User Manual Manual

Functions 3-32
Publication 825-UM001B-EN-P January 2001
Figure 3.17 Isolated network: Earth (Ground) Fault on the Leads on the Motor
Side
The basic unit measures the earth current component through C
M
.
Figure 3.18 Network Earthed through a High Impedance: Earth (Ground) Fault on
the Motor Leads
The basic unit measures the vector sum of the earth currents through C
N
and the earthing resistance R.
Compensated network: The basic unit measures the vector sum of the earth currents through C
N
and the compensating coil L.
Figure 3.19 Isolated Network: Earth (Ground) Fault in the Motor
The nearer the fault is to the motor star-point, the smaller the fault current.
Figure 3.20 Network Earthed through a High Impedance: Earth (Ground) Fault on
the Motor
The basic unit measures vector sum of the earth currents through C
N
and the earthing resistance R.
Compensated network: The basic unit measures the vector sum of the earth currents through C
N
and the compensating coil L.
The nearer the fault is to the motor star-point, the smaller the fault current.
3 AC
U
3
U
1
U
2
T
1
2
3
K1
825-M
M1
C
N
I
E
C
M
3 AC
U
3
U
1
U
2
T
1
2
3
K1
825-M
M1
C
N
I
E
C
M
RL
3 AC
T
1
2
3
K1
825-M
M1
C
N
I
E
C
M
U
3
U
1
U
2
3 AC
T
1
2
3
K1
825-M
M1
C
N
I
E
C
M
U
3
U
1
U
2
RL