AC and DC Power Transmission ( ACDC 2018 ) Design and application of condition monitoring for power transmission and transformation equipment based on smart grid dispatching control system

With the increasing demand for power supply reliability and the transmission equipment is an important part of power generation, transmission and distribution engineering. In the study, which makes use of the advantages and the mechanism of responsibility area of D5000 system platform, in combination with other related applications, the system architecture, software architecture, and related main functions are designed for on-line monitoring application, and realised the comprehensive analysis of the on-line monitoring and collecting data of the transmission and transformation equipment, to obtain the characteristic parameters of the reaction state of the equipment, equipment fault diagnosis, analysis and judge the running state of the equipment, to fill the domestic electrical equipment condition monitoring and analysis system of electrical equipment and States unified data processing, analysis and judgment of technology gaps. The active maintenance system based on multidimension data analysis and fault prediction is formed from the state of equipment and referring to the running history of equipment state.


Introduction
The state grid is carrying out the construction of the 'three sets and the five major' system.In order to meet the requirements of the 'big operation' construction of 'three sets and the five major' system, it is necessary to integrate the power grid dispatching and substation operation resources, and promote the integration of centralised monitoring and operation of power transformation equipment and power grid dispatching operation, so as to achieve the integration of all levels of regulation and control.The implementation of regulation and control integrates the centralised monitoring of transformer, on-line monitoring and analysis of transmission and transformation equipment status into the unified management of corresponding dispatching organization.The dispatching organization has increased the function of centralised monitoring of equipment operation, on-line monitoring, and analysis of transmission and transformation equipment status [1].
Transmission and transformation equipment is an important part of the power generation, transmission and distribution of power system.The stable operation of the power grid and the power transmission are directly related to the life, performance and safety of the transmission and transformation equipment.The application of on-line monitoring and analysis of the state of the transmission and transformation equipment, which can standardises the data collection, transmission, processing and control, and monitor the running state of the transmission and transformation equipment in real time etc.It also can realise the application functions of early warning, analysis, statistics and diagnosis for transmission and transformation equipment [2], and to provide comprehensive and accurate standardised status monitoring data for other related applications [3], so as to provide strong support for the operation and management of transmission and transformation equipment.Through the advanced monitoring method, the state analysis system is adopted to make a comprehensive analysis and scientific judgement on the running state of the equipment, and to find out the abnormal signs of the equipment early, so as to ensure the power transmission and transformation equipment play a role in the power grid stability.

Analysis of D5000 system architecture for integrated online monitoring application
The smart grid dispatching control system (D5000) with the advanced and applicable technology as the means, is based on unified specifications and standards, under the support of the basic platform, which realises the four kinds of application functions of real-time monitoring and warning [4], scheduling plan, security checking, and scheduling management.
The main monitoring equipment information of the on-line monitoring and transmission status monitoring is as follows: the dissolved gas information in oil of transformer/reactor, the insulation information of the casing, the insulation information of voltage and current transformer, the leakage current of metal oxide arrester, the micro-meteorological information of the overhead line, the tilt information of the rod tower, and the current information of the cable protection layer etc.
Monitoring data modelling is realised on the basis of real-time monitoring of main equipments in smart grid dispatching control system, and on-line monitoring related information is added.The data acquisition function of the on-line monitoring and transformation application is realised by using the data acquisition function of the basic platform, and the data acquisition is sent through the message bus to send the related data to the data processing program.According to the information of power grid real-time monitoring and early warning applications, monitoring information and tidal current information is applied to achieve relevant application analysis functions.The on-line monitoring application of transmission and transformation equipment provides information to power grid real-time monitoring, operation analysis and evaluation, integrated intelligent analysis and alarm, and to dispatching management applications.The on-line monitoring application of transmission and transformation equipment supports the multi-access mode of monitoring information (Smart Substation Monitoring Information Access and PMS data access).By judging the rationality check and priority of multi-source data and sending it to subsequent applications, the priority order can be set flexibly by users.The alarm integration processing uses the trans-security zone message transfer service to transfer the alarm information of the two area transmission and transformation equipment to the security zone, and carries out real-time warning and acousto-optic prompt.The system man-machine interface can be customised to display online monitoring data, on-line monitoring device, and device working condition and alarm information.The data statistics function is responsible for the comprehensive query and statistics of state monitoring data, equipment running data, alarm data and so on, in order to achieve the purpose of statistical analysis of the state of transmission and transformation equipment.Using the trend graph, the threshold method, the three ratio method, the David triangle method and so on, combined with the multi-platform information sharing and the data comprehensive analysis, it provides the good technical support for the fault analysis.

Design of on-line monitoring application based on D5000 system
The system master substation architecture of the smart grid dispatching control system D5000 is shown in Fig. 1.The on-line monitoring application is deployed in the security II area of the smart grid dispatching control system.The channel uses dispatching data network, the main station is configured with two pre-servers and the data server is used to realise the collection and storage of information.The on-line monitoring of transmission and transformation equipment is integrated on the D5000 platform, and relevant applications are deployed in zone II.
The status monitoring information of the substation equipment in the intelligent substation is connected to the dispatching data network through the switch of the II area communication network [5].The status monitoring information of the transmission equipment is connected to the secure access area through the wireless network, and through the lateral security isolation device transmits to the secure II area transmission and transformation online monitoring server.The power dispatching data network is used to realise the direct transmission of data from the substation end to the control main station.The on-line monitoring application function module supports the data interface of the production management system and realises the data exchange [6,7].
The information of on-line monitoring [8] of the transmission and transformation equipment is integrated into the integrated application server of the intelligent substation monitoring system.The information access through the power dispatching data network realises the direct transmission of data from the substation end to the regulate and control main station, and the integrated application server communicate with the monitoring device through the I1 interface specification, the communication protocol conforms to the DL/T860 communication standard.The integrated application server interacts with the II area data communication network and sends data to the control terminal main station system based on the DL/T860.The communication between the II area data communication network and the regulation and control terminal main station system uses the DL/T476 or IEC61870-1-104 protocol for information interaction.The on-line monitoring device for process layer equipment is directly interacted with the integrated application server via DL/T860 standard.

Design of on-line monitoring application software architecture
The on-line monitoring application of the transmission and transformation equipment is configured in the security II area of the D5000 platform.Through communication with substation online monitoring platform, it realises continuous or instant detection of electrical and mechanical state parameters of the important electrical equipment in the dispatching centre, and obtains information about the running state of the equipment's electrical and mechanical performance [9].Using the platform advantage and the responsibility area mechanism, the alarm information of the transmission and transformation equipment can be monitored in time through the real-time alarm window and the voice alarm in the 1area [10].For multiple access and multi-source data priority, combined with other applications, the data is analysed synthetically to obtain the characteristic parameters that reflect the state of the equipment.Based on the characteristic parameters, the fault of the equipment is diagnosed synthetically, and the operation state of the equipment is judged by analysis, then, the alarm information is generated.
The structure of the on-line monitoring application software is shown in Fig. 2. The software mainly includes data acquisition, data processing and storage, alarm processing, data statistics, equipment (device) modelling and maintenance, intelligent analysis, graphics display, data interface, and other modules.The Fig. 1 Schematic diagram of the D5000 system master substation architecture system obtains the power grid model from the basic platform of the dispatching system, and provides alarm data to the application of the power grid operating steady state monitoring, integrated intelligent alarm, operation analysis, and evaluation.

Multi source data acquisition and processing
In the application of data acquisition, there are many sources of data collected from different channels at the same station, mainly including the source data of multiple transmission channels from different communication networks, data transmitted by other dispatching centre, data transmitted by external systems etc.According to the duty of the channel, after the data received, sending the only data to the only on duty channel to subsequent applications solve the problem of multi-source data.
The multi-data source of the same point is sent to the follow-up application according to the manual priority, and the order of priority can be set by the user flexibly.It supports data comparison from multiple data sources, and if there is a large statistical deviation in value, it will issue an alarm.

Data processing and storage
Data processing and storage are used to update the production data of transformer, circuit breaker, capacitive equipment, line and so on.Through reasonable inspection and correction, the data will be collected into the database and archived historical data according to the cycle.Data processing and storage provide basic data for advanced application functions such as fault diagnosis, trend judgement, early warning, data reliability analysis and so on.

I/II area alarm integrated processing
Integrated alarm processing, using cross security area message transmission service, transmit the alarm information of II area transmission and transformation equipment to the safe I area, and deal with the original regulation and primary equipment protection alarm uniformly, and display it on the same interface, as shown in Fig. 3.The real time alarm window in I area is the monitoring interface with the highest usage rate of monitors.Through this interface, the monitor can see the alarm information of all the running states of the equipment within the responsibility area.
The integrated alarm monitoring process can also be implemented.
i. Comprehensive analysis of multiple monitoring measurements combined with monitoring data can reduce the miscarriage of judgment by the inspectors.ii.A comprehensive analysis of state monitoring information is carried out in combination with relevant information of secondary equipment.

Data and information statistics
The state monitoring data, equipment operation data and alarm data are querying, statistics and displayed, so as to achieve the purpose of statistical analysis of the operation state of transmission and transformation equipment.At the same time, the results of data statistics and analysis can provide basic analysis data to advanced applications such as fault identification.Meanwhile, the monitoring and inquiry function of each monitoring and monitoring device of power transmission and transformation equipment is realised.Combined with equipment condition based maintenance data, the comprehensive data of monitoring device is counted.Statistics can be in accordance with the operation and maintenance of the unit, the number of monitoring substation, substation voltage level, device type, volume type, monitoring time and monitoring the amount of monitoring data range and other conditions, and device status display list (including icon), operation and maintenance of the unit, the substation voltage level, substation, monitoring equipment, device name, monitoring time such information can be derived, and the query results, and provide for the historical data of maximum, minimum and average value calculation function.

Fault diagnosis
Based on the D5000 platform, the information of the equipment is shared and the data collected is analysed comprehensively to realise the analysis and alarm of the monitoring results of primary equipment, which can determine the device fault nature, type, degree and causes and trend of fault development, to provide timely information for operation and maintenance personnel.
Aiming at the key equipment in power grid, we use expert analysis algorithm library, including trend diagram, threshold method, three ratio method and David triangle method, which provide good technical support for equipment failure analysis.

Engineering application
In November 2014, the application of on-line monitoring and analysis of transmission and transformation equipment was successfully applied to the intelligent dispatching system, which realised the functions of collecting, monitoring, basic analysis, warning, and other functions of the on-line monitoring data of the state of the 500 kV transmission and transformation equipment in Liaoning, such as Figs. 4 and 5.
Since the system is running, the performance index is good.The data processing period is not > 5 s, the integrated alarm display time is not >5 s, the accuracy rate of primary equipment fault recognition is >95%.The data processing and storage applications, alarm processing applications, fault diagnosis and other advanced application functions, the annual availability rate is >99.5%.
The on-line monitoring and analysis of transmission and transformation equipment is based on the unified platform of D5000 for the first time, which realises the basic model and data sharing, the unified processing, analysis and judgment of the electrical and state data of the equipment, and provides a full range of monitoring and analysis functions for the monitoring and transformation equipment.

Conclusion
The on-line monitoring and analysis application of the power transmission and transformation equipment based on the smart grid dispatching control system has very strong practicability.With advanced scheme design, control strategy and system configuration, the ability of control of substation centralised monitoring is improved, and realised the information, intensive, and intelligent of the company's production and operation management.
However, there is still greater space for the determination of online monitoring data, and the current decision method is also limited to the traditional threshold warning method.With the continuous increase of the experience data of the system, the data of the history library is constantly improved.A more accurate online monitoring and decision can be achieved by comparing with the typical alarm data curve.

Fig. 2 Fig. 3
Fig. 2 Schematic diagram of on-line monitoring application software

Fig. 4 Fig. 5
Fig. 4 Main interface of power transmission and transformation monitoring based on intelligent dispatching system