Smart Grid System Engineering：Substation Automation Solution

Since there are many different private communication protocol submitted by manufactures, unified regulation or standard are nowhere in the traditional substation system communication network. Different communication protocols and message descript ways caused serious probloms of collaboration between instruments from different manufactures. To structure a system, multiple categories of protocol converter are needed and result in a long period, high-expense, low-reliability system integration and the inconvenience of maintenance.

IEC61850 is based on substation automation standard of network communication platform which requests specify demands for substation automation network instrument including reliability, usability, latency requiremnets, etc.

IEC61850 represents the latest trends of substation automation system, which is the only common international power system network communication standstard, aiming to realize the final goal, "One World, one tech, one standard."

Comparison between traditional substation and substation automation

Substation automation according to the IEC61850 standard, a three-layer two-network architecture is adopted. The three layers are the program layer, the stall layer and the substation layer. The two networks are the program layer network and the substation layer network respectively. Program layer network connection program level equipment and gear level equipment, substation layer network gear level equipment and substation machine control equipment connection.

According to IEC61850 standard and substation automation application demand, TruePower company combined with years of engineering design and practical experience to provide a complete IEC61850 solution from planning, design, construction to testing. Program layer function lies in the device status and analog voltage and current inputs, such as the switch status, alarm monitoring and data sampling, through the network transmission and gear device communication. For the analog voltage and current inputs, we sampled through the merging unit and combined the multiplexed voltage and current signals into IEC61850-9-2 samples.

After the signal is sent to the stall level secondary protection and measurement equipment to achieve fast, stable, shareable total station sample service. Intelligent devices are devices that convert traditional equipment such as circuit breakers and disconnectors into digitized signals. Transmission through fiber optic networks avoids environmental interference and effectively reduces cable laying, and completely replaces traditional RTU systems. In addition, we provide a new generation of optical flow ratio device, the dynamic current measurement of a wide range of high accuracy, there is no magnetic saturation and secondary open-circuit problems, and can be around the optical ratio of the device design, but without power construction Directly installed in GIS and transformer casing, suitable for the transformation of existing substation automation.

The gear level mainly has secondary protection and measuring equipment. TruePower provides a complete series of protective relay devices. It fully supports IEC61850 standard and can receive sample voltage and current output from the program layer. The devices can communicate with each other through GOOSE Exchange, GOOSE is a kind of fast information transmission mechanism in IEC61850, used for transmitting the important real-time signal between IEDs in the substation, wide range of applications, such as protection, output of jump command, device lockout, circuit breaker failure . GOOSE uses network signals instead of the cable transmission between traditional substations, greatly simplifying the second cable wiring substation, on the one hand to reduce project costs, on the other hand, it simplifies the implementation of the project. In addition, GOOSE through the communication mechanism of self-test, to achieve the loop between the monitoring device to effectively improve the reliability of secondary circuit substation.

The substation layer is the realization of SCADA for data collection and monitoring system. IEC 61850 MMS standard is adopted to realize the real-time exchange of information between the monitoring host and IEC equipment under the network by modeling the actual equipment and its functions. Its purpose is to establish a standard for the communication behavior of devices so that devices from different vendors can interoperate with each other to make the system integration easy and convenient so as to solve the bottleneck of inter-device communication caused by the unification of protocols and to reduce the construction and maintenance cost.

IEC61850 substation automation is based on the network, when the substation uses GOOSE and SV transmission technology for network communication, a reasonable network structure and configuration for the protection of the station's real-time and reliability is very important. For IEC61850 applications, we use industrial switches to provide functions such as VLAN zoning, priority transmission, fast disconnection and port mirroring through configuration. As the whole station using optical network construction, a substantial reduction in cable routing, but also makes subsequent maintenance and testing easier.

As the information is transmitted in substation automation through network communication, the sampling and transmission of digital signals must be based on a unified time synchronization basis to ensure its accuracy, reliability and effectiveness. In particular, line differential protection and transformer differential protection equipment, the need for simultaneous sampling of multiple voltage and current to avoid amplitude and phase angle error, to prevent the occurrence of misoperation. For substation automation applications, TruePower based on IEEE1588 precision time synchronization standards which can reach microseconds (1us). IEEE1855 network-based, to reduce re-wiring, which has a time delay compensation calculation to ensure time synchronization between devices is not affected by the distance. IED devices that do not support IEEE 1588 capability can be synchronized with the 1 PPS conversion signal via IRIG-B. For the time synchronization of the whole station and substation, we can transmit the time through IEEE1588 through the existing communication lines of the Taipower, and ensure the time between the IED devices in the entire power system can be maintained without the need to reconstruct the communication lines Consistent and unaffected by external environment and GPS.

Smart Grid System Engineering Subjects