电力系统指由发电、输电、变电、配电和用电等环节组成的电能生产与消费系统，其功能是将自然界的一次能源如煤炭、石油、天然气、风能、太阳能、地热能、水能、潮汐能、核能、生物质能等通过发电装置转化为电能，经过输电、变电及配电后供应到各负荷中心——用户，再通过各种设备将电能转化为动力、热、光等不同形式的能源。电力是经济发展的先行部门，从1910年到2010年的100年中，美国电力装机、用电量、电网规模一直位居世界第一。随着经济的发展，我国的电力规模也在快速增长，据中国电力企业联合会数据，截止2013年底，我国电力工业规模全面超过美国：12.4亿kW左右的发电装机，110万km的110kV及以上输电线路，5.245万亿kWh的年用电量，9家电力企业进入世界500强，构成了世界最大的电力工业体量。
The power system consists of power generation, transmission, substation, distribution and electricity sectors such as the composition of electricity production and consumption system, its function is the nature of this energy such as coal, petroleum, natural gas, wind energy, solar energy, geothermal energy, hydropower, tidal energy, nuclear energy, biomass power generation device into the after electricity, transmission, substation and distribution after the supply to the load center of the user, and then convert electrical energy to power, heat, light and other forms of energy through a variety of devices. Electricity is the first Department of economic development. From 1910 to 2010, power installed, electricity consumption and power grid have been the first in the world in the 100 years. With the development of economy, the scale of electric power in our country is also growing rapidly, according to the China Electricity Council data, by the end of 2013, the scale of China's electric power industry: comprehensive than the United States about 1 billion 240 million kW installed, 1 million 100 thousand km 110kV and above transmission lines, electricity consumption of 5 trillion and 245 billion kWh years, 9 electric power enterprises to enter the world top 500, constitute the world's largest volume of power industry.
液体传动的基础是帕斯卡原理。狭义的液压传动技术指以矿物油作为工作介质，利用液压泵将原动机的机械能转换为液体的压力能，经过各种控制阀和管路来传递与控制液体压力能，借助缸或马达等液压执行元件转换为机械能来驱动工作机构，实现直线往复运动或回转运动。具有功率大、速度低、平稳等优点，在工业生产特别是在机械驱动中被广泛应用。但矿物型液压油存在容易泄漏导致环境污染的问题，同时，矿物油在一定环境下会燃烧。
The foundation of the liquid transmission is the Pascal principle. Hydraulic transmission technology in narrow sense refers to the mineral oil as a working medium, the motive of the mechanical energy into fluid pressure energy use through a variety of hydraulic pump, control valve and the pipeline to transfer and control of fluid pressure, the cylinder or motor and other hydraulic actuators is converted to mechanical energy to drive the working mechanism, realize the linear reciprocating motion or rotary motion. It has many advantages, such as high power, low speed, smooth and so on. It is widely used in industrial production, especially in mechanical drive. However, there is a problem of environmental pollution caused by the leakage of mineral hydraulic oil easily. At the same time, the mineral oil will burn in a certain environment.