera mounted within a handheld device, which has an opening for the connectorized fiber and a USB output for connection to a display device such as a laptop. This makes the activity of looking for damage or dirt on the connector face much safe.

High intensity light emitted in the LED by applying large DC voltage is transmitted through these fiber-optic cables. And, these fiber-optic cables are designed at required rated capacity.

CHAPTER-4

CONVERSION OF LIGHT INTO ELECTRICITY

Photovoltaic (PV) is the name of a method of converting solar energy into direct current electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon commonly studied in physics, photochemistry and electrochemistry. A photovoltaic system employs solar panels composed of a number of solar cells to supply usable solar power. The process is both physical and chemical in nature, as the first step involves the photoelectric effect from which a second electrochemical process takes place involving crystallized atoms being ionized in a series, generating an electric current. Power generation from solar PV has long been seen as a clean sustainable energy technology which draws upon the planet’s most plentiful and widely distributed renewable energy source – the sun. The direct conversion of sunlight to electricity occurs without any moving parts or environmental emissions during operation. It is well proven, as photovoltaic systems have now been used for fifty years in specialized applications, and grid-connected PV systems have been in use for over twenty years.^]They were first mass-produced in the year 2000, when German environmentalists including Eurosolar succeeded in obtaining government support for the 100,000 roofs program.

Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaic has declined steadily since the first solar cells were manufactured, and the levelised cost of electricity from PV is competitive with conventional electricity sources in an expanding list of geographic regions. Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have supported solar PV installations in many countries.^[7] With current technology, photovoltaic recoups the energy needed to manufacture them in 1.5 to 2.5 years in Southern and Northern Europe, respectively.

Solar PV is now, after hydro and wind power, the third most important renewable energy source in terms of globally installed capacity. More than 100 countries use solar PV. Installations may be ground-mounted (and sometimes integrated with farming and grazing) or built into the roof or walls of a building (either building-integrated photovoltaic or simply rooftop).

In 2014, worldwide installed PV capacity increased to at least 177 gigawatts (GW), sufficient to supply 1 percent of global electricity demands. Due to the exponential growth of photovoltaic, installations are rapidly approaching the 200 GW mark – about 40 times the installed capacity of 2006. China, followed by Japan and the United States, is the fastest growing market, while Germany remains the world's largest producer, with solar contributing about 7 percent to its annual domestic electricity consumption.

Since the late 1800s, scientists have dreamed of achieving wireless power transmission – the delivery of power to a distant location without wires. Laser power beaming uses a laser to send concentrated light through the air or fiber optic cable to a remote receiver that converts the light to electricity. It works much like solar power, where sunlight shines on solar cells that generate electricity, but instead it uses high intensity laser light aimed at specialized photovoltaic (PV) cells that convert the laser light into electricity. Key differences from solar power are that the laser is much more intense than the sun, it can be aimed anyplace in line-of-sight of the transmitter (including with the aid of a telescope or mirrors), and it can operate 24 hours/day. Consequently, laser power beaming has numerous advantages over solar power.

The wireless power system starts with a laser running on power supplied from a standard industrial electrical outlet or a generator.  The laser light is shaped by a set of optics to define the beam size at its destination.  This light then propagates through air, the vacuum of space, or through fiber optic cable until it reaches the PV receiver.  This array of PV cells then converts the light back into electricity.

Electricity is traditionally transmitted using wires (usually made of copper). Among their less desirable traits are that electrical power lines are expensive to install ($20,000 or more per mile for low power residential lines, and $250,000 or more per mile for high-voltage transmission lines), can require significant time before an installation is completed, could fail at any point along their entire length, and cannot be moved to a different location once installed. Perhaps most importantly, though, there are many places where electrical power lines are impractical (e.g., to an aerial vehicle), uneconomical (e.g., to distant, remote locations), or simply impossible to install (Earth to Moon).

Wireless power delivery, on the other hand, requires physical installations at only the transmitting and receiving points, and nothing in between (an “invisible extension cord”). The receiver can be moved to a different location, closer or further away, without changing the cost of the system. Power can be available as soon as the elements are placed and turned on, instead of having to wait for wires to be buried or hung from poles.

Therefore, high intensity light is converted to electricity. Total efficiency of system depends these photovoltaic cells. Hence, it is important stage in total system. However, recent development makes photovoltaic cell somewhat efficient. Since input is high intensity light, hence PV cells works at higher efficiency.

CHAPTER-5

CONVERSION OF DC TO AC

Inversion is the conversion of dc power to ac power at a desired output voltage or current and frequency. A static inverter circuit performs this transformation. The terms voltage-fed and current-fed are used in connection with inverter circuits. A voltage-fed inverter is one in which the dc input voltage is essentially constant and independent of the load current drawn. The inverter specifies the load voltage while the drawn current shape is dictated by the load.  A current-fed inverter (or current source inverter) is one in which the source, hence the load current is predetermined and the load impedance determines the output voltage.  The supply current cannot change quickly. This is achieved by series dc supply inductance which prevents sudden changes in current. The load current magnitude is controlled by varying the input dc voltage to the large inductance; hence inverter response to load changes is slow. Being a current source, the inverter can survive an output short circuit thereby offering fault ride-through properties. Voltage control may be required to maintain a fixed output voltage when the dc input voltage regulation is poor, or to control power to a load. The inverter and its output can be single-phase, three-phase or multi-phase.  Variable output frequency may be required for ac motor speed control where, in conjunction with voltage or current control, constant motor flux can be maintained. Inverter output waveforms are usually rectilinear in nature and as such contain harmonics which may lead to reduced load efficiency and performance. Load harmonic reduction can be achieved by either filtering, selected harmonic reduction chopping or pulse-width modulation.

Power inverters are designed at required rated capacity.

                                                Fig.(5)

CONCLUSION

Power by Light (PBL) Systems are attractive to use in harsh environments and special applications due to their convenient characteristics, immunity to all forms of electromagnetic interference, short circuits and sparks. Over the last years a lot of research works in the field of optical powering and development of PBL systems has taken place. During that time the understanding of fiber technologies for optical data and energy transmission and the behavior of semiconductor materials regarding data detection and optical power conversion has increased a lot. The main aspect of correct PBL system designing is to match the requirements. 

An important fact for the future is the flexibility of processes to apply PBL systems with a high selectivity. Applications for optical fibers on printed circuit boards or directly on devices in the automotive industry to power remote sensor systems are possible. Many applications do not need very high data rates or lot of energy but a low cost production process. Leading to a high degree of flexibility and selectivity a new approach for processing of optical fibers has been developed. With micro dispensing it is possible to create optical fibers on 3D shaped devices. Furthermore, direct contacting of electro-optical elements is possible. The capability of MGDM for optical power and data transmission within short distances was shown.

ABSTRACT

The use of optical fibers for power transmission has been investigated intensely. An optically powered device combined with optical data transfer offers several advantages compared to systems using electrical connections. Optical transmission systems consist of a light source, a transmission medium and a light receiver. The overall system performance depends on the efficiency of op to-electronic converter devices, temperature and illumination dependent losses, attenuation of the transmission medium and coupling between transmitter and fiber. This paper will summarize the state of the art for optically powered systems and will discuss reasons for negative influences on efficiency. Furthermore, an outlook on power transmission by the use of a new technology for creating polymer optical fibers via micro dispensing will be given. This technology is capable to decrease coupling losses by direct contacting of op to-electronic devices.