HVAC-HVDC-HVAC Transmission Link - Report Example

Electrical Technical Reports Name Institution Date Course Title: ‘HVAC-HVDC -HVAC Transmission Link’ Abstract This report evaluates a HVAC-HVDC-HVAC transmission system in the context of the technologies used within a specified HVDC system. Introduction It is believed that direct current (DC) was the first commercial electricity to be generated; so was the first electric transmission system. However, HVAC was later preferred since the low power DC could not be transmitted to far destinations and this could be easily solved by HVAC’s ease of transformation from one voltage level to another. HVDC transmission was later used after the development of high voltage valves. The HVDC system is basically achieved through the conversion of current from AC to DC by rectification at the transmitting end, and then its reconversion from DC to AC by inversion at the receiver end. These conversions are achieved through the use of natural commutated converters, capacitor commutated converters (CCC) and forced commutated converters. In the modern world’s electric industry, given the liberalisation as well as the increased pressures to ensure environmental conservation, HVDC systems have become increasingly desired due to their increased transmission capacity, the low losses when transmitting over long distances, the possibility of underground or under the sea transmission, better control of power flow, as well as power stability, quality and the asynchronous interconnections that can be carried out. HVDC Transmission System Brazil – Argentina Review of the HVDC link The Argentina-Brazil HVDC system that is a privately owned installation demonstrated the benefits of the modular back-to-back interconnection concept as applied in transmission between countries operating at different frequencies (Argentina at 50Hz and Brazil at 60 Hz). It consisted of 490 KM overhead line with a substation in northern Argentina and another in southern Brazil and a HVDC converter station at Garabi near the Brazilian border. The asynchronous interconnection was achieved through the use of HVDC frequency converters erected in a back-to-back configuration. A capacitor commutated converter (CCC) type high voltage converter was used instead of constructing a synchronous compensator at Garabi. All the 1,100 MW phases were divided into 2 blocks each rated at 550MW (ABB, 2017; Graham, Jonsson & Moni, 2014). The CCC design was combined with ConTune technology in the converter to enable the secured and efficient operation of the system during low short circuit levels. The combination also ensures improvement in the power control as well as the provision of even and continuous control of voltage and power flow. By adopting this converter station’s modular design construction concept, the civil design was greatly simplified and an environmentally friendly solution was realized within the shortest period of time (ABB, 2017). The transmission system enabled the two nations utilize electricity resources in an efficient and cost effective manner with a reliable system that allows for secondary energy trades. Technical Schematic Diagram Brazil – Argentina HVAC-HVDC-HVAC Link The diagram is shown below: Fig: Technical Schematic Diagram Technical Function explain the function of each the major component parts of the schematic produced along with information on matters relating to ratings of component parts. PLC filter This component is installed for the elimination of disturbances in the line in the 30-500 KHZ range. On the 50HZ side they were rated at 9Mvar while on the 60HZ side the filters were rated at 22Mvar. Line reactor Line rector on the 50 HZ side of the installation has a rating of 92.5 MVar. It is used to keep the voltage down when the load is low. The line reactor installed on the 60HZ side was rated at 250 Mvar. HPL compact module It is made up of an HPL breaker, two disconnectors and one digital optical current transducer housed within a single unit. In the AC substation, there were installed 5 HPL compact modules in a ring bus arrangement on either side of the converter AC filter These units were employed to eliminate the harmonics generated by the converter and at the same time to ensure compensation of the reactive power consumed by the converter. Four filter banks were used at the converter station, two on each side of the converter. Each filter is composed of four branches which are tuned to a unique harmonic: one branch tuned to the 13th harmonics, a high pass filter tuned to the 24th harmonics, other branch tuned to the 11th harmonics with the last branch being a high pass filter that was tuned for the 36th harmonics. The 11th and 13th harmonics filters include the conTune reactor which is able to have a continuous adjustment of its inductance to the filter tunes when, for instance, the frequency changes. The filter installation includes a spare phase that can be switched to accommodate any of the phases when there is need. Converter transformer This converter transformer used was of single phase 3-winding design, rated at 192 MVA Thyrister valve Thyrister valves were designed into enclosures that converted the AC power into DC. A single unit is composed of four such thyrister enclosures. These enclosures are a valve function made up of 36 thyristers assembled in a series arrangement. Commutation capacitors The feature that made this installation unique was the series capacitor that was connected between the converter transformer and the converter valves. This unit was responsible for the compensation of the reactive power absorbed by the converter becoming very useful when the installation is connected with weak AC networks. This, together with the converter makes up the Capacitor Compensated Converter. On the 50HZ side, the capacitors installed were rated at 32MVar, while on the 60HZ side the installed capacitors were rated at 54MVar (ABB, 2012). Each block is dimensioned to 550MW, the voltage on the DC side + 70 KV, with a current rating of 4000A. Smoothing reactor Two smoothing reactors were installed per pole, each of them dimensioned to 50mH The complete installation’s main information was: Power rating – 2,200 MW No. of circuits – 4 Type of link: Back-to-back station with CCC DC voltage - +70KV AC voltage: 500 kV on both sides Main reason for using HVDC: to achieve a synchronous link between a 60Hz and a 50HZ system. Summary and Conclusion This project was one of the first of its kind and has become a major learning point for future designs. It was designed to provide the link between two grid systems operating at different system. The design was useful in achieving great environmental efficiency as well as the completion of the project within a short deadline. The designed used a back-to-back HVDC system to interconnect the two asynchronous AC systems and achieve bulk energy transfer between the countries and also achieve stable system performance. In the HVDC back-to-back system, there is no installation of overhead conductors between the rectifier and inverter and this has enabled to system to carry very high current at low voltage increasing the capacity of the installation. With the CCC design, the installation has guaranteed satisfactory system performance at low short circuit levels as well as a reduction of the effect of reactive power variations. Title: ‘Energy Map of the UK 2030’ Abstract This report briefly evaluates the following UK energy electrical energy generation resources: Fossil Fuel, Hydro, Nuclear, Wind and Solar PV in the context of their technology how electrical l energy is produced, and their likely contribution of each fuel source to the 2030 energy map of the UK Introduction The UK has embraced several technologies in the generation of electrical energy from the use of fossil fuels to other renewable sources of power. During the 1960s and the 1970s, UK’s electrical energy capacity was hugely by use of coal with a number of generation stations being developed with capacities between just below 1, 000 MW to stations producing about 4, 000 MW. After to 1970s, there has been little growth of coal stations installed capacities as focus shifted to other emerging technologies. This paper aims at studying these previous energy technologies, current technologies as well as how the future will look like. As will be seen in the discussion below, the UK has been keen on embracing renewable energy technologies as it seeks to meet the EU targets on renewable energy sources. The biggest motivation has been the global concern about the emission of carbon and carbon compounds into the atmosphere which has resulted to significant global warming. As highlighted in the discussion below, the UK has made significant steps toward the realization of its plan to have renewable technologies as the major energy sources for electric power. Energy Sources Fossil Fuel Fossil fuels are basically the remains of organism that lived on earth 100 million to 400 million years ago that have undergone transformation under immense heat and pressure to form oil, gas and coal. To produce electricity, these fuels are burn and the steam produced after evaporation of water is used to drive steam turbine generators. Although the UK still has about 20 GW of coal capacity, now new coal plant has been build since 1986 (Carbon brief, 2015). Following the closure of major coal stations up to last year, coal generated power fell to only 6% of total energy generated in spring last year while gas generated 45%. Given its efficiency and the comparatively low carbon emission, gas continues to replace traditional coal power generation. By 2030, UK plans to have done away with coal as source of electricity Fig: Electric generation from coal and gas in the UK, 2013-2016 (source: The guardian, 2016). Hydro power This one of the common renewable sources of energy since it does not use up any natural resources nor does it emit any pollutants. This power is obtained from flowing water in rivers or winter and spring runoff from raised areas/mountains. The kinetic energy of the water is used to turn a turbine that is coupled to a generator to produce power. Hydro power stations have only contributed a small percentage of the UK power demands with many stations limited to Scotland and Wales since these regions experience considerably higher rainfalls, have mountains and are sparsely populated (Carbon brief, 2016). Hydro power station required huge areas of land and are associated with great environmental disturbances. With a capacity of 1.3GW in 2007, this capacity has not significantly increased. It is expected, however, that together with wave, solar, geothermal and wave, the renewable sources will contribute about 19% of UK’s power by 2030. Nuclear power Nuclear energy is that which is contained within the nucleus of atoms. At the nucleus of each atom, there are neutrons and protons that are held together by the nuclear energy. This energy is harnessed through splitting the atom’s nucleus and combination of smaller nuclear through processes called nuclear fusion and nuclear fission. The released energy is used to superheat water to produce steam which is used to drive turbine generators. In the effort to have a balanced mix of generation technologies, the UK has projected that about 14GW of new nuclear generating stations will have been built by 2035. The challenge of nuclear development is the huge upfront costs and the fact that these stations take long to complete. The last nuclear plant to be constructed was completed in 1995 (The department of Energy & Climate Change, 2016) Wind power Wind energy technologies utilize the kinetic energy of the wind to generate power. Wind energy comes from the sun’s uneven heat on the atmosphere, the irregular surface of the earth and the revolution of the earth around the sun. Many of these technologies are used are employed as standalone applications. For big installations, several turbines are erected in a wind farm where they are driven by wind to produce huge amount of electrical energy. The UK is keen to further develop onshore and offshore wind technologies by ensuring that developers can access timely and low cost access to the network. By 2015 UK had installed capacity of 3.7 GW of offshore wind power with projections indicating that offshore wind energy capacity could be equivalent to 35% of total installed power capacity of the UK by 2030. This is in an effort to totally eradicate the use of fossil fuels (Dong energy, 2015). Combined onshore and offshore sources could represent over 55% of UK electric power. Solar PV This energy sources converts energy from the sunlight into electric power either through the direct use of photovoltaics or indirectly by the use of concentrated solar power where lenses and/or mirrors are and tracking technologies are used to concentrate a huge area of sunlight into a smaller beam. The photvoltaics panels carry out the conversion of the sun’s rays into electric power through the excitation of electrons within silicon cells using the sunlight’s energy. The excited electrons are harnessed as electricity. The UK is keen to harness the potential of solar power as it seeks to see reduced power costs and enhancement of renewable sources. The National grid estimates that by 2020, the UK will have an installed solar capacity of 18GW, against an earlier prediction of 20GW, if policy support was diverted to it. By 2030, predictions by the consumer power scenarios indicate that the capacity could have reached 29GW (Stoker, 2015). Summary and Conclusion The UK has been keen on the revolution of its electricity general sources by reducing the initial reliance of fossil fuels in form of coal and gas. Over the past few years, gas sources have predominantly replaced coal generation as the UK strives to reduce carbon emission. More recently, the UK has passed laws and put in place policies to ensure the development of renewable energy sources and a total eradication of fossil fuels by 2030. Of the various renewable energies, the use of onshore and offshore wind resources has taken centre stage with projections indicating that up to 55% of UK’s generation sources will be onshore and offshore wind. Other sources like nuclear, hydro and solar are also expected to play a significant role. Given the ease of installations and the new technologies being developed, solar energy is expected to grow very fast as compared to nuclear energy that required huge cost and employs more complex technologies. Below is a summary of the trends: Fig: comparison of energy mix 2010 & 2030 (source: FOE, 2012) List of References ABB, 2017, Brazil-Argentina HVDC Interconnection, retrieved on 14th March 2017 from < http://new.abb.com/systems/hvdc/references/brazil-argentina-hvdc-interconnection> ABB, 2012, Brazil-Argentina HVDC Interconnection, [Online video], 3, October 2012, retrieved on 14th March 2017 from Graham, J, Jonsson, B & Moni, RS, 2014, The Garabi 2000MW interconnection back-to-back HVDC to connect weak ac systems, retrieved on 14th March 2015 from < https://library.e.abb.com/public/0d50a8fce76db2c9c1256fda003b4d43/THE%20GARABI%202000%20MW%20INTERCONNECTION.pdf> The department of Energy & Climate Change, 2016, Nuclear power in the UK, retrieved on 14th March 2017 from < https://www.nao.org.uk/wp-content/uploads/2016/07/Nuclear-power-in-the-UK.pdf > Carbon brief, 2015, Mapped: How the UK generates its electricity, retrieved on 14th March 2017 from < https://www.carbonbrief.org/mapped-how-the-uk-generates-its-electricity> The guardian, 2016, Coal electricity generation falls to record UK low this spring, retrieved on 14th March from < https://www.theguardian.com/environment/2016/sep/29/coal-electricity-generation-falls-to-record-uk-low-this-spring> Dong energy, 2015, Offshore wind could supply 35% of UK electricity by 2030, retrieved on 14th March 2017 from < http://www.dongenergy.co.uk/news/press-releases/articles/offshore-wind-on-track-with-cost-reductions-and-ready-to-supply-35-per-cent-of-uk-electricity-demand-by-2030> Stoker, L, 2015, Solar capacity could reach 18 GW by 202, estimates National Grid, retrieved on on 14th March 2017 from < http://www.solarpowerportal.co.uk/news/solar_capacity_could_reach_18gw_by_2020_estimates_national_grid_1404> FOE, 2012, Summary: A Plan for Clean British Energy, retrieved on 14th March from Read More