Substation Abstract

SUBSTATION AUTOMATION Abstract In the era of automatic operation Substations which forms a vital node in the transmission of electrical power system, also needs automation. The automation of a substation started earlier in 1900 with the introduction of relays, and is going on till now with the introduction of new technology which provides communication between two substation to improve the reliability and for better efficiency. This paper deals with the time line history of automation, the automation technique and the networking between substations, Concepts which were used to develop intelligent substation. The paper also gives a brief introduction of the latest protocol (IEC61850) developed for the interoperability of substations. Index terms:--Automation, IEC 61850, IED, relays. Substation communication. I.INTRODUCTION Substation automation is a system to enable an electric utility to remotely monitor, control and coordinate the distribution component installed in the substation. It started with the advancement in relays. Relay is an automatic device which senses an abnormal condition in an electric circuit and closes its contact. The first relay was developed in 1900 and then onwards their function has been improved to a protective device and more to an automatic device. The development of relays can be divided into three main stage: Electromechanical relays, (1900), static or electronic relays, (1960), microprocessor based relay or PLC based (1980). The most advanced form of relays is known as intelligent electronic devices (IEDs). Introduction of IED embarked the communication in between two equipments. This communication is nothing but the data sharing module of equipments. A software development tried to build a system considering the runtime behaviour and assembly of properties than can be obtained from the pattern of interaction. Recently, in 2006 the International Electro technical Committee (IEC) developed a protocol (IEC61850) which provides interoperability of substations, to make the control more effective and direct. II. A CONVENTIONAL SUBSTATION According to the reference of paper a conventional Substation forms vital nodes in power networks because, among others, they make possible modifications in the configuration of networks during the operation of the EPS by means of switching devices that can be controlled by computer-based control systems or PLC (programmable logic controller) based control system.

Fig1. Architecture of a substation Electric power substations consist of two essential parts main (high or extrahigh voltage) circuits, also called primary circuits and auxiliary circuits also called secondary (low- medium voltage ) circuits. The main circuit of a substation composed of a bus bar system and connection of power lines, power transformers, etc. to the bus bar system through switching devices. A Substation is divided into bays. If a bay is used to connect a power line to the bus bar system, it is called a line bay, if it is used for connecting a power transformer to the bus bar system, it is called a transformer bay, and so on. Normally, a substation contains a number of line and transformer bays and also other bays. All bays are similar to the line bay. Auxiliary circuits are electrical circuits which contain measurement, signalling, control and protection devices. in a primary circuit always plays a critical role because all functions connected with EPS protection, automation and control operation realized by a substation are realized by switching devices. III. TIMELINE DEVELOPMENT The reference paper [2], deals with year wise development of relays and effect of this development on automation of substation. (a) Relay operation Electromechanical relays: The first relay function were integrated in the breaker design and acted as over current trips. The first stand-alone electromechanical relay was designed in 1904. The first relay of induction type was delivered 1912 to a hydropower station in the north of Sweden, built to deliver power at 16 2/3 Hz to the railway

Fig.2. Electromechanical relay [2] These were mainly used for high power substations. Static relays: It was introduced in the form of timers, time over current relays etc. The measurement is performed by electric, magnetic, optical or other components with the help of comparison and measurement.

Fig. 3.Static relay Advantages:  Moving parts and contacts are eliminated.  More precise and high speed operation These [3] were famous for their high speed operation (i.e. 21ms or less) which insures high security  Microprocessor based relays: It operates by critical filtering of time, performed with analogue electronics. These are also known as numeric or programmable relay. Advantages:  Display information about faulted part  Includes many features such as fault diagnostic, fault locator etc.

 Capable of replacing all specific purpose relay by a single relay for various fault. The protection, monitoring and control were also easier for this relay. (b) Remote terminal units (RTU): RTU Modelling of intelligent substation which started with the introduction of static relays. Each bay is controlled, protected with different units (e.g. circuit breaker) and provided with multifunction meters (e.g. a fault recorder and an event recorder). The basic definition and working of RTU. An RTU is an electronic device which interfaces data from physical world to control system by telemetry so that The operator sitting at control centre can monitor the substation and take appropriate decision. The idea of synchronized operation of RTU and the interfacing device used. The interfacing device used is Supervisory Control And Data Acquisition (SCADA) system. It has a synchronized sampling rate which made the working of RTU time dependent and reliable. (c) Programmable logic control (PLC): The communication of substation is being consider which mainly started with the introduction of PLC. It was introduced in 1980 for substation control with the integration of RTU . It has been used for switching, load shedding and restoration and emergency generator control. With the introduction of SCADA its utility increases. specially emphasise the changes occurred in a substation when PLC is introduced. It includes features like automatic switching, self monitoring, interfacing the substation with graphical user interface (GUI) and human machine interface (HMI). The interfacing was done over ethernet. A better monitoring, control and monitoring was done.

III. INTELLIGENT AUTOMATION SYSTEM: The modelling of architecture of a current substation to make it an intelligent substation. In the diagram a system architecture for 400 kV and for 66 kV separate subsystems are interconnected via the station bus. This allows the data exchange with the local workplace as well as to the maintenance server. The data exchange with SCADA and EMS as well as with the back office is enabled via the corporate information system. Real time interaction between protection and control IEDs via the fibre-optic inter bay bus allows automation functions as well as adaptive protection schemes. Two most intelligent systems are neural networks and fuzzy logic system. Neural networks: a neural network techniques are very attractive because they do not require tedious knowledge acquisition, representation and writing stages. But they were adapted only to some problem. like recognition of speech, pictures and waves. It concern mainly security assessment, alarm handling, fault diagnosis. • Station level functions: Station level functions are of two type: (a) Process related functions: it act on the data obtained from multiple bays. They submit the control commands from the primary equipments (e.g. CB) and collect the data like voltage, current and power factor.

(b) Interface related function: it interfaces the substation automation system to a local station operator HMI (human machine interface) or to the remote monitoring system. The two station and process buses are realized through the standard Local Area Network (LAN). Multi-port Ethernet switches are installed in station bus which connected HMI through routers. Router facilitates data communication between substation and MCC. HMI enables the operator to monitor and operate the switching element in substation through Graphical User Interface (GUI). Suppose station level node has to communicate with process level, it will send message to bay level node through Ethernet switch. This bay level node executes its function and forwards the message to process level node through merging unit. Merging unit acts like a switch and provides the appropriate path to message. Finally, the function will be performed by the process level devices. • STATION LEVEL FUNCTIONS:

Station level functions are of two type: (a) Process related functions: it act on the data obtained from multiple bays. They submit the control commands from the primary equipments (e.g. CB) and collect the data like voltage, current and power factor. (b) Interface related function: it interfaces the substation automation system to a local station operator HMI (human machine interface) or to the remote monitoring system. The two station and process buses are realized through the standard Local Area Network (LAN). Multi-port Ethernet switches are installed in station bus which connected HMI through routers. Router facilitates data communication between substation and MCC. HMI enables the operator to monitor and operate the switching element in substation through Graphical User Interface (GUI). Suppose station level node has to communicate with process level, it will send message to bay level node through Ethernet switch. This bay level node executes its function and forwards the message to process level node through merging unit. Merging unit acts like a switch and provides the appropriate path to message. Finally, the function will be performed by the process level devices. and different protocols are being developed to provide better communication in between two such equipment. Some predictable methodology and simulating model to develop a theoretical solution of fault occurred were also used which tried to predict a fault earlier than its occurrence. In the series of advancement the latest protocol developed by International Electro technical Committee is IEC 61850. It has been developed for interoperability of substation. i.e. to provide a better communication protocol. It is in the initial stage of development and promises a better communication between substations. IV. CONCLUSION:

A substation has gone through many phases of development during its automation. Initially devices were used for protection, monitoring and control purpose using relays, PLC etc. Now a days networking between substation via LAN through ethernet is in practice after the introduction of IEDs and different protocols are being developed to provide better communication in between two such equipment. Some predictable methodology and simulating model to develop a theoretical solution of fault occurred were also used which tried to predict a fault earlier than its occurrence. In the series of advancement the latest protocol developed by International Electro technical Committee is IEC 61850. It has been developed for interoperability of substation.

i.e. to provide a better communication protocol. It is in the initial stage of development and promises a better communication between substations.