This document provides an overview of protective relaying principles and the career path for young protection engineers. It discusses the need to protect power systems from faults, the different types of relays and their functions. It also outlines the challenges facing young protection engineers such as gaining practical experience and developing a solid understanding of power systems. Mentorship and continuous learning are emphasized as important for success in this field.

1. PRINCIPLES AND PHILOSOPHY
OF PROTECTIVE RELAYING
P1-COURSE PRESENTATION
BY
ENGR.W.A ASONMWONRIRI

2. PERSONAL INFORMATION
NAME: Engr. Wilfred Amen Asonmwonriri (MNSE)
DATE OF BIRTH: September 1970
Married
Protection Engineer
FORMAL EDUCATION
M.ENG(POWER AND MACHINES)
B.ENG(ELECTRICALAND ELECTRONICS)
PROFESSIONALAND TECHNICAL EDUCATION
Travelling waves systems: QUALITROL
Power System Engineering: Power System Training Institute: - New Delhi
Protective Relay Testing using Omicron Test set :OMICRON
Condition-Based evaluation of power transformer:HIVOTEC-UNILAG
Reyrolle Protective Relays Applications……REYROLLE
Power system training methods(Israel Electricity Training School. Tel-Aviv)

3. PRINCIPLES AND PHILOSOPHY OF
RELAYING PROTECTION
The electric power system is designed to generate
and supply energy to meet the demands of the
users on a continuous basis.
It comprises of many diverse equipment that are
very expensive
The whole system must be kept in operation
continually without major breakdown so as to
prevent severe disruption to the normal routines
of modern society

4. • To keep the power system in operation
continually adequate protection must be
provided.
• Protective relays detect abnormalities or faults
and eliminate such abnormalities by isolating
the smallest portion of the system.

5. Faults on transmission line –
possible causes
• Lightning
• Switching
• Pollution
• Salt storms
• Growing trees
• Bush fires
• Damage or sabotage
The most often!

6. RELAYS
• Relays are the devices, which monitor the conditions of a
circuit/device and give instructions to isolate it under
unhealthy conditions.
• The conditions of a circuit or equipment are monitored
from the electric power system parameters, the most basic
of which are voltage, current, frequency and power.
• The power system parameters have predetermined values
under healthy conditions.
• . Any shift from this normal behaviour therefore, could be
the result of a fault condition.

7. PRIMARY AND SECONDARY RELAYS
• Primary Relays are the first line of defense in the
system. They are generally high-speed relays. The
primary relay scheme is designed to remove
minimum equipment from service.
• Secondary Relays also called backup relays are
intentionally delayed in their operation so as to
give the primary relays a chance to operate first.
The backup relays scheme is independent of the
primary relay scheme and operates if the primary
relay scheme fails to operate.

8. ELECTRICAL POWER SYSTEM DEVICE
NUMBERS AND FUNCTIONS
• 1 Master Element
•
• 2 Time Delay Starting or Closing Relay
• 3 Checking or Interlocking Relay
• 4 Master Contactor
• 5 Stopping device
• 6 Starting Circuit breaker
• 7 Anode Circuit breaker
• 8 Control Power Disconnecting Device

9. 9 Reversing Device
10 Unit Sequence Switch
11 RESERVED FOR FUTURE APPLICATION
12 Over Speed device
13 Synchronous Speed device
14 Under Speed device
15 Speed or frequency matching device

10. • 16 RESERVED FOR FUTURE APPLICATION
• 17 Shunting or Discharge switch
• 18 Accelerating or Decelerating device
• 19 Starting to Running Transition Contactor
• 20 Electrically Operated Valve
• 21 Distance Relay
• 22 Equalizer Circuit breaker

11. • 23 Temperature Control device
• 25 Synchronizing or Synchronism Check device
• 26 Apparatus Thermal device
• 27 Under Voltage relay .
• 28 Flame Detector .
• 31 Separate Excitation device
• 32 Directional Power relay

12. • 37 Undercurrent or under power relay
• 40 Field relay
• 50 Instantaneous over current or rate of rise relay
• 51 A.C. Time Over current relay
• 52 A.C. Circuit breaker
• 55 Power Factor Relay
• 81 Frequency Relay

13. • 59 Over voltage Relay
• 63 Pressure switch
• 64 Ground Protection Relay
• 65 Governor
• 67 A.C Direction or Over-current Relay
• 79 A.C. Reclosing relay

14. • Power system protection is realized by
protecting the different primary equipment
that variously constitute the power system.
• A faulted component needs to be isolated
from the entire grid as quickly as possible to
prevent the fault from spreading to other
parts of the grid and to prevent damage to
equipment and personnel.

15. Main purposes of protective relays
• To ensure uninterrupted power supply.
• To reduce equipment damage.
• To maintain quality of service.
• To guarantee safety of life and property.
• To ensure operation of equipment at peak
efficiency.

16. ATTRIBUTES OF PROTECTIVE RELAYING
• (a) Sensitivity
A relay must be sensitive to the least fault
conditions for which it has been configured.
• (b) Reliability
• It must be relied upon at all times to respond
to any fault by relaying signals that will cause
the faulty part to be isolated.

17. • (c) Selectivity
The relay must be able to discriminate between
faults and abnormal conditions.
• (d) Simple
For a relay to be effectively used, its
construction and operation has to be simple in
nature.

18. • (e) Speed of Operation
To be able to prevent damage to the associated
equipment the relay is protecting, it must act
fast before the damage is done.
• (f) Cost
The relay should not be so expensive as to
outweigh the benefit of using it to protect the
associated equipment.

19. CATEGORIES OF FAULTS
• Single phase to ground fault
• Double phase to ground fault
• Three phase to ground fault
• Phase to phase fault
• Three phase fault.
The commonest, in occurrence, of the above fault
conditions, is the single phase to ground fault
which is about 70%.

20. Protective relaying was introduced in practice as
early as the first power systems were invented to
make sure that faults are detected and damaged
or faulted components are taken out of service
quickly.
Faults occur randomly and may be associated
with any component of the power system.
The longer the fault duration, the larger is the
extent of damage.

21. EFECTS OF FAULTS IN A POWER
SYSTEM
• Over heating
• Over voltage (surge)
• Over load
• Fire disaster
• Unbalanced loading
• Loss of synchronism
For the faults and abnormal conditions enumerated
above protective relays are designed to isolate and
reduce damage to the system equipment.

22. RELAY TYPES AND CLASSIFICATIONS
Relays are classified according to the following:
• Input - voltage, current, frequency.
• Operating Principle 􀂱 percentage or restraining.
• Function - Monitoring, Regulating, Auxiliary,
Programming or Protection.
• Performance characteristics - Definite time,
Inverse time or Distance.
• Structure - Static, Electromechanical or Thermal

23. RELAY PERFORMANCE
Performance of relays can be classified as:
• Correct
• Incorrect
• Inconclusive.
Incorrect Operation
• This can be due to the following factors:
• Incorrect Relay Setting
• Personnel Error
• Equipment Malfunction

24. Incorrect tripping may be either failure to trip or false
tripping.
Failure to trip can be caused by faulty associated
instrument transformer, circuit breakers, control cables
and wiring and station batteries.
• Inconclusive Operation
• This is the last resort when no evidence is available
either for a correct or incorrect operation. Quite often,
this is a personal involvement.

25. RELAY OPERATING TIME
Relays can be classified in terms of their operating
times as follows:
• High Speed Relays - operate in less than three (3) cycles
• Slow speed relays - operate in three (3) cycles or more
• Time delay relays - have built in time delay facility to
allow co-ordination with other relays within the power
system.
• Instantaneous relays - have no deliberate time delay
facility. They operate instantaneously.

26. BASIC COMPONENTS OF A
PROTECTION SYSTEM
• CURRENT TRANSFORMERS
• VOLTAGE TRANSFORMERS
• CAPACITOR VOLTAGE TRANSFORMERS
•
• CIRCUIT BREAKERS
• RELAYS
• CONTACTORS
• DC BATERRY BANKS

28. EQUIVALENT CIRCUIT OF A CVT

29. BASIC COMPONENTS OF LINE
PROTECTION
PROTECTION
EQUIPMENT
TRIP
COIL
TELE
COM
DC SYSTEM
FAULT
VOLTAGE
TRANSFORMER
CURRENT
TRANSFORMER
CIRCUIT BREAKER

30. ZONES OF PROTECTION
• For effective protection of the system with
minimum part disconnected during fault,
protection zones are mapped out.
• Motor Protection Zone
• Generator Protection Zone
• Transformer Protection Zone
• Bus bar Protection Zone
• Lines Protection Zone

31. Zones of Protection
 To limit the extent of the power system that is disconnected when
a fault occurs, protection is arranged in zones
 Zones of protection should overlap, so that no part of the power
system is left unprotected
 Location of the CT connection to the protection usually defines
the zone
 Unit type protections have clear zones reach e.g Diff. Relay, REF
relay

32. RELAY OPERATING TIME
Relays can be classified in terms of their
operating times as follows:
• High Speed Relays - operate in less than three (3)
cycles
• Slow speed relays - operate in three (3) cycles or
more
• Time delay relays - have built in time delay
facility to allow co-ordination with other relays
within the power system.
• Instantaneous relays - have no deliberate time
delay facility. They operate instantaneously.

33. DEVICES PERFORMING MORE THAN
ONE FUNCTION
If one device performs two relatively important functions in an
equipment so that it is desirable to identify both of these functions,
this may be done by using a double device function such as: 50/51 -
An over-current relay with an instantaneous element and an inverse
element.

34. SUFFIX NUMBERS
• If two or more devices with the same function number and suffix letter (if
used) are present in the same equipment then these are distinguished as
follows 52x-1, 52x-2, 52x-3 etc
SUFFIX LETTERS
Suffix letters are used with device numbers for various purposes. The
meaning of each suffix letter or combination of letters should be clearly
indicated in the legend on the drawings or publications accompanying the
equipment. Example: 52 TC – Tripping coil of the breaker

35. COMMONLY USED LETTERS
• R - Raising relay or for remote operation
• L - Lowering relay or for local operation
• O - Opening relay or contactor
• C - Closing relay or contactor
• CS - Control Switch
• CC - Closing Coil
• TC - Trip Coil
• PB - Push Button
• G - Generator
• T - Transformer
• L - Line
• F - Feeder etc

36. REPRESENTATION OF DEVICE
CONTACTS
• There are almost in all electrical devices,
particularly in circuit breakers and relays, a set
of contacts which are normally open and
another set of contacts which are normally
closed.
• When the device operates, the contact
position reverses. Those normally open
become closed and vice versa.

39. CARRER GUIDE FOR YOUNG
PROTECTION ENGINEERS
The protection engineer is saddled with ensuring
the reliability and stability of the power system.
As a protection engineer you are an electrical
engineer with specialisation in power systems
and protection systems.
It is obviously a great field as it forces you to fully
understand the technical aspects of the power
industry.

40. The major challenges facing the young
protection engineers
Bridging the gap between schooling and the
real world as most engineering students are
bombarded with abstractions without ideas of
the big picture let alone a sense of the value
of work they will be doing.
Entry –level position and qualification is
another challenge as the protection engineer
requires a solid foundation in electric power
systems to be successful.

41. • A deep understanding of the operation of all the
elements of the power system is required as one
cannot protect an equipment which operation he
does not know.
• He requires a solid understanding of many
technical features of the power system
including:machine design parameters,bus
configuration, trip circuits, symmetrical
components,fault currents, unbalanced power
flow and much more

42. • For an early success in the protection
engineering career the young engineer should
undergo the following:
• He should be made to pass through training
courses that are tailored specifically for
protective relaying.

43. • He should place himself on a continous
professional development program by accessing
power system references and training materials
which include textbooks,relay manuals, standards
and technical papers.
• He should place himself on a continous
professional development program by accessing
power system references and training materials
which include textbooks,relay manuals, standards
and technical papers.

44. • The young engineer needs to develop good
hands-on-the job skills with ability to stay on
the job untill he gets result.

45. • The young engineer should be passionate
about his work as he requires the positive
mental attitude that goes with love for work
to succeed.
• He needs to be quick and able to learn new
things all the time

46. • He needs a mentor for guidance as he
progresses in his career.
• He needs to develop or join an existing
professional network or peer group in the
industry.

47. – This is quite a lot to ask of any one person but the
professional and psychological reward can be very
great.I cannot imagine a better field to begin a
power engineering career than protective relaying
as the challenges it provides are endless and the
learning process a life- long one.