seminar report on numerical relay

7/27/2019 Seminar report on Numerical Relay

1/20

SEMINAR REPORT

ONNUMERICAL RELAY

Submitted by:MD. ASAHAD

In partial fulfilment of requirements for the award of the degree ofBachelor of Technology

inELECTRICAL AND ELECTRONICS ENGINEERING

SCHOOL OF ENGINEERING

COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY

KOCHI - 682 022

NOVEMBER 2013


2/20

COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY

DIVISION OF ELECTRICAL ENGINEERING

SCHOOL OF ENGINEERING

KOCHI - 682 022

CERTIFICATE

This is to certify that this report titledNUMERICAL RELAYis a bona fide

record of the seminar presented by MD ASAHAD. This seminar has to be included to-

wards the partial fulfilment of the requirement for the award of B.Tech. Degree in

Electrical and Electronics Engineeringat Cochin University of Science and Technolo-

gy.

Staff Co-ordinator Head of the Department


3/20

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


4/20

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.


5/20

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.


6/20

CONTENTSS.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

10

FUNDAMENTAL REQUIREMENTS OF NUMERICAL

RELAY

6

11ADVANTAGES AND SPECIAL FEATURES OF

NUMERICAL RELAY

7

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


7/20

Seminar Report 2013 Numerical Relay

Page | 1

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 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 the relay pictured is closed, and the other set is open.


8/20


Page | 2

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 isdesigned 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.


9/20


Page | 3

CIRCUIT DIAGRAM OF A TYPICAL RELAY:

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:

1. The relay applies A/D (analog/digital) conversion processes to the incoming voltagesand currents.

2. The relay analyses the A/D converter output to extract, as a minimum, magnitude ofthe incoming quantity; most commonly using Fourier transform concepts (RMS and

some form of averaging are used in basic products). Further, the Fourier transform is

Figure 1 Typical Relay's Circuit Diagram


10/20


Page | 4

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 capable of analysing whether therelay 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 panelswitches or moving of jumpers on a circuit board.

5. The relay has some form of advanced event recording. The event recording wouldinclude 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 frequencycomponent of the incoming AC waveform.

7. The relay has an extensive collection of settings, beyond what can be entered via frontpanel 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 andcommunication protocol ports, allowing the relay to become a focal point in a

SCADA system.


11/20


Page | 5

DEVELOPMENT CYCLE OF A NUMERICAL RELAY:

BLOCK DIAGRAM OF A NUMERICAL RELAY:

Figure 3 Block Diagram

Figure 2 Development Cycle


12/20


Page | 6

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 REQUIREMENTS OF NUMERICAL RELAY:

SPEED: The relay system should disconnect the faulty section as fast as possible forthe following reasons:

Electrical apparatus may be damaged if they are made to carry the fault current for along time.

A failure on the system leads to a great reduction in the system voltage. As a result thesystem may become unstable.

The high speed relay system decreases the possibility of development of one type offault into the other more severe type.

SENSITIVITY: It is the ability of the relay system to operate with low value ofactuating 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.


13/20


14/20


Page | 8

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 systemoperating 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 afterthe arc is extinguished.

Fiber optical communication with substation LAN. Adaptive relaying scheme. Permit historical data storage.

DISADVANTAGES 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.


15/20


Page | 9

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 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)


16/20


Page | 10

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 modemsor audio amplifiers.

2. Control a high-current circuit with a low-current signal, as in the starter solenoid of anautomobile.

3. Detect and isolate faults on transmission and distribution lines by opening and closingcircuit breakers (protection relays).


17/20


Page | 11

4. Isolate the controlling circuit from the controlled circuit when the two are at differentpotentials, 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 connectingnormally 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 logicalelements 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 tonuclear 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 setof 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 longertime periods, a mechanical clockwork timer is installed.


18/20


Page | 12

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 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.


19/20


Page | 13

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 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.


20/20


Page | 14

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. ; PowerSyst. Res. Group, Saskatchewan Univ., Saskatoon, Sask., Canada ; Sidhu, T.S.

; McLaren, P.G.

seminar report on numerical relay

Documents