Research And Realization On All-in-one Device In 110kv And Below Degree Smart Substation

As the core of construction and development of smart power grid,the smart substation has the integration as one of its development trends.The goal of integrated smart substation is to simplify the equipment in the station and to reduce the subsequent operation &maintenance costs,on the precondition of not reducing the application functions and the reliable equipment performance.The current integration solutions mainly focus on the lay level or process level,e.g.the fusion of relay protection function and measurement & control function,or the fusion of merging unit and smart terminal.This Paper discusses a more comprehensive integration solution,which is the combination of the single-interval bay level function and the process level function into an individual device,i.e.the secondary all-in-one device.With analyzing the communication needs both inside and outside the device and the data flow direction under the overall integration solution,this Paper provides a theoretical analysis on the load and feasibility of three-in-one network.The solution of secondary all-in-one device changes the network structure of smart substation,in addition to realizing the overall integration of functions in a single interval.In the standard smart substation of three-tier architecture,the bay level equipment and the process level equipment are interconnected with optical fiber to transmit process level information,i.e.SV and GOOSE.The all-in-one device covers all functions for the single-interval bay level and the process level,the communication of optical fiber interconnection is transformed into the bus communication inside the equipment.This Paper puts forward a M-LVDS-based device-inside high-speed communication bus,which supersedes the previous optical fiber intercommunication.Based on the data interaction features of both process level function and bay level function,the bus is designed to adopt the simultaneous multi-master competition mode,where the token and priority mechanism always keep the equal utilization of bus by every equipment on the bus,hence guaranteeing the real-time needs for data communication between process level and bay level.The AC value sampling system of smart substation is in a distributed condition,but such distributed system requires the coordination in both transverse and longitudinal directions.In the transverse direction,the interval sampling shall be synchronized due to needs from current differential protection function;in the longitudinal direction,the sampling value requires the conversion of sampling frequency when it is transmitted from the process level to the bay level.Either sampling synchronization or sampling frequency conversion is involved in interpolation of sampling values,i.e.the re-sampling technology.The current popular interpolation algorithm is the first-order linear interpolation,where the straight line is used to fit the sampling wave curve.However,this kind of interpolation algorithm carries the interpolation error,hence influencing the reliable operation of smart equipment.This Paper creatively analyzes the sampling value error caused by the first-order linear interpolation in the re-sampling technology.Further,with the theoretical calculation and the practical verification,this Paper specifically studies the amplitude error and phase error caused to every harmonic by two core factors,i.e.sampling frequency and interpolation location,with the provision of improvement advices as feasible as from the perspective of engineering.Specific to the overall integration scheme,this Paper discusses the prototype design and engineering verification of secondary all-in-one device.Based on the idea of platform,the device's architecture contains hardware platform,software platform,application software andauxiliary debugging software.The hardware platform,with the function module as its unit,adopts the standard interface design,for the purpose of flexibility and tailing capability;the software platform is based on the real-time operation system,has the software base applicable to power system automation products,and contains the built-in application software;and the auxiliary debugging software contains the logic diagram and other configuration software,hence providing the quick development and commissioning of products.The secondary all-in-one device has come into service in a provincial 220 kV outdoor GIS smart substation,and each of its performance indicators is better than the same of non-integration solution.On these grounds,the initial design objective is realized,and the secondary all-in-one device is worth further promotion.