Smart Distribution

Recently, Guizhou Power Grid Corp., which supplies electrical energy to 40 million people in the Guizhou province of south-central China, invested in supervisory control and data acquisition (SCADA) systems for the remote monitoring and operation of high-voltage substations (110/10 kV and 35/10 kV). Also, in some areas, the utility installed remote control of a limited number of load switches on the 10-kV network to provide automation for fault isolation and supply restoration.

Prior to these upgrades, network assets were managed in isolated databases and did not interface with IT systems, while geographical presentation and network modeling were not available.

Modernization Project

Guizhou Power (GP) is one of five provincial utilities managed by China Southern Power Grid Co. Ltd. (CSG), the state-owned utility for the generation and distribution of electric energy in southern China. In 2009, GP launched a modernization project to integrate separate data islands and technical systems in the utility and provide advanced applications for network operation support.

The new system had the following objectives:

System integration and interaction with SCADA systems, distribution automation systems, marketing management and automation systems (measurements, selling and billing of electric energy, customer service system)
Asset data management according to CSG's new information sorting and coding standard (ISCS)
Geographical presentation of asset data, with interrogation and reporting capabilities
Advanced network modeling for electrical calculations
Advanced applications for network management, analysis, optimization and planning.

Functionality

Following market research and system testing, GP launched a pilot project to install an advanced distribution management system (DMS) based on a solution available from Telvent.

Covering a limited area of Guiyang city, the pilot project tested and proved all the required DMS functionality:

Network modeling with advanced graphical tools for data management and automated data import from external systems
Network presentation in geographical and schematic displays generated from the network model database together with an advanced user interface with efficient and user-friendly tools
Asset data management according to ISCS, with display and reporting features in the same DMS user interface and environment, and common information model (CIM) data export to other IT systems
Interfaces with several existing Chinese SCADA systems, the customer information system, the marketing system, the scheduling work system and GPS
Advanced applications for network calculations (state estimation, power flow, topology analysis and coloring), network management fault location, isolation and supply restoration, switching scheduling and testing), network analysis (short circuits, relay protection analysis and setting, loss reporting, security and reliability analysis), network optimization (feeder reconfiguration, volt/volt-ampere-reactive control) and network planning (load forecasting and construction analysis)
Specific graphical control facilities (embedded DMS Web clients) in an external IT Web-based system for scheduling work management
Full localization in the Chinese language and characters, including software and documentation
Compliance with specific IT security requirements with strong protection between four security zones.

During the pilot project, GP staff received complete training on the new DMS system and actively participated in on-site installation, testing, changes and upgrades. GP selected its own Grid Information & Communication branch (GICC) to support the project, arranged the completed knowledge transfer and, later, provided the services for the rollout. GICC staff were successfully trained on-site and visited the Telvent European training center for specialized training and knowledge on the DMS.

DMS Deployment

Following a 12-month period of deployment and testing, the pilot project was completed and formally accepted by GP in November 2010. International tenders were invited and Telvent was the successful bidder as it offered the best technical solution at an economic cost.

The new contract with Telvent was signed to roll out the DMS system for all the distribution networks in GP, supplying a population of 40 million. The installation of the DMS was completed in all nine districts in the Guizhou province by the beginning of 2012. The Chinese GICC team is now providing the full on-site services and system support, and will be responsible for maintenance of the system in the future.

GP's IT network consists of several security zones. The DMS is deployed in zone 1, which is the high-security zone for real-time monitoring of the distribution network, scheduling maintenance and network operations analysis. The DMS also is deployed in zone 3, which is the corporate, less-secure zone, to support data engineering, model testing and network simulations. Network data between the zones is synchronized over a special security device, following all GP security protocols.

The main idea of the DMS in zone 1 (DMS 1) is interactive real-time data with the SCADA systems for monitoring network state and controlling equipment. Its principal users are the load dispatchers. OPEN3000 is an automation system that covers all of the 220-kV and 110-kV substations in the Guiyang area and is operated by the district-level dispatch and control center. It provides the DMS for the high-voltage substations.

Another SCADA system the DMS interfaces with is the distribution automation system, which is conducted by the county-level dispatch center. It controls the local automation load switches on 10-kV feeders with remote terminal units, with the DMS providing real-time data on the state of the feeders. Through the International Electrotechnical Commission (IEC) standard protocols, additional SCADA systems can be connected to the DMS system and provide effective data for advanced DMS applications (for example, state estimation).

The DMS in zone 3 (DMS 3) is necessary to obtain and share information with the other IT systems used by data engineering. It is used by users who are responsible for network operations, management and planning, and is integrated with many other systems. The transformer terminal unit system and the selling and billing system in zone 3 provide the DMS with the data to generate the load profile for each load point on the network. To monitor the network loading conditions, DMS 2 has the ability to interface with the SCADA system. From the pilot project, the ON2000 system, a county-level SCADA system that controls the 35-kV substations, was controlled by running in the county's zone 1 network, but it has no connection to the zone 1 network to the Guiyang center.

The difference between DMS 2 and DMS 1 is that DMS 2 has a relational database management system for asset data management for the low-voltage network monitoring while DMS 1 can send commands to control devices through the SCADA system.

The data within the DMS system can be shared in two ways. First, in DMS 2, the electrical parameters, topology and asset of distribution network can be exported by the CIM. Second, the DMS graphical function can be used by third-party systems with the DMS Web client (controlware by JavaScript API). For example, the distribution production system — a Web system provided by Comtop — is used to manage the work flow of distribution management using the data from DMS in both ways.

Challenges

The main issue with the project development was collecting, entering and validating data in the new system. In the pilot project, data was managed manually using advanced graphical tools for network building and data validation. In this way, typical models of substations and objects were generated as well as a library of typical equipment parameters. In the rollout stage, automated data input and network model generation were provided using typical models and templates for data collection in the field, thus accelerating data input to manage all asset data for high- and low-voltage equipment.

Another issue was to provide useful data for correct load modeling in the distribution network, as a condition for accurate state estimation and load-flow calculation. Previously, GP used the automated meter-reading system for consumption data collection on the secondary side of the 10/0.4-kV distribution transformers. This data was uploaded to the DMS, processed by a load-profile generator and downloaded to the DMS database in the form of typical load curves and peak indicators for typical customer classes and time periods. Such accurate load curves are an excellent starting point (virtual measurements) for the state estimator, which is processing virtual and real-time measurements and providing the inputs for extremely fast load-flow calculations.

Load-flow results were tested in the field and high accuracy was confirmed, providing GP a detailed real-time insight into the distribution network load and voltage conditions. Based on the real-time load-flow calculation, load dispatchers are able to monitor network conditions, optimize network performances and resolve outages with high efficiency and in minimal time. The DMS also has the ability to simulate the system, providing a full environment for different network analysis, optimization, planning and reporting.

The final issue was the interfaces with other IT systems. This was resolved by using international standards. Communication between the DMS and SCADA system was supported by the IEC 61870-5-104 protocol, providing dynamic data exchange. The Web-based business processes were able to support data exchange between off-line systems, while network model data and asset data stored in the DMS database became available to other IT systems over CIM export.

Benefits

In the pilot project, GP users could test and experience the benefits of using the DMS. The main benefits include efficient network data management, searching and reporting, supporting the ISCS. It also provides a user-friendly environment with advanced applications to support network operation, analysis, optimization and development. An important additional benefit is the reduction in fault outage times, thereby improving customer service. Finally, there is support to external systems for data exchange and Web services.

Li Fei ([email protected]) is a doctoral candidate in major technical and automation equipment at the University of Electronic Science and Technology of China. Fei joined Guizhou Power Grid Co. in 1996, where he was engaged in design, development and project management of the power system dispatching automation.

Luo Sixi ([email protected]) is a professor-level senior engineer in Guizhou and an information senior adviser at the Guizhou Power Grid Information & Communication Co. Currently, she is engaged in power system and distribution automation, technical research and management.

Zou Qing ([email protected]) is the general manager of Guizhou Power Grid Information & Communication Co., where his responsibilities include power system automation, technical research and management.

Zhou Yongji ([email protected]) is an engineer working for the Guizhou Guangsi Network Co. Ltd. Yongji is responsible for the Guizhou Power Grid distribution management system project.