Power Engineering Guide. Free Download The Power Engineering Guide is a manual for everyone who is involved in the generation, transmission and distribution of electrical energy — from system planning, to implementation and control. It is designed to assist engineers, technicians, planners and advisors and support students, trainees, electrical engineering teachers and energy technology teachers including university lecturers.
Beyond that the guide is useful as a reference work for technical questions and in supporting continuing education in technical fields. To address this need, Siemens has developed SIHARBOR, a shore-to-ship connection system that meets the requirements of port operators, shipping companies, dockyards and power supply companies. It consists of two self-commutated IGBT pulse-controlled converters that are interconnected through a DC intermediate circuit. The converters are connected on one side to the local power supply network and on the other side to the ships onboard system.
SIPLINK is thus able not only to feed the onboard system from the distribution network, but also to match the various different parameters to one another and to interlink them. Up to 5 MVA of power can be transmitted with a medium-voltage plug and socket connection. After connecting the plug-in connector in the ship, the automation system installed on shore automatically initiates the system start-up.
The user dialog for this process is conducted from the ship. The ships power supply is not interrupted. The diesel generators for the onboard power supply can then be shut down, and the complete onboard network can be supplied in an environmentally friendly way from the shore-based power distribution system. Advantages of this system include: p Flexible connection of all types of onboard systems, regardless of voltage or frequency p A single MV cable connection instead of several LV connections p Electrical separation of shoreside and onboard network, to keep the respective protection schemes and avoid galvanic corrosion The system also takes into account the different types of ships, such as passenger ships, container ships and ferries.
Thanks to its modular basis, any combination of 50 Hz and 60 Hz power supply systems is possible, as are all voltage levels. The particular advantage here is that in the event of supply bottle- necks in one network, available power reserves in another network can be used to make up for the shortfall g.
The amount of costly energy that needs to be brought in from outside, especially during periods of peak demand is decreased. This allows signicant cost savings. Other advantages, aside from minimizing energy purchases, include the following: p The reliability of the supply and voltage quality are improved. SIPLINK provides unlimited options for switching electricity between two or more networks at a medium-voltage level exactly according to the individual requirements in the particular network.
This capability ensures improved supply reliability and better voltage quality at the distribution level. The protection afforded acts in both directions. Sensitive loads are protected against unclean networks, and conversely, networks are protected against problematical consumers.
It is possible under certain circumstances to avoid using additional diesel generators to cover peak loads if less power is needed in another subnet- work at that particular moment.
A high-availability power supply is essential for certain industrial processes. In such cases, two independent incoming feeders can jointly supply one load Y-circuit.
If one of these feeders fails, the second takes over without interruption so that the change- over is not noticeable at the consumer load g. It is also possible to divide the load between the two feeders in any desired ratio, thus balancing the two feeders. At the same time, an OPEN command is sent to the normal feeding switch on the busbar.
As soon as the contacts of the switch are opened about 50 ms , the voltage on the busbar increases immediately to the rated voltage g. The Multi Feed conguration is simpler in design than the Y-circuit and is used where short voltage dips are acceptable. The technology, proven in various applications, became a rst-rate, highly reliable one.
FACTS, based on power electronics, have been developed to improve the performance of weak AC systems and to make long distance AC transmission feasible.
FACTS can also help solve technical problems in the interconnected power systems. Their utilization has almost no effect on the short-circuit power but it increases the voltage at the point of connection.
This device is an MSC with an additional damping circuit for avoidance of system resonances. Static Var Compensator SVC Static Var compensators are a fast and reliable means of controlling voltage on transmission lines and system nodes g.
The reactive power is changed by switching or controlling reactive power elements connected to the secondary side of the trans former. The most common application is the xed series capacitor FSC. FSCs comprise the actual capacitor banks, and for protection purposes, parallel arresters metal- oxide varistors, MOVs , spark gaps and a bypass switch for isolation purposes g.
Fixed series compensation provides the following benets: p Increase in transmission capacity p Reduction in transmission angle When system voltage is low, the SVC supplies capacitive reactive power and rises the network voltage. When system voltage is high, the SVC generates inductive reactive power and reduces the system voltage. Static Var Compensators perform the following tasks: p Improvement in voltage quality p Dynamic reactive power control p Increase in system stability p Damping of power oscillations p Increase in power transfer capability p Unbalance control option The design and conguration of an SVC, including the size of the installation, operating conditions and losses, depend on the system conditions weak or strong , the system conguration meshed or radial and the tasks to be performed.
For indoor installations, converter modules with approximately MVAr are available. Parallel operation of converter modules is also possible, resulting in higher ratings. It is also possible to control the current and thus the load ow in parallel transmission lines, which simultaneously improves system stability.
Further applications for TCSC include power oscillation damping and mitigation of subsynchronous resonance SSR , which is a crucial issue in case of large thermal generators. Additional benets of thyristor-controlled series compensation: p Damping of power oscillations POD p Load-ow control p Mitigation of SSR subsynchronous resonances p Increase in system stability Thyristor-Protected Series Capacitor TPSC When high power thyristors are used, there is no need to install conventional spark gaps or surge arresters.
Due to the very Power Transmission and Distribution Solutions 2. TPSCs are the rst choice whenever transmission lines must be returned to maximum carrying capacity as quickly as possible after a failure g. If the designed short-circuit level of the existing equipment is exceeded, an extension of the network, without extremely costly replacement of the existing equipment, is not possible. This no-go criteria can be avoided by using the Siemens short-circuit current limiter. In case of a system fault, the thyristor valve will be red, bypassing the series capacitor.
The corresponding short-circuit current will be limited by the reactor to the design values g. Results of these investigations show that the bulk of the insulating gas for industrial projects involving a considerable amount of gas should be nitrogen, a non-toxic natural gas.
However, another insulating gas should be added to nitrogen in order to improve the insulating capability and to minimize size and pressure. Additionally, the arcing behavior is improved using this mixture. Tests have proven that there would be no external damage or re caused by an internal fault. The technical data of the GIL is shown in table 2.
Jointing technique In order to improve gas tightness and to facilitate laying of the lines, anges have been avoided as a jointing technique. Instead, welding has been chosen to connect the various GIL construction units. The welding process is highly automated, with the use of an orbital welding machine to ensure high quality of the joints. This orbital welding machine contributes to high productivity in the welding process and therefore speeds up laying the lines. The reliability of the welding process is con- trolled by an integrated computerized quality assurance system.
Laying The laying technique must be as compatible as possible with the landscape and must take the change of seasons of the year into Fig. GIL exhibit the following differences from cables: p High-power ratings transmission capacity up to 3, MVA per system p High overload capability p Autoreclosure functionality p Suitable for long distances km and more without compensation of reactive power p High short-circuit withstand capability including internal arc faults p Possibility of direct connection to gas-insulated switchgear GIS and gas-insulated arresters without cable entrance tting p Non-ammable; no re risk in case of failures The latest innovation of Siemens GIL is the buried laying technique for GIL for long-distance power transmission.
SF 6 has been replaced by a gas mixture of sulphur hexauoride SF 6 and nitrogen N 2 as an insulating medium. Siemenss experience When SF 6 was introduced in the s as an insulating and switching gas, it became the basis for the development of gas- insulated switchgear. On the basis of its GIS experience, Siemens started to develop SF 6 gas-insulated lines to transmit electrical energy.
In the early s initial projects were planned and implemented. GIL were usually used within substations as busbars or bus ducts to connect gas-insulated switchgear with overhead lines. The aim was to create electrical lines with smaller clearances than those that were obtainable with air-insulated overhead lines. Implemented projects include laying GIL in tunnels, in sloping galleries, in vertical shafts and in open-air installations. Flanging as well as welding has been applied as a jointing technique.
The gas-insulated transmission line technique is highly reliable in terms of mechanical and electrical failures. After a system is commissioned and in service, it runs reliably without any dielectri- cal or mechanical failures, as experience over the course of 30 years shows. For example, one particular Siemens GIL now in service did not have to undergo its scheduled inspection after 20 years of service, because there were no indications of any weak point.
Basic design In order to meet mechanical stability criteria, gas-insulated lines comprise considerable cross-sections of enclosure and conduc- tor. Herewith high-power transmission ratings are given. Because the insulating medium is gas, low capacitive loads are given so that compensation of reactive power is not needed, not even for longer distances. A further important requirement taken into account is the situation of an earth fault with a high current of up to 63 kA to earth.
Power Transmission and Distribution Solutions 2. The laying techniques for pipelines have been improved over many years, and these techniques are applicable for GIL as a pipeline for electrical current, too. However, GIL need slightly different treatment, and the pipeline technique has to be adapted. The laying process is illustrated in g.
The assembly area needs to be protected from dust, particles, humidity and other environmental factors that might disturb the dielectric system. Clean assembly, therefore, plays an important role in setting up cross-country GIL under normal environmental conditions. A high level of automation of the overall process makes clean assembly and enhanced productivity possible. Anti-corrosion protection The most recently developed Siemens GIL are also designed for directly buried laying.
Directly buried gas-insulated transmission lines will be safeguarded by a passive and active corrosion protection system. The passive corrosion protection system comprises a coating and ensures at least 40 years of protection. The active corrosion protection system provides protection potential in relation to the aluminum sheath.
This result conrms more than 30 years of eld experi- ence with GIL installations worldwide. The test procedure consisted of load cycles with doubled voltage and increased current as well as frequently repeated high-voltage tests. The assembly and repair procedures under realistic site conditions were also examined. The Siemens GIL was the rst in the world to have passed these tests, without any problems.
References Siemens has gained experience with gas-insulated transmission lines at rated voltages of up to kV and with phase lengths totalling more than 40 km The rst GIL stretch built by Siemens was the connection of the turbine generator pumping motor of a pumped storage station with the switchyard. The kV GIL is laid in a tunnel through a mountain and has a single-phase length of 4, m g.
This connection was commissioned in at the Wehr pumped storage station in the Black Forest in Southern Germany. Table 2. The portion of overhead transmission lines within a transmission and distribution network depends on the voltage level as well as on local conditions and practice. In densely populated areas like Central Europe, underground cables prevail in the distribution sector, and overhead power lines in the high-voltage transmission sector. In other parts of the world, for example, in North America, overhead lines are often also used for distribution purposes within cities.
Siemens has planned, designed and erected overhead power lines for all important voltage levels in many parts of the world. Selection of line voltage For the distribution and transmission of electric power, standardized voltages according to IEC are used world- wide.
Lines on the medium-voltage level supply small settlements, individual industrial plants and large consumers; the transmis- sion capacity is typically less than 10 MVA per circuit. The high- voltage circuits up to kV serve for subtransmission of the electric power regionally, and feed the medium-voltage network.
This level is often chosen to support the medium-voltage level even if the electric power is below 10 MVA. Moreover, some of these high-voltage lines also transmit the electric power from medium-sized generating stations, such as hydro plants on small and medium rivers, and supply large-scale consumers, such as sizable industrial plants or steel mills.
They constitute the connection between the interconnected high-voltage grid and the local distribution networks. The bandwidth of electrical power transported corresponds to the broad range of utilization, but rarely exceeds MVA per circuit, while the surge imped- ance load is 35 MVA approximately. In Central Europe, kV lines were used for interconnection of power supply systems before the kV level was introduced for this purpose. Long-distance transmission, for example, between the hydro power plants in the Alps and consumers, was done by kV lines.
Nowadays, the importance of kV lines is decreasing due to the existence of the kV transmission network. The kV level represents the highest operation voltage used for AC transmission in Central Europe.
It typically interconnects the power supply systems and transmits the energy over long distances. Large power plants such as nuclear stations feed directly into the kV network. Overhead power lines with voltages higher than kV AC will be required in the future to economically transmit bulk electric power over long distances, a task typically arising when utilizing hydro, wind and solar energy potentials far away from consumer centers.
The voltage level has to be selected based on the task of the line within the network or on the results of network planning. Siemens has carried out such studies for power supply companies all over the world.
High-voltage direct current However, when considering bulk power transmission over long distances, a more economical solution is the high-voltage direct current HVDC technology. Siemens is in the position to offer complete solutions for such interconnections, starting with network studies and followed by the design, assistance in project development and complete turnkey supply and construction of such plants.
For DC transmission no standard is currently available. The DC voltages vary from the voltage levels recommended in the above-mentioned standardized voltages used for AC. HVDC transmission is used for bulk power transmission and for system interconnection. The line voltages applied for projects worldwide vary between kV, kV, kV, kV and recently , kV.
The selection of the HVDC line voltage is ruled by the following parameters: p Amount of power to be transferred p Length of the overhead power line p Permissible power losses p Economical conductor size The advantages of DC transmission over AC transmission are: p A DC link allows power transfer between AC networks with different frequencies or networks that cannot be synchronized. This graph must be seen as a general guideline. Any project should be separately evaluated on a case-by-case basis.
The budgets established for this evaluation are based on gures. The line and converter costs have been added, and transferred into a cost factor per MW power and km of transmission line. The result shows that for long-distance HVDC transmission, the kV voltage level is not the optimal solution refer to kV below. However, this voltage level is useful in short HVDC interconnectors such as the Thailand-Malaysia Interconnector, which has a line length of km.
The line and converter costs have been added, and transferred into a cost factor per megawatt power and kilometer of transmission line length. The result shows that the kV voltage level is a suitable solution for line lengths of to 1, km with transmitted power of to 1, MW. The result shows that the kV voltage level is a suitable solution for the line lengths of 1, km to 1, km with transmitted power of 1, to 2, MW.
However, the kV voltage level can also be competitive in this range of power and line length. The result shows that the kV voltage level is a suitable solution for the line lengths of km to 3, km with transmitted power of 2, MW, and 3, MW for lines up to 2, km.
However, the kV voltage level can still be competitive in parts of this range. The line and converter costs have been added, and transferred into a cost factor per megawatt power and kilometer of transmission line. The result shows that the kV voltage level is a suitable solution for the line lengths of 2, km and above with transmitted power of 2, and 3, MW. However, shorter line lengths of 1, to 3, km with power rating of 3, to 7, MW can be economically covered with an kV solution.
For many years, aluminum and its alloys have been the prevailing conducting materials for power lines due to the favorable price, the low weight and the necessity of certain minimum cross-sections. However, aluminum is a very corrosive metal. But a dense oxide layer is formed that stops further corrosive attacks.
Therefore, up to a certain level, aluminum conductors are well-suited for areas in which corrosion is a problem, for example, a maritime climate. For aluminum conductors, there are a number of different designs in use. All-aluminum conductors AAC have the highest conductivity for a given cross-section; however, they possess only a low mechanical strength, which limits their application to short spans and low tensile forces.
To increase the mechanical strength, wires made of aluminum-magnesium-silicon alloys are adopted. Their strength is approximately twice that of pure aluminum. But single-material conductors like all-aluminum and aluminum alloy conductors have shown susceptibility to eolian vibrations.
Compound conductors with a steel core, so-called aluminum conductor, steel-reinforced ACSR , avoid this disadvantage. The ratio between aluminum and steel ranges from 4.
An aluminum-to-steel ratio of 6. Conductors with a ratio of 4. Conductors with a ratio higher than 7. But because of lower conductor strength, the sags are bigger, which requires higher towers. Experience has shown that ACSR conductors, just like aluminum and aluminum alloy conductors, provide the most economical solution and offer a life span greater than 40 years. Conductors are selected according to electrical, thermal, mechanical and economic aspects.
The electric resistance as a result of the conducting material and its cross-section is the most important feature affecting the voltage drop and the energy losses along the line and, therefore, the transmission costs. The cross-section has to be selected so that the permissible temperatures will not be exceeded during normal operation as well as under short-circuit condition.
With increasing cross-section, the line costs increase, while the costs for losses decrease. Depending on the length of the line and the power to be transmitted, a cross-section can be determined that results in the lowest transmission costs. The heat balance of ohmic losses and solar radiation against convection and radiation determines the conductor temperature. A current density of 0. High-voltage results in correspondingly high-voltage gradients at the conductors surface, and in corona-related effects such as visible discharges, radio interference, audible noise and energy losses.
Since the sound of the audible noise of DC lines is mainly caused at the positive pole and this sound differs from those of AC lines, the subjective feeling differs as well. Therefore, the maximum surface voltage gradient of DC lines is higher than the gradient for AC lines. The line voltage and the conductor diameter are one of the main factors that inuence the surface voltage gradient.
In order to keep this gradient below the limit value, the conductor can be divided into subconductors. This results in an equivalent conductor diameter that is bigger than the diameter of a single conductor with the same cross-section. This aspect is important for lines with voltages of kV and above. Therefore, so-called bundle conductors are mainly adopted for extra-high-voltage lines.
From a mechanical point of view, the conductors have to be designed for everyday conditions and for maximum loads exerted on the conductor by wind and ice. Earth wires, also called shieldwire or earthwire, can protect a line against direct lightning strikes and improve system behavior in the event of short-circuits; therefore, lines with single-phase voltages of kV and above are usually equipped with earth wires.
Earth wires made of ACSR conductors with a sufciently high aluminum cross-section satisfy both requirements. Since the beginning of the s, more and more earth wires for extra-high-voltage overhead power lines have been executed as optical earth wires OPGW.
This type of earth wire combines the functions just described for the typical earth wire with the additional facility for large data transfer capacity via optical bers that are integrated into the OPGW. Such data transfer is essential for the communication between two converter stations within an HVDC interconnection or for remote controlling of power stations. The OPGW in such a case becomes the major communication link within the interconnection.
One-layer designs are used in areas with low keraunic levels small amount of possible lightning strikes per year and small short-circuit levels. Selection of insulators Overhead line insulators are subject to electrical and mechanical stresses, because they have to isolate the conductors form potential to earth and must provide physical supports. Insulators must be capable of withstanding these stresses under all conditions encountered in a specic line.
The electrical stresses result from: p The steady-state operating power-frequency voltage highest operation voltage of the system p Temporary overvoltages at power frequency p Switching and lightning overvoltages Insulator types Various insulator designs are in use, depending on the require- ments and the experience with certain insulator types: p Cap-and-pin insulators g.
The individual units are connected by ttings of malleable cast iron or forged iron. The insulating bodies are not puncture-proof, which is the reason for a relatively high number of insulator failures. These insulators are puncture-proof. Failures under operation are extremely rare. Long-rod insulators show superior behavior, especially in polluted areas. Because porcelain is a brittle material, porcelain long-rod insulators should be protected from bending loads by suitable ttings.
This insulator type provides superior performance and reliability, particularly because of improvements over the last 20 years, and has been in service for more than 30 years. In order to avoid brittle fracture, the glass ber rod must additionally be sealed very carefully and durably against moisture.
This is done by application of silicone rubber. Nowadays, high temperature vulcanized HTV silicone is used. The silicone rubber has two functions within this insulator type: p Sealing the glass ber rod p Molding into insulator sheds to establish the required insulation Metal ttings are compressed onto the glass ber rod at both ends of the insulator, either with a ball socket or clevis connec- tion tting.
Since the s, compression ttings have been the prevailing type. The sealing of the area between tting and silicone housing protecting the rod is most important, and is nowadays done with special silicone elastomer, which offers after vulcanization the characteristic of a sticky solid, similar to a uid of high viscosity. Advantages of the composite long-rod insulator are: p Light weight, less volume and less damages p Shorter string length compared to cap-and-pin and porcelain long-rod insulator strings p Up to kV AC and kV DC, only one unit of insulator practical length is only limited by the ability of the production line is required p High mechanical strength p Vandalism resistance p High performance in polluted areas, based on the hydrophobicity water repellency of the silicone rubber Advantages of hydrophobicity are: p Silicone rubber offers outstanding hydrophobicity over the long term; most other polymeric housing material will loose this property over time p Silicone rubber is able to recover its hydrophobicity after a temporary loss of it p The silicone rubber insulator is able to make pollution layers on its surface water-repellent, too hydrophobicity transfer p Low surface conductivity, even with a polluted surface and very low leakage currents, even under wetted conditions.
Insulator string sets Suspension insulator sets carry the conductor weight, including additional loads such as ice and wind, and are arranged more or less vertically. There are I-shaped g. Tension insulator sets g. They are loaded by the conductor tensile force and have to be rated accordingly. Multiple single, double, triple or more sets handle the mechanical loadings and the design requirements. Design of creepage distance and air gaps The general electrical layout of insulation is ruled by the voltages to be withstood and the pollution to which the insulation is subjected.
The standards IEC and IEC as well as the technical report IEC , which provides four pollution classes the new version will have ve classes , give guidance for the design of the insulation.
Therefore, these creepage distances have to be multiplied by the factor 3. Furthermore, it should be noted that the AC voltage value refers to a mean value, while the DC voltage is comparable to a peak value, which requires a further multi- plication with factor 2. Insulators under DC voltage operation are subjected to a more unfavorable conditions than they are under AC, due to a higher collection of surface contamination caused by the constant unidirectional electric eld. Therefore, a DC pollution factor has to be applied.
The results shown were conrmed by an experienced insulator manufacturer in Germany. The correction factors shown are valid for porcelain insulators only. When taking composite insulators into consider- ation, an additional reduction factor of 0. The values for a DC system must be seen as a guideline only, that must be veried on a case-by-case basis for new HVDC projects. To handle switching and lightning overvoltages, the insulator sets have to be designed with respect to insulation coordination according to IEC and IEC These design aspects determine the gap between the earthed ttings and the live part.
However, for HVDC application, switching impulse levels are of minor important because circuit-breaker operations from AC lines do not occur on DC back-to-back lines. Such lines are controlled via their valve control systems. In order to coordinate the insulation in a proper way, it is recommended to apply and use the same SIL and BIL as is used for the equivalent AC insulation determined by the arcing distance.
Selection and design of supports Together with the line voltage, the number of circuits AC or poles DC and type of conductors, the conguration of the circuits poles determines the design of overhead power lines. Additionally, lightning protection by earth wires, the terrain and the available space at the tower sites have to be considered. In densely populated areas like Central Europe, the width of right- of-way and the space for the tower sites are limited.
In the case of extra-high-voltages, the conductor conguration affects the electrical characteristics, the electrical and magnetic eld and the transmission capacity of the line.
Very often there are contradicting requirements, such as a tower height as low as Power Transmission and Distribution Solutions 2. The arrangements of insulators depend on the application of a support within the line.
Suspension towers support the conductors in straight-line sections and at small angles. This tower type offers the lowest costs; special attention should therefore be paid to using this tower type as often as possible. Angle towers have to carry the conductor tensile forces at angle points of the line. The tension insulator sets permanently transfer high forces from the conductors to the supports. Finally, dead-end towers are used at the terminations of a transmission line.
They carry the total conductor tensile forces on the line side even under unbalanced load condition, e. Various loading conditions specied in the respective national and international standards have to be met when designing towers. The climatic conditions, the earthquake requirements and other local environmental factors are the next determining factors for the tower design.
When designing the support, a number of conditions have to be considered. High wind and ice loads cause the maximum forces to act on suspension towers. In ice-prone areas, unbalanced possible and a narrow right-of-way, which can only be met by compromises.
The minimum clearance of the conductors depends on the voltage and the conductor sag. In ice-prone areas, conductors should not be arranged vertically, in order to avoid conductor clashing after ice shedding.
For low-voltage and medium-voltage lines, horizontal conductor congurations prevail; these congurations feature line post insulators as well as suspension insulators. Poles made of wood, concrete or steel are preferred. Earth wires are omitted at this voltage level. For high-voltage and extra-high-voltage power lines, a large variety of congurations are available that depend on the number of circuits AC or poles DC and on local conditions.
Due to the very limited right-of-way, more or less all high- voltage AC lines in Central Europe comprise at least two circuits. Arrangement e is called the Danube conguration and is often adopted. It represents a fair compromise with respect to width of right-of-way, tower height and line costs. For AC lines comprising more than two circuits, there are many possibilities for conguring the supports. In the case of circuits with differing voltages, those circuits with the lower voltage should be arranged in the lowermost position g.
DC lines are mechanically designed according to the normal practice for typical AC lines. The differences from AC Line layout are the: a Fig. Addition- ally, special loading conditions are adopted for the purpose of failure containment, that is, to limit the extent of damage. Finally, provisions have to be made for construction and maintenance.
Depending on voltage level and the acting forces of the over- head line, differing designs and materials are adopted. Poles made of wood, concrete or steel are very often used for low- voltage and medium-voltage lines. Towers with lattice steel design, however, prevail at voltage levels of kV and above g. Guyed lattice steel structures are used in some parts of the world for high-voltage AC and DC lines. Such design requires a relatively at topography and a secure environment where there is no threat from vandalism and theft.
Guyed lattice steel structures offer a substantial amount of cost savings with respect to tower weight and foundation quantities. However, a wider right-of-way has to be considered. Foundations for the supports Overhead power line supports are mounted on concrete foundations.
The foundations have to be designed according to the national or international standard applicable for the particular project. The selection of foundation types and the design is determined by the: p Loads resulting from the tower design p Soil conditions on the site p Accessibility to the line route p Availability of machinery p Constraints of the particular country and the site Concrete blocks or concrete piers are in use for poles that exert bending moments on the foundation.
FACTS devices can significantly increase the power transmission capacity of existing alternating current AC systems and extend maximum AC transmission distances by balancing the variable reactive power demand of the system. Reactive power compen-sation is used to control AC voltage, increase system stability, and reduce power transmission losses.
These are highly standardized compact devices that can easily be implemented in demanding network environments; for example, to allow connection of large offshore wind farms.
AC technology has proven very effective in the generation, transmission and distribution of electrical power. Nevertheless, there are tasks that cannot be performed economically or with technic. If you can't read please download the document. Post on Dec views. Category: Documents 0 download. At the same time, the density and complexity of urban power supply systems are also increasing 7Siemens Energy Sector Power Engineering Guide Edition 7. Information and communica-tion systems within the network will be systematically expanded 8 Siemens Energy Sector Power Engineering Guide Edition 7.
Siemens knows the markets and needs of its customers, and offers innovative and sustainable solutions in all parts of the power matrix Fig. Whereas the generation of power in conventional power supply systems depends on consumption levels, a Smart Grid is also able to control consumption depending on the availability of electrical power in the grid 9Siemens Energy Sector Power Engineering Guide Edition 7. Energy Management 7. Engineering Formulas, 7th Edition.
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