Research On Fast Electrical Distribution Feeder Protection Principle And Its Communication Technology

The electrical distribution network is becoming to a mesh configuration with multiple switches.In theory,the electrical distribution network may operate in a more ecumenical and higher quality state via the switches' on or off.Yet,various operation modes deteriorate the performance of traditional distribution relaying.In another word,traditional distribution relaying limits primary operation too strictly. There are no rigid match grades between these distributed switches,so it is impossible to attain whole selectivity by simply current coordination.Hence when fault occurs,traditional relaying can only isolates it with great loss of healthful power supply zones.The finite selectivity between one or two switches make the average tripping time becomes longer.Consequently the distribution power supply reliability and quality cannot be assured.Thus it is so important to research in new type fast distributional relaying and to its realization.This new type fast distributional relaying can reduce the hard strict to primary operation and can get the whole selectivity and speedability for all switches to enhance power supply reliability and quality.The fault location methods serving to DA(Distribution Automation)have high selectivity and sensitivity,but their central processing mode and complex algorithms cannot meet the strictly real-time acquirement of relay protection.In this paper,the topology of one feeder is saved in the relay units of the switches along it,so the fault location can process distributed.This paper gives a new fault location algorithm which is named as Backtrack Location Method.This method can apply to feeders' fast relay protection as it has low computational complexity.As a utilization,this paper proposes a schedule to realize fast relaying via fiber communication networks which have already exited in some of China's big cities.This schedule need not change any existing hardware.Simulation shows that its delaying time is short enough to meet the fast relaying need.Because the distribution equipments have a large amount and the power supply capacity is enlarged quickly,the foremost determining factor for the realization of relaying schedule is low cost.But this often goes with lower hardware reliability and computing speed of relay units and communication system. To ensure the reliability and speedability,the new type feeder protection must have high fault tolerance and low computational complexity.Based on the information theory,this paper brings forward a new fault location algorithm based on multi-switch information fusion.This algorithm has a high fault tolerance,and it can assure the real-time demand of relaying protection,too.It depends on information communication to get the relaying states to realize fast feeder protection.Communication via wire media,such as fiber or electric wire cartier,is in defect of such high economical or flexible character.On the contrary,it is the advantage of wireless medium.Consequently,this paper tries to apply modem WMAN(wireless metropolitan area network)to carry out distribution relaying communication.CDMA technique is the core technique of Public Wireless Mobile Communication;it is one of the most popular WMAN techniques.This paper puts forward a CDMA communication and feeder protection schedule which can coexist with Public Wireless Mobile CDMA system.With this schedule the interference to public wireless mobile system can be neglected but the communication quality is very high.At the same time,Simulation shows that the speedability is high enough even in situation of multiple feeders' faults occurs synchronously.Based on wireless WMAN communication such as CDMA,this paper puts forwards the constitution of fast feeder protection,which includes fast feeder main protection,fast feeder backup protection and reclosing and the traditional delaying current protection as overall backup.With a reality distribution network,this paper gives the calculating procedure and makes an evaluation to its performance.To enhance the independence,it is necessary to establish specialty electric communication WMAN.The protection communication based on it can achieve average economical efficiency,too.This paper proposes a specialty electric WMAN structure based on WiMAX and brings forward a WiMAX communication schedule which serves to fast feeder relaying protection.Mainly from the point of communication protocol,this paper proposes the communication rule which meets the real-time need for fast feeder protection.This WiMAX communication schedule fits to international standard,thus it will not be washed out with the development of WiMAX.In addition,this schedule uses very little wireless resource,so other electric communication services can realize at the same time. The speedability can meet the command of relaying protection,as is proved by a following simulation.To sum up,this paper presents a new type feeder protection,gives its principle and its communication methods.This protection frees the limits to primary system operation modes and makes it possible to realize high quality and economical operation in distribution system.In addition,it minimizes the influence of fault so that it can greatly enhance power supply reliability and quality. Consequently,it will bring remarkable economic and social benefit.