1. Advanced Protective Relaying Based on Rogowski Coil Current Sensors
Ljubomir A. Kojovic Martin T. Bishop
Cooper Power System
Thomas A. Edison Technical Center
Franskville, Wisconsin, USA

2. Iron-Core Current Transformer Rogowski CoilIp RB
Iron Core Ip
Air Core RB M IP IS IP IS VB VB IE Lm RB RB
High Impedance
Burden
Low Impedance
Burden IS VB
 0 IE
 90
I’P
IP’

3. V-I Characteristics Voltage Non-Gapped Iron-Core Current Transformer
No Air-Gap
Increasing Air-Gap
Air-Gap 1
Air-Gap 2
Linear Coupler
Operating point
Rogowski Coil
Current

4. Design Criteria
Relative Position of the Primary Conductor inside the Coil Loop
The Impact of Nearby Conductors (external electromagnetic fields)

5. Printed Circuit Board Rogowski Coil
Relative Position of the Primary Conductor inside the Coil Loop
Printed Circuit Board Rogowski Coil
Winding imprints S n
i(t) m RB
Air Core
(non-saturable)
v(t) - = dt
di(t) M nS t v ) ( m

6. Electromagnetic Fields
External
Electromagnetic Fields
Current
Voltage
v(t)
PCB1
PCB2
PCB2 wound
in opposite direction
to PCB1
i(t)

7. Designs Interior Applications Exterior Applications
Split-Core Type Rogowski Coil
Parallel Conductors

8. Printed Circuit Board Rogowski Coil Shielded Cable and Connectors
Comparison to CTs
Heavy Gauge Wires
Multi-Function Relay
Primary
Current
2000/5 A, C800
Current Transformer
10 cm
Terminal
Blocks
Weight: 90 kg
64 cm
30 cm
Printed Circuit Board Rogowski Coil
Multi-Function Relay
Primary
Current
Width 2 cm
Weight: 2 kg
30 cm
Shielded Cable and Connectors

9. Spot Networks SN1 SN2 SN3 Rogowski Coil Circuit Breaker Network
Protector
Fuse

10. Integrated Relay Protection Solutions
Zone 1 R
Network 1 G
Zone 5
Network 2
Zone 4
Bus
Zone 2
Zone 3
Load

11. Integrated Relay Protection Solutions
Zone 1
RC1
RC2 R
Network 1 G
Relay2
Network 2
Relay1
RC3
Load

12. Integrated Relay Protection Solutions
Network 1 G
Network 2
Zone 2
RC1
RC2
Fiber Optic
Cable
Relay1
Relay2
Load
Ethernet
Switch
other IEDs

13. Busbar Protection Summing Block Protected Busbar Relay Rogowski Coils

14. Traveling Wave Based Protection

15. Traveling Wave Based Protection

16. Rogowski Coil Current Sensors
Field Experience with Differential Protection of Power Transformers Based on
Rogowski Coil Current Sensors
Ljubomir A. Kojovic Martin T. Bishop
Cooper Power System
Thomas A. Edison Technical Center
Franskville, Wisconsin, USA

17. Differential Protection of Power Transformers
Fault
RMS
Difference
False differential current
causes nuisance protection operation CT

18. Differential Protection of Power Transformers
Blocking
Zone
Differential Current
Restraint Current
Operating
Zone with
Current Transformers
Expanded Operating
Rogowski Coils

19. Differential Protection of EAF Transformers
Split-Core
Rogowski Coil
Non Split-Core
Rogowski Coil
EAF
Transformer
Water Cooled Leads
50 kA – 100 kA
Tap
position
EAF
Multifunction
Relay

20. Differential Protection of EAF TransformersB C
34.5 kV
1000 V
“Water-Cooled”
Conductors
EAF
Transformer
Multi-function
Relay
Primary RCs
Secondary
RCs
Tap
Position
Shielded Cables
with Connectors

21. Differential Protection of EAF Transformers
25 MVA
32 kV/395 V
138 kV/32 kV
Filter C L
Current
Measurement
200/5 A
Rogowski Coils
Rogowski
Coils
Multi-Function
Relay
Tap
Transformer

22. RMS Values averaged per one second10 20 30 40 50 60 70 80 90
Time [minutes]
Current [kA]
EAF C-Phase Currents
RMS Values averaged per one second 10 20 30 40 50 60 70 80 90
100
Time [minutes]
Current [kA]
EAF C-Phase Currents
Min and Max Values averaged per one second
Max
Min

23. 0.12
0.14
0.16
0.18
-4000
-2000
2000
4000
Time [s]
Current [A]
0.02
0.04
0.06
0.08
-4000
-2000
2000
4000
Time [s]
Current [A]

24. 0.02
0.04
0.06
0.08
A-Phase
-4000
-2000
2000
4000
Time [s]
Current [A]

25. Circuit Breaker Operates
Relay Operates
Fault Inception
Primary Currents
Secondary Currents
Operate Signals
Restraints Signals
Trip Signals