0 Introduction The JD2000 integrated automation system adopted by the Yintian 35kV substation has three main characteristics: a fieldbus-based control system based on a digital communication network; an integrated hierarchical distributed design concept oriented towards primary equipment; and flexible and rich hardware and software configuration functions. The JD2000 system adopts a number of new computer technologies, integrates the latest research results and algorithms in relay protection at home and abroad, and forms a new generation of substation integrated automation system. [b]1 Functional Overview[/b] The basic task of this system is to quickly, accurately, and comprehensively collect the substation's operating status information, realize relay protection functions, and reliably transmit relevant information to the county dispatch master station's computer system for processing. The computer system displays the information on a graphical display terminal through human-machine dialogue, and promptly informs the dispatcher of the processing and calculation results so that relevant decisions can be made or corresponding measures can be taken in a timely manner, achieving the requirement of unmanned operation. To this end, this system provides functions such as data acquisition, relay protection, switch remote control, accident retrieval and event sequence recording, human-machine dialogue, and voice alarm. 1.1 Data Acquisition: This system can perform real-time data acquisition, processing, forwarding, and fault handling for the Yintian Substation. 1.2 Relay Protection Functions: It implements three-stage current protection for 10kV lines, including instantaneous overcurrent, time-limited instantaneous overcurrent, and overcurrent protection; three-phase single-phase reclosing and subsequent acceleration; and three-stage current protection for the low-voltage side switches of the main transformer. 1.3 Remote Control Operation: Using the display screen on the county dispatch terminal, operators can directly select the control target for remote control operation. After the operator sets the operator's password, the system promptly performs a verification operation before actual operation can proceed, ensuring accurate control. 1.4 Fault Handling: When a fault occurs, the corresponding substation screen is displayed on the county dispatch terminal, showing the time of the fault, the name of the fault, the status, and the fault current value; it also generates a fault alarm or a warning alarm based on the nature of the fault; and records the fault for future reference. 1.5 Broadcast Clock The county dispatch center broadcasts the clock to each unit box of the Yintian substation to ensure system clock consistency and avoid errors caused by time discrepancies between the main and substations in accident handling and event sequence recording. This system broadcasts to each unit box once every 5 minutes. 2. Main Technical Features 2.1 Hierarchical Distributed System Structure The system adopts a modular, hierarchical, distributed, and open structure to ensure the reliability and upgradeability of each control and protection function. This integrated automation system has a two-layer structure: a station-wide control level (station control layer) and a local control level (interval layer), interconnected by a network. The system adopts a principle of decentralization in function allocation; functions that can be implemented at the local control level do not rely on the communication network. Even when the communication network is completely disconnected, each subsystem continues to perform its own interval protection, measurement, and display functions, while the operation of switches can be performed by simple manual switches retained within the station. As shown in the system configuration diagram 1, the secondary system structure of the entire substation is very clear. All equipment consists only of microcomputer-based line protection and control units, microcomputer-based main transformer protection and control units, etc. The local control level is composed of AC sampling microcomputer protection and control devices for the equipment, etc., and centralized control of the entire station is achieved by a remote county-level dispatch monitoring system. The two levels are interconnected via a network, enabling unmanned operation. 2.2 Integrated Protection and Control Device for Primary Equipment An integrated device refers to a microcomputer device that integrates the protection, measurement, control, and communication functions of a specific bay unit of primary equipment. It fully utilizes the versatility and flexibility of computer hardware and software to achieve resource sharing and comprehensive utilization, thereby improving efficiency, ensuring reliable operation, and facilitating maintenance. [img=339,344]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/hndl/2002-4/31-1.jpg[/img] The hardware structure of each bay unit is standardized, regulated, and interchangeable. It uses assembly language programming, and the software implementation is modular, structured, and configurable. Protection functions are mainly determined by the software running on the CPU, while the hardware systems providing the operating platform for the software are all the same. Taking the Yintian 35kV substation as an example, its 10kV outgoing line protection and control device has the following functions: a. Acquisition of analog quantities IA, IB, IC, Ua, Ub, Uc, and related switching quantities for this line. b. Calculation of current, voltage, and power of this line during normal operation. c. Various protection functions such as instantaneous overcurrent protection, overcurrent protection, reclosing protection, and underfrequency load shedding. d. Energy pulse metering function. e. Transmit various measurement and calculation results, switch position changes, protection action reports, and information storage via communication network. f. Receive circuit breaker opening and closing operation commands from remote county dispatch centers. Due to the increased integration of the device and the enhanced CPU function, this device has only 6 modules: AC module, protection CPU module, logic module, output module, power supply module, human-machine dialogue communication module, and base plate. This facilitates production and debugging. 2.2.1 AC Input Module This module is used to convert the high-voltage signals from the secondary side of the system voltage transformer and current transformer into the low-voltage signals required by the protection device. The current and voltage are converted into small current signals by the current transformer, then into voltage signals by the voltage forming circuit, and output after low-pass filtering and limiting. It also has electromagnetic isolation anti-interference function. This module uses imported high-current terminals, which can effectively prevent the TA circuit from opening and can be hot-swapped. 2.2.2 Protection CPU Module This module is a complete microcomputer system. Main functions: 12-channel digital input, 8-channel digital output, 14-channel analog input, serial communication, frequency tracking, and watchdog self-reset function. The structure is shown in Figure 2. The input analog signals are converted from analog to digital and then processed by the microprocessor and compared with a set value. When a protection action is triggered, the signal is driven through the I/O port and the output circuit. This module has complete and strict anti-interference measures: a. It can suppress interference introduced by the power line. b. It uses MAXIM power management and watchdog chips, combined with the 80C196 chip's own monitor timer, enabling the CPU to reset and return to normal operation under conditions such as unstable power supply voltage, strong electromagnetic interference causing program errors, or hardware damage. Simultaneously, it blocks the protection output power supply and issues an alarm signal when repeated reset failures occur. c. The software has a complete dynamic self-test function. During operation, it periodically checks the analog-to-digital converter, program memory, data memory, setpoint memory, and output drive optocoupler. If a fault is detected, it can promptly alarm and lock out the output power supply. 2.2.3 Power Supply Module This module is an inverter power supply. The input DC 220V voltage first passes through a filter circuit to filter out high-frequency interference before being introduced. It provides three sets of protection power supplies: +24V, +5V, and ±15V, which are not grounded. They are floating and not connected to the casing. It also provides one normally closed contact for power voltage reduction or disappearance signals. It has overvoltage protection, undervoltage protection, and overpower protection. 2.2.4 Human-Machine Interface Module (Communication, Display Panel) This module mainly completes the centralized information collection and human-machine interface functions for the protection CPU. It has a keyboard interface, LCD display, CPU module information collection, human-machine interface function, serial communication interface, local clock function, and "watchdog" self-reset function. 2.2.5 Logic Board: To protect the CPU board output, it features a starting relay to prevent malfunctions, local and remote reset functions for modules, and can lock the device output and issue an alarm in case of hardware or software failure. It also includes intermediate relays for protection and remote tripping/closing outputs. 2.2.6 Output Module: Provides control operation outputs for circuit breakers, possessing complete anti-pumping and circuit breaker position indication functions, and easily enabling local manual operation. 2.2.7 Base Plate: Enables connections between modules in the unit box and facilitates device input/output. 2.3 Relay Protection Functions are Relatively Independent: The reliability of relay protection in an integrated automation system must not be compromised. In this system, relay protection is independently set according to the protected object, directly inputting electrical quantities from the relevant TV and CT. After activation, the output is via contacts, directly operating the trip coil of the corresponding circuit breaker. The protection function within the device is completed using an interrupt method, with the highest priority. Other functions are completed using the significant idle time of the CPU during normal operation. The protection current is taken from a dedicated protection CT to ensure a large current dynamic range under line fault conditions. After a protection action, a report is provided to the system via the substation's digital communication network. However, the protection function is completely independent of the communication network; even if the network fails, the protection functions of each subsystem can still operate independently. 2.4 Substation Communication Network For a hierarchical distributed substation integrated automation system, network reliability is crucial to the entire system. The selection of a network is mainly based on the following considerations: network topology, communication medium, and medium occupancy control method. This system adopts the internationally advanced LonWorks fieldbus network, connecting each subsystem through the LonWorks network. The remote dispatch center and the local system are connected via a modem, receiving dispatch instructions and transmitting real-time telemetry, telesignal, and event sequence records upwards, realizing remote dispatch and unattended operation functions; it supports CDT or polling protocols; the substation communication medium uses shielded twisted-pair cable. The entire substation communication network is simple, reliable, clear, real-time, and has strong anti-interference capabilities. 2.5 Comprehensive Telecontrol Functions This system provides comprehensive telecontrol functions, enabling the dispatch center to collect real-time operating data in a timely manner. Its telemetry, telesignal, remote control, and remote adjustment functions significantly improve real-time dispatch efficiency. The remote control function is completed through the intelligent interface unit (communication management unit). When performing telemetry and remote signaling functions, real-time information is collected through the local communication network, processed, packaged, and uploaded to the county dispatch center. When performing remote control functions, the received control or dispatch commands from the dispatch center are transmitted to each unit through the local communication network. 2.6 The system has strong anti-interference capability and high reliability. The hierarchical distributed system structure, with each protection and control unit being relatively independent, is a crucial factor in improving reliability. Even when the communication network is completely disconnected, each bay can still operate normally, especially the relay protection function, which is completely independent, thus ensuring the safe operation of the system. The design adopts a combination of redundancy and interlocking principles, and measures to prevent misoperation are incorporated into the hardware and software design. Manual operation links such as simple high-voltage control circuits are retained, allowing for manual operation even if the microcomputer and communication systems fail. The software has an adjustable debouncing time function for switch quantity changes, preventing jitter caused by poor signal circuit contact and electromagnetic interference. AC sampling uses dynamic frequency tracking technology, reducing measurement errors caused by frequency changes. The system employs signal isolation and filtering technologies, overvoltage surge suppression, lightning protection, and other anti-interference measures to ensure reliability and stability. The device has thermal recovery functionality and power outage protection measures; in the event of deadlock or power failure, existing accumulated data and important generated data will not be lost. During self-recovery, switch position information reflects the actual switch position and will not upload erroneous switch position information to the dispatch center. All these measures improve the system's reliability. This system is a hierarchical distributed integrated automation system combining computer technology, control technology, communication technology, graphic display, and power engineering technology. Due to the adoption of advanced international technologies in some key components, the system is flexible in configuration, highly expandable, highly reliable, and functionally complete, representing the current development trend of integrated substation automation systems. Actual operation shows that the system has good stability and reliability and has significant application value.