田国政　中国电力科学研究院 China Electric Power Research Institute


　　

Abstract: the communication network of substation automation system of different types have different requirements, the implementation process of the data communication network and protocol of substation automation system project selection are analyzed, and the direction of development of substation automation system has carried on the preliminary discussion.

Keywords: substation automation; communication network; transmission protocol

1 Introduction

Substation automation system is essentially a hierarchical and distributed control system composed of multiple microcomputer, including computer monitoring, microcomputer protection, power quality automatic control sub system. In each subsystem, often consists of a plurality of intelligent module. For example: in the microcomputer protection subsystem, a transformer protection, capacitor protection, line protection etc.. Therefore, in the internal of substation automation system, must be through the internal data communication, realize the sharing of information exchange between subsystems and each subsystem and internal information, in order to reduce duplication of configuration two substation equipment and simplifying the interconnection of subsystems, which not only reduces repeated investment, and improve the safety and reliability of the whole system.

2 the requirements of substation communication network

Due to the importance of data communication in substation automation system, economic and reliable data communication becomes the core technology of the system, but because of the special environment of substation automation system and the requirements of substation automation system data network should meet the following requirements: fast real-time response ability; reliability is high; the excellent electromagnetic compatibility; the hierarchical structure of <1>.

1997 August CIGRE session, the WG34.03 working group put forward the communication network in substation transmission time requirements: equipment layer and interlayer between, interval between each equipment, spacer layer between bay units 1~100ms, 10~1000ms between the bay level and substation layer, 1000ms between substation and control center and between each equipment of the substation layer. Each layer of data flow between the peak: about 250kb/s data flow between equipment layer and interlayer, sampling rate depends on the analog, about 60kb/s or 130kb/s data flow between each unit interval layer, depending on whether using distributed bus protection; between bay level and substation layer and other link data stream at approximately 100kb/s and the following.

3 internal data network selection

Data communication network are a key link of substation automation system, the standardization of internal communication network is one of the difficulties in the substation automation to the standardization, affected by the performance and price, hardware, software, user policy and many other factors, the current in the choice of what "interface network" is very difficult to reach an agreement.

Network characteristics is mainly determined by the topology structure, transmission media, media access mode. Network selection shall comply with the relevant standards of international and domestic; should choose the current mainstream products, should be soft and hardware business strong support; products should meet the requirements of substation operation; to have the high performance price ratio <2>.

摘 要：不同类型的变电站对自动化系统的通信网络有不同的要求，文章对变电站自动化系统工程实施过程中的数据通信网络及传输规约的选择进行了分析，并对变电站自动化系统的发展方向进行了初步探讨。

　　关键词：变电站自动化；通信网络；传输规约

1 引言

　　变电站自动化系统实质上是由多台微机组成的分层分布式控制系统，包括微机监控、微机保护、电能质量自动控制等多个子系统。在各个子系统中，往往又由多个智能模块组成。例如：在微机保护子系统中，有变压器保护、电容器保护、各种线路保护等。因此在变电站自动化系统内部，必须通过内部数据通信，实现各子系统内部和各子系统之间的信息交换和信息共享，以减少变电站二次设备的重复配置并简化各子系统的互连，既减少了重复投资，又提高了系统整体的安全性和可靠性。

2 变电站通信网络的要求

　　由于数据通信在变电站自动化系统内的重要性，经济、可靠的数据通信成为系统的技术核心，而由于变电站的特殊环境和自动化系统的要求，变电站自动化系统内的数据网络应满足下列要求： ① 快速的实时响应能力； ② 很高的可靠性； ③ 优良的电磁兼容性能； ④ 分层式结构 <1>。

　　1997年8月国际大电网会议上，WG34.03工作组提出了变电站内通信网络传输时间要求：设备层和间隔层之间、间隔内各设备之间、间隔层各间隔单元之间为1~100ms，间隔层和变电站层之间为10~1000ms，变电站层各设备之间、变电站和控制中心之间为1000ms。各层之间的数据流峰值为：设备层和间隔层之间数据流大概250kb/s，取决于模拟量的采样速度，间隔层各单元之间数据流大概60kb/s或130kb/s，取决于是否采用分布母线保护；间隔层和变电站层之间及其他链路之间数据流大概在100kb/s及以下。

3 内部数据通信网的选择

　　数据通信网是构成变电站自动化系统的关键环节，内部通信网络的标准化是使变电站自动化迈向标准化的难点之一，受性能、价格、硬件、软件、用户策略等诸多因素的影响，目前在选择什么 “接口网络”上很难达成一致。

　　网络特性主要由拓扑结构、传输媒体、媒体存取方式来决定。网络的选择应符合国际国内的有关标准；应选择当前的主流产品，应得到实力雄厚的软硬件商的支持；产品应满足变电站运行要求；具有较高的性能价格比<2>。

　　(1) 35kV substation communication network

In the small scale 35kV substation and 110kV terminal substation, can consider to use RS422 and RS485 network; when the substation is in large scale should be considered when selecting a fieldbus network. RS422 and RS485 serial transmission rate index is good, transfer rate up to 100kb/s within 1000m, the short distance speed can reach 10Mb/s, RS422 serial port for full duplex, RS485 serial port to half duplex, media access mode from the question and answer, belongs to the bus structure. The two problems of the web is that contact number is less, unable to realize the multi master redundant, there is a bottleneck problem, the way RS422 works for point to point, a host computer communication port can at most 10 nodes, RS485 serial port to form a master multiple slave, only 32 nodes, in addition to the intermediate signal reflection the problem, node. All nodes in the LonWorks online is equal, CAN network can be multi master structure composed of convenient, not the bottleneck problems, the number of nodes in a network of two than RS485 times the number of nodes expanded, the theory of CAN network is not restricted, generally can connect 110 nodes.

(2) 110kV substation communication network

Medium hub 110kV substation node number is generally about 40, multi master redundant requirements and an increase in the number of nodes RS422 and RS485 competency. Fieldbus can handy, bus network will be online all the nodes are connected together, can increase or decrease the node convenient; with point on the function of a point to multipoint and broadcast transmission of data points,; commonly used with LonWorks net, CAN net. Two networks are of medium speed network, 500m LonWorks network transmission rate up to 1Mb/s, up to 1Mb/s in CAN network is less than 40m, the CAN network can automatically resection and bus connections in node error, LonWorks network can make the nodes from a network in the automatic monitoring network node is abnormal, media access CAN network for Q & a type LonWorks network as the carrier sense multiple access / collision detection (CSMA/CD) method, the internal communication follows the Lon Talk protocol.

CAN network overhead is small, the transmission format of a frame 8 bytes of the service is subject to some limitations, the LonWorks net as passive network, pulse transformer isolation, has strong ability of anti electromagnetic interference, important information priority. According to the recent domestic hundreds of standing experience, LonWorks net can be used as the current general medium 110kV hub substation automation communication network.

CAN bus is a serial data communication protocol, it is a multi master bus, communication medium can be twisted pair, coaxial cable or optical fiber, communication speed can reach 1Mb/s. CAN bus communication interface is integrated with the physical layer and data link layer of CAN protocol functions, can complete the frame processing of the communication data, including a fill, data block code, cyclic redundancy check, priority discrimination work etc.. One of the biggest characteristic of CAN protocol is the abolition of the traditional address coding, and the coding of the communication data block. The advantages of using this method can make the number of nodes in the network is not limited in the theory, the data block identifier may be composed of 11 bit or 29 bit binary number, data length up to 8 bytes, which can satisfy the control command, in the industrial field working condition and test data of the general requirements. 8 bytes will not take bus time is too long, which ensure the real-time data communication.

(3) 220kV and above substation communication network

The number of 220~500kV substation node, station distribution of hundreds of CPU, data information flow, high requirement on the rate index (request rate 130kb/s), LonWorks real-time, broadband and time synchronization index will do. Consideration should be given to the Ethernet network or Profibus network. Ethernet net is a bus type topological structure, using CSMA/CD medium access method, high transfer rate up to 10Mb/s, can accommodate 1024 nodes, a distance of up to 2.5km. The physical layer and link layer follow the IEEE802.3 protocol, TCP/IP protocol adopts the application layer.

（1）35kV变电站通信网络

　　在小规模的35kV变电站和110kV终端变电站，可考虑使用RS422和RS485组成的网络；当变电站规模较大时应考虑选择现场总线网络。RS422和RS485串口传输速率指标是不错的，在1000m内传输速率可达100kb/s，短距离速率可达10Mb/s，RS422串口为全双工，RS485串口为半双工，媒介访问方式为主从问答式，属总线结构。这两个网络的不足在于接点数目比较少，无法实现多主冗余，有瓶颈问题，RS422的工作方式为点对点，上位机一个通信口最多只能接10个节点，RS485串口构成一主多从，只能接32个节点，此外有信号反射、中间节点问题。LonWorks网上的所有节点是平等的，CAN网可以方便的构成多主结构，不存在瓶颈问题，两个网络的节点数比RS485扩大多倍，CAN网络的节点数理论上不受限制，一般可连接110个节点。

　　（2）110kV变电站通信网络

　　中型枢纽110kV变电站节点数一般为40个左右，多主冗余要求和节点数量增加使RS422和 RS485难以胜任。现场总线却能得心应手，总线网将网上所有节点连接在一起，可以方便的增减节点；具有点对点、一点对多点和全网广播传送数据的功能；常用的有LonWorks网、CAN网。两个网络均为中速网络，500m时LonWorks网传输速率可达1Mb/s，CAN网在小于40m时达1Mb/s，CAN网在节点出错时可自动切除与总线的联系，LonWorks网在监测网络节点异常时可使该节点自动脱网，媒介访问方式CAN网为问答式，LonWorks网为载波监听多路访问/冲撞检测（CSMA/CD）方式，内部通信遵循Lon Talk协议。

　　CAN网开销小，一帧8位字节的传输格式使其服务受到一些限制，LonWorks网为无源网络，脉冲变压器隔离，具有强抗电磁干扰能力，重要信息有优先级。据近年国内数百个站的经验， LonWorks网可作为目前一般中型110kV枢纽变电站自动化通信网络。

　　CAN总线是一种串行数据通信协议，它是一种多主总线，通信介质可以是双绞线、同轴电缆或光纤，通信速率可达1Mb/s。CAN总线通信接口中集成了CAN协议的物理层和数据链路层功能，可完成对通信数据的成帧处理，包括位填充、数据块编码、循环冗余校验、优先级判别等项工作。CAN 协议的一个最大特点是废除了传统的站地址编码，而对通信数据块进行编码。采用这种方法的优点可使网络内的节点个数在理论上不受限制，数据块的标识码可由11位或29位二进制数组成，数据段长度最多为8个字节，可满足工业领域中控制命令、工作状态及测试数据的一般要求。8字节不会占用总线时间过长，从而保证了数据通信的实时性。

　　（3）220kV及以上变电站通信网络

　　220~500kV变电站节点数目多，站内分布成百上千个CPU，数据信息流大，对速率指标要求高（要求速率130kb/s），LonWorks网络的实时性、宽带和时间同步指标会力不从心。应考虑 Ethernet网或Profibus网。Ethernet网为总线式拓扑结构，采用CSMA/CD介质访问方式，传输速率高达10Mb/s，可容纳1024个节点，距离可达2.5km。物理层和链路层遵循IEEE802.3协议，应用层采用TCP/IP协议。

4The present situation of substation automation system of 4 transmission protocol

And substation automation system network standardization requirements compared, data transmission protocol standard is a more urgent need. Whether it is between different manufacturers of equipment or connections in the station and remote scheduling, caused by protocol conversion software programming debugging problems become the largest amount of actual engineering project, the consumption of both human and material resources, the maintenance is not convenient operation, is a big problem to <2> automation technology development at present.

(1) the transmission protocol between substation and dispatching center

At present all the local situation is not a field, most of the use of various forms of protocol such as CDT, SC-1801, u4F, DNP3.0 and some other protocol, in order to achieve the purpose of 1995 IEC exchange between compatible devices, the promulgation of the IEC60870-5-101 transmission protocol, in order to make our country adopts the remote transmission of international standards as soon as possible, in 1997 the former Electricity Department issued the international statute of 101 domestic version of DL/T634-1997, and implementation of conference in Guilin on 1998. The protocol sets standards for the transmission of information between the dispatching end and the station end, remote control transmission protocol in substation automation equipment should use the 101 protocol.

(2) communication protocol in local network

At present, the manufacturers basically each password, difficult communication devices from different manufacturers and later maintenance hidden connection. IEC issued the IEC60870-5-103 protocol in 1997, the State Economic and Trade Commission promulgated the statute of 103 domestic version of DL/T667-1999 in 1999, and publicizing in Nanchang conference in 2000, 103 of the statute for the relay protection and the spacer (IED) equipment and substation equipment of data communication transmission sets the standard for future station, substation automation protocol require the use of 103 protocol.

(3) the measurement of electric energy of power system transmission protocol

For the measurement of electric energy acquisition and transmission system, IEC issued in 1996, the IEC60870-5-102 standard, which is the standard DL/T719-2000 in the electric power industry of China, are we in the implementation of substation electric energy metering system of the need to comply with the.

These three criteria namely, 101, 102, 103 protocol, used in the three layer reference model (EPA) on the physical layer, link layer and application layer structure, are three important criteria for quite a long time to guide the development of substation automation technology. These international standards in accordance with the needs of non balance and balance telecontrol information transmission formulation, fully able to meet a variety of network topological structure of power system, has been widely applied.

With the rapid development of network technology, so as to meet the application of network technology in power system, through the network transmission of telecontrol information, IEC TC57 developed IEC60870-5-104 transmission protocol based on IEC60870-5-101 telecontrol tasks supporting standards, the use of balanced transmission mode of IEC60870-5-101, the realization of the network transmission of telecontrol information through the TCP/IP protocol, which is suitable for PAD (points the assembly and disassembly of the data network).

At present the hierarchical distributed object-oriented ideas have been accepted by the people, the structure of substation automation system is divided into 2 layers, which are connected through a communication network of the spacer layer and substation layer, substation to the dispatching end communication the phasing out of MODEM mode, using TCP/IP model on the internet.

4 变电站自动化系统传输规约的现状

　　和变电站自动化系统的网络标准化的要求相比，数据传输规约统一标准化的要求更为迫切。无论是站内不同厂家设备之间还是在和远方调度的连接中，由规约转换问题引起的软件编程成为实际工程调试量最大的项目，既耗费人力物力，运行维护也不方便，是目前自动化技术发展的一大问题 <2>。

　　（1）变电站和调度中心之间的传输规约

　　目前各个地方情况不一，现场大多采用各种形式的规约如CDT、SC-1801、u4F、DNP3.0等一些规约，1995年IEC为了在兼容的设备之间达到互换的目的，颁布了IEC60870-5-101传输规约，为了使我国尽快采用远动传输的国际标准，1997年原电力部颁布了国际101规约的国内版本 DL/T634-1997，并在1998年的桂林会议上进行了宣贯。该规约为调度端和站端之间的信息传输制定了标准，今后变电站自动化设备的远方调度传输协议上应采用101规约。

　　（2）站内局域网的通信规约

　　目前各生产厂家基本上各作各的密码，造成不同厂家设备通信连接的困难和以后维护的隐患。 IEC在1997年颁布了IEC60870-5-103规约，国家经贸委在1999年颁布了103规约的国内版本 DL/T667-1999，并在2000年的南昌会议上进行了宣贯，103规约为继电保护和间隔层（IED）设备与变电站层设备间的数据通信传输规定了标准，今后变电站自动化站内协议要求采用103规约。

　　（3）电力系统电能计量传输规约

　　对于电能计量采集传输系统，IEC在1996年颁布的IEC60870-5-102标准，即我国电力行业标准DL/T719-2000，是我们在实施变电站电能计量系统时需要遵守的。

　　上述的三个标准即101、102、103协议，运用于三层参考模型（EPA）即物理层、链路层、应用层结构之上，是相当一段时间里指导变电站自动化技术发展的三个重要标准。这些国际标准按照非平衡式和平衡式传输远动信息的需要制定，完全能满足电力系统中各种网络拓扑结构，得到了广泛的应用。

　　随着网络技术的迅猛发展，为满足网络技术在电力系统中的应用，通过网络传输远动信息， IEC TC57在IEC60870-5-101基本远动任务配套标准的基础上制定了IEC60870-5-104传输规约，采用IEC60870-5-101的平衡传输模式，通过TCP/IP协议实现网络传输远动信息，它适用于PAD （分组装和拆卸）的数据网络。

　　目前分层分布面向对象的思想已为人们所接受，变电站自动化系统的结构为2层，即通过通信网络连接的间隔层和变电站层，变电站到调度端通信逐步淘汰MODEM方式，采用TCP/IP模式上网。

5 development direction of substation automation system architecture

With the development of technology, some years later, photoelectric CT, PT gradually replace electromagnetic CT, PT, process layer began to appear, the network structure is divided into 3 layers, namely the substation layer, bay level and process level. Substation automation and international standards, system structure more reasonable. The process layer finish sending I/O, analog acquisition and control commands, and complete with a device related functions, interlayer is the use of the interval data on the interval of a device function, interval layer function more and more to process layer; instead of analog adaptive protection principle of traditional insurance protection will appear substation; functional will be extended to the on-line monitoring equipment, electric energy billing system, parts of the distribution automation, automatic reactive power compensation and remote viewing, structure of substation automation in accordance with the IEC61850 standard will gradually establish.

IEC61850 substation communication system is divided into 3 layers: the substation layer (second layer), a spacer layer (first layer), the process layer (layer zeroth). In the substation layer and interlayer between the network uses the abstract communication service interface is mapped to the manufacturing message specification (MMS), transmission control protocol / Internet Protocol (TCP/IP) Ethernet or optical fiber network. In the bay level and process level network using single point to multipoint unidirectional transmission of ethernet. The IEC61850 standard does not relay protection management machine, intelligent electronic equipment in the transformer substation (IED), control unit and the relay protection are the use of a unified agreement, to exchange information through the network <3>.

About telecontrol information network access has been relatively easy to implement IEC60870-5-104, it is currently the only available network access protocol. IEC TC57 will make the seamless communication architecture, with transmission protocol uniform application of open and network open IEC61850. The agreement will be substation (RTU or substation automation system) the only communication protocol to the control center, is also the process of substation automation system and even to the only communication protocol control center.

5 变电站自动化系统体系结构的发展方向

　　随着技术的发展，再过几年，光电CT、PT逐步取代电磁CT、PT，过程层开始出现，网络结构分成3层，即变电站层、间隔层和过程层。变电站自动化和国际标准接轨，系统结构更趋合理。过程层完成I/O、模拟量采集和控制命令的发送等，并完成与一次设备有关的功能，间隔层是利用本间隔数据对本间隔的一次设备产生作用，越来越多的间隔层功能下放到过程层；替代模拟传统保护原理的自适应保护将出现；变电站功能将扩展到设备在线监测、电能计费系统、部分配电自动化、无功自动补偿和遥视等，符合IEC61850标准的变电站自动化体系结构将逐步建立。

　　IEC61850将变电站通信体系分为3层：变电站层（第2层）、间隔层（第1层）、过程层（第0 层）。在变电站层和间隔层之间的网络采用抽象通信服务接口映射到制造报文规范（MMS）、传输控制协议/网际协议（TCP/IP）以太网或光纤网。在间隔层和过程层之间的网络采用单点向多点的单向传输以太网。IEC61850标准中没有继电保护管理机，变电站内的智能电子设备（IED）、测控单元和继电保护均采用统一的协议，通过网络进行信息交换<3>。

　　关于远动信息的网络访问已经有比较容易实现的IEC60870-5-104，它是目前唯一可供选择的网络访问协议。IEC TC57即将制定无缝远动通信体系结构，具有应用开放和网络开放统一的传输协议IEC61850。该协议将是变电站（RTU或者变电站自动化系统）到控制中心的唯一通信协议，也是变电站自动化系统甚至过程到控制中心的唯一的通信协议。

6 Conclusion

The communication network of substation automation system of different types have different requirements, in the 35kV substation can use RS-485 or field bus station can be used as the system network; field bus network to realize the data communication between the equipment located in the 110kV substation, when the station control layer and equipment more, substation layer can adopt Ethernet connection; in EHV substation 220~500kV, as the station number of nodes, should consider using the Ethernet or PROFIBUS network. Many kinds of transmission protocols currently used in substation automation system, all the company's products use standard is not unified, system interconnection and interoperability is poor, the use of 101 protocol should be between substation and control center, using 103 protocol should be in the substation, the electric energy metering and billing system should use the 102 protocol. After the new standard IEC61850 promulgation and implementation of communication protocol of substation automation system from the process layer to the control center will use a unified.

6 结论

　　不同类型的变电站对自动化系统的通信网络有不同的要求，在35kV的变电站可以采用RS-485 或现场总线作为站内系统网络；在110kV变电站可以采用现场总线网络实现间隔层设备数据通信，当站控层设备较多时，变电站层可采用以太网连接；在220~500kV的超高压变电站，由于站内节点数目多，应考虑使用以太网或profibus网。目前变电站自动化系统中使用的传输规约种类较多，各个公司的产品使用的标准尚不统一，系统互联和互操作性差，在变电站和控制中心之间应使用 101规约，在变电站内部应使用103规约，电能量计量计费系统应使用102规约。新的国际标准 IEC61850颁布实施之后，变电站自动化系统从过程层到控制中心将使用统一的通信协议。

Reference

<1> Huang Yi Zhuang. The substation integrated automation technology. Beijing: Chinese electric power press, 2000

<2> Shi Shuping, Ma Yunrong. Study on the current situation and requirement of the development of substation automation technology. Relay, 2000 (10).

<3> Tan Wenshu (Tan Wenshu). Communication networks and systems in substations IEC61850 protocol (An introduction to substation introduced communication network and system-IEC 61850). Power system technology (Power System Technology), 2001, 25 (9):8-11.

参考文献

<1> 黄益庄．变电站综合自动化技术. 北京：中国电力出版社，2000．

<2> 石树平，马运荣．论变电站自动化技术发展现状及要求．继电器，2000(10)．

<3> 谭文恕（Tan Wenshu）．变电站通信网络和系统协议IEC61850介绍（An introduction to substation communication network and system-IEC 61850）．电网技术（Power System Technology），2001，25(9)：8-11．