Numerical relays provide several advantages over traditional electromechanical relays including improved dependability, self-checking capabilities, programmable flexibility, and ability to store historical fault data. Power Grid is extensively using numerical relays for new transmission lines and retrofitting old relays. Numerical relays consolidate several protection functions into a single device and provide fault reports and data that system engineers can use to analyze power system faults and relay operations for maintenance and restoration purposes.

1. APPLICATION OF
APPLICATION OF
NUMERICAL DISTANCE
NUMERICAL DISTANCE
RELAYS
RELAYS
A PRESENTATION BY
A PRESENTATION BY
OS DEPARTMENT
OS DEPARTMENT
ER
ER-
-II,KOLKATA
II,KOLKATA

2. FOREWORD
FOREWORD
Gazette Notification from GOI dated
Gazette Notification from GOI dated
09.03.2007 regarding Grid
09.03.2007 regarding Grid
connectivity standards applicable to
connectivity standards applicable to
Transmission lines substation
Transmission lines substation-
-
Part
Part-
-III(3) stipulates that:
III(3) stipulates that:
“Two Main Numerical Distance
“Two Main Numerical Distance
“Two Main Numerical Distance
“Two Main Numerical Distance
protection scheme shall be provided
protection scheme shall be provided
on all the Transmission Lines of
on all the Transmission Lines of
220KV above for all new
220KV above for all new
substations. For existing
substations. For existing
substations,this shall be
substations,this shall be
implemented in a reasonable time
implemented in a reasonable time
frame”
frame”

3. POWERGRID’s compliance
POWERGRID’s compliance
“Technology made large populations
“Technology made large populations
possible; large populations now make
possible; large populations now make
technology indispensable
technology indispensable
POWERGRID is extensively using
POWERGRID is extensively using
Numerical relays for protection schemes of
Numerical relays for protection schemes of
all new Lines substations.
all new Lines substations.
All regional OS departments have
All regional OS departments have
undertaken retrofitting of old relays with
undertaken retrofitting of old relays with
All regional OS departments have
All regional OS departments have
undertaken retrofitting of old relays with
undertaken retrofitting of old relays with
New generation Numerical relays.
New generation Numerical relays.
POWERGRID,ER
POWERGRID,ER-
-II has completed 1
II has completed 1st
st
stage of retrofitting of Numerical distance
stage of retrofitting of Numerical distance
protection. The work for the 2
protection. The work for the 2nd
nd stage is
stage is
presently being executed.
presently being executed.
Old static type differential relays for all EHV
Old static type differential relays for all EHV
Transformers are also being retrofitted with
Transformers are also being retrofitted with
New Numerical differential protection.
New Numerical differential protection.

4. ADVANTAGES
ADVANTAGES
Improves dependability as well
as security
Has Self checking facility
Offers Very low burden
Offers Very low burden
More flexible because of
programmable capability
Adaptive relaying schemes
Permit Historical data storage

5. ADVANTAGES…Contd.
ADVANTAGES…Contd.
Fiber optical communication with
substation LAN
Allow GPS (Geographical
Positioning System) Time stamping
Positioning System) Time stamping
Numerical relays simplify interfacing
with CTs and VTs
Separate connection is not required,
zero sequence voltages and currents
can be derived inside the processor

6. ENGINEERS CHOICE
ENGINEERS CHOICE
Numerical relays represent
best compromise between:
a) Economy and performance
Dependability and security
b) Dependability and security
c) Complexity and simplicity
d) Speed and accuracy
e) Credible and conceivable

7. COMPARISON STATEMENT
COMPARISON STATEMENT

8. Numerical Distance Relay
Numerical Distance Relay
main functions
main functions
A single Numerical distance relay
has:
Distance protection
Power swing Blocking
Switch on to fault
Switch on to fault
Phase-fault (highset) overcurrent
protection
Directional earth-fault protection
Sensitive earth-fault protection
Overvoltage and undervoltage
protection

9. SPECIAL FUNCTIONS
SPECIAL FUNCTIONS
Broken conductor detection - To
detect network faults such as open
circuits, where a conductor may be
broken but not in contact with
another conductor or the earth.
another conductor or the earth.
Circuit breaker failure protection -
Generally set to back-trip upstream
circuit breakers, should the circuit
breaker at the protected terminal fail
to trip.

10. Numerical Distance protection
Numerical Distance protection
Other functions
Other functions
Control
Control
Autoreclose
Check synchronising
Monitoring
Monitoring
Voltage transformer supervision
System data
Sequence of event records
Fault records
Disturbance recorder

11. Existing Numerical Distance
Existing Numerical Distance
protection in POWERGRID
protection in POWERGRID-
-ER
ER-
-II
II

13. Numerical Differential relay
Numerical Differential relay
main functions
main functions
A single Numerical differential relay
has:
DIFFERENTIAL PROTECTION
DIFFERENTIAL PROTECTION
…
…Matching to the vector group
…Stabilization under inrush
(eg:based on the presence of second
harmonic components
harmonic components
…Stabilization under overfluxing
conditions
(eg:based on the ratio of the fifth harmonic
the ratio of the fifth harmonic
to the fundamental wave)
to the fundamental wave)
RESTRICTED EARTH FAULT
PROTECTION
DEFINITE TIME AND INVERSE TIME
OVERCURRENT PROTECTION

14. Numerical Differential protection
Numerical Differential protection
main functions…Contd.
main functions…Contd.
THERMAL OVERLOAD PROTECTION
OVER-/UNDERVOLTAGE PROTECTION
OVER-/UNDERFREQUENCY PROTECTION
OVEREXCITATION PROTECTION
…Overexcitation protection detects
…Overexcitation protection detects
impermissible high magnetic flux densitiy in
the iron core of power transformers in case of
increase in voltage and/or decrease in
frequency. Flux density above the rated value
saturates the iron core result in power
transformer overheating due to large iron
losses.

15. Numerical Differential
Numerical Differential
protection:Other functions
protection:Other functions
Monitoring
Voltage transformer
supervision
System data
System data
Sequence of event records
Fault records
Disturbance recorder

16. Existing Numerical Differential
Existing Numerical Differential
protection in POWERGRID
protection in POWERGRID-
-ER
ER-
-II
II
MICOM P-633
RET-670
RET-670
7UT613

17. A TOOL TO SYSTEM
A TOOL TO SYSTEM
ENGINEERS
ENGINEERS
Numerical relays provide comprehensive
Numerical relays provide comprehensive
fault reporting data for the analysis of
fault reporting data for the analysis of
power system faults and relay operations.
power system faults and relay operations.
Valuable information from relays
Valuable information from relays
throughout their grid may be gathered.
throughout their grid may be gathered.
After a fault, most precise fault location can
After a fault, most precise fault location can
After a fault, most precise fault location can
After a fault, most precise fault location can
be reached to narrow the search for
be reached to narrow the search for
possible damage on the line and to cut the
possible damage on the line and to cut the
down time for restoration.
down time for restoration.
Software system for relay fault records can
Software system for relay fault records can
provide the desired precision to the utility
provide the desired precision to the utility
personnel.
personnel.

18. FAULT STUDY
FAULT STUDY

19. Disturbance report
Disturbance report-
-1
1
Complete and reliable
Complete and reliable
information about disturbances
information about disturbances
in the primary and/or in the
in the primary and/or in the
secondary system together with
secondary system together with
continuous event
continuous event-
-logging is
logging is
accomplished by the
accomplished by the
accomplished by the
accomplished by the
disturbance report functionality.
disturbance report functionality.
The disturbance report, included
The disturbance report, included
in the IED, acquires sampled
in the IED, acquires sampled
data of all selected analogue
data of all selected analogue
input and binary signals
input and binary signals
connected to the function block
connected to the function block

20. Disturbance report
Disturbance report-
-2
2
Any change in Digital Inputs or
Any change in Digital Inputs or
Analog Thresholds function
Analog Thresholds function
blocks may be set to trigger the
blocks may be set to trigger the
disturbance recorder
disturbance recorder.
.
All signals from start of pre
All signals from start of pre-
-fault
fault
All signals from start of pre
All signals from start of pre-
-fault
fault
time to the end of post
time to the end of post-
-fault
fault
time, will be in the recording.
time, will be in the recording.
Every disturbance report
Every disturbance report
recording is saved in the IED in
recording is saved in the IED in
the standard formats.
the standard formats.

21. Event recorder
Event recorder
Quick, complete and reliable
Quick, complete and reliable
information about disturbances
information about disturbances
in the primary and/or in the
in the primary and/or in the
secondary system is vital e.g.
secondary system is vital e.g.
time tagged events logged
time tagged events logged
during disturbances.
during disturbances.
during disturbances.
during disturbances.
This information is used for
This information is used for
different purposes in the short
different purposes in the short
term (e.g. corrective actions)
term (e.g. corrective actions)
and in the long term (e.g.
and in the long term (e.g.
Functional Analysis).
Functional Analysis).

22. Time synchronization
Time synchronization
Time synchronization source
Time synchronization source
selector selects a common
selector selects a common
source of absolute time for the
source of absolute time for the
IED.
IED.
This makes comparison of
This makes comparison of
This makes comparison of
This makes comparison of
events and disturbance data
events and disturbance data
between all IEDs possible.
between all IEDs possible.
It is done now with the IRIG
It is done now with the IRIG-
-B
B
Protocol available with the GPS
Protocol available with the GPS
Clock.
Clock.

23. STATION COMMUNICATION
STATION COMMUNICATION
Each IED is provided with a communication
Each IED is provided with a communication
interface, enabling it to connect to one or
interface, enabling it to connect to one or
many substation level systems or equipment,
many substation level systems or equipment,
either on the Substation Automation (SA)
either on the Substation Automation (SA)
bus or Substation Monitoring (SM) bus.
bus or Substation Monitoring (SM) bus.
IEC 60870
IEC 60870-
-5
5-
-103 communication protocol
103 communication protocol
A single glass or plastic port allows design
A single glass or plastic port allows design
of simple substation automation systems
of simple substation automation systems
including equipment from different vendors.
including equipment from different vendors.
including equipment from different vendors.
including equipment from different vendors.
Disturbance files uploading is provided.
Disturbance files uploading is provided.
IEC 61850
IEC 61850-
-8
8-
-1 communication protocol
1 communication protocol
Single or double optical Ethernet ports for
Single or double optical Ethernet ports for
the new substation communication standard
the new substation communication standard
IEC61850
IEC61850-
-8
8-
-1 allows intelligent devices
1 allows intelligent devices
(IEDs) from different vendors to exchange
(IEDs) from different vendors to exchange
information and simplifies SA engineering.
information and simplifies SA engineering.

24. Return on Investment
Return on Investment
Investing on Numerical relays
Investing on Numerical relays
has greater return as it was not
has greater return as it was not
required to invest for discrete
required to invest for discrete
relays line OV/UV,LBB,AR,
relays line OV/UV,LBB,AR,
FL,DR etc.
FL,DR etc.
FL,DR etc.
FL,DR etc.
Failure Rate of Numerical relays
Failure Rate of Numerical relays
in POWERGRID has been very
in POWERGRID has been very
small, requiring less
small, requiring less
maintenance cost.
maintenance cost.

25. Return on Investment
Return on Investment
A simple example.
A simple example.
As per the New tariff regime, Outage of a
As per the New tariff regime, Outage of a
420/220/33 KV 315MVA Autotransformer
420/220/33 KV 315MVA Autotransformer
results a monetary loss of Rs. 2.5L per
results a monetary loss of Rs. 2.5L per
Day.
Day.
Tripping in case of even for extraneous
Tripping in case of even for extraneous
reasons not on Transformer fault follows
reasons not on Transformer fault follows
Health check test program,requiring a full
Health check test program,requiring a full
reasons not on Transformer fault follows
reasons not on Transformer fault follows
Health check test program,requiring a full
Health check test program,requiring a full
day.
day.
DR print, if available may help detect the
DR print, if available may help detect the
above Transformers can be restored
above Transformers can be restored
within 10
within 10-
-15 Minutes.
15 Minutes.
A single event of that order may render
A single event of that order may render
saving of the amount invested for a new
saving of the amount invested for a new
Numerical differential protection
Numerical differential protection

26. POWERGRID NUMERICAL
POWERGRID NUMERICAL
RELAYS
RELAYS
“Technology does not drive
change -- it enables change
All new substations in POWERGRID
All new substations in POWERGRID
are coming with Substation
are coming with Substation
Automation,which inevitably comes
Automation,which inevitably comes
Automation,which inevitably comes
Automation,which inevitably comes
with numerical relays with IEC61850
with numerical relays with IEC61850
Communication protocol.
Communication protocol.
Automation alongwith Numerical
Automation alongwith Numerical
relays eventually results in cost
relays eventually results in cost
effectiveness as well as Better grid
effectiveness as well as Better grid
security.
security.

27. TYPICAL ARCHITECTURE
SUBSTATION AUTOMATION SYSTEM IN
POWERGRID

28. POWERGRID NUMERICAL
POWERGRID NUMERICAL
RELAYS.. Cond.
RELAYS.. Cond.
“Once a new technology rolls over you, if
“Once a new technology rolls over you, if
you're not part of the steamroller, you're
you're not part of the steamroller, you're
part of the road
part of the road
For Older stations, POWERGRID is
For Older stations, POWERGRID is
replacing old obsolete relays with
replacing old obsolete relays with
numerical relays.
numerical relays.
numerical relays.
numerical relays.
Competitive bidding for Numerical distance
Competitive bidding for Numerical distance
relays has resulted an average cost of Rs.
relays has resulted an average cost of Rs.
1.5L per relay for the retrofitting work.
1.5L per relay for the retrofitting work.
In a few cases, repairing of old relays has
In a few cases, repairing of old relays has
been found costlier than retrofitting with a
been found costlier than retrofitting with a
new numerical relays.
new numerical relays.

29. ADAPTATION
ADAPTATION
“Our very survival depends on our ability to
“Our very survival depends on our ability to
stay awake, to adjust to new ideas, to
stay awake, to adjust to new ideas, to
remain vigilant and to face the challenge of
remain vigilant and to face the challenge of
change”
change”
Control relay schemes usually came
Control relay schemes usually came
from OEM’s like ABB,AREVA,
from OEM’s like ABB,AREVA,
SIEMENS,ER etc .
SIEMENS,ER etc .
SIEMENS,ER etc .
SIEMENS,ER etc .
POWERGRID has achieved expertise in
POWERGRID has achieved expertise in
adaptation of Numerical relay of Make say
adaptation of Numerical relay of Make say
“X” to be installed in the CR scheme of
“X” to be installed in the CR scheme of
Make “Y
Make “Y”.
”.
However, problem of Lower Making
However, problem of Lower Making
capacity of the Numerical relays in
capacity of the Numerical relays in
comparison to the old distance relay had to
comparison to the old distance relay had to
be solved by incorporating CMR’s of
be solved by incorporating CMR’s of
suitable capacity.
suitable capacity.

30. LASTWORD
LASTWORD
“Science and technology
“Science and technology
revolutionize our lives, but
revolutionize our lives, but
memory, tradition and myth
memory, tradition and myth
frame our response.”
frame our response.”
Numerical relays are here as the
Numerical relays are here as the
best available technology
best available technology
best available technology
best available technology
product as on date.
product as on date.
The advantages are many
The advantages are many
nobody can deny that the
nobody can deny that the
Numerical relays came to stay
Numerical relays came to stay
for years until a further better
for years until a further better
product replaces them.
product replaces them.