Distribution system, not only circuit breakers , there are many other electrical appliances, the need to consider the circuit breaker and the upper and lower protection of electrical characteristics with the best protection of the electrical characteristics of each painted on the coordinates to compare their characteristics with the situation The cooperation must consider the following conditions. 1, the long delay characteristics of circuit breakers below the protected object (such as wires, cables, motors, transformers, etc.) promised to overload characteristics. 2, low-voltage side of the main switch short delay release and high-side over-current protection circuit breaker with the level difference of 0.4 ~ 0.7s, depending on the type of high-voltage side of the protection relay may be. 3, the low-voltage side of the main switch overcurrent release protection characteristics lower than the high-pressure fuse along the melting characteristics. 4, the higher circuit breaker short delay setting current ≥ 1.2 times the lower circuit breaker short delay or instantaneous (if no short delay) to set the current. 5, the superior circuit breaker protection features and lower circuit breaker protection features can not cross in the cascade protection mode, you can cross, but the intersection of short-circuit current should be under the circuit breaker with 80%. 6, Circuit breakers and fuses , the general fuse as a backup protection. Should choose the transfer current is less than the circuit breaker short-circuit off capacity of 80%, when the short-circuit current is less than the fuse should be action. 7, in the case of short-time and instantaneous action, the upper circuit breaker instantaneous setting current ≤ lower circuit breaker delay off capacity, and ≥ 1.1 times the lower circuit breaker short circuit current. On January 14, China's Ministry of Communications issued a circular calling for all new heavy-duty trucks and semi-trailer tractors to enter the transportation market and should install Beidou / GPS dual-mode vehicle-mounted terminals. However, according to insiders, the current civil Compass car navigator in the test phase, cost and accuracy are not imagined high, as GPS. From December 28 last year, Beidou satellite navigation system officially provides trial service, which means that Beidou satellite navigation from the military began to shift to the civilian market. The Beidou satellite navigation system is a self-developed global satellite positioning and communication system (BDS) developed by China. It is the third mature satellite navigation system after the United States Global Positioning System (GPS) and Russia GLONASS. From December 28 last year, Beidou satellite navigation system officially provides trial service, which means that Beidou satellite navigation from the military began to shift to the civilian market. At present, 95% of civil navigation market have been occupied by GPS. In 2009, the annual output value of China's satellite navigation industry is 40 billion yuan, with an annual output value of 50 billion yuan in 2010, but Compass products account for only 5% of the total market share. Big Dipper is China's Beidou navigation system, one of the many support systems for the Beidou satellite construction system to provide civil and aerospace operations and construction services. Other companies are also doing, but not as good as the Dipper Star. Star Alliance public relations charge surnamed introduced, Big Dipper Star has its own car navigation electronic business section, there are operating vehicle networking. There are currently three production bases in Jiangsu and Shenzhen in Chongqing. In all the navigation business, the more prominent is the chip research, is the first chip compatible with major systems. Zhou Ru Xin, chairman of Beidou Starlink, said in an interview that at present, Beidou's revenue has accounted for more than 50% of the entire company's revenue. He also revealed that in 2011, Big Dipper Star until the third quarter to maintain revenue growth of more than 50%. Zhou Ruxin also said that it should actively develop the domestic market, with Bei Dou to occupy more of the domestic market share, even if the GPS can not be fully squeezed out, at least in China have a larger share. IBTimes Chinese network understanding, car satellite positioning system is the most important component of the chip. A Shanghai-based GPS positioning system company Shanghai Xuan Hui communications insiders told IBTimes Chinese network, they are still testing Beidou car navigation, there is no official push. Because compared with GPS, Beidou Navigator, one is not cost-effective, the second is the accuracy is not good. Compared with GPS, Beidou is currently expensive, so if you want to expand the civilian sector, the state must give appropriate support. China may be able to subsidize Beidou purchases or formulate appropriate navigation standards to increase Beidou's market share.