Abstract. Nowadays modern overhead transmission lines (OHL) constructions having several significant differences from conventional ones are being used in power grids more and more widely. Implementation of compact overhead lines equipped with FACTS devices, including phase angle regulator settings (compactcontrolled OHL), appears to be one of the most effective ways of power grid development. Compactcontrolled AC HV OHL represent a new generation of power transmission lines embodying recent advanced achievements in design solutions, including towers and insulation, together with interconnection schemes and control systems. Results of comprehensive research and development in relation to 110–500kV compactcontrolledpower transmission lines together with theoretical basis, substantiation, and methodological approaches to their practical application are presented in the present paper.
The operation standard of series APF is based on isolation of the harmonics in between the nonlinear burden and the source. This is got by the injection of harmonic voltages (vf) across the interfacing transformer. The injected harmonic voltages are added/subtracted, to/from the source voltage to maintain a untainted sinusoidal voltage waveform across the nonlinear burden. The sequence APF can be considered of as a harmonic isolator as shown in Figure 7. It is controlled in such a way that it presents none impedance for the fundamental constituent, but appears as a resistor with high impedance for harmonic frequencies components. That is, no current harmonics can flow from nonlinear load to source, and vice versa. Sequence APFs are less widespread than their competitor, i.e. the shunt APF. This is because they have to handle high burden currents. The producing high capability of burden currents will increase their current rating considerably contrasted with shunt APF, particularly in the lesser side of the interfacing transformer. This will increase the I 2 R losses. Although, the major benefit of sequence APFs over shunt one is that they are ideal for voltage harmonics elimination. It presents the load with a pure sinusoidal waveform, which is significant for voltage perceptive apparatus (such as power scheme protection devices). With this characteristic, sequence APF is apt for improving the value of the distribution source voltage.
Different research works in [6, 12, 13, 18-20, 22, 29, 30-33] have been carried out to evaluate the effect of electromagnetic field radiation from nearby highvoltage transmission lines and other sources of magnetic fields on humans. Similarly, a number of well-established effects of exposure to low-frequency EMFs on the nervous system in [22, 29] include the direct stimulation of nerve and muscle tissue, and the induction of retinal phosphenes. It was reported in [31, 32] that exposure to electromagnetic field at power frequency (50/60Hz) may increase the risk of many diseases, due to the current induced in the human tissue. Also, research works in [7-9] pointed out that magneto-hydrodynamic effect from magnetic field forces on moving charged particles at very high static field levels can alter cardiac function and blood flow, and can cause vertigo. More also, nerve and muscle excitation can be induced by magnetic fields as well as through contact currents. Furthermore, the International Agency for Research on Cancers (IARC) (2002) pointed out that 50Hz or 60Hz magnetic fields have been classified in the list of possible carcinogenic agents .
A thyristor-controlled reactor (TCR) is a reactance connected in series with a bidirectional thyristor valve. The thyristor valve is phase- controlled, which allows the value of delivered reactive power to be adjusted to meet varying system conditions. Thyristor-controlled reactors can be used for limiting voltage rises on lightly loaded transmission lines.The current in the TCR is varied from maximum (determined by the connection voltage and the inductance of the reactor) to almost zero by varying the firing delay angle.
For that task, an important contribution can be taken from recent research that has examined public attitudes towards highvoltagepowerlines. Devine- Wright (in press) argues that literature on public acceptance of renewable energy technologies has followed two explanatory pathways: first, focusing on personal and place related factors (e.g. age, education, feelings of rootedness or place attachments, e.g. Vorkinn & Riese, 2001) and second, project related factors, including trust (Midden & Huijts, 2009), degree of information about the infrastructure (Furby et al., 1988), perceived proximity to the development (Priestley & Evans, 1996), or perceived local impacts (Upham & Shackley, 2006). The analysis integrated these two sets of factors to explain attitudes towards a highvoltagepower line to be built in South West England. Results show that personal and place related factors were each able to explain 4% of the variance of the attitude towards the power line, while project-related factors (perceived impacts, trust and procedural justice) explained an
Transmission systems are part of the overall electrical power supply systems. Transmission system consists of conductors carried on steel towers linking generation stations to users through the distribution system. They deliver bulk power from power stations to the load centers and large industrial consumers beyond the economical service range of the regular primary distribution lines . Like many transmission systems in the world, Nigeria’s transmission system is characterized by high technical and non-technical losses, overloading, voltage instability, radial lines having no redundancy, results of de-regularization of the electricity market and obsolete substation equipment ,,.
Today, Industry automation utilizes power electronic based power processing devices for getting higher efficiency, accurate controllability, faster response and compact size. But on the other side, due to the switching actions of these power electronics devices (SCR, MOSFET, BJT and IGBT) behave as non-linear loads. And they draw non-sinusoidal and or lagging/leading current from the supply resulting to poor displacement and distortion factors. Hence these power converters draw considerable reactive volt-amperes from the utility and inject harmonics in distribution networks. The harmonic current from these power converters flows through the line and source impedance of the power system can cause voltage distortion and excessive voltage drop and line losses , . The distorted supply voltage results in malfunction of control, protection, and metering equipment used in other sensitive loads and industrial automation monitoring devices. Harmonic currents can also cause unwanted system resonance with passive filters, overloading of power factor correcting capacitors, a decrease of overall system efficiency due to increased line and machine losses, interference with communication and control signals, and saturation and overheating of distribution transformers and lines.At the same time, an increase of sensitive loads involving digital electronics and complex process controllers requires a pure sinusoidal supply voltage for proper control and load operation. This forces the industries to filter the harmonics and compensate reactive power. The immediate and cheap solution is passive filters. But it has its own limitations such as harmonic resonance and harmonic amplification due to varying line impedance. In addition to this, the effectiveness of the passive filters is purely based on line and source impedance and load parameters,which is highly unpredictable.
Delay Element (DE) is a vital block in Delay Lock Loop (DLL) , Phase Lock Loop (PLL) , microprocessor and memory circuits  and Time-to-Digital Converters . The aim is to design a delay element, which assists in time interval (TI) measurement  with high resolution (< 200 ps) for High Energy Physics (HEP) experiments. A variety of DEs already has been reported in the literature  with their merits and limitations. The Current Starved Inverter (CSI) is used as a delay element in time measurement circuits. This structure ensures wide delay regulation range and low power consumption. The reported delay using CSI is 244 ps  in 0.35 µm CMOS process.
The active filter is based on a PWM voltage source inverter is connected to the PCC through interface filter; the active filter is connected in parallel with the AC/DC converter. This inverter uses dc capacitor as supply and can switch at high frequency to generate the current that will cancel the harmonics from AC/DC converter. The current waveform for canceling harmonics is achieved by using VSI in the current controlled mode and the interface filter. This interface filter provides smoothing and isolation for high frequency components. The desired currents are obtained by accurately controlling the switching of the MOSFET inverter. We can Control the wave shape of current by limiting the switching frequency of the inverter and by the available driving voltage across the interfacing inductance.
Electrical powerlines were originally designed to transmit power from the generators to consumers at 50 or 60 Hz. Now efforts are being made to use the same ubiquitous power grid for long-haul data communication. This is a challenging task because powerlines and communication systems operate at two extremes. Powerlines operate at very low frequency and highpower, while communication systems operate at very high frequency and very low voltage. While early power line communication (PLC) mainly employed narrowband communications, broadband (or high-speed) PLCs have emerged in the later 1990s .
In many countries throughout the world there are some regions where the distribution network is not developed mainly because of very dispersed and low load level compared to the investment needed to supply them. In some of these locations, it is remarkable to notice that HV trunk line are going through these region but cannot feed any of the small villages or farms leaving close to such important lines (220, 400 and 735 kV). Such HV lines are bringing power from large power station (hydraulic f.e.) to large town some hundreds of km far away. If such a situation is not common in Europe, it is a very common one in Africa, Canada, Russia, China ... The lack of power may have dramatic effect on social life, pushing young people out of their community to go where development is possible and more comfort available. No power means limited economic activity, limited access to water and no possible development. Such a situation is particularly sad for African communities, like in Congo-Brazzaville where only 2% of the rural population has access to electricity, despite some existing long 220 kV OHL going through the country, bringing power from Inga (RDC) and from some few local hydraulic plants to Brazzaville and Pointe Noire. Hundreds of km of HV lines exist with very limited loads and hanging over a very large number of small villages splitted all around the country, many of them being not so far from such trunk lines. Access to petrol in remote location is also a problem so that even local power is not possible most of the time. So they have to live without lighting, without fridge (to maintain food in good conditions) and have to walk several km every day to bring bad water from dirty river. That was the situation of MAKOLA, 30 km far from Pointe Noire in Congo-Brazzaville. About 500 people are leaving there in a complete poorness, a few meters away from a 220 kV trunk line. The amount of power needed has been evaluated by UNESCO to about 50 kVA as a first short term target.
The current system that distributes highvoltage to the hadronic calorimeter TileCal of the AT- LAS experiment at CERN was manufactured in the late 1990s and now many of its components are obsolete. In addition to this, the continuous exposition to high levels of radiation that results from the LHC collision affects the whole system. The calorimeter itself will be upgraded and a faster and low noise electronic will be needed. Given this, an update was proposed to mitigate these problems: a new highvoltage distribution system (HVDS) placed outside of the detector, a remote system which will not be affected by the radiation, that maximize the reliability and robustness of the system. For this new system it is necessary to produce a dedicated board that provides the necessary primary supplies. Therefore, the presented work consists in the development of a power supply board capable of providing both highvoltage (HV), −830 V and −950 V, and low voltage, ±12 V and 3.3 V, with low noise, resorting to DC/DC converters. Each HVDS provides the supply to 48 photomultipliers tubes (PMTs) of the detector. Due to the current needed, two highvoltage sources are available, each one to supply just half of the PMTs. The values of the provided HV supplies are digitally controlled to one of the referred values, so each PMT of the detector can receive the right voltage to work correctly. Besides that, this board is controlled by a serial peripheral interface (SPI) communication protocol and has an analog to digital converter (ADC) and an analog multiplexer that are used to provide the user monitoring of all supply voltages and currents in real-time as well as the temperature, in two different positions of the board, in real time. A graphical user interface (GUI) has also been developed which allows easy communication between the power supply board and the user.
33 A closed loop-needless PID controller along with increasing the arm inductance are considered to evaluate the effects of output voltage and current total harmonic distortion (THD) response in a modular multilevel converter . Reference  presents a control strategy based on calculating the differential current references to provide desired operation for the MMCs in HVDC applications. Various dynamic models of the MMCs and their limitations in presenting robust control methods for these converters are investigated in . In this work, a complete derivation of the proposed switching state functions without losing any circuital characteristics of the converter is accomplished and a switching-cycle control approach proposed based on unused switching states of the MMCs. A modulation technique is proposed in  based on a fixed pulse pattern fed into the SMs to maintain the stability of the stored energy in each SM, without measuring capacitor voltages or any other sort of feedback control. It also removes certain output voltage harmonics at any arbitrary modulation index and any output voltage phase angle. A current control design for independent adjustment of several current components and a systematic identification of current and voltage components for balancing the energy in the arms of an MMC is presented in . In , a control strategy based on adding a common zero-sequence voltage to the reference voltages is proposed for balancing the arm currents of the MMCs under unbalanced load conditions. To reach it, a relationship between the DC-link active power and AC-link average active power is achieved and then, the DC component of the arm current is calculated through the AC-link average active power in the corresponding phase . In the medium voltage systems, the energy storage can be embedded in MMC that causes several SMs to operate at significantly lower voltages . In the structure presented in , the low-frequency components of the SM’s output currents are removed by utilizing the interfaced batteries through the non-isolated dc/DC converters. Control algorithms proposed in this work are developed to balance the state of charge of batteries. A compact and clear representation of differential equations is obtained for the MMC by introducing two nonlinear coordinate transformations in . In the proposed model, two candidate outputs leaded to the internal dynamics of second or third order and a quasi-static feedback generates a linear input-output behaviour. Other different aspects of MMC application in HVDC system such as DC fault and DC solid-state transformers operating conditions are assessed in the references of –.
It is today generally accepted in the scientiic community that AC signals from highvoltagepowerlines can inluence the corrosion of nearby installed protected metallic structures like pipelines. In these cases locally high current densities might pass through small defects of the protective coatings. While it seems to be consolidated that the rate of AC corrosion increases with the increase of the amplitude of AC density, thus predicting risks for damaged coatings, the existence of a safe lower limit of the amplitude is still in question. Equivalent studies of the AC inluence on the metallic structure of the transmission towers itself had not been reported so far in the literature. Our ield studies have qualitatively shown that the AC signal can also inluence the corrosion of the buried metallic structure of the transmission tower, although the AC is not conined to coating defects and might have, therefore, a much lower amplitude.
Single-phase switch mode ac-dc converters are being used as frontend rectifiers for a variety of applications due to the advantages of high efficiency and power density. These classical converters, however, draw-non- sinusoidal input ac currents leading to low input power factors and injection of harmonics into the utility lines. Research in improved power quality utility interface has gained importance due to stringent power quality regulation and strict limits on Total Harmonic Distortion (THD) of input current placed by standards such as IEC 61000-3-2 and IEEE 519-1992. This has led to consistent research in the various techniques for power quality improvement. Research into switch mode power factor corrected ac-dc converters has been in two directions namely buck and boost type topologies. On the other hand the boost type converter generates DC voltage, which is higher than the input ac voltage. However, the input current in these converters flows through the inductor and therefore can easily be actively wave-shaped with appropriate current mode control. Moreover, boost converters provide regulated dc output voltage at unity input power factor and reduced THD of input ac current.
We then empirically demonstrated the importance of considering these aspects by presenting results from a study of highvoltagepowerlines, with data collected through surveys conducted with a national sample – representative of UK residents – and with local ones – representative of four settlements (three towns and one village) in England and Wales that are affected by proposals for highvoltagepowerlines to be constructed nearby. Bearing in mind recent critiques of the use of opinion polling and surveys (e.g., Aitken 2010; Ellis, Barry, and Robinson 2007), we also aimed to illustrate how surveys may be used in a way that allows for a more complex and context-sensitive approach and can inform this literature in articulation with other methodologies, namely qualitative ones.
(VCO) using amorphous Indium Gallium Zinc Oxide (a-IGZO) thin-film transistors (TFTs). This circuit consists of a high- gain OpAmp, a comparator and a relaxation oscillator. The implemented relaxation oscillator shows a power consumption of 700 µW, when it is simulated with a supply rails of ±5 V. It shows a frequency of oscillation range from 327 to 560 Hz, when the tuning capacitance value is in varying from 1.6 to 5 pF. On the other hand, the VCO has a power dissipation of 1.3 mW with frequency ranging from 400 to 556 Hz with a controlling voltage from -5 to 5 V. In-house oxide TFT model is used for circuit simulations in Cadence environment. This circuit would find potential applications in large-area flexible systems, namely smart packaging, biomedical and wearable systems, which needs clocks with different frequencies.
The core circuit of VCO draws 4.39mA current while consuming 4.39mW power through 1.0V supply voltage. The spectrum measurement results illustrated in Fig. 5 to Fig. 6; the oscillator frequency can be varied from 32.09GHz to 34.59GHz by 1.0V tuning controlledvoltage; and this VCO has 2.50GHz tuning range. The output power of the VCO at 32.09GHz is -21.64dBm and at 34.59GHz is -18.08dBm. Phase noise of Ka-Band VCO is not able to measure directly in Signal Source Analyzer, thus down-conversion of the oscillated signal is necessary. There are two helpful solutions, one is dividing the frequency, and the other is mixing the mm-wave frequency. In this case, we choose to divide the mm-wave signal which is shown in Fig. 7. The divisor is set as 8, and the measurement frequency is down-converted into 4.235GHz. In Figure 7, the VCO oscillated signal will go through a pre-amplifier in order to make the divider sense the weak signal from VCO. The measured phase noise is -103.3dBc/Hz at 1MHz offset and -134.7dBc/Hz at 10MHz offset which is illustrated in Figure 8. But the phase noise is measured at 4.235GHz; it should be compensated 18.06dB which is expressed in equation (3). After compensating, the actual phase noise at 33.88GHz is -85.24dBc/Hz at 1MHz offset and -116.64dBc/Hz at 10MHz offset. The figure-of-merit (FOM) is expressed in equation (4) where
Abstract. This paper presents an improved electronic circuit for testing photovoltaic (PV) modules or strings by tracing their I-V and P-V characteristics. It consists of an electronic fast varying load based on a power MOSFET controlled by means of an innovative sweeping gate-source voltage in order to improve the tracing of the I-V characteristics on an oscilloscope. In order to prevent damage of data acquisition systems and mainly for use with highvoltage PV strings, galvanic isolation is introduced for the sweeping signal as well as current and voltage measurements. In spite of this improved characteristics, the developed electronic circuit keeps the advantages of low cost and simplicity. Experimental results obtained with the electronic circuit are presented.
Key words: Power system, Unified Power Flow Controller (UPFC), transient stability, HighVoltage Direct Current (HVDC), Flexible AC Transmission System (FACTS), injected current, thyristor controlled phase shifter, series transformer, voltage source, leakage reactance, equivalent circuit