Adaptive Relaying,Report

Adaptive Relaying
SIET, VIJAYAPUR Dept. of EEE Page 1
Chapter 1: INTRODUCTION
1.1 Background: Adaptive relays
Modern electric power systems can deliver energy to users very reliably. Protective
relays in the power system play an important role in assuring this continuous service. Relays
monitor the status of the system continuously and detect failures or abnormalities within their
assigned zone of protection.
The control action takes place by opening a minimum number of circuit breakers to
isolate the defective element an element that would have otherwise caused excessive damage
or possibly collapse of the power system.
Although protective relays should detect all system abnormalities quickly, other
considerations might detract from this primary objective.
In general, a relay system is designed to achieve the highest levels of speed,
reliability, selectivity, simplicity, and economics. Since it is impractical to satisfy all
requirements simultaneously, compromises must be made. A typical conflictory objective is
embedded in the reliability of a relay system. The dependability and security of a relay
system establish its reliability.
Dependability is a measure of the relay system to perform properly in removing
system faults. Security is a measure of the relay tendency in not initiating an incorrect trip
action. There is always a compromise between security and dependability. The dependability
or security can be enhanced significantly by utilizing redundant relays.
If the contact of the redundant relay is connected in parallel with the original relay,
then the dependability is increased. On the other hand, if the contacts are connected in series,
the security is enhanced. With conventional relays, the protective system design is either
biased toward the dependability or the security. Therefore, the highest levels of dependability
and security can‟t be achieved at the same time.

Adaptive Relaying
1.2 Motivation
 Enabling the introduction of new relaying concepts capable to design smarter, faster, and
more reliable digital relay, Examples of new concepts: integrated protection schemes,
adaptive protection & predictive protection.
 Conventional schemes: cannot adapt to changing operating conditions, affected by
noise& depend on DSP methods (at least 1-cycle).
 Single-pole tripping or auto re-closer SPAR requires the knowledge of faulted phase (on
detecting SLG Single-pole tripping is initiated, on detecting arcing fault recloser is
initiated).
 Changing the fault condition, particularly in the presence of DC offset in current
waveform, as well as network changes lead to problems of under-reach or over-reach.
 Conventional schemes suffer from their slow response.
 If the generator is grounded by high impedance, detection of ground faults is not easy
(fault current < relay setting).Conventional algorithms suffer from poor reliability and
low speed (1-cycle).
 Conventional differential relays may fail in discriminating between internal faults and
other conditions (inrush current, over-excitation of core, CT saturation, CT ratio
mismatch and external faults).

Adaptive Relaying
Chapter 2: Working Principle of Adaptive Relaying
2.1 Working Principle
The diagram shows an inner section diagram of a relay. An iron core is surrounded
by a control coil. As shown, the power source is given to the electromagnet through a control
switch and through contacts to the load. When current starts flowing through the control coil,
the electromagnet starts energizing and thus intensifies the magnetic field. Thus the upper
contact arm starts to be attracted to the lower fixed arm and thus closes the contacts causing a
short circuit for the power to the load. On the other hand, if the relay was already de-
energized when the contacts were closed, then the contact move oppositely and make an open
circuit.
The working of a relay can be better understood by explaining the following diagram
given below.
Fig .2.1: Working principle of Basic Relay
Relays are mainly made for two basic operations. One is low voltage application and
the other is high voltage. For low voltage applications, more preference will be given to
reduce the noise of the whole circuit. For high voltage applications, they are mainly designed
to reduce a phenomenon called arcing.
As soon as the coil current is off, the movable armature will be returned by a force
back to its initial position. This force will be almost equal to half the strength of the

Adaptive Relaying
magnetic force. This force is mainly provided by two factors. They are the spring and also
gray.
Fig .2.2: Switching circuits
2.2 Components of an adaptive protection system
Every adaptive protection consists of three main components: hardware,
communication system and software.
2.2.1 Hardware:
The hardware of adaptive protections is mainly protective relays' hardware. The
possible hardware architectures are: Contacts, Batteries, Ct‟s, Pt‟s, Relay coil, trip coil,
computers, etc.
A single computer performs all the functions in a substation. With this alternative,
since all protection operations depend on a single computer, which can cause a serious
unavailability problem, it is hard to convince protection engineers to accept this
alternative.
12 A set of relays implements a specified protection function. For example, the
protection of a single transmission line may consist of over-current, distance and traveling-
wave-based relays. „
This alternative is in close conformation with existing protection practices, a relay
with multiple processors to realize a single protection scheme.

Adaptive Relaying
For example, a relay may be realized by multiple processors to achieve higher
computational speed.
Chapter 3: TYPES OF RELAYS
There are three basic types of relays they are as follows:
 Electromagnetic Relay.
 Solid-state Relays (SSRs).
 Microprocessor Based relay.
3.1 Electromagnetic Relay
In our simple relay above, we have two sets of electrically conductive contacts.
Relays may be “Normally Open”, or “Normally Closed”. One pair of contacts are classed as
Normally Open, An example of this arrangement is given below:
Fig .3.1: Electromagnetic Relay
Relays may be “Normally Open” ,or “Normally Closed”. One pair of contacts are
classed as Normally Open, (NO) or make contacts and another set which are classed as
Normally Closed, (NC) or break contacts.

Adaptive Relaying
In the normally open position, the contacts are closed only when the field current is
“ON” and the switch contacts are pulled towards the inductive coil.
In the normally closed position, the contacts are permanently closed when the field current
is “OFF” as the switch contacts return to their normal position.
These terms normally Open, Normally Closed or Make and Break Contacts refer
to the state of the electrical contacts when the relay coil is “de-energized”, i.e. no supply
voltage connected to the inductive coil.
Electromagnetic relays are those relays which are operated by electromagnetic action.
Modern electrical protection relays are mainly micro processor based, but still
electromagnetic relay holds its place. It will take much longer time to be replaced the all
electromagnetic relays by micro processor based static relays. So before going through detail
of protection relay system we should review the various types of electromagnetic relays.
Practically all the relaying device are based on either one or more of the following types of
electromagnetic relays.
 Magnitude measurement,
 Comparison,
 Ratio measurement.
Principle of electromagnetic relay working is on some basic principles. Depending upon
working principle these can be divided into following types of electromagnetic relays.
 Attracted Armature type relay,
 Induction Disc type relay,
 Induction Cup type relay,
 Balanced Beam type relay,
 Moving coil type relay,
 Polarized Moving Iron type relay.
3.1.1 Electromagnetic Relay Working
Practically all the relaying device are based on either one or more of the following types of
electromagnetic relays.
 Magnitude measurement.
 Comparison.
 Ratio measurement.
Principle of electromagnetic relay working is on some basic principles. Depending upon
working principle these can be divided into following types of electromagnetic relays.

Adaptive Relaying
 Attracted Armature type relay,
 Induction Disc type relay,
 Induction Cup type relay,
 Balanced Beam type relay,
 Moving coil type relay,
 Polarized Moving Iron type relay.
3.1.2 Attraction Armature Type Relay
Attraction armature type relay is the most simple in construction as well as its working
principle. These types of electromagnetic relays can be utilized as either magnitude relay or
ratio relay. These relays are employed as auxiliary relay, control relay, over current, under
current, over voltage, under voltage and impedance measuring relays. Hinged armature and
plunger type constructions are most commonly used for these types of electromagnetic relays.
Among these two constructional designs, hinged armature type is more commonly used. We
know that force exerted on an armature is directly proportional to the square of the magnetic
flux in the air gap, if we ignore the effect of saturation.
The operation of relay is influenced by
 Ampere – turns developed by the relay operating coil,
 The size of air gap between the relay core and the armature,
 Restraining force on the armature.
Fig .3.2: Conceptual view of Balanced Beam Relay

Adaptive Relaying
3.1.3 Construction of Attracted Type Relay
This relay is essentially a simple electromagnetic coil, and a hinged plunger.
Whenever the coil becomes energized the plunger being attracted towards core of the coil.
Some NO-NC (Normally Open and Normally Closed) contacts are so arranged mechanically
with this plunger, that, NO contacts become closed and NC contacts become open at the end
of the plunger movement. Normally attraction armature type relay is dc operated relay. The
contacts are so arranged, that, after relay is operated, the contacts cannot return their original
positions even after the armature is de energized. After relay operation, this types of
electromagnetic relays are reset manually. Attraction armature relay by virtue of their
construction and working principle is instantaneous in operation.
3.2 Solid-state Relays (SSRs)
Fig 3.3 Solid-state Relays
SSRs use semiconductor output instead of mechanical contacts to switch the circuit.
The output device is optically-coupled to an LED light source inside the relay. The relay is
turned on by energizing this LED, usually with low-voltage.

Adaptive Relaying
3.3 Microprocessor Based relay
Fig 3.4 Microprocessor Based relay
 A microprocessor-based digital protection relay can replace the functions of many
discrete electromechanical instruments.
 These convert voltage and currents to digital form and process the resulting
measurements using a microprocessor.
Fig 3.5: Microprocessor based relay is connected to overhead Transmission Line
 The digital relay can emulate functions of many discrete electromechanical relays in
one device, simplifying protection design and maintenance.

Adaptive Relaying
 Each digital relay can run self-test routines to confirm its readiness and alarm if a
fault is detected.
 Numeric relays can also provide functions such as communications (SCADA)
interface, monitoring of contact inputs, metering, waveform analysis, and other useful
features.
3.3.1 Digital relay consists of:
 Analogue input subsystem,
 Digital input subsystem,
 Digital output subsystem,
 A processor along with RAM (data scratch pad),
 Main memory (historical data file) and Power supply.
3.3.2 Digital relaying involves digital processing of one or more analog
signals in three steps:
 Conversion of analogue signal to digital form.
 Processing of digital form.
 Boolean decision to trip or not to trip.
3.3.3 Advantages of Digital Relay
 High level of functionality integration.
 Additional monitoring functions.
 Functional flexibility.
 Capable of working under a wide range of temperatures.
 They can implement more complex function and are generally more accurate.
 Self-checking and self-adaptability.
 Able to communicate with other digital equipment (pear to pear).
 Less sensitive to temperature, aging
 Economical because can be produced in volumes.
 More Accurate.
 plane for distance relaying is possible.
 Signal storage is possible.

Adaptive Relaying
3.3.4 Limitations of Digital Relay
 Short lifetime due to the continuous development of new technologies.
 The devices become obsolete rapidly.
 Susceptibility to power system transients.
 As digital systems become increasingly more complex they require specially trained
staff for Operation.
 Proper maintenance of the settings and monitoring data.
Chapter 4: Characteristics of Adaptive Relaying
4.1 Reliability:
It must operate when it is required. Inherent reliability is a matter of design based on
experience. This can be achieved partly by,
 Simplicity and robustness in construction.
 High contact pressure.
 Dust free enclosures.
 Good contact material.
 Good workmanship.
 Careful maintenance.
4.2 Selectivity:
It should be possible to select which part of the system is faulty and which is not and
should isolate the faulty part of the system. It is achieved by two ways:
 Unit system of protection.
 Non unit system of protection.
4.3 Speed: -A protective relay must operate at required speed. It should neither be too slow
nor too fast may result in undesired operation during transient fault.
There must be a correct coordination provided in various power system protection
relays in such a way that for fault at one portion of the system should not disturb other
healthy portion. Fault current may flow through a part of healthy portion since they are

Adaptive Relaying
electrically connected but relays associated with that healthy portion should not be operated
faster than the relays of faulty portion otherwise undesired interruption of healthy system
may occur. Again if relay associated with faulty portion is not operated in proper time due to
any defect in it or other reason, then only the next relay associated with the healthy portion of
the system must be operated to isolate the fault. Hence it should neither be too slow which
may result in damage to the equipment nor should it be too fast which may result in undesired
operation.
4.4 Sensitivity: - A relay should be sufficiently sensitive so that it operates reliably when
require under the actual condition in the system which produce the least tendency for
operation.
4.5 Sensitivity: - A relay should be sufficiently sensitive so that it operates reliably when
require under the actual condition in the system which produce the least tendency for
operation.
Chapter 5: Application & Advantages
5.1 Applications
In adaptive relaying, the system can be regularly monitored and analyzed so that when
fault occurs, the system can be isolated while in conventional relays we need to add a voltage
restraint or to compromise the setting. When a network is out of the service for a long time,
the inrush current is very high while restoration. Due to high inrush current the relays will be
blocked and the circuit is reclosed. Since cold load pick up is a sequence of events followed
by outages plus the restoration time, so the computer derived calculation is amenable. In case
of transformer protection, an idea of computer algorithm has been proposed in a recent work
that is adaptive and utilized filtering. This algorithm relies on monitor transformer currents to
determine the state of transformer. By changing the monitoring states the algorithm can adapt
to different operation conditions.

Adaptive Relaying
The adaptive relaying system summarizes the following application areas:
 Proactive load shedding.
 Multi-terminal distances relay coverage.
 Fault type changing speed of operation.
 Load flow compensation.
 Variable breaker failure problems.
 Adaptive reclosing.
 Permissive reclosing.
 Operating time depending on distance to fault.
 Adaptive last-resort islanding.
 Variable breaker-failure timing.
 Adaptive re-closing.
 Adaptive zone-1 ground distance.
 Adaptive sequential instantaneous tripping.
 Adaptive multi-terminal relay coverage.
5.2 Advantages
Detect system failures when they occur and isolate the faulted section from the remaining
of the system.
Minimize risk of fire, danger to personal and other high voltage systems.
5.2.1 Electromagnetic Relays (EMRs)
 Simplicity.
 Not expensive.
 Mechanical Wear.
5.2.2 Solid-state Relays (SSRs)
 No Mechanical movements.
 Light weight
 No sparking between contacts.

Adaptive Relaying
4.2.3 Microprocessor-based Relay
 Much higher precision and more reliable and durable.
 Improve the reliability and power quality of electrical power systems before, during
and after faults occur.
 Capable of both digital and analog input/output.
 High accuracy.
5.2.1 Electromagnetic Relays (EMRs)
 Simplicity.
 Not expensive.
 Mechanical Wear.
5.2.2 Solid-state Relays (SSRs)
 No Mechanical movements.
 Light weight
 No sparking between contacts.
5.2.3 Microprocessor-based Relay
 Much higher precision and more reliable and durable.
 Improve the reliability and power quality of electrical power systems before, during
and after faults occur.
 Capable of both digital and analog input/output.
 High accuracy.

Adaptive Relaying
Chapter 6: Disadvantages of Adaptive Relaying
 If relays change their settings themselves, there is a chance that the relays will not
coordinate with each other properly.
 Risk of Liability,
 Expensive to design,
 Chance that communication systems may fail,
 Have to develop fallback position and safety check
Chapter 7: Objective of Power System Protection
The objective of power system protection is to isolate a faulty section of electrical
power system from rest of the live system so that the rest portion can function satisfactorily
without any severer damage due to fault current.
Actually circuit breaker isolates the faulty system from rest of the healthy system and
this circuit breakers automatically open during fault condition due to its trip signal comes
from protection relay.
The main philosophy about protection is that no protection of power system can
prevent the flow of fault current through the system, it only can prevent the continuation of
flowing of fault current by quickly disconnect the short circuit path from the system.
For satisfying this quick disconnection the protection relays should have following
functional requirements.

Adaptive Relaying
Chapter 8: Future Scope
The example study described in this chapter is intended to demonstrate the
effectiveness of the adaptive protection concept. Further work is needed in studying more
complex voltage disturbance cases by using dynamic response curves rather than static curves
as used in this study.
Further, the proposed relay models should conform to the dynamic system
performance. The objective of this chapter is to demonstrate that the proposed adaptive
protection can tune the bias continuously based on the level of system stress and
vulnerability, as well as response from other peer relays. The logic described in chapter 3
adjusts the protection system behavior during a disturbance to avoid an otherwise
catastrophic failure.
Future work could be related to the points discussed in the previous paragraphs,
whereas three major questions arise:
 How should future distribution systems be designed to simplify integration of
DG (towards a plug-and-play system)?
 How can islanded parts of distribution systems be operated and
resynchronized?
 How can DG be dispatched centrally (if wanted), and what data infrastructure
is needed to achieve this?

Adaptive Relaying
Chapter 9: Conclusion
Technology to design the adaptive distribution protection system, utilize computer
over current relaying concept, is more expensive than the electromagnetic relays. Adaptive
relaying protection being a new protection scheme is a recurring topic on every agenda. The
ADPS utilize the changes in actual system conditions as a basis for online adjustment of
power system relay setting.
It provides the required flexibility and stability of power system distribution system
without affecting the speed and selectivity of the system.
Digital relays with adequate software and communication system make these devices
ideal for adaptive relaying. The use of adaptive relaying system provides faster protection of
distribution system as compared to old conventional relays, shorter tripping times and
improvement in selectivity.
In this article a new protection philosophy suited to the new and demanding
environment of the modern power system have been presented. The relaying community will
accept the challenges it presents and will use it for designing & developing the new
protection schemes.

Adaptive Relaying
Reference
[1]. Ms. Rachna was born on Nov 10, 1991 in Haryana. She did schooling from 35-model
school in Chandigarh and later she chose to become an electrical engineer. Currently, she is
pursuing M.Tech from Delhi College of Engineering, DTU. Her specialization is power
system and research area is Power system protection.
[2].http://www.slideshare.net/surabhivasudev/adaptive-relaying?qid=f0dfad9f-0be5-4f4d-
8f02-8b43fe99c0e1&v=&b=&from_search=1
[3].http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=481373&url=http%3A%2F%2Fie
eexplore.ieee.org%2Fiel1%2F45%2F10272%2F00481373
[4]. https://en.wikipedia.org/wiki/Adaptive-relaying#Classification
[5]. http://www.electrical4u.com/protection-system-in-power-system/
[6]. http://www.electrical4u.com/trip-circuit-supervision/
[7].https://www.google.co.in/search?q=Attraction+Armature+Type+Relay&biw=1366&bih=
667&espv=2&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjqu6Gu3-
XLAhVGC44KHQNNCwEQ_AUIBigB&dpr=1#imgrc=sM2o0GYDlVfqSM%3A
[8]. http://electrical-engineering-portal.com/few-words-about-digital-protection-relay

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