Paper Keywords: electrical automation; Control system; Design ideas; System function

Abstract: This paper introduces the functions of electrical integrated automation system, discusses the design idea of electrical automation control system at present (taking power plant as an example), and looks forward to the future development trend of electrical automation control system. The improvement of intelligence makes it possible to accurately grasp the situation of field equipment, and the development of communication technology provides a platform for large-capacity data transmission. In the field of industrial automation, Pc-based control system is being adopted more and more because of its flexibility and easy integration.

I. Functions of Electrical Integrated Automation System

According to the characteristics of unit operation and electrical control, the control of generator-transformer unit and auxiliary power should be included in ECS monitoring. Its basic functions are:

1. Control and operation of 220kV/500kV circuit breaker and disconnector at generator-transformer unit outlet.

2. Generator-transformer protection, auxiliary high-voltage transformer protection and excitation transformer protection control.

3. Generator excitation system. Including excitation and demagnetization operations, control mode switching, magnetization and demagnetization operations and PSS (Power System Stabilizer) switching.

The 4.220 kV/500 kV switch is automatically and manually connected to the power grid.

5.6kV high-voltage auxiliary power supply monitoring, operation, state monitoring, switching back of auxiliary voltage quick-switching device and manual start, etc.

6.380 V low-voltage auxiliary power supply monitoring, operation and low-voltage standby automatic switching device control.

7. Control and operation of high voltage starting/standby transformer (two machines).

8. Control and operation of diesel generator set and security power supply.

9. Monitoring of 9.DC system and LPS system.

For the main protection and safety automatic devices such as generator-transformer protection, it is still difficult to realize all their functions in DCS because of the mature equipment, which may increase considerable expenses, so it can be retained. However, they need to be connected with DCS, and the control is hard wired. The information of automatic devices is transmitted through communication, and accidents can be recalled through DCS.

Second, the design idea of electrical automation control system

1. Centralized monitoring mode

The advantages of this monitoring method are convenient operation and maintenance, low protection requirements for control stations and simple system design. However, the main feature of centralization is that all the functions of the system are concentrated on one processor, so the task of the processor is quite heavy and the processing speed is affected. Because all electrical equipment is under monitoring, with the large number of monitored objects increasing, the redundancy of the host decreases, the number of cables increases, the investment increases, and the interference introduced by long-distance cables may also affect the reliability of the system. At the same time, the operation locking of the disconnector and the interlock of the circuit breaker are hard wired, and the equipment cannot be operated because the auxiliary contacts of the disconnector are often not in place. The secondary wiring of this kind of wiring is complicated, and it is inconvenient to check the wiring, which greatly increases the maintenance amount, and there is also the possibility of misoperation due to the complicated wiring during the wiring inspection or transmission.

2. Remote monitoring mode

The remote monitoring mode has the advantages of saving a lot of cables, saving installation costs, saving materials, high reliability and flexible configuration. Because of the communication speed of various field buses (such as Lonworks bus and CAN bus). The requirements are not very high, and the communication volume of the electrical part of the power plant is relatively large. These methods are suitable for small system monitoring, but not for the construction of the electrical automation system of the whole plant.

3. Fieldbus monitoring mode

At present, computer network technologies such as Ethernet and field bus have been widely used in substation integrated automation system, accumulated rich operating experience, and intelligent electrical equipment has also developed rapidly, laying a good foundation for the application of network control system in power plant electrical system. Fieldbus monitoring mode makes the system design more targeted, and it can have different functions for different intervals, so it can be designed according to intervals. In addition to all the advantages of remote monitoring, this monitoring method can also reduce a large number of isolation equipment, terminal cabinets, I/O cards, analog transmitters and so on.