Seminar Report On Numerical Relay
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SEMINAR REPORT ON NUMERICAL RELAY
Submitted by: MD. ASAHAD
In partial fulfilment of requirements requirements for the awar award d of the degr degree ee of Bachelor of Technology in ELECTRICAL AND ELECTRONICS ENGINEERING
SCHOOL OF ENGINEERING COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY KOCHI - 682 022 NOVEMBER 2013
COCHIN UNIVERSITY UNIVE RSITY OF SCIENCE AND TECHNOLOGY DIVISION OF ELECTRICAL ENGINEERING SCHOOL OF ENGINEERING KOCHI - 682 022
CERTIFICATE This is to certify that this report titled NUMERICAL RELAY RELAY is a bona fide record recor d of the seminar presented by MD ASAHAD. This seminar has to be included towards the partial fulfilment of the requirement for the award of B.T B.Tech. ech. Degree in Electrical and Electronics Engineering at Cochin University of Science and Technolo gy.
Staff Co-ordinator
Head of the Department
DECLARATION I declare that this is a bona fide report of the S7 seminar titled NUMERICAL RELAY
done towards the
partial fulfilment of the
requirement for the award of B. Tech. Degree in Electrical and Electronics
Engineering
at
Cochin
University
of
Science
and
Technology.
Submitted by: MD. ASAHAD
ACKNOWLEDGEMENT
This seminar would not have been successfully materialized had it not been for the several people who have directly or indirectly helped me. I am extremely indebted to all of them and I whole heartedly thank everyone for their valuable support. I am grateful to Dr. G. Madhu my principal for providing us with good facilities and a proper environment for this accomplishment. I thank Dr. Usha Nair, Head of the Department of Electrical and Electronics Engineering for her support and appreciation. I thank Dr. C.A. Babu and Dr. Asha E. Daniel in guiding us reach such a standard to deliver a seminar with no hesitation. I am grateful to Mrs. Sheena K. M., my class co-ordinator for all her guidance and I am highly obliged to everyone all for their valuable suggestions, appraisal and guidance. I am also thankful to my seniors, friends and those people who helped us with valuable information through several discussion boards over internet. I truly admire my parents for their constant encouragement and enduring support, which was inevitable for the success of my ventures. Above all, I thank God Almighty for the ever abiding kind blessings.
ABSTRACT
Modern numerical relays have many new features that were not available in electromechanical or analog designs. These new features include setting groups, programmable logic, and adaptive schemes. Although these features make numerical relays very powerful, they also create a need for reviewing commissioning methods. Although there are several references regarding commissioning of electromechanical relays. Most methods employed today are based on experience. With the advent of numerical relays, the emphasis has shifted from hard ware to soft ware. Hard ware is more or less the same between any two numerical relays,what distinguishes one numerical relay from the other is the software.
CONTENTS S.NO.
TOPIC
PAGE
1
INTRODUCTION
1
2
RELAY
1
3
BASIC OPERATION
1
4
CIRCUIT DIAGRAM
3
5
NUMERICAL RELAY
3
6
DESCRIPTION AND DEFINITION
3
7
DEVELOPMENT CYCLE OF A NUMERICAL RELAY
5
8
BLOCK DIAGRAM OF A NUMERICAL RELAY
5
9
BASIC PRINCIPLE
6
FUNDAMENTAL REQUIREMENTS OF NUMERICAL 10
6 RELAY ADVANTAGES AND SPECIAL FEATURES OF
11
7 NUMERICAL RELAY RELAY
12
ADAPTIVE PROTECTION
8
13
DISADVANTAGE
8
14
PROTECTIVE ELEMENT TYPES
9
15
MANUFACTURERS
10
16
APPLICATIONS
10
17
SERVICE LIFE OF NUMERICAL RELAY
12
18
CONCLUSION
13
19
REFERENCE
14
Seminar Report 2013
Numerical Relay
INTRODUCTION:
Numerical
relays
have
revolutionized
protection,
control,
metering
and
communication in power systems. Functional integration, new methods of communication, reduced physical size, and an enormous amount of available information are but a few of the benefits of this revolution. Having made the initial conceptual adjustment of relating rela ting objects from electromechanical technology such as rotating discs and moving armatures to such electronic technology as analog to digital
converters
and
comparators
protection
practitioners then must deal with programming a relay. Initially programming was no more than selecting values for relay settings. Further advancement in digital technology, however has made possible advanced and sophisticated programming of logical functions and analog quantities. A good understanding of relay programming is necessary to take full advantage of the many functions integrated into numerical relays and use these functions in different applications to enhance operation of a power network. Unfortunately many users avoid relay programming, considering it too complex. Because of this perceived complexity, not all users investigate the use of relay programming to realize automation and control applications. Many cost saving opportunities and simple engineering solutions to automation applications are reliably achieved by using the protection relay programming features. RELAY:
Relay is an automatic device which senses the faults and recloses its contacts and gives adequate alarm and trip signal. BASIC OPERATION :
A simple electromagnetic relay, such as the one taken from a car in the first picture, is an adaptation of an electromagnet. It consists of a coil of wire surrounding a soft iron core, an iron yoke, which provides a low reluctance path for magnetic flux, a moveable iron armature, and a set, or sets, of contacts; two in the relay pictured. The armature is hinged to the yoke and mechanically linked to a moving contact or contacts. It is held in place by a spring so that when the relay is de-energised there is an air gap in the magnetic circuit. In this condition, one of the two sets of contacts in i n the relay pictured is closed, and the other set is open.
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Other relays may have more or fewer sets of contacts depending on their function. The relay in the picture also has a wire connecting the armature to the yoke. This ensures continuity of the circuit between the moving contacts on the armature, and the circuit track on the Printed Circuit Board (PCB) via the yoke, which is soldered to the PCB. When an electric current is passed through the coil, the resulting magnetic field attracts the armature and the consequent movement of the movable contact or contacts either makes or breaks a connection with a fixed contact. If the set of contacts was closed when the relay was de-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open. When the current to the coil is switched off, the armature is returned by a force, approximately half as strong as the magnetic force, to its relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in industrial motor starters. Most relays are manufactured to operate quickly. In a low voltage application, this is to reduce noise. In a high voltage or high current application, this is to reduce arcing. If the coil is energized with DC, a diode is frequently installed across the coil, to dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise generate a voltage spike dangerous to circuit components. Some automotive relays already include that diode inside the relay case. Alternatively a contact protection network, consisting of a capacitor and resistor in series, may absorb the surge. If the coil is designed to be energized with AC, a small copper ring can be crimped to the end of the solenoid. This "shading ring" creates a small out-of-phase current, which increases the minimum pull on the armature during the AC cycle. By analogy with the functions of the original electromagnetic device, a solid-state relay is made with a thyristor or other solid-state switching device. To achieve electrical isolation an optocoupler can be used which is a light-emitting diode (LED) coupled with a photo transistor.
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Numerical Relay
CIRCUIT DIAGRAM OF A TYPICAL RELAY:
Figure 1 Typical Relay's Circuit Diagram
sd sd NUMERICAL RELAY:
A numerical relay utilizes a microcontroller with software based protection algorithms for the detection of electrical faults. DESCRIPTION AND DEFINITION:
The numerical relay, also called a digital relay by some manufacturers and resources, refers to a protective relay that uses an advanced microprocessor to analyse power system voltages and currents for the purpose of detection of faults in an electric power system. There are grey areas on what constitutes a digital/numeric relay, but most engineers will recognize the design as having the majority of these attributes: attri butes: 1. The relay applies A/D (analog/digital) conversion processes to the incoming voltages and currents. 2. The relay analyses the A/D converter output to extract, as a minimum, magnitude of the incoming quantity; most commonly using Fourier transform concepts (RMS and some form of averaging are used in basic products). Further, the Fourier Fourier transform is
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commonly used to extract the signal's phase angle relative to some reference, except in the most basic applications. 3. The relay is capable of applying advanced logic. It is i s capable of analysing anal ysing whether the relay should trip or restrain from tripping based on current and/or voltage magnitude (and angle in some applications), complex parameters set by the user, relay contact inputs, and in some applications, the timing and order of event sequences. 4. The logic is user-configurable at a level well beyond simply changing front panel switches or moving of jumpers on a circuit board. 5. The relay has some form of advanced event recording. The event recording would include some means for the user to see the timing of key logic decisions, relay I/O (input/output) 6. changes, and see in an oscillographic fashion at least the fundamental frequency component of the incoming AC waveform. 7. The relay has an extensive collection of settings, beyond what can be entered via front panel knobs and dials, and these settings are transferred to the relay via an interface with a PC (personal computer), and this same PC interface is used to collect event reports from the relay. 8. The more modern versions of the digital relay will contain advanced metering and communication protocol ports, allowing the relay to become a focal point in a SCADA system.
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DEVELOPMENT DEVELOPME NT CYCLE OF A NUMERICAL RELAY:
Figure 2 Development Cycle
BLOCK DIAGRAM OF A NUMERICAL RELAY:
Figure 3 Block Diagram
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BASIC PRINCIPLE:
Low voltage and low current signals (i.e., at the secondary of a VT and CT) are brought into a low pass filter that removes frequency content above about 1/3 of the sampling frequency (a relay A/D converter needs to sample faster than 2x per cycle of the highest frequency that it is to monitor). The AC signal is then sampled by the relay's analog to digital converter at anywhere from about 4 to 64 (varies by relay) samples per power system cycle. In some relays, the entire sampled data is kept for oscillographic records, but in the relay, only the fundamental component is needed for most protection algorithms, unless a high speed algorithm is used that uses sub cycle data to monitor for fast changing issues. The sampled data is then passed through a low pass filter that numerically removes the frequency content that is above the fundamental frequency of interest (i.e., nominal system frequency), and uses Fourier transform algorithms to extract the fundamental frequency magnitude and angle. Next the microprocessor passes the data into a set of protection algorithms, which are a set of logic equations in part designed by the protection engineer, and in part designed by the relay manufacturer, that monitor for abnormal conditions that indicate a fault. If a fault condition is detected, output contacts operate to trip the associated circuit breaker(s). FUNDAMENTAL FUNDAMENTA L REQUIREMENTS OF NUMERICAL RELAY:
SPEED: The relay system should disconnect the faulty section as fast as possible for
the following reasons:
Electrical apparatus may be damaged if they are made to carry the fault current for a
long time.
A failure on the system leads to a great reduction in the system voltage. As a res result ult the
system may become unstable.
The high speed relay system decreases the possibility of development of one type of
fault into the other more severe type.
SENSITIVITY: It is the ability of the relay system to operate with low value of
actuating quantity.
RELIABILITY: It is the ability of the relay system to operate under the pre-
determined conditions, without reliability the protection would be rendered largely in effective and could even become a liability.
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SELECTIVITY: It is the ability of the protective system to select correctly that part of
the system in trouble and disconnect the faulty part without disturbing the rest of the system.
SIMPLICITY: The relaying system should be simple so that it can be easily
maintained. Reliability is closely related to simplicity. The simpler the protection scheme the greater will be its reliability.
ECONOMY: The most important factor in the choice of a particular protection
scheme is the economic aspect. Sometimes it is economically unjustified to use an ideal scheme of protection and a compromise method has to be adopted. As a rule, the protective gear should not cost more than 5% of the total cost.
ADVANTAGES AND SPECIAL FEATURES OF NUMERICAL RELAY:
Ability to combine a large number of protective and monitoring functions in a single
relay unit. In the earlier protection systems, separate relay units were necessary for each main function resulting in more number of units, more wiring, and lesser reliability. Measured values are processed digitally by microprocessor.
High level of flexibility: the relay meets the most complex protective and monitoring
requirements.
Various protective functions can be freely selected and allocated to the various
auxiliary relays by means of software tripping matrix.
The memory of the relay enables the relay to retain the values of variables responsible
for tripping, time taken to operate etc.
No need for measuring instruments at the output as data can be seen digitally.
Comprehensive self-monitoring self-checking feature.
Allow GPS (Geographical positioning system) time stamping.
Increased reliability due to self-checking.
Data interface access – increased communication ability. These relays can
communicate with other
Relays, protected equipments, and control and protection devices in the substation.
User friendly, yet highly capable.
Relay provides fault designations and information.
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Numerical Relay
High speed.
Save quantized data from faults and disturbances.
ADAPTIVE PROTECTION:
Numerical relays can be designed to include abilities to change their settings automatically. Some of the functions that can be made adaptive are:
Using the most appropriate algorithms during a disturbance.
Changing settings of relays of a disturbance network as the system loads or
configuration change.
Changing the settings of second and third zone disturbance relays as the system
operating state changes.
Compensating for the CT & PT errors.
Changing the allowable overload of circuits and equipment as the ambient conditions,
especially the temperature change.
Changing the circuit auto-reclosers delays to ensure that the circuit is reclosed after
the arc is extinguished.
Fiber optical communication with substation LAN.
Adaptive relaying scheme.
Permit historical data storage.
DISADVANTAGES DISADVANTAG ES OF NUMERICAL RELAY:
High initial cost
Requires stable power supply.
If used for multifunction in a single feeder, failure of relay may cause total protection
failure for the equipment.
Requires EMC environment.
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Numerical Relay
PROTECTIVE ELEMENTS TYPE:
Protective Elements refer to the overall logic surrounding the electrical condition that is being monitored. For instance, a differential element refers to the logic required to monitor two (or more) currents, find their difference, and trip if the difference is beyond certain parameters. The term element and function are quite interchangeable in many instances. For simplicity on one-lines, the element/function is usually identified by what is referred to as an ANSI device number, and hence there are three terms (element, function, device number) in use for approximately the same concept. In the era of electromechanical and solid state relays, any one relay could implement only one or two protective elements/functions, so a complete protection system may ma y have many relays on its panel. In a digital/numeric relay, many functions/elements are implemented by the microprocessor programming. Any one digital/numeric relay may implement one or all of these device numbers/functions/elements. A relatively complete listing of device numbers is found at the site ANSI Device Numbers. A summary of some common device numbers seen in digital relays is:
21 - Impedance (21G implies ground impedance)
27 - Under Voltage (27LL = line to line, 27LN = line to neutral/ground)
32 - Directional Power Element
46 - Negative sequence current
47 - Negative sequence voltage
50 - Instantaneous Over Current (subscript N or G implies Ground)
51 - Inverse Time Over current (subscript N or G implies Ground) 59 - Over Voltage (59LL = line to line, 59LN = line to neutral/ground)
67 - Directional Over Current (typically controls a 50/51 element)
79 - Auto-reclosure
81 - Under/Over Frequency
87 - Current Differential (87L=transmission line diff; 87T- Transformer diff;
87G=generator diff)
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MANUFACTURERS:
There are many more than listed here. This especially becomes true when one includes relays manufactured for niche or regional markets, and manufactures that offer relays in part hidden and buried within a larger product mix.
GE Multilin ABB
AREVA T&D
Basler
Bresler
Beckwith
Cooper
Cutler Hammer
DEIF
General Electric
RFL
Schneider Electric
Schweitzer
Siemens
Orion Italia
VAMP
ZIV
NARI
APPLICATIONS:
Relays are used to and for: 1. Control a high-voltage circuit with a low-voltage signal, as insome types of modems or audio amplifiers. 2. Control a high-current circuit with a low-current signal, as in the starter solenoid of an automobile. 3. Detect and isolate faults on transmission and distribution lines by opening and closing circuit breakers (protection relays). Page | 10
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Numerical Relay
4. Isolate the controlling circuit from the controlled circuit when the two are at different potentials, for example when controlling a mains-powered device from a low-voltage switch. The latter is often applied to control office lighting as the low voltage wires are easily installed in partitions, which may be often moved as needs change. They may also be controlled by room occupancy detectors in an effort to conserve energy. 5. Logic functions. For example, the Boolean AND function is realised by connecting normally open relay contacts in series, the OR function by connecting normally open contacts in parallel. The change-over or Form C contacts perform the XOR (exclusive or) function. Similar functions for NAND and NOR are accomplished using normally closed contacts. The Ladder programming language is often used for designing relay logic networks. 6. Early computing. Before vacuum tubes and transistors, relays were used as logical elements in digital computers. See ARRA (computer), Harvard Mark II, Zuse Z2, and Zuse Z3. 7. Safety-critical logic. Because relays are much more resistant than semiconductors to nuclear radiation, they are widely used in safety-critical logic, such as the control panels of radioactive waste-handling machinery. 8. Time delay functions. Relays can be modified to delay opening or delay closing a set of contacts. A very shorts (a fraction of a second) delay would use a copper disk between the armature and moving blade assembly. Current flowing in the disk maintains magnetic field for a short time, lengthening release time. For a slightly longer (up to a minute) delay, a dashpot is used. A dashpot is a piston filled with fluid that is allowed to escape slowly. 9. The time period can be varied by increasing or decreasing the flow rate. For longer time periods, a mechanical clockwork timer is installed.
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SERVICE LIFE OF NUMERICAL RELAY:
A typical service life of numerical relays is between fifteen and twenty years. For comparison electro mechanical relays had a service life of 20years.Numerical relays are sophisticated devices with printed circuit board. In case of hardware faults the relay has to be replaced because of computer technology. For errors in software the requirement is to download a correct or a new version of relay software into the relay hardware. When feeder protection has to be updated or modified, it is easier to replace all protection especially if i f the different manufacturer employed for protection modification. Sometimes the numerical protection is replaced a few years after the first installation. Rapid changes in computer technology causes a shorter life of current numerical relays because of requirements for relay replacements when other protection and control assets are being replaced. Once when the computer technology stabilises the real service life of the numerical relays will be available.
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CONCLUSION:
Numerical relays are highly compact devices, characterised with fast operation, high sensitivity, self-monitoring, and low maintenance. Online remote data exchange between numerical relays and remotely located devices offers remote relay settings applications, data processing for network operations and maintenance or remotely analysing analysing recorded fault data. With numerical protection because of the numerous and complex settings to be entered it is important to have procedures, processes and standards in place to ensure careful management of the modern numerical relay. It has been found possible to standardise on the large number of settings entered, leaving a few site specific settings to be determined. It is important that the settings are not entered manually on site, but downloaded into the relay after careful checking and factory tests. Numerical relays are environment friendly because of very small amount of raw material used for their manufacturing easy dismantling and the good component rate of recovery and recycling. Only printed circuit boards have to be separated and processed separately.
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REFERENCES:
1. A comprehensive approach for numerical relay system evaluation and test : Sato, H. ; Mitsubishi Electr. Corp., Japan ; Takano, T. ; Inoue, S. ; Oda, S. 2. Commissioning numerical relays : Closson, J.R. ; Basler Electr. Co., Highland, IL, USA ; Young, M. 3. Issues and opportunities for testing numerical relays : Sachdev, M.S. ; Power Syst. Res. Group, Saskatchewan Univ., Saskatoon, Sask., Canada ; Sidhu, T.S. ; McLaren, P.G.
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