Analysis on the main points of upgrading and transformation of integrated automation technology in digital substation

According to the basic development trend of digital substation technology, the necessity, superiority and feasibility of upgrading traditional substation digital technology are discussed. This paper analyzes and studies the technical approaches and schemes of digital substation technology upgrading, and connecting with practical work experience, sums up and puts forward the technical points of process layer, interval layer and station control layer in the process of digital substation technology upgrading.

Substation; Integrated automation system; Digitization; Technical upgrading and transformation

1, principle of digital transformation of substation

In order to ensure the high economy of the digital substation reconstruction project, in principle, the primary electrical equipment in the substation includes large equipment such as circuit breakers, disconnectors and transformers. When the performance meets the requirements of digital substation, it is generally not replaced directly, but the electronic voltage (current) transformer is used in the process layer to complete the real-time acquisition of electrical data information in the whole substation system. The standard communication protocol of Ш C618500 is adopted between the IED intelligent electronic design and the station control layer in the interlayer, and the real data information is interactive, shared and interoperable. The traditional circuit breaker cooperates with the intelligent automatic operation control box to realize the digital transformation of circuit breaker equipment and complete the online remote centralized control of control, data acquisition and manipulation functions. With the development of power grid system with high parameters, large capacity and complex structure, the wiring of substation becomes more and more complicated in the process of digital transformation. In order to realize the technical upgrading and transformation under the condition of uninterrupted operation of the whole station, it is necessary to plan and design the whole system to ensure the safety, reliability, efficiency and stability of the transformation project.

2. Advantage analysis of technical transformation of digital substation.

Digital substation integrated automation system has the advantages of fully sharing data and information, strong interoperability and reducing the daily maintenance cycle cost of substation, which will surely become an important direction of substation automation system research and development in the future. Digital substation automation system takes the digitization of primary and secondary system information of substation as the research object, carries out virtual informatization on physical equipment in substation according to unified modeling rules, and adopts unified and standardized network communication platform to realize real-time communication, sharing and interoperability of data information among intelligent ied devices, which can meet the functional requirements of modern intelligent substation dispatching and operation, such as safety, stability, reliability, energy saving and economy.

3, digital substation technology upgrade scheme

The upgrading of conventional substation digital technology mainly includes three parts: digital transformation of process layer, digital transformation of interval layer and digital transformation of station control layer. However, the whole substation digital transformation project involves many specialties and a large workload. Therefore, in the actual process of digital transformation of substations, a phased transformation scheme should be formulated according to the current situation of existing primary and secondary equipment systems in substations.

In the process of digital transformation of substation, high voltage incoming and outgoing lines, main transformers, etc. One or several sets of centralized measurement and control protection devices supporting IEC6 1850 international standards are needed (each set should be configured according to the principle of redundancy design) to form the high-voltage part of the digital substation spacing system based on IEC6 1850 standards; For the voltage level of 35kV and below, the arrangement of switch cabinets is usually adopted in practical projects, and the feeders are usually equipped with conventional transformers. Therefore, the intelligent electronic devices of the separated layer IED supporting IEC6 1850 standard can be distributed in the switchgear to realize the measurement, control and protection functions of 35kV and below. For large and complex substation systems, step-by-step transformation measures should be taken during digital transformation. For example, for a 220kV substation system, to realize the digital transformation of the whole station, it should be divided into two stages: low voltage and high voltage. The first stage is the upgrading of low-voltage 35kV and 10kV digital technologies; The second stage is to upgrade the digital technology of 220kV, 1 10kV and main transformer at equal intervals. At the same time, all protections, fault recording, remote control, secondary public equipment and metering equipment in the substation system should be upgraded in strict accordance with IEC6 1850 standard system. In fact, the upgrading of substation digitalization technology is based on the requirements of digitalization of primary equipment, integration of secondary equipment network and standardization of communication data platform. Through intelligent primary equipment and integrated networked secondary equipment, the real-time communication, sharing and interoperability of data information among intelligent electrical equipment in substation system are realized.

4, digital substation technology upgrade points

4. 1 Key points of digital transformation of process layer

Intelligent terminal is an important guarantee foundation to realize the digital technical transformation of primary equipment in conventional substation. Intelligent terminal mainly includes MU merging unit, main transformer intelligent unit and intelligent operation box. In order to reduce the comprehensive cost of digital transformation, in the original primary equipment of substation, conventional electrical signals are converted into optical signals through intelligent terminals, and then the data information interaction and sharing between the conventional primary equipment of substation and interlayer measurement and control protection devices are completed through optical fiber network. The intelligent operation box effectively solves the communication protocol conversion interface problem between the primary equipment of the conventional substation and the digital communication network. As an intelligent terminal for remote operation of local primary switchgear in digital substation, the intelligent operation box can organically interconnect the conventional primary switchgear with the protection and measurement and control devices in the bay unit through optical fiber network, and complete the opening and closing operations of local circuit breakers, disconnectors (grounding switches) and other circuit breakers. After the intelligent operation box receives the corresponding opening, closing and locking commands sent to the circuit breaker or breaker by the measurement and control protection device of the bay layer through the GOOSE network, it will be converted into corresponding pulse signals to drive the relay hard contacts to complete the corresponding remote operation.

4.2 Key points of digital transformation of spacer layer

Based on IEC6 1850 standard, the measurement and control protection device with input and output function of GOOSE communication network is used to upgrade the conventional substation mezzanine equipment digitally. The measurement, control and protection devices in the middle compartment of substation integrated automation system should be interconnected according to the dual Ethernet structure. The intelligent IED devices in each compartment can share the analog and switch information in the system through the dual networks, and then complete the action logic of protection action and the locking function between compartment units after analysis and operation by the internal DSP data processing unit. Analog transmission in digital substation system adopts unicast sampling value (SMV) service in IEC6 1850 standard, and switching value transmission adopts general object-oriented substation event (GOOSE) service in IEC6 1850 standard. The CC618500 standard has realized the fast transmission of data information in the substation system through the GOOSE communication server system. Through GOOSE network, the rapid transmission and interactive sharing of data information related to remote communication, remote control and protection tripping in substation system can be realized, which effectively simplifies the secondary system of substation and improves the comprehensive reliability of substation integrated automation system.

4.3 Main points of digital transformation of station control layer

In the station control layer, the monitoring host, engineer station, remote machine, Baoxin substation and GPS network are organically interconnected by 1000/ 100M industrial Ethernet, and the network is configured according to the principle of double redundancy. The interval layer and the station control layer exchange data through 1000/ 100M industrial Ethernet according to the message specification format MMS.

5. Concluding remarks

The construction and technical upgrading of digital substation has become the inevitable direction of substation development in the future. According to the present situation of original primary and secondary equipment in substations, combined with national standards such as IEC6 1850, how to adopt appropriate and effective digital technical transformation scheme to realize the smooth, stable, safe and reliable transition from conventional substations to digital information substations has become a practical problem that must be solved in the technical upgrading and transformation of digital substations.

refer to

[1] Gao Xiang. Application technology of digital substation [M]. Beijing: China Electric Power Press, 2008.