基于低、中阻抗的母线差动保护原理与计算

Principles and Calculation of Bus Differential Protection Based on Low and Medium Im⁃pedance

随着海上油气平台电网规模的逐渐扩容,平台电力系统安全、稳定运行亟需关注。母线作为电能集输的关键元件,一旦发生线路故障,挂接在该母线下的所有支路将全部失电,若故障发生在电站中心平台,则周边依托该中心平台供电的井口平台将大面积停电,直接影响到平台的正常生产运营。因此,必须采取相应的措施消除或减少母线故障所造成的后果。以海上某中心平台为例,采用差动保护对系统母线进行保护,以低阻抗母差保护和中阻抗母差保护为重点,基于母差保护的基本原则及工作原理,根据母差保护区内外故障判别,整定计算,饱和、不饱和制动原则,采用相位比较方法来辨识区内故障,比例制动及电流互感器饱和识别技术可实现母线差动保护区外故障不动的要求。

With the gradual expansion of the power grid scale of the offshore oil and gas platform,the safe and stable operation of the power system needs urgent attention.Bus is a key component of power gathering and transmission.Once there is a fault,all branches connected to the bus will lose power.If the fault occurs in the center platform power station,the wellhead platform which requires power supply from the central platform will cause power outage in a large area.Besides,this will directly affect the normal production and operation of the platform.Therefore,corresponding measures must be taken to eliminate or reduce the consequences caused by bus failures.Taking a central offshore platform as an example,differential protection is used to protect the bus of the system,focusing on low impedance and medium impedance bus differential protection,based on the basic principles and working principles of bus differential protection,according to the principles of fault identification inside and outside the bus differential protection zone,setting calculation,saturation and unsaturated braking,the phase comparison method is used to identify the faults inside the bus differential protection zone.The proportional braking and current transformer saturation identification technology can achieve the requirements of preventing misoperation when the fault occurs outside the bus differential protection zone.