Best of DA/DSM(TM) Asia

Best of DA/DSM(TM) Asia

Design and Construction of SCADA/EMS Systems for East China Power System

By Yaliang Yang, East China Electric Power Design Institute, Ministry of Electric Power Industry

East China`s economy registers the quickest growth and also possesses the largest electrical power system in the country. East China`s electrical power system consists of the Jiangshu Province, the Zhejiang Province, the Anhui Province and the Shanghai Municipal electrical power system. In 1994, the total installed capacity of all of East China was 31,000 MW, the majority of which is generated from thermal power plants. By the year 2000, the installed generating capacity will be about 54,000 MW. East China Power also owns more than 16,000 km of transmission line.

The power system control centers are organized according to administrative division. There are four layers of hierarchy: a regional control center (RCC) at the East China Electrical Power Network Dispatch Center; four provincial control centers (PCC) at Jiangshu, Zhejiang, Anhui Province and Shanghai Municipal; the 41 district control centers (DCC); and hundreds of county control centers (CCC).

Challenges and Considerations of System Design

All of East China`s PCCs, DCCs and the RCC have been equipped with SCADA systems, but their function and size are a bit different. In China, practicalization means the operation of SCADA must reach an optimal level of dispatcher acceptance, such as the rate of acquisition, generation and load summation, qualified dispatching reports, and data accuracy. The 41 DCCs of the East China power system will meet the practicalization requirements after the RCC and the four PCCs. The practicalization of the regional, provincial and district levels of dispatching in East China all perform basic EMS/SCADA system functions. The development of AGC and other advanced applications is now undergoing extensive review.

The existing SCADA systems in East China all have concentrated configurations. The host computers are VAX11/785 for the RCC, VAX4300 for the Shanghai PCC and Cyber830A for the Zhejiang and Jiangshu PCCs. The computer for Anhui PCC and most DCCs are PC-based.

All systems have various problems with the low processing capability, the high CPU load-factor and the low expandability. In addition, PCCs and DCCs cannot support the expansion requirements of the power system and the dispatching functions. Therefore, the existing SCADA configuration needs expanding and updating.

Before the hierarchical structure of data acquisition is set up, the computer data communication network between the upper-level and lower-level dispatching centers needs establishing. Next is the second-level package switching network between the RCC and PCCs, followed by the third-level package switching network between PCC and DCCs. This should allow limitations on 220-kV data, making it possible for the DCCs to directly collect lower-voltage substations.

The information, after being processed by the DCC, will be transmitted to the proper RCC or PCC. The information of 500-kV substations and large power plants will be directly collected by the RCC and PCC. After that, a part of the information will be transmitted to the concerned DCC from the PCC. This will reduce the information required to be transmitted and will raise the reliability of the information transmission.

The data computer communication network of East China Power System will be established as a proprietary package, switching network, mainly servicing the power dispatching. The network will improve the data collection system from a two master-station mode to hierarchy mode.

In addition, it will implement the transmission of the quasi-real-time data and management data between every dispatching center, e.g. the exchanging of dispatching schedule, operation reports, hierarchical calculation of state estimation and security analysis, the data exchanging of the energy telecounting, etc. The X-25 has been defined as the protocol for the lower three layers of network information.

The Establishment of Energy Telecounting

Due to the development of market economics and open policy, the China energy price system has been under gradual reform. It will be changed from unique energy pricing to different energy tariffs according to when energy is consumed such as in peak-load periods or in valley-load periods.

It is important to provide the function of energy telecounting in addition to the SCADA/EMS system. As energy telecounting is an accumulating count value, the requirement of data acquisition and transmission is different from that of the real-time data in a SCADA system.

The reliability of energy telecounting must be high, because the loss of data means the loss of money. Therefore, the telecount-filed equipment requires considerable capacity for its transmitting buffer memory to keep all the data waiting for transmittal. Real-time transmittal is not important for telecounting.

Statistical results from the East China Electric Power System Operation Record report the availability of the SCADA system is approximately 96 percent due to failure of RTU and communication media. Furthermore, the existing RTUs have no sufficient storage capacity for the energy telecounting data waiting for transmittal.

Therefore, a proposal is on the table to establish an independent Energy Telecounting System in design for the RCC and PCC dispatching. The proposal includes recommendations to adopt proprietary energy metering and a specific energy-pulse-encoder and transmit the counting value to the Energy-Master-Station via PSTN. This system of energy price balancing shall first be applied between the large power plants and the power system.

As to energy price balancing between the wide range of DCCs and large customers, the problem is expected to be resolved in further developments and additions of energy telecounting functions to the existing SCADA systems.

Concluding Remarks

The East China region is undergoing great economic development and the East China Power System is faced with increasing requirements for SCADA/EMS upgrades. The existing configuration of the SCADA/EMS cannot meet these expanding requirements, thus upgrading to a new open architecture system is in the planning stages. In addition, there are two hot points in the design: the establishment of second- and-third level data computer communication networks for the dedicated transmission of the power industry and the establishment of a dedicated energy telecounting system. How to combine and integrate these two systems into SCADA/EMS is key to the system design.

Author Bio

Yaliang Yang graduated from the electrical engineering department, Qinghua University in 1957. From 1957 to the present, he has been engaged in system planning and design of SCADA/EMS systems. He is the deputy director, telecontrol committee of China Society of Electrical Engineering and the director, telecontrol committee of Shanghai Society of Electrical Engineering.

Author

  • The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at Jennifer.Runyon@ClarionEvents.com.

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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at Jennifer.Runyon@ClarionEvents.com.

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