The Research Of Bus Arc Protection Based On IEC60870-5-103 Protocol

With the accretion of the power network capacity,medium and low voltage switchgear occurs arc short-circuit fault caused by its multi-outlet and frequent operation have led to loss of switchgear equipment or even threated the safety of the staff.At present,there are two ways to protect the switchgear equipment.One of the methods is to use transformer overcurrent protection,circulation principle of high impedance bus protection and other programs.These methods have many disadvantages such as long resection time and harsh demands of the CT installation location.The other method is to use the structure of the switchgear to improve the switchboard arc resistance.This method will greatly increase the costs.Arc protection has become the ideal,mature medium and low voltage bus protection program at the present stage because of low cost,high accuracy,rapid action and other characteristics.Nowadays,most of the existing bus arc protection methods are based on centralized protection program.This method has many defects such as risk concentration,poor reliability,and weak identification of the fault on the outlet side.In order to overcome the shortcomings of centralized bus arc protection,a decentralized bus arc protection scheme is proposed.The scheme is based on the basic principle of arc protection for current and arc double criteria.Using a distributed network topology,decentralized arc protection devices are independent.A set of distributed arc protection device is installed every switchgear,collecting the field arc signal and current signals and jumps into the line switch and outlet switch according to the position where the arc fault occurs.The scheme can not only solve the problem of the low reliability of centralized bus protection,but also can make up for the shortcomings of the long fault removal time of the switchgear on the outlet side depending on the current three-stage protection.According to the basic working principle of decentralized arc protection scheme,a decentralized bus arc protection device is designed by using dual CPU modular method.The device can be divided into the main CPU system part and the man-machine part.The main CPU system part adopts the 32-bit high-speed floating-point DSP chip as the micro-processer and is responsible for collecting and processing current signals and arc signals.The man-machine part applies the ARM chip as a microcontroller for monitoring and controlling the condition of the DSP operation.Due to the linear nature of the existing photo sensor,it is not possible to distinguish between the arcs belonging to the strong light field and the maintenance lights?fluorescent lamps belonging to the low light category,This paper designs a nonlinear arc sensor that responds only to the strong light;The main CPU system part of the communication side is divided into two parts,internal communication with the man-machine part,external communication with integrated automation system communication;Taking into account the substation integrated automation system mostly use IEC60870-5-103(hereinafter referred to as IEC103)protocol to communicate with relay protection equipment,in order to the decentralized arc protection device access to the substation conveniently,the device used standard IEC103 protocol Communication process in external communications.In view of the IEC103 protocol standard communication process complexity,and the man-machine part of the communication requirements are relatively simple,internal communication using a simplified IEC103 protocol communication process;The field testing has proved that decentralized arc protection device can quickly and accurately remove the arc short-circuit fault and protect the medium and low voltage switchgear from arc short-circuit fault damage.