The objective of a protection scheme in a power system is to minimize hazards to personnel and equipment while allowing the least disruption of power service. Shortcircuit calculations are a prerequisite for a coordination study. The results establish the minimum and maximum current levels for which coordination must be evaluated and which aid in setting or selective the devices for adequate protection. Typically the coordination study has been performed graphically by manually plotting time-current operating characteristics of various devices, along with conductor and transformer damage curves to illustrate the quality of protection and coordination possible. Computer programs that provide a graphical representation of the device coordination as it is developed are replacing the manual curves.
This microprocessor is unique in the fact that its 1.4 Billion transistor count, capable of a teraflop of performance, is almost entirely dedicated to logic (Itanium's transistor count is largely due to the 24MB L3 cache) . Current designs, as opposed to the earliest devices, use extensive design automation and automated logic synthesis to lay out the transistors, enabling higher levels of complexity in the resulting logic functionality. Certain high-performance logic blocks like the SRAM cell, however, are still designed by hand to ensure the highest efficiency (sometimes by bending or breaking established design rules to obtain the last bit of performance by trading stability). The main challenging areas in VLSI are performance, cost, and power dissipation. Due to switching i.e. the power consumed testing, due to shortcircuit current flow and charging of load area, reliability and power. The demand for portable computing devices and communications system are increasing rapidly. These applications require low power dissipation VLSI circuits. The power dissipation during test mode is 200% P more than in normal mode. Hence it is important aspect to optimize power during testing. Power optimization is one of the main challenges. Test Pattern generation has long been carried out by using conventional Linear Feedback Shift Registers (LFSR’s5). LFSR’s are a series of flip-flop’s connected in series with feedback taps defined by the generator polynomial. The seed value is loaded into the outputs of the flip- flops. The only input required to generate a random sequence is an external clock where each clock pulse can produce a unique pattern at the output of the flip-flops. This random sequence at the output of the flip-flops can be used as a test pattern. The number of inputs required by the circuit under test must match with the number of flip-flop outputs of the LFSR. This test pattern is run on the circuit under test for desired fault coverage. The power consumed by the chip under test is a measure of the switching activity of the logic inside the chip which depends largely on the randomness of the applied input stimulus. Reduced correlation between the successive vectors of the applied stimulus into the circuit under test can result in much higher power consumption by the device than the budgeted power. A new low power pattern generation technique is implemented using a modified conventional Linear Feedback Shift Register.
In Fig 7 for phase-to-ground fault condition related simulation results, the synchronous generator output current, terminal voltage, synchronous generator excitation voltage and speed were examined thoroughly. In case of failure nominal effective value of the stator terminal voltage being 13,8 turned into = 10,96 ( = 15,5 )at the moment the shortcircuit occurred but after eliminating shortcircuit and reached levels of = 15,10 ( = 21,35 )when a steady state of the system was obtained, it arose to the level of the nominal value of the terminal voltage. The stator current with a nominal effective value being1506 , when the shortcircuit occurred at the impact short-circuit current read as = 3260 ( = 4610 )and continuous short-circuit current read as = 3220 . Excitation voltage reached to the maximum value of 11.5 pu when the shortcircuit occurred and made oscillations in a short period of 6 seconds and died away. The nominal value of synchronous generator with a speed value of 300 rpm dropped to 297 rpm at the moment of shortcircuit. 40 seconds after the failure its condition became stable by making oscillations. As a result of the simulation, in faulted phase, as expected, the voltage dropped and current was recorded to rise.
In light of the above situation, this paper investigates the results of DG penetration in a large-scale MV distri- bution network as a pilot application. The network is fed by three power substations and it consists of twenty one MV lines. The DG resources to be connected are mainly PV units, with a total capacity of about 32 MW. Their locations are predetermined. Specifically, the influence of these units on the network branch currents, voltage profile, power flow, short-circuit level (SCL) at the MV busbars of the infeeding power substations, and losses are examined using a commercial-grade software pack- age. The results arising from this real-world case study can be used as a pilot for the relevant analysis required for every relative network.
Aircrafts are equipped with a variety of lights that are used for navigation, safety and to improve visibility during flight or when taxiing on the ground . Lighting systems on aircrafts' are exterior lighting, interior lighting and emergency lighting. Exterior lighting system consists of landing lights, taxi lights, logo lights, wing illumination lights, service lights, position lights, anti-collision lights and strobe lights. The landing light is light for night landing. And it is located on wing leading edge or landing gear. The voltage rating that landing light use is 28 V DC or 115 V AC. Its power rating is 600 W. Past and present technologies include ordinary incandescent lamps, halogen lamps, various forms of arc lamps and discharge lamps and LED lamps. The airplanes have both transformer-rectifiers to turn the 400 Hz AC voltage into DC voltage for the 28 volts buses, and a static inverter to create the AC 400 Hz in case the aircraft power decreases up to the battery power. The aircraft battery offers a short-term power storage capability . Most of aircrafts' electrical systems use a three-phase, 400 Hz, AC bus supplied by engine driven generators. However, most aircrafts' lighting systems use only 28 V DC. Due to aircraft generating power is 115 V, 400 Hz AC and the required voltage level for the landing light is 28 V DC, the input AC voltage must be converted into required DC output voltage.
In DCVS-LS if PUN and PDN are not properly matched then it will result heavily contention current or in worst case circuit not function properly. Then output of DCVS- LS is several time lower than the applied input voltage. Hence to improve the driving strength of PUN, the chirality of PUN can be fixed at lower index i.e. (7, 0) that result PUN have high threshold voltage for proper level shifting. And chirality of PDN is fixed at medium value (22, 0) while the number of nanotubes of PDN is kept at N=30 and analyze driving strength of the DCVS-LS circuit of PUN by varying the number of nanotube from 1 to 7 as shown in Fig.5. The PUN become stronger than PDN by increasing the number of nanotubes above N=4. And if any mismatch between PUN and PDN then output transition are very slow and contention current comes into picture for large duration. This is shown in fig.6. The DCVS-LS have lesser PDP by keeping N=1, but circuit is more credulous by changing the diameter of CNTFET . Reducing this problem due to statistical averaging by using more number of CNTs. Delay and power dissipation is large if number of nanotube N=7. So kipping number of nanotube N=4 in the PDN for better performance. In next for optimize the PDP and reducing the contention current by varied the number of nanotube of PDN.
Abstract: The objective of this work is to size & integrate various components like PV module, charge controller, inverter, battery bank, LT panel to switch load from PV to Grid and Vice versa, LED lights for 3.5 KW PV system for street lighting. This is battery connected system has designed to supply electricity during night hours i.e. 12 hours, in which battery store energy generated during the day in battery bank for use at night or during cloudy periods. Arrangement is also done to switch load from PV to grid if sufficient energy from PV is not available or in case of PV system maintenance or troubleshooting activity. System cost estimation, energy saving calculations and payback analysis is done to show whether it is economically viable or not. This project will be used as understudy for possible rooftop power plant at Mindtree Ltd Pune Campus.
The temperature effects on the electrical performance of a large area multicrystalline silicon solar cell with back-contact technology have been studied in a desert area under ambient conditions using the current shunt measuring technique. Therefore, most of the problems encountered with traditional measuring techniques are avoided. The temperature dependency of the current shunt from 5ºC up to 50ºC has been investigated. Its temperature coefficient proves to be negligible which means that the temperature dependency of the solar cell is completely independent of the current shunt. The solar module installed in a tilted position at the op- timum angle of the location, has been tested in two different seasons (winter and summer). The obtained so- lar cell shortcircuit current, open circuit voltage and output power are correlated with the measured incident radiation in both seasons and all results are discussed.
Shortcircuit studies are very important from the operating and planning points of view. Abnormal conditions can arise in a power system owing to short circuits between two phases, or a line snapping and making contact with ground or a lightning stroke hitting a particular transmission line. These give rise to heavy current in the system. Before these current can do any damage to equipments such as expensive generator and transformer, the faulty parts of the transmission system must be isolated . This is done by circuit breakers
Abstract— The present world aims in designing low power devices due to the rampant usage of portable battery powered gadgets. The proposed static random access memory (SRAM) design furnishes an approach towards curtailing the hold power dissipation. The design uses a tail transistor which aids in limiting the shortcircuitpower dissipation by disrupting the direct connection between supply voltage and ground. This tail transistor also brings down the subthreshold current by providing stacking effect, which subsequently reduces hold power dissipation. A supply voltage of 0.8V is used which makes it eligible for low power applications. The designed SRAM cell has single ended write and read operations and is simulated using Cadence 45nm CMOS technology. Statistical and corner analysis is also performed for the proposed design for its robustness. The proposed SRAM cell has a hold power dissipation of 4.74154pW which is much less as compared to the standard 6T SRAM cell.
As CHIP density increases relentlessly along Moore’s law, power consumption is emerging as a major burden for Contemporary systems . Dynamic energy is proportional to the square of the supply voltage. Thus, a lower voltage level yields a quadratic reduction in the energy consumption. To further reduce the dynamic power, systems-on-chip (SoCs) are partitioned into voltage islands with separate supply rail and unique power characteristics –. Moreover, as devices keep shrinking, the channel length shortens and the gate oxide thickness reduces, increasing the gate-induced drain leakage, the gate oxide tunneling current, and the junction leakage . Many techniques have been presented in the literature for reducing static power. One common approach is to synthesize the circuit using dual-V t libraries . High-V t cells reduce the
In the paper, different network architectures have been tested in order to forecast the electric power generated by a PV module in real conditions. Data used to train the networks were acquired using two different types of PV modules connected to calibrated electrical loads. Climatic variables were acquired by means of a weather station. The performances evaluation of the ANNs was performed by comparing the prediction with the real power output and the errors were generally contained within the 0.05–1% of the module peak power output. ANNs with simpler architecture generally required longer training time while more complex ANNs have requested shorter training time. Results show that adaptive techniques are able to predict the power output of a PV panel with great accuracy and short computational time. These algorithms can play a dominant role concerning remote management of PV in a probable future when this technology will be extremely widespread in the territory.
A paramount part of adding ESSs to a system is choosing the proper Energy Storage Device (ESD) for the application among several different technologies, namely Pumped Hydro Storage, Compressed Air Energy Storage, Flywheel, Fuel Cell, Rechargeable Batteries, Super Capacitor, etc. There have been some studies comparing ESDs features, for instance, in  price, energy density, power density, specific power, specific energy, discharge/charge rate, life cycle, depth of discharge, lifespan, energy conversion efficiency, daily self-discharge rate,and ramp time of several ESDs, to provide uninterruptible power supply to data centres, are presented. A deeper com- parison of ESDs is presented in , where several ESDs are numerically analysed presenting their specific energy, energy density, specific power, power density, efficiency, lifespan, life cycle, life cycle, daily self-discharge rate and scale, cost.
Thermal annealing can provide benefits on photovoltaic process of P3HT/PCBM based OSC, such as improvement in surface morphology and crystallinity of photoactive materials, furthermore contact resistance between active materials and electrode to aid charge generation, transport and collection . However, thermal annealing can also bring problems on photovoltaic process of P3HT/PCBM based OSC if thermal annealing is too much, like PCBM aggregation, phase separation between P3HT and PCBM to lower PCE . Selecting annealing temperature is one of the key factors in improving shortcircuit current density (J sc ), open circuit voltage (V oc ) and PCE .
ABSTRACT:-Worldwide interest for power is expanding while generation of energy from petroleum derivatives is declining and in this manner the undeniable decision of the perfect energy source that is inexhaustible and could give security to advancement future is energy from the sun. As of late ithere has been a developing consideration itowards utilization iof solar energy. The principle points of interest of iPhotovoltaic systems utilized for tackling isolar energy are iabsence of greenhouse gas emission, low maintenance cost, concerning site of establishment and, mechanical commotion emerging from moving parts. Photovoltaic energy is a standout amongst the most critical energy sources since it is spotless and limitless. It is critical to work PV energy transformation systems in the maximum power point (MPP) to boost the yield energy of PV clusters. A MPPT control is important to extricate maximum power from the PV exhibits. As of late, an extensive number of procedures have been proposed for tracking the maximum power point. This review paper propose assortment and executed of MPPT techniques.
together with less efficient charge extractions. Mobilities above the optimum value lead to decreases in the open circuit voltage and no significant increase in the dissociation rate of polaron pairs. 3 This leads to a lower voltage at the maximum power point, thus reducing the efficiency. 3 Tress et al. 4 showed that Langevin type recombination leads to an optimum mobility while mobility-independent recombination leads to no optimum value.
The basic gun uses a wire feeder to push the electrode from a remote location through the conduit, a distance of typically about 12 ft. (3.7 m). Several other designs are also available, including a unit with a small electrode feed mechanism built into the gun. This system will pull the electrode from a more distant source where an additional drive may also be used to push the electrode into the longer conduit needed. Another variation is the “spool-on-gun” type in which the electrode feed mechanism and the electrode source are self-contained. Wire Feed Motor. Lincoln wire feeders provide the means for driving the electrode through the gun and to the work. The LN-7 GMA, LN-742, LN-9 GMA, LN-10, LN-25, DH-10, STT-10, Power Feed 10 and Power Feed 11 semiautomatic, constant speed wire feeders have trouble-free solid state elec- tronic controls which provide regulated starting, automatic compression for line voltage fluctuations and instanta-neous response to wire drag. This results in clean positive arc start- ing with each strike, minimizes stubbing, skipping and spatter, and maintains steady wire feeding when welding. All compo- nents are totally contained within the feeder box for maximum protection from dirt and weather, contributing to the low main- tenance and reliable long life of these wire feeders.
Motor Torque and speed are increased when protective circuit is added during F3 fault. Shortcircuit fault in 3-phase inverter (F4): The Figure 9a shows the inverter short-circuit fault (F4) in the T3 switch. During the short-circuit fault, there is a low impedance path created and overcurrent condition occurs and current will flow through all the 3 phases. But the duration of the overcurrent is minimized significantly, due to the buck converter and redundant inverter leg.
ABSTRACT: The shading due to clouds, buildings, tree’s etc. may affect the performance of a photovoltaic array. Including this variation in temperature, solar separation is some more factors which affect the performance. The complete or partial shadowing of PV array tremendously affects its performance. In case of large PV array systems installed for distributed power generation schemes, the situation may get more complex under partially shaded condition. The multiple peaks generated due the shadowing affect may make PV characteristics more complex. It is significant to understand the maximum peak possibilities in order to extract the maximum possible power. This paper is an attempt to describe the MATLAB-based modeling and simulation scheme suitable for studying the I–V and P–V characteristics of a PV array under a non-uniform isolation due to partial shading. The present paper will explain a comparative study and give a glimpse on different method for maximum power point tracking system.
In an electric power system, a fault is any abnormal flow of electric current. For example a shortcircuit is a fault in which current flow by passes the normal load. An open circuit fault occurs if a circuit is interrupted by some failure. In three phase systems, a fault may involve one or more phases and ground, or may occur only between phases. In a “ground fault” or “earth fault”, current flows into the earth. The prospective shortcircuit current of a fault can be calculated for power systems. In power systems, protective devices detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure.