The communication management unit plays a crucial role as a centralized data forwarding device in a substation automation system. This article introduces the new requirements for communication management units in the IEC-61850 substation automation communication network standard during the transition from integrated automation to digitalization in substations, and the solutions provided by Advantech's products.
Keywords: IEC-61850, digital substation, communication management unit, modular
1. Brief Introduction to Digital Substations
Traditional substation automation systems suffer from numerous problems, including limited dynamic measurement range, inability to unify logic layer information models, and poor interoperability of secondary equipment. These issues restrict the further development of substation automation. Therefore, my country officially began research and trial operation of digital substations around 2005-2006; by the end of 2008, the number of digital substations in operation nationwide had exceeded 100. Following the general pattern of power systems, after 4-5 years of operational observation, digital substations are expected to fully replace current integrated automation substation systems from top to bottom around 2010.
A digital substation is a substation in which the processes of information acquisition, transmission, processing, and output are completely digitized. The entire station uses a unified communication protocol, IEC61850, to build a communication network. Systems such as protection, measurement and control, metering, monitoring, remote control, and VQC all use the same network to receive current, voltage, and status information, enabling information sharing among all systems.
In a conventional integrated automation substation, primary equipment collects analog signals, which are then transmitted via cable to a monitoring and control protection device. This device performs analog-to-digital conversion, processes the data, and then transmits the digital signals to the backend monitoring system via network cable. Simultaneously, the monitoring system and the monitoring and control protection device control the primary equipment by transmitting analog signals via cable.
In a digital substation, primary equipment collects information, converts it into digital quantities locally, and uploads it to the monitoring and protection device via fiber optic cable. This data is then transmitted to the backend monitoring system. The monitoring system and the monitoring and protection device also control the primary equipment by transmitting digital signals via fiber optic cable. A comparison between a conventional integrated automation substation and a digital substation is shown in the figure.
2. Communication Management Unit
IEC-61850 proposes a three-layer structure model for substations, consisting of the process layer, bay layer, and station control layer.
Digital substations use low-power, digital optoelectronic instrument transformers instead of conventional ones, directly converting high voltage and high current into digital signals. Equipment within the substation interacts via a high-speed network, eliminating redundant I/O interfaces in secondary equipment. Conventional functional devices are transformed into logical functional modules, achieving true data and resource sharing through the use of standard Ethernet technology. Networking technology, network redundancy technology, data flow modeling, network performance, reliability analysis, novel synchronization methods for the substation process layer, and substation information security are key technologies for constructing the signal path of the entire system.
As a centralized data forwarding node, the communication management unit plays a crucial role in affecting the stability and real-time performance of the entire system. In conventional integrated automation stations, various measurement, control, and protection devices mostly use RS2332/422/485 interfaces. The communication management unit collects data through serial ports, performs protocol conversion, and then uploads it to the control layer via Ethernet. Therefore, the communication management unit is required to have multiple serial ports.
One of the characteristics of digital substations is data sharing via Ethernet, making multiple network ports a new requirement for communication management units. Simultaneously, data signals from multiple nodes can be transmitted on the same cable, significantly saving equipment space and cabling costs.
3. Equipment Requirements: IEC-61850 has strict requirements for communication management units:
In terms of performance: It is required to support fast store-and-forward mode and QoS service quality to ensure that important GOOSE packets in the network are transmitted in real time;
In terms of electromagnetic compatibility: it is necessary to pass electromagnetic interference tests such as electrostatic discharge immunity, electrical fast transient/burst immunity, and surge immunity, as well as tests for electric shock and lightning strikes.
Regarding ambient temperature: it must meet a wide operating temperature range (-40℃ to 85℃), and the storage temperature must also meet a wide temperature range.
In terms of mechanical structure: it must pass special tests for withstanding strong vibrations and impacts; meet specific dustproof and moisture-proof requirements; and have good heat dissipation conditions.
4. Advantech Solution
The SPC-0209 is a low-power, fanless, original equipment manufacturer (OEM) with multiple network ports designed for digital substation applications in the power industry. It meets the high EMC protection requirements of the power industry and features a modular design that satisfies various hardware platform requirements of the communication management unit in the power industry's system communication layer.
4.1 Performance
The SPC-0209 uses Intel's latest PINEVIEW-D processor—the D510, a dual-core 1.66GHz processor that supports Hyper-Threading, allowing four threads to run simultaneously, providing powerful data processing capabilities. Paired with the ICH8M southbridge chip, the overall power consumption is less than 60W, meeting the product's requirements for high performance and low power consumption.
4.2 Structure
Given the widespread concerns in the power market regarding the stability of gold finger connectors, SPC-0209 adopted the design concept of cPCI and developed a 3U external chassis. Each expansion module uses a European pin configuration to connect to the motherboard, which not only provides higher stability but also facilitates maintenance and replacement of functional modules.
The requirement for long-term stable operation is driving the development of industrial computers towards fanless design. The SPC-0209 has a power consumption of less than 60W and uses a chassis for heat dissipation. It not only has a wider operating temperature range, but its sealed chassis design can also adapt to harsh working environments with dust.
4.3 I/O Interface
According to IEC-61850, the best signal transmission mode is fiber optic transmission, which not only has high bandwidth but is also unaffected by interference during transmission. However, it is currently unrealistic to equip all equipment from all companies that manufacture secondary equipment with fiber optic interfaces. Each company has different R&D and production capabilities, and their system architectures also differ. Therefore, in the short term, digital substations will inevitably feature a combination of serial ports, Ethernet ports, and fiber optic ports.
The SPC-0209 implements all I/O ports as interface modules, using European-style sockets to connect to the motherboard. This allows engineering companies to select the appropriate interface modules for different project equipment, increasing the flexibility of the entire system.
SPC-0209 Serial Port Module (with Isolation High Voltage)
4.4 Overall machine parameters and insulation performance
Insulation resistance: The insulation resistance between all circuits of the device and the casing shall not be less than 100 MΩ under standard test conditions.
Dielectric strength: The conductive parts of the device can withstand an AC 50 Hz test with a voltage of 2 kV (RMS) for 1 min between the outer casing or exposed non-conductive metals, and between electrically unconnected energized conductive circuits, without insulation breakdown or flashover.
Impulse voltage: The ability of a device’s conductive parts to withstand a short-term impulse voltage with an amplitude of 5 kV and a standard lightning waveform between the device and the casing or exposed non-conductive metal, as well as between electrically unconnected charged conductive circuits, under specified test conditions.
Damp heat resistance: Capable of withstanding the damp heat test specified in Chapter 20 of GB/T 7261-2000. The test temperature is +40℃±2℃, the relative humidity is (93±3)%, and the test duration is 48 hours (each cycle is 24 hours). Within 2 hours before the end of the test, measure the insulation resistance between each conductive circuit and exposed non-conductive parts and the casing, and between electrically unconnected circuits; the insulation resistance should not be less than 1.5 MΩ; the dielectric strength should not be less than 75% of the dielectric strength test voltage value specified in 2.3.
Electromagnetic interference resistance
Radiated electromagnetic interference test: able to withstand radiated electromagnetic interference of the severity level specified in Chapter 4 of GB/T 14598.9-2002;
Fast transient interference test: Fast transient interference of severity level A as specified in GB/T 14598.10-2007.
Pulse group interference test: The pulse group interference shall conform to the frequency of 1 MHz and 100 kHz damped oscillation wave (the first half wave is a voltage amplitude of 2.5 kV common mode and 1 kV differential mode) as specified in GB/T 14598.13-1998.
Electrostatic discharge interference resistance test: Complies with the severity level III of GB/T 14598.14-1998 for electrostatic discharge interference resistance.
Electrostatic discharge interference test: Complies with the severity level A of power frequency interference specified in GB/T 14598.19-2007.
Surge immunity test: Surge disturbances of severity level IV as specified in GB/T 17626.5-1999.
Immunity test for conducted interference induced by radio frequency field: Conforms to the severity level III of conducted interference induced by radio frequency field as specified in GB/T 17626.6-1998.
Power frequency magnetic field immunity test: Complies with the severity level V power frequency magnetic field interference specified in GB/T 17626.8-2006.
Pulse magnetic field immunity test: Complies with the severity level V pulse magnetic field interference specified in GB/T 17626.9-1998.
Damped oscillating magnetic field immunity test: Complies with the severity level V damped oscillating magnetic field interference specified in GB/T 17626.10-1998.
Mechanical properties
Vibration: The device can withstand vibration durability tests of severity level I as specified in GB/T 7261-2000 16.3.
Impact: The device can withstand the impact durability test of severity level I specified in GB/T 7261-2000 17.5.
Collision: The device can withstand a collision capability test of severity level I as specified in Chapter 18 of GB/T 7261-2000.
5. Conclusion
The main advantages of the information interaction network in new digital substations are: flexible selection of network topology according to actual needs; easy use of redundancy technology to improve system reliability; and no impact on substation functionality from changes in network topology. Using network cables instead of conductors significantly reduces the number of secondary circuit connections within the substation, thereby improving system reliability.
The SPC-0209 is a power industry-specific product designed for future digital substations. Compared to commonly available communication management units, it offers broader coverage, supports more communication modes, boasts more powerful processing capabilities, and strictly adheres to the IEC61850 standard and the specific requirements of digital substations. It provides an ideal communication solution for harsh industrial application environments such as substations and power plants.
References:
1. Design Code for Power System Dispatch Automation (DL5003-91)
2. Application Layer Protocol for Real-Time Data Communication in Power Systems (DL476-92)
3. Substation Communication Network and System Protocol (IEC 61850)
About the author: Ma Linke (1977-), male, Bachelor's degree, Product Director of Advantech Intelligent Technology Co., Ltd.
