For a long time, because it is relatively simpler to exchange and generate electricity, does not need to commutate, and AC transmission benefits voltage transformation, easy to adopt transmitting electricity in order to reduced and loss under high pressure, AC transmission has been a main way to transmit electricity all the time. But with the development of electric system, transport the increase of capacity and distance, the steady problem and cutting off the short circuit capacity scheduling problem under the trouble to complicate day by day in AC transmission, silicon controlled rectifier, direct-current transmission are automaticallied control,etc. today of new technical development in high-power, the direct-flow technology of transmission of electricity became perhaps and development has been already used widely worldwide quickly.
Direct-current transmission is mostly the direct-current transmission of both ends at present, namely sent the receiveside after the originating modem current conversion, reverse, send into the network of supplying power, there is no branch in the middle, have not formed single-flow electric wire netting.
Direct-current transmission, compared with AC transmission, his advantage is as follows:
1Do not exist and stabilize the problem. Because direct-current transmission does not require both ends that it links to move ahead simultaneously, there is no impedance on the power transmission line, therefore neither stabilize problems, nor there are restrictions on transmission distance and capacity that caused.
2Direct-current transmission not only itself have, stabilize question, can improve the intersection of it and the intersection of both ends and stability of alternating current system. Because for alternating current system, it has had no power that load angle limits that the direct-flow system has increased by one, it can improve static stability and dynamic stability of the alternating current system linked with it.
3D.c.line fabrication cost low, the intersection of step voltage and 65% of alternating current circuit about, the nonferrous metals is little in consumption.
4Transport the capacity to be great. The peak voltage is 21/2 times of the rated value at the time of AC transmission, it is both equal that direct-current transmission is left, the wattless current of AC transmission is limited to active current. Direct current does not have this restriction, so under building expense condition in identical insulation level and circuit, the power which can be transported in direct-current transmission is about 1.5 times of the power of AC transmission of equal voltage.
5System losses are little. There are no wattless current and electricity in direct-current transmission, under transmitting the same power, the electric current of the circuit and loss ratio of the power are low in AC transmission, do not produce the compensatory reactive power of the need either. In addition, there is no electromagnetic field of alternation around the wire, its corona losses is little too.
6When systematic to expand and link with other systems, adopt AC transmission often because of the increase of the systematic short circuit capacity, cause the broken circuit undercapacity of the switch in the original system, need to change the high-capacity switch. Can separate failure current of alternating current system with direct-current transmission, make it entry perfect the system, therefore does not increase the systematic short circuit capacity, can also make the voltage of the alternating current system unlikely to reduce excessively at the same time. At the time of own trouble of the direct-flow system, its electric current is cut off, does not influence the alternating current system either.
7The ones that increased to power and transmission voltage in direct-current transmission had a good adaptability. Because direct-flow construction expenditure low power transmission line and convertor station fabrication cost high, can adopt the circuit once according to planning the construction of goal finally, one adopts and transmits electricity with the system scale and strengthens the number of groups of the multiple-series connection of stepping up in the converter unit, make direct-current volts and the intersection of electric current and increscent the intersection of way and construction progressively, make syste planning obtain the preferably whole result of target planned period.
Study the computer of the electric system and protect the algorithmic purpose and lie in finding out the good algorithm, enable it on the premise of meeting project precision and requirement of speed of response, reduce data acquisition amount and computation time as much as possible, reduce to inputting the machine format particular requirement. As to this, people have already carried on a large amount of research, it is suitable for the protective algorithmic method of the computer to propose a lot of. Introduce and analyze the pluses and minuses with own it to the commonly used exchange sampling algorithm briefly as follows.
The algorithms of 2 sine functional models
The algorithm of the so-called sine functional model supposes the signal voltage, electric current sampled are the sine wave known in frequency, neither contain the aperiodic component, nor contain other harmonic wave, how to calculate the amplitude of the voltage, electric current and method of the phase place from it.
2.1 bipunctate product algorithms
The product algorithm of the bipunctate is separated by 4 / T to sample to the circuit medium voltage and electric current at arbitrary moment, through calculating the mean value, active power and reactive power of obtaining voltage and electric current. As to alternating current of mains frequency, the data window of the product method of the bipunctate is T/4 =5ms, its advantage is to calculate simply fast, are overcome a bit and sampled the law and demanded to input the three-phase current of the symmetry and shortcoming of the voltage, but it does not have filter action too, and suffer a tremendous influence from DC component. The product method of the bipunctate demands to equal T/4 to the time to sample accurately, otherwise the error will emerge.
The formula asking impedance R, X according to electric current I and voltage U is:
His length of data window is 1/4 cycles in the product algorithm of the bipunctate, it is 5ms as to 50Hz mains frequency. In fact, simple harmonic quantity the intersection of bipunctate and adjacent sampled value any can calculate mean value and phase angle, can make bipunctate product algorithm the required data window is a very much short sampling interval only.
Algorithm of total mark of 2.2 half cycle
The algorithmic principle of the total mark of half cycle is a simple harmonic quantity the total mark of absolute value is a constant within arbitrary half a cycle. The required length of data window of integration method of half cycle is 10ms, algorithm has certain filter capacity. The plus-minus half cycle of the high frequency commponent of even-order totally repeals by implication in the total mark of the half cycle of mains frequency, although odd harmonic fails to totally compensate, its influence is much smaller, it can’t inhibit the DC component, so can mix the simple differential filter separately or weaken the influence of aperiodic component in the electric current with impedance converter if necessary. As to accuracy requirement not high protection of operation, can improve the action speed of the protective device in case of major failure while using this algorithm.
2.3 derivative algorithms
The derivative algorithm is named the differentiation too. The algorithm need, know, input simple harmonic quantity in a certain the intersection of moment and sampled value and derivative of moment this of t1 only, can calculate its mean value and initial phase. Take electric current as examples, set i1 as t1 electric current actual value at moment, the expression is:
The derivative of electric current is this moment:
The above show, so long as know the electric current in sampled value and derivative at a certain moment, can find mean value and initial phase of the electric current. The same can utilize the aboving principle to find mean value and initial phase of the voltage too. This algorithm is actually a derivative which has utilized sine and its has 90
The circuit breaker is applied to the low-voltage distribution system extensively, it is a kind of protection electrical apparatus element. While designing the low-voltage distribution system, should pay attention to the selectivity of the circuit breaker, choosing to the excessive load release rated current of the circuit breaker and setting, guarantee to fully give play to the role of electric current release; When the ambient temperature is greater than or smaller than the base measuring temperature value, should adjust the specified current value of the low-voltage circuit breaker according to temperature and current carrying capacity correction factor that manufacturers offer.
First, several kinds of current characteristics of the circuit breaker
The rated current In of the circuit breaker, refer to the electric current that the release can be passed for a long time, rated current of the only release.
The rated current Inm of the housing-frame grade of the circuit breaker, show with the maximum release rated current installed in the same chassis or cabinet similar to structure of basic geometric dimensions. Specified current value of maximum of release which it has determined to install. For example, DW15
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In order to realize the strategic objective that 5% of the electricity comes from the solar energy by 2030, the government of Dubai, to the small-scale solar energy apparatus, especially the concern of the solar energy of the roof is strengthened day by day.
” In the near future, we will surf the Net for solar energy and generate electricity to create better legal environment. ” Person in charge Ivano Iannelli of remarkable centre carbon of wholly-owned Dubai of advisory company of the government shows, ” In the following 1 years, we will see solar energy infrastructure increase constantly, not merely have the large-scale independent facilities like water pump of solar energy, have in the villa, park and small-scale facility of construction in the community of house ” .
Have insider show the intersection of roof and become the pillar type energy technology of the United Arab Emirates solar energy. Solar energy panel installed on house, office building and factory roof, not only offer the electricity for work of daily life, can also create the electricity of surplus to incorporate into electric wire netting.
Employ the country of small-scale solar electrical energy generation earlier in those, the rate for incorporation into the power network that suppliers have already obtained the government is replenished, make the expensive solar energy panel lucrative. Dubai considers introducing this preferential policy too.
Hydroelectric board of Dubai DEWA Have already set about advancing the solar energy Net surfing plan. DEWA general manager and concurrently chief executive officer Syed
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In order to improve electric supportability, and brownout strengthens environmental protection, Thailand will work along both lines in improving the generating capacity and popularizing LED electricity-saving lamp, in order to seek practical results.
The national power office chief’s plain tower of Thailand shows, in country’s energy supply development plan, 70% of the electricity consumption comes from natural gas power. It is passive that it causes the country to supply power that more exhaustedly in order to avoid natural gas resources, need to increase the proportion that the coal generates electricity. For this reason, the national power office has already made the power plant and development plan of 5 years of power supply system from 2013 to 2017, master budget is ancient unit of weight, equal to 1/24 liang 300 billion, among them 60% make the investment for the power plant, other 40% make the investment for the power supply system. Among them 4 heat power plants amount to 7 aircrews and 2 aircrews of a hydroelectric power plant after the transformation is extended, will reduce the coal consumption and cost and increase electric energy production greatly.
Meanwhile, the Thai power office, through determining, will expand the experimental range of LED electricity-saving lamp in China this year and next year after trial and error method, strive for and popularize and use LED electricity-saving lamp in China in unison as soon as possible.
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According to May 20 of Japanese Kyodo News Service, the economic industry province of Japan holds the energy fact-finding meeting meeting of comprehensive resource on the 20th, announce that estimates the result claims, the whole world will increase 90-370 nuclear power stations by 2030. The ones that bring the energy demand in global economic growth are expanded as the major cause why the nuclear power increases, carrying on this estimated purpose and offering basis for promoting the nuclear power exit of Japan.
About 400 nuclear power stations operated at present in the whole world. International Atomic Energy Agency IAEA Have predicted the installed capacity of nuclear power station will be increased by 25-100% as compared to at present, the multiparity province is according to this result, infer the power of each nuclear power station on average for 1 million kilowatts and convert. Estimate the result thinks, emerging nations such as China, Russia, India of Israel,etc. newly build the nuclear power station for the chief commander.
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According to the 20th of news agency of Algeria, A has excellent energy and mining’s minister plain good fortune
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[According to May 15, 2013 of Smartplanet website ] a series of members of congress in Japan appeal for resuming running in the nuclear power station, in order to help Japan to overcome and import financial difficulties that the fossil fuel initiates.
Japanese Kyodo News Service reports, ” Several dozen members of congress of Liberal Democratic Party initiate the appeal of restarting the nuclear reactor closed of this country on Tuesday, claim the stable electricity supply is the key to realizing economic growth. ” It is led that this group is rich from a former chief cabinet secretary’s thin field, he warns recently, if does not resume running in the nuclear power station, Japan’s economy will stagnate.
Since the accident of Fukushima nuclear power station happened two years agoing, 48 of 50 nuclear reactors of Japan have still kept the inactive state. The nuclear power accounts for about 30% of the Japanese China Power. Because Japan cost a huge sum of money, increased the discharge amount of the harmful gas carbon dioxide importing fossil fuel such as the liquefied natural gas at the same time.
The advisory group of a government showed a few days ago, can save 20 billion dollars for the country while restarting some nuclear power stations. Japanese prime minister Shinzo Abe took up an official post since last December, has been promoting and resuming the nuclear power. Information institute of kernel Zhang JiaQi
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Recently, a report that the electric undertaking federation of Japan releases reveals, April, 10 utilities in Japan sell the electric quantity to reduce by 6% compared with the same period of last year, has already reduced compared with the same period of last year for 4 months in succession. This is mainly because Japanese enterprises produce the activity depressingly, the large electricity consumption demand is reduced. Analyze, therefore Shinzo Abe’s regime was implemented ” Abe’s mixed economic policy ” Have not appeared yet for benefit that Japanese enterprises bring.
According to news, ” the Sankei Shimbun ” of Japan, May 21, Japan electric the intersection of undertaking and federation deliver the electric demand to report the actual achievement report to in April. The report reveals, in April, 10 utilities in Japan total and sell the electric quantity to reduce by 6% over the same month last year, it is 66,131 million ten million o’clock. 10 utilities have sold the electric quantity and has already been lower than last year for 4 months in succession. This is mainly because Japanese enterprises produce the activity depressingly, large electric sales volume is reduced. Moreover, raise because of the temperature, it is to influence the factor of selling the electric quantity and dropping that the increase in demands of family heating stagnates.
The industry sold the electric quantity to reduce by 4% compared with the same period of last year last year with the large electricity, it was 21,257 million kilowatt-hour. Already negative growth has appeared for 11 months in succession in this data. Face selling electric quantity and is all lower than last year of 7 main trades such as the machinery and steel. As to this, the electric undertaking federation claims: ” Enterprises produce and stagnate ” Cause selling the electric quantity and reduce the reason. It is obvious, Shinzo Abe’s regime was implemented ” Abe’s mixed economic policy ” Have not appeared yet for benefit that Japanese enterprises bring. Face the Japanese family ” The electric light ” Sell by electric quantity last year last 8.6%,22,185 million kilowatts.
Every utility reveals, the utility of middle part sells the electric quantity to reduce by 8.5% compared with the same period of last year last year, it is at the largest range to reduce. Tokyo utility sells the electric quantity to reduce by 5.2% compared with the same period of last year last year; Kansai Electric Power reduced by 7.8% compared with the same period of last year last year.
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The summit of European Union held on the 22nd determines to further strengthen the technology research and development of new energy, help to realize European Union requiredly ” But one that bear and very persistent energy ” ,In order to promote the economic growth, increase employment and improve the whole competitiveness of European Union.
The meeting proposes, the direction of strengthening technology research and development of new energy includes improving efficiency, low cost develop regenerated energy, strengthen the intersection of information technology and should use, develop intellectual energy, wait for furthering in the field of energy.
Fan LongPei, president of European Council, emphasizes at the news briefing of the summit, a energy revolution is rising in the whole world, European Union will continue investing in the technology research and development of new energy, modern infrastructure and input of new energy technology research and development field in the energy of European Union will not be lower than 1,000 billion euro 2020 years ago.
In addition, this summit also determines to set up Europe and unify the energy market, further promote the structural pluralism of energy.