IED used in SCADA

Chapter 1

Introduction

            The term “intelligent electronic device” is multifunction electronic device that possesses some kind of local intelligence can be called IED. However, concerning specifically the protection and power system automation industry, the term really came into existence to describe a device that has versatile electrical protection functions, advanced local control intelligence, monitoring abilities and the capability of extensive communications directly to a SCADA system. This is the definition of IED that will be applied throughout this book.

            The ability of an IED to perform all the functions of protection, control, monitoring, and upper level communication independently and without the aid of other devices like an RTU (remote terminal unit) or communications processor (not including interface modules) is the identifying feature of an IED. Common types of IEDs include protective relaying devices, load tap changer controllers, circuit breaker controllers, capacitor bank switches, recloser controllers, voltage regulators, etc.

            Digital protective relays are primarily IEDs, using a microprocessor to perform several protective, control, and similar functions. A typical IED can contain around 5-12 protection functions, 5-8 control functions controlling separate devices, an auto reclose function, self monitoring function, communication functions etc. Hence, they are aptly named as Intelligent Electronic Devices.

            Intelligent electronic devices (IED’s) are the equipments of the future power system automation, monitoring and control. These change the way a modern power system works leading to an intelligent or an smart grid of the future. Recent advances in power system automation and protection has led various protection and control function which are proprietary with specific protocols wherein devices of different manufacturers could not communicate with each other this lead to the evaluation of  the IEC 61850 communication standard for substation automation. IEC 61850 help in standardizing the data to be communicated so that devices from various wonders could communicate without the use of protocol converters. This communication between devices taken place at various levels in the substation.

Evaluation of IED

            The 1990s saw a new wave in the power industry, especially in the fields of protection, remote control and substation automation. As protection relays became more advanced versatile and flexible with the introduction of microprocessor based relays. The initial communication capabilities of relays were intended mainly to facilitate commissioning. Protection engineers realized the advantages of remotely programming relays; the need developed data retrieval, and so the communication aspects of relays become steadily more advanced. PLC functionality became incorporated into relays, and with the development of small RTUs (Remote Terminal Units), it was soon realized that relays could be much more than only protection devices. Why not equip protection relays with advanced control functions? Why shouldn’t protection functions be added to a bay controller? Bothe of these approaches have been followed, with different manufacturers (and sometimes different approaches to the question of protection, control and communications. This resulted in an extensive range of devices on the market, some stronger on control, and the term protection to describe these devices. This resulted in the term “intelligent electronic devices”  (IED).

IED structure

            Figure 1 provides the typical configuration of an IED. The IED derives its name from the various functions the device can select and perform in an inherently fashion. An important issue is the enormous task of incorporating intelligence, in terms of hardware (flexible logical circuits) and software (programmable intelligent agents) into the IED. Advances in the techniques of software programming and hardware development are essential for the construction and realization of an IED. Some IEDs may be more advanced than the others, but these main functionalities should be incorporated to a greater or lesser degree.

IED configuration consist of

1.      Analog/ digital  input from power equipment and sensors

2.      Analog to Digital Convertor (ADC) /Digital to Analog Converter (DAC)

3.      DSP (digital signal processing) Unit

4.      Flex-logic unit

5.      Virtual input/ output

6.      Internal RAM/ROM

7.      Display

8.      Power supply etc.

Input – IED receives signal from different equipment like CTs, PTs, and from sensors like temperature, humidity, vibration etc. Generally input from CT’s, PTs and other power equipment is in analog form and input from sensors is in digital form.

ADC (analog to digital convertor) - As IED is microprocessor based device it able to work only on digital signal thus there should ADC is used to convert analog data in to digital form.

DSP (digital signal processing) – Digital signal processing (DSP) is concerned with the representation of discrete time, discrete frequency, or other discrete domain signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing.

Flex-logic unit – All arithmetic and logical calculation are done by this unit according program.

Virtual input / output – IED receives signal from server through this virtual input port and IED sends signal to any server or equipment using virtual output port generally this signals are in digital form and uses fiber optic cable for communication.

Internal RAM/ROM – IED have its own memory according its application different range of memory is used. IED record all value of electrical parameter and physical parameter also records all fault values.       

Display – In case if IED is mounted on panel board it is combined with digital display which is able to show all recorded as well as real time values of electrical parameter of equipment or system.

Power supply – IED required some power for its operation but power required ids very less as compared to old system.

Chapter 2

IED and conventional protection system

            The growth in the number of IEDs has resulted a significant increase in the volume of substation data. This data is usually primitive and stored in a digital form. It has to be processed and analyzed before any user is able to utilize the benefit of it.

            Figure 2 shows a conventional protection system in which the data and control signal from the relay are sent via an RTU to the SCADA system. Extensive and costly cables may be required between various bays in the substation and the control room.

           

            Figure 3 shows a modern protection system utilizing an IED relay. The connection diagrams of Figure 2 and 3 may look similar except that the interconnection wiring between transducers and meters is no longer required for the IED relay. The data and control signals from the IED relay are sent directly to the SCADA system via the high-speed dedicated communication network. The volume of data increases drastically when an IED is used as the control element and data source.

            Table 1 presents a comparison of the data quantities between a conventional RTU and an IED in a 10-feeder substation. Considering real time values only and not including data from incoming lines or transformers, it can be seen that the

SCADA system and substation data is a factor of 10 larger when IEDs are used

1.      Remote Terminal Unit (RTU) is a device installed at a remote location that collects data, processes and codes the data into a format that is transmittable and transmits the data back to a central or master station.

2.      Supervisory Control and Data Acquisition (SCADA) is the system that collects data from IEDs in the network and utilizes it for control and monitoring. It also provides a remote access to substation data and devices to the control centre.

With the wealth of information that an IED can produce, engineers are no longer facing the lack of data problem.

            In each IED, there are two types of data namely, operational and nonoperational. Operational data is instantaneous values of volts, amps, MW, MVAR and etc. It is typically conveyed to the SCADA system using the communications protocol. This operational data path from the substation to the SCADA system is continuous. Non-operational data, on the other hand, is the IED data that is used for analysis and historical archiving, and is not in a point format as operational data e.g. fault event logs, metering records and oscillography. This data is more difficult to extract from the IEDs since the IED vendor’s proprietary ASCII commands are required for extraction of this non-operational data. Operational data is critical for SCADA dispatchers to effectively monitor and control the utility’s power system. However, the non-operational data has also tremendous value to the utility. In this substation data analysis, only the operational data from IEDs has been considered. The proposed algorithm can however identify the certain IED relays that carry the crucial information. This not only reduces our attention span, but also saves our time in selecting which IEDs may contain the non-operational data we need for detailed post-fault analysis.

Chapter 3

Substation Network

            To provide the necessary connectivity between the various components of the SA system, a LONWORKS Local Operating Network (LON) is utilized. This open standard network was selected because the majority of the IEDs utilized in the SA system were embedded with the LONTALK Protocol. This protocol is specifically designed to cater to control networks, as opposed to data networks, and has become a de facto standard in certain industries such as building control and automation.

            Speed and performance are the key factors in designing a network for control applications such as this. The LONWORKS network is event driven, meaning that information is transmitted only when a value has changed. In critical times, such as during fault clearing, network traffic will be the highest and collisions may be frequent, as a number of devices all attempt to transmit information which has all changed in a very short period of time. In order to decrease the number of network collisions and therefore increase performance, the LON was separated into 3 sub network as shown in Figure 3. Each of these sub network utilized starcouplers to facilitate communications between up to 30 nodes per coupler. As well, two starcouplers were equipped with a router card to allow for peer-to-peer communication between the sub network. The allocation of IEDs to specific sub network was carefully planned based on the following criteria:

1.      The impact of the loss of a starcoupler was to be minimized by ensuring that IEDs associated with the same bay in the substation were to be allocated to different star couplers.

2.      In order to keep the performance as high as possible, inter-sub network communication was to be kept to a minimum. Therefore, backup protection relays, which required very little inter-sub network communication, were placed on a common sub network.

To improve the reliability of the network, each starcoupler was equipped with redundant power supplies, each fed from a separate station battery system.

            Besides the various IEDs connected to the starcouplers, the two PC based servers were each equipped with three LON interface cards to allow both of the servers to communicate directly to all three subnetworks without channelling communication through the router cards.

By doing this, the vertical communication performance between the servers and the IEDs was greatly improved.

            Due to the close proximity of most nodes in the system, the physical media for most of the network was plastic fibre optics cables. The use of plastic fibre optics made for faster and more economical field installation compared with the use of glass-based fibre optics.

            As previously noted, the LON network is event driven. While minimizing network traffic, event driven networks pose certain problems in terms of detecting loss of communication as lack of data transmission is always assumed to be due to a lack of change in information. In order to determine the health of the IED communications, two check algorithms were developed.

            The first algorithm was implemented within the programming of those IEDs that communicated peer-to-peer or what is also known as horizontal communication. This data is packaged into 8 bit blocks by the originating IED and ‘published’ to the network where it is read by those IEDs that ‘subscribe’ to that information. Since these blocks are only published when one of the bits change state, an eighth bit was reserved for a toggling input that changed state every 5 seconds. This forced the block to be transmitted at regular intervals.

            All subscribers of this block of data were programmed with timers that would reset when the eighth bit in the block changed state. If this timer reached 15 seconds (which corresponds to three consecutive failed data transmissions), the communication would be considered to be defective. Since the majority of this data was used for interlocking purposes, the receiving

IED was programmed to assume the worst case in terms of determining if interlocking requirements had been fulfilled. This would protect against any potentially unsafe switching until such time that the communication was restored.

            The second algorithm was used to confirm the vertical communication and was performed by software in the station servers. These servers would conduct a simple poll of each IED in the station once every 30 seconds. Should the server not obtain a response within 2 successive polls, an alarm is generated indicating the failure.

Chapter 4

Basic function of IED

            A functional overview of an IED can be observed in the figure 4. The protection functions of the IED evolved from the basic over current and earth fault protection functions of the feeder protection relay (hence certain manufacturers named their IEDs feeder terminals). This is because a feeder protection relay is used on almost all cubicles of a typical distribution switchboard, and that more demanding protection functions are not required to enable the relay’s microprocessor to be used for control functions. The IED is also meant to be as versatile as possible, and is not intended to be a specialized protection relay, for example generator protection. This also makes the IED affordable. The following is a guideline of protection related function s that may be expected from the most advanced IEDs (the list is not all-inclusive, and some IEDs may not have all the functions). The protection functions are typically provided in discrete function blocks, which are activated and programmed independently. Communication capability of an IED is one of the most important aspects of modern electrical and protection systems, and is the one aspect that clearly separates the different manufacturer’s devices from one another regarding their level of functionality.

Fig.5 Functional View of IED

Protection

            IED consist of different types of protection system according to its application or use. Generally following protection will be provided by IED

1.      Over / Under voltage

2.      Over current

3.      Harmonic

4.      Differential protection

5.      Over temperature

IED also able to provide protection for particular device separately like

1.      Generator

2.      Circuit breaker

3.      Transformer

4.      By controller

5.      Auxiliary equipments

Control

            IED can be use as Power Factor Controller, auto voltage controller, by controller etc. Also IED can be controlled by operator from any remote place either in normal condition as well as in abnormal condition.

1.      Power factor controller – IED is connected to capacitor bank, IED sense the power factor and connect capacitors as per requirement. Which keep power factor unity, thus overall power factor of systems get increases.  

2.      Voltage regulator – IED is also connected to on line tab changer of transformer and changes the tabs according variation in supply voltage.  

Metering

            IED continuously records all data of electrical parameter consist of Active power, Reactive power also measures energy (KWH) consumed by the consumer. IED also helps for Time of day tariff, which is the measure advantage of IED that it records power consumed at different time of day (hourly).

Communication

             IED’s are able to communicate with multiple channels at a time. It continuously sends data to system server which consists of all electrical and physical parameter. According to IEC 61850 two different IED’s are able to communicate with each other also. The range of frequencies used by this IED is 50khz to 500khz.

Monitoring
IED continuously monitor different parameter as shown in table 1, Generally IED monitor first only four input voltage from PT’s, current from CT’s, power factor, and frequency. By using this data IED calculate different values as shown in table and send it to server.

Input	Calculating /monitoring/ recording continuously
Ø  Voltage (phase/ line)	Ø  Voltages Vr/Vy/Vb/Vry/Vyb/Vrb
Ø  Current	Ø  Current Ir/Iy/Ib
Ø  Power factor	Ø  Power :- KWr/KWy/KWb/KW3
Ø  Frequency	KVarr/KVary/KVarb/KVar3
	Ø  Energy :-KWHr/KWHy/KWHb/KWH3
	KVarHr/KVarHy/KVarHb/KVarH3
	Ø  Frequency
	Ø  Power Factor
	Ø  Status (open/ close/ target) of relay/ C.B.

Chapter 5

IEC 61850     

IEC 61850 is a standard for the design of electrical substation automation. IEC 61850 is a part of the International Electrotechnical Commission's (IEC) Technical Committee 57 (TC57) reference architecture for electric power systems. The abstract data models defined in IEC 61850 can be mapped to a number of protocols. Current mappings in the standard are to MMS (Manufacturing Message Specification), GOOSE, SMV and soon to Web Services. These protocols can run over TCP/IP networks or substation LANs using high speed switched Ethernet to obtain the necessary response times below four milliseconds for protective relaying

            The IEC 61850 standard has been defined in cooperation with manufacturers and users to create a uniform, future-proof basis for the protection, communication and control of substations. In this brochure, we present some application examples and implemented stations with the new IEC 61850 communication standard. IEC 61850 already has an excellent track record as the established communication standard on the worldwide market for the automation of substations.

Its chief advantages are:

• Simple substation structure: No more interface problems. With IEC 61850, protocol diversity and integration problems are a thing of the past.
• Everything is simpler: From engineering to implementation, from operation to service. Save time and costs on configuration, commissioning and maintenance.
• Reduction of costs: IEC 61850 replaces wiring between feeders, control switches, and signaling devices.
• More reliability: You only use one communication channel for all data – in real time, synchronized via Ethernet.

SCADA

SCADA or Supervisory Control And Data Acquisition is a large scale control system for automated industrial processes like municipal water supplies, power generation, steel manufacturing, gas and oil pipelines etc. SCADA also has applications in large scale experimental facilities like those used in nuclear fusion.

SCADA systems monitor and control these operations by gathering data from sensors at the facility or remote station and then sending it to a central computer system that manages the operations using this information. The sheer size and of the operations we saw earlier demands that the control system be equally elaborate to handle the requirements. This is where SCADA scores. The SCADA system is equipped to manage anything from a few thousands to a million input/output channels. The technology is still evolving and we can expect an expansion of the market for SCADA.

A fully fledged SCADA system is made up of signal hardware for input/ output, networks, control equipment, user interface (sometimes called the Human-Machine Interface or HMI), communication equipment and the software to go with it all. And here we are talking about the central command system of SCADA. The central system is often miles away from where the operations take place. Thus the system also needs on-site sensors to collect and monitor data.

How SCADA Works

The measurement and control system of SCADA has one master terminal unit (MTU) which could be called the brain of the system and one or more remote terminal units (RTU). The RTUs gather the data locally and send them to the MTU which then issues suitable commands to be executed on site. A system of either standard or customized software is used to collate, interpret and manage the data.

SCADA as of now uses predominantly open-loop control systems, though some closed-loop characteristics are often built in. As this is an open-loop system, it means that SCADA system cannot use feedback to check what results its inputs have produced. In other words, there is no machine-learning.

SCADA and Other Control Systems

There are several other systems that are used for similar purposes as SCADA. These are generally called Distributed Control Systems (DCS). The functions are the same; the difference is in the range. Distributed Control Systems are typically effective within a confined area like a factory complex. Thus the communication is carried out through a local area network (LAN). These networks are highly dependable and fast, and can manage closed-loop (feedback based) control.

DCS networks have their limitations. They cannot cover large territories. This is where SCADA comes in handy. However the communication systems are not as reliable as a LAN, and therefore it is not viable to implement closed-loop control. Right now, the size and scope is what mark SCADA.

Chapter 6

Types of IED

According to use of IED there are different types of IED listed below

1.      Used in generating station

2.      Used for transmission substation

3.      Used for distribution substation

There is some little difference between these different IEDs. For generating station reverse power protection, generator protection, exciter supply control, etc. must be provided. While for transmission line substation IEDs are able to communicate directly with each other like IED placed at sending end able to communicate with IED placed at receiving end directly. For distribution substation IED is specially used for on line voltage regulator and for power factor correction.

According to application over particular device

1.      Generator protection

2.      Circuit breaker protection and control

3.      On line tab changer control

4.      Transformer protection

IEDs can be used for protection and control of particular device as listed above in a substation. Generally for IED there is IED 670 series of electronic devices is used

1.      RED 670 used for overhead line and cables protection

2.      REL 670 used for transmission overhead line protection

3.      REG 670 sued for generator

4.      RET 670 use for any type of transformer

5.      REC 670 used for any type of switchgear

6.      REB 670 used for busbar protection and monitoring

Let’s see in detail of IED 670 series

1.      RET670 – optimized for transmission applications

RET670 IEDs provide customized or pre-configured protection solutions for any type of transformer and shunt reactor application. The customized RET670 gives freedom to select functionality entirely according to your needs. The pre-configured RET670 variants simplify handling since the basic functionality is included and pre-configured. If needed, we can add optional functions to increase the functionality of the pre-configured RET670 IEDs to meet the specific requirements of your transformer or shunt reactor.

The extremely fast differential protection function with automatic CT ratio matching and vector group compensation makes RET670 the ideal solution for the most demanding applications. Furthermore, one RET670 IED can be extended to contain two differential protection functions to protect the most advanced system configurations. This transformer protection IED is designed to operate correctly over a wide frequency range in order to accommodate power system frequency variations during disturbances and generator start-up and shut-down. It has very low requirements on the main CTs, and no interposing CTs are required.

RET670 features also several functions for local and remote apparatus control on all sides of the transformer. Secure bay and station wide interlocking allows you to avoid dangerous or damaging switchgear operations and to ensure personnel safety.

2.      REG 670

            REG670 IED (Intelligent Electronic Device) provides protection and monitoring for generators, prime movers and step-up transformers in hydro-, pump-storage-, gas-, combined cycle-, steam- and cogeneration stations. With excellent performance, flexibility and scalability it fulfills the demanding requirements of every corner of the world for both new installations and retrofits.

Based on ABB's extensive experience, REG670 takes generator protection to a new performance level. Up to 24 analog inputs permit integration of main and back-up protection in one IED. Alternatively, additional objects, such as transformers, can be included in the generator protection scope. This enables full duplication of the protection in main one and main two. All this reduces the number of IEDs needed to protect the entire generating station, increasing availability at the same time. This in turn simplifies the installation and reduces its lifecycle cost from commissioning to maintenance and spare parts. Its functions also incorporate intelligent fault criteria to ensure unrivalled selectivity and sensitivity.

A generator protection system with REG670 meets the requirements for maximum dependability and availability. The generator differential protection features extremely fast detection criteria, with a typical operate time of 15 ms - and yet the IED maintains high security.

REG670 also features injection-based 100% stator and rotor earth-fault protection and 3rd harmonic based 100% stator earth-fault protection. These solutions enable a new way to optimize the cost-performance ratio of the protection system in relation to the importance or size of the generating station. ABB's innovated implementation of the injection principle allows injection via a neutral point VT or even via an open-delta VT located in the generator terminals. As no changes need to be made in the primary circuit or in the grounding resistor, the design, installation and commissioning of the protection system is easy and fast. The 3rd harmonic based 100% stator earth-fault protection utilizes the differential principle, which provides high sensitivity and security. This ensures correct operation even during low load conditions.

3.      REC670 – optimized for transmission applications

REC670 IEDs (Intelligent Electronic Device) provide control solutions for any type of switchgear and different switchgear configurations. The customized REC670 gives you the freedom to select the functionality entirely according to your needs. The pre-configured REC670 variants simplify handling since the basic functionality is included and pre-configured. If needed, you can add optional functions to easily increase the functionality of the REC670 IEDs to meet the specific requirements of your switchyard.

REC670 integrates advanced voltage control for transformers in a substation in a single IED. The IEDs feature a large HMI for local control and instant access to important data, such as settings, events and disturbance information.

The outstanding I/O capability in REC670 enables control of several bays with complete measurement with only one IED. For instance, one REC670 IED is capable of handling control of all apparatuses in one entire diameter in 1 ½ breaker arrangement including breaker failure protection for all breakers.

4.      RED 670

The RED670 IED (Intelligent Electronic Device) is designed for protection, monitoring and control of overhead lines and cables. In addition, this IED is capable of handling transformer feeders, generator and transformer blocks. It provides an extensive functionality with configuration opportunities and expandable hardware to meet your specific requirements.

The RED670 IEDs are delivered pre-configured, type tested and set with default parameters for fast and efficient commissioning. These IEDs are equipped with complete functionality adapted for single pole breaker or multi-breaker arrangement with single or three phase tripping. If needed, they can also be easily adapted to meet the specific requirements of your power system. The wide application flexibility makes these IEDs an excellent choice for both new and retrofit installations.

The RED670 IEDs feature phase-segregated current differential protection with excellent sensitivity for high resistive faults and secure phase selection for up to five line terminals. Two- or three-winding power transformers can be included in the protected zone.

5.      REB 670

The REB670 IED (Intelligent Electronic Device) is designed for the protection and monitoring of busbars, T-connections and meshed corners from medium to extra high voltage levels. Due to its extensive I/O capability, REB670 protects single and double busbars with or without transfer bus, double circuit breaker or one-and-half circuit breaker arrangements.

It provides selective, reliable and fast fault clearance for all types of internal phase-to-phase and phase-to-earth faults in solidly earthed or low-impedance earthed power systems. It can also handle all internal multi-phase faults in isolated or high-impedance earthed power systems.

6.      REL670 – optimized for transmission applications

REL670 IEDs (Intelligent Electronic Device) provide versatile protection, monitoring and control functionality with maximum flexibility and performance optimized for transmission overhead lines and cables. The powerful IED provides distance protection for double circuit, parallel operating and series compensated lines. This, together with flexible and expandable hardware, allows the IED to meet your specific requirements. As a result, you can benefit from applications with multiple algorithms and comprehensive bay control functionality, including synchronizing, synchro-check, deadline detection and auto-reclosing.

Furthermore, REL670 IEDs are able to protect and control several objects, for instance a combination of a line and a transformer with a single IED.

REL670 provides protection of power lines with high sensitivity and low requirement on remote end communication. Measurements and setting of all five zones with six setting groups are made completely independent, which ensures high reliability for all types of lines. The distance and earth-fault protection functions can communicate with remote end in any communication scheme. It offers full control and interlocking functionality required for control of apparatuses in a substation.

REL670 provides both customized and pre-configured protection solutions. The pre-configured IEDs are equipped with complete functionality adapted for four different configuration alternatives

Chapter 7

Application of IED

IEDs (intelligent electronic device) are used with SCADA (supervisory control and data acquisition) system. SCADA system is mainly used for power system automation and for stronger protection and control of any system. Power system automation is the act of automatically controlling the power system via instrumentation and control devices. Substation automation refers to using data from Intelligent electronic devices (IED), control and automation capabilities within the substation, and control commands from remote users to control power system devices.

Since full substation automation relies on substation integration, the terms are often used interchangeably. Power system automation includes processes associated with generation and delivery of power. Monitoring and control of power delivery systems in the substation and on the pole top reduce the occurrence of outages and shorten the duration of outages that do occur. The IEDs, communications protocols, and communications methods, work together as a system to perform power system automation. The term “power system” describes the collection of devices that make up the physical systems that generate, transmit, and distribute power. The term “instrumentation and control (I&C) system” refers to the collection of devices that monitor, control, and protect the power system

Application of IED

1.      Substation automation

2.      Mass transit system

3.      Traction signaling and control system

4.      Water supply management system

5.      Automation industries

6.      Robotics

7.      Smart grid

8.      Condition monitoring

Substation automation

The major advantage is SA (Substation automation) software for monitoring and control, microprocessor based RTU, remotely operable load break switches, data communication interfaces, distribution network simulator and necessary field instrumentation. The substation IEDs can be used to retrieve the substation data. Use of IEDs simplifies the SA installation at the substation level. Further, conversion of protocol from proprietary (with existing relays) to DNP3 has been addressed. The capabilities of the developed Substation Automation System include:

1.      Monitoring of voltage, current, power factor, real power, reactive power, voltage and current unbalance

2.      etc. on in-coming / out-going feeders and transformers

3.      Monitoring of circuit breaker, manual switch and isolator status and operation history

4.      Alarm generation under abnormal operating conditions

5.      Monitoring of local / remote selector switch status

6.      Monitor transformer health status

7.      Remote operation of 33kV, 11kV and 415 V breakers and bus couplers

8.      Detailed engineering tools for data acquisition and automation implementation

           

Mass transit

             Transit authorities use SCADA to regulate electricity to subways, trams and trolley buses; to automate traffic signals for rail systems; to track and locate trains and buses; and to control railroad-crossing gates.

Smart grid

In the Smart Grid, protection engineers should be provided with advanced tools to execute event analysis more effectively making sure the system is restored as quickly as possible. Since the manual event analysis is a time consuming process, this IED proposes a scheme for real-time automated collecting, analyzing, archiving, and displaying of Substation Intelligent Electronic Device (IED) data generated during a power system events. How the relevant information is extracted to generate a customized report, especially considering protection engineers' needs is discussed. Several intelligent IED data analysis application tools are incorporated for the purpose of effective IED data processing. A software application named “Report Generator” is developed for the purpose of data integration and information exchange to create the report with a predefined format. A simulation case is given for more detailed description of the automation process. This solution ensures high efficiency in root-course analysis aimed at understanding and trouble-shooting relay operations, resulting in improved reliability of power system operation

Traction control

Control of electric traction power supply networks associated with electrified railways has been a requirement in Britain since the turn of this century. The first electrification schemes lacked remote control facilities, each large sub-station site being manned. The author looks at the gradual introduction of high resolution graphics man/machine interfaces in the control rooms with SCADA systems. The involvement of the operators in the design of the system is also described

Condition monitoring

 As IED continuously monitor all electrical as well as physical parameter of power equipment it can be used for condition monitoring of a device with some advanced devices. Condition monitoring is the process of monitoring a parameter of condition in machinery, such that a significant change is indicative of a developing failure. It is a major component of predictive maintenance. The use of conditional monitoring allows maintenance to be scheduled, or other actions to be taken to avoid the consequences of failure, before the failure occurs. Nevertheless, a deviation from a reference value (e.g. temperature or vibration behavior) must occur to identify impeding damages. Predictive Maintenance does not predict failure. Machines with defects are more at risk of failure than defect free machines. Once a defect has been identified, the failure process has already commenced and CM systems can only measure the deterioration of the condition. Intervention in the early stages of deterioration is usually much more cost effective than allowing the machinery to fail. Condition monitoring has a unique benefit in that the actual load, and subsequent heat dissipation that represents normal service can be seen and conditions that would shorten normal lifespan can be addressed before repeated failures occur. Serviceable machinery include rotating equipment and stationary plant such as boilers and heat exchangers.

Chapter 8

Benefits of IED

1.      Saves Time

             IED operates at very high speed. It continuously monitor the system parameter and if any abnormal condition is occur IED will take corrective action immediately and send detail report of fault to operator. IED’s also capable to communicate with multiple devices at a time. Thus IED reduces the operation time of system.

2.      Economical

      IED operate at very less power as it consists of only electronic devices. Generally less than 1 watt (+12v/-12v) power is required for its operation. Therefore running cost of IED is very less. Maintenance of IED system is very less or no maintenance required, thus maintenance cost is less.

3.      Reduces manpower need

      With use of advanced SCADA system IED’s are able to reduces large amount of human interference and reduces the man power need for operation of substation.

4.      Reliable

       IED’s are much sensitive to abnormal condition therefore IED protects all equipment thus system is more reliable as compare to conventional system.

Advantages of IED

1.      Can be operated and control from remote place

      IED’s are able to communicate with multiple channels at a time and we can send any control command to any type of IED. Also IED’s have capability of self decision over any abnormal condition. IED control all electrical equipment like switchgear and online tab changer or voltage regulator, or automatic power factor correction i.e. selection of capacitor banks

.

2.      Communication

       There is different ways for communication of IED with operator and control.

                          i.            Using Ethernet

                        ii.            Using GPS (global positioning system)

                      iii.            Using modem

                      iv.            Using fiber optic cable

                        v.            Using wi-fi area

                      vi.            Using 3G technology

                    vii.            Using Internet

Generally SCADA operated substation uses 5kHz to 500kHz frequency for wireless communication.

3.      Reporting

  If any abnormal condition is occur IED will take corrective action and send detail report of what action is to be done and condition of fault to operator. Example of fault report is as follow.

Report shows date, time, station number, fault values, and status of all equipment.

4.      Monitoring

      IED monitor all values of Electrical as well as physical values hence can be used for condition monitoring of power equipment like generator, transformer, busbar, switchgears etc.

5.      Space required is less

      As IED consist of all electronic parts, hence space required for IED is very less and IED can be mounted on panel board as well as near to power equipment.

6.      Self decision capability

      IED is programmed in such fashion that it is able to take self decision over any abnormal condition like tripping of circuit breaker, generate a alarm signal at substation etc.

Chapter 9

Disadvantages of IED

1.      Provision for manual operating

IED consist of all electronic component hence in case any fault occur on system total system control may get loose hence there is necessary to keep another provision of control and operating of equipments at substation.

2.      Initial cost of system is high

In this system Substation Automation consist of software and hardware combination. IED consist of electronic component which are multifunctional and programmed. Thus initial cost of system gets increased as compared to ordinary system.

3.      Required excellent operators  to keep control on system

As we seen it is a combination of hardware and software. So operator should know about programming of devices and should have some computer knowledge.

References
 

Magazines

1.      “Electrical India”, January 2009 , A Chery Publication.

2.      “IEEE journals”

Websites

1.      www.ee.qub.ac.uk/power

2.      www.crestuk.org

3.      www.abb.com/substationautomation

4.      www.teshmont.com

Conclusion

           

With proper control and protection equipment like IED (Intelligent Electrical equipment) with use of SCADA system substation automation gets more stronger on protection , control, communication, metering etc. and increases the reliability of system through advanced way. Major advantage of system is fault report immediately send by IED to operator thus he can read it get understand easily as well as take corrective action further.

A complete system solution for automated integration of substation Intelligent Electronic Device (IED) data is to generate a customized event report for protection engineers as we seen in paper. Detailed strategy for IED data processing and information exchange to meet the needs of protection engineers is advanced as compare to conventional system. 

Gaurav Anil Gaikwad