1. RELAY CO-ORDINATION
WITH FAULT CALCULATION
MD. SAROWAR ALAM
ASSISTANT MANAGER (Technical)
SYSTEM PROTECTION AND METERING DIVISION
CHITTAGONG.
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
2. Objectives
To determine proper relay setting
To improve the system reliability
To avoid un-wanted tripping
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
3. Co-ordination of protective relays refers to co-
relating the settings of various relays/protection
systems for harmonious and selective operation.
CO-ORDINATION
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
4. Basic requirements of a good protection
system include selectivity, discrimination,
adequateness, stability, sensitivity, reliability and
time characteristics .To achieve these desirable
requirements proper co-ordination of relay
settings is essential.
CO-ORDINATION
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
5. CO-ORDINATION
Neighboring protective zones overlap. Hence
there is a need for co-ordinating the time settings
so that only faulty part gets quickly disconnected
without disturbances to healthy part .
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
6. TYPES OF CO-ORDINATION
1. Current Graded
2. Time Graded
3. Both Current and Time Graded
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
7. 1. Current Graded
Current graded co-ordination means
downstream has lower current setting than
upstream.
Current
I3
I2
I1
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
8. Disadvantage of Current
Graded
Although upstream has higher current setting,
so it causes damage of equipment due to
high current passing for long time.
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
9. 2. Time Graded
Time graded co-ordination means downstream
has lower time setting than upstream.
Time
t3
t2
t1
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
10. Disadvantage of Time Graded
Although upstream has higher time setting, so
when fault occurs near to the bus then high
current pass through equipment for long
time and causes damage of equipment.
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
11. 3. Time and Current Graded
The principle of Both Time and Current
Graded is that higher the current lower the
relay trip time.
Time
Current
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
12. 1. Fault calculation
2. Time grading (Grading Margin)
3. Switching transient current (Inrush)
NECESSARY FACTORS FOR
CO-ORDINATION
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
13. Grading Margin
Operating time difference between two
devices to ensure that downstream device
will clear fault before upstream device trips.
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
14. Grading Margin includes
I. Breaker opening time
II. Allowance for errors
III. Relay overshoot time
IV. Safety margin
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
15. • Traditional (Grading margin - between relays)
Breaker opening time - 0.10 Sec.
Allowance for errors - 0.15 Sec
Relay overshoot - 0.05 Sec.
Safety margin - 0.10 Sec.
Total - 0.40 Sec
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
16. Fault Calculation Procedure
Two Methods:
I. Per Unit method (100MVA Base)
II. MVA method (No Base MVA)
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
25. Per Unit method
15.8074.36516.73φ – φ - G
12.6145.35915.23φ - G
9.0886.00912.1φ - φ
10.496.9313.983φ
Rampur 11kV
Bus Fault (kA)
Rampur 33kV
Bus Fault (kA)
Halisahar 33kV
Bus Fault (kA)
Fault Type
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
26. FEATURES OF THE SOFTWARE
1. Graphical view of single line diagram.
2. Fault Calculation for different configuration.
3. Relay setting flexibility.
4. Curve plotting to cross check the co-ordination
5. Finally shows the settings sheet.
Prepared by-
MD. SAROWAR ALAM,
ASSISTANT MANAGER,
SPMD-CTG, PGCB.
08-11-2012
