Design and application of electric power communication network comprehensive simulation training system

To solve the problem that current communication network training tools have limited functions and can’t effectively support the electric power communication network training, a new communication network comprehensive training simulation system is designed and implemented. This paper introduces the architecture of the system and function of each part. Then the simulation model principle is explained. The paper introduces the key technologies of 3D modeling, mechanism modeling, communication network scenario automatic generation and network fault simulation. Finally, the system application is introduced and the results show that the system builds a multi-functional training tool to meet the requirements of training and assessment for electric power communication network personnels.

system executes the control commands from the instructor system, and collects the operation records and uploads them to the instructor system.

Communication equipment modeling
In this system, the model structure and construction method of different equipment, cable, instrument, facilities are similar. Due to the complexity of hardware structure and logic function of SDH equipment, this paper takes SDH equipment as an example to introduce the structure and modeling method of communication equipment simulation model. SDH equipment simulation model is a comprehensive simulation of the hardware and functional characteristics of real equipment. It not only realizes the 3D status display and 3D operation functions of SDH equipment, but also realizes the communication signal sending, receiving and processing functions. The structure of SDH equipment simulation model is shown in Figure 1. The real SDH equipment in the physical space is abstracted into the three-dimensional model and machanism model in the simulation space. Through the interaction of status attributes and status parameters, the two models form a unified SDH equipment simulation model. The functional characteristics of SDH equipment can be abstracted as a mechanism model composed of five processing modules. Each processing module corresponds to a board type in 3D model to realize the data processing logic of the board. According to the configuration parameters, the communication data is exchanged between the modules, and the equipment status parameters are updated.
In real SDH equipment, functional characteristics and physical characteristics are two closely linked parts. The change in one characteristic will cause change in another characteristic in real time. In this system, the status attributes and status parameters are stored in the real-time database, and the related data are associated, such as the SRV_Color attribute of Circuit Board 3D model_and Fault_Status parameter of Circuit Board mechanism model are associated. Through the synchronous updating of status attributes and status parameters, the 3D model and the mechanism model realize real-time collaborative simulation. For example, during the running of Circuit Board mechanism model, if abnormal situation is detected, then alarm is generated, and status parameter is changed (Fault_Staus=YES). The 3D model finds the change of status parameters, updates the associated status attribute (SRV_Color=RED), and displays the new status in 3D scenario (SRV light of Circuit Board turns red).

3D modeling
The process of establishing 3D model of SDH equipment is: 1) Measuring physical properties and collecting operation data of equipment. 2) Various 3D components with physical appearance characteristics are created by 3ds Max modeling tool at four levels: Rack, Subrack, Board and Element, and operation animation is created at the same time. 3) In Unity3D, components are assembled as 3D models of equipment according to assembly rules, and effect rendering and attribute settings are made. 4) The corresponding operating procedures of 3D components are developed by using C # language. 5) The 3D model is debugged, optimized and released, and stored in the model database.

Mechanism modeling
In order to flexibly and accurately reproduce the data processing logic, alarm generation and propagation logic of SDH equipment under various normal and abnormal situations, the system uses the data processing and interaction algorithm based on ITU-T specification to establish the logic mechanism model. According to SDH specification, the main internal functional components of the equipment are divided into 18 basic logic functional units. Each functional unit independently realizes some processing process. In this system, according to the logical function of SDH equipment from main manufacturers (Huawei, ZTE, etc.), the logical functional units are combined into five modules: Circuit Board, Branch Board, Ethernet board, Cross Clock Board and Main Control board. The five modules correspond to the five kinds of boards in 3D model. Through the data interaction between modules, the five modules constitute the logic model of SDH equipment, and realize the signal receiving and sending, data multiplexing and mapping, overhead analysis, alarm generating, and cross connection functions of the SDH equipment.

Automatic generation of communication network simulation scenarios
The communication network simulation scenario is composed of models of communication room, communication equipment, distribution frame, cable, test instrument, etc. In different training cases, network topology, number of equipments, equipment type are different, and the corresponding network simulation scenario is different. If the communication network simulation scenario is built manually, the efficiency is low. In this system, an automatic generation method of communication network simulation scenario is proposed, which reads and interprets the network simulation script file, loads various models automatically, and generates communication network scenario. By modifying the script file, various communication network simulation scenarios can be generated flexibly and dynamically.
Communication network simulation script file is a self-defined XML format file, including three types of information: network scenario data, configuration data, fault trigger data. The network scenario data defines the communication room, rack, equipment and connection information related to the scenario. Its structure is divided into four layers. The first layer defines the room name, room type and number of racks. The second layer defines the rack name, rack type, rack coordinates, number of equipments, and number of test instruments. For different types of equipment, the content of the third layer definition is different: for example, for communication equipment, the third layer defines the equipment type, equipment location and board configuration; for optical distribution frame (ODF) and digital distribution frame (DDF), the third layer defines the frame type, frame location and number of ports; for test instrument, the third layer defines the instrument type. The fourth layer defines the cable type, cable identification and connection location.
The automatic scenario generation function uses the top-down sequence to scan the network scenario data in a hierarchical manner: load the corresponding communication room model according to the first layer data to generate the 3D communication room; load the corresponding 3D rack models according to the second layer data, and place the models in the 3D communication room according to the location coordinate information; load the corresponding 3D equipment models according to the third layer data and place the models in the corresponding rack, then load the corresponding test instrument models and placed them in the toolbox; according to the fourth layer data, the corresponding optical fiber, 2M cable, Ethernet cable, communication power cable model, etc. are loaded, and the corresponding ports of equipment or distribution frame are connected according to the connection information. After the model is loaded successfully, the configuration data in the communication network simulation script file is read, and the respective logical models are started to receive, send and process the simulation communication data.

Communication network fault simulation
Based on the dynamically generated network simulation scenario, the fault simulation function and equipment model are coordinated to realize the communication network fault simulation. The fault simulation function first reads and interprets the fault triggering data in communication network simulation script file. The fault trigger data includes information such as the number of faults, the type of each fault and the fault point. According to the type of each fault, corresponding fault model is found to obtain the processing logic change data and parameter change data caused by the fault. Then according to the fault point information, the specific equipment and its mechanism module where the fault is located is found, and the module is informed to run the changed logic program based on the new parameters. After processing the overhead field of communication data among the modules, related alarm is generated automatically and sent to the network management simulation function, and the status parameters of mechanism model are changed.
The 3D model and network management simulation program are combined to realize the presentation of fault phenomenon. The 3D model reads the changes of status parameters in the mechanism model, and presents the hardware fault status in the 3D scenario, such as the board indicator light's color change and the buzzer on. The network management simulation function monitors the generation of alarm data, and displays the corresponding alarm information in the "browse current alarm" window, such as alarm level, alarm name, alarm source, location information, alarm occurrence time, clearing status, etc.

System deployment and application
The electric power communication network comprehensive simulation training system has been successfully deployed and applied in the several provincial training centers of State Grid, such as Hebei, Shanxi and Jiangxi training center. Through the simulation training system, the trainees drill the training cases related to equipment operation, hardware maintenance, data configuration and fault handling. The training case truly reproduces the different kinds of communication network scenarios. It supports the simultaneous simulation of 2-100 equipments, supports various network topologies, and supports 18 kinds of communication network fault, such as communication link interruption, optical fiber degradation, fan failure, Circuit Board fault, Branch Board fault, Cross board fault, protection fault and data configuration error, etc.

Conclusion
In this paper, the unique 3D/mechanism integrated communication equipment modeling technology, communication network simulation scenario automatic generation technology and communication network fault simulation technology are used to design and develop an electric power communication network comprehensive simulation training system, which has been applied in several provincial training centers of State Grid Corporation of China. The system solves the problem that the existing communication simulation system can not simulate the three-dimensional scenario and equipment logic mechanism at the same time, and can not present the hardware status and network management information at the same time. The system solves the problem of high cost of building a real training network, and it supports flexible triggering of multiple types of communication network faults. Through the use of the system, trainees can quickly learn and master the communication equipment O&M skills and configuration skills, improve the fault analysis and processing ability, shorten the training cycle and reduce the training cost. At the same time, the architecture and technical implementation method of the system also provide reference for the design and development of simulation training system in other fields.