Eaton Digitrip 520 - Page 16

16
Instructional Leaflet IL70C1037H05
Effective October 2009
Digitrip models 520, 520i; and 520M, 520Mi,
520MC, 520MCi trip units for use only in
Magnum and Magnum DS circuit breakers
EATON CORPORATION www.eaton.com
Figure 13. Zero Sequence Sensing Scheme for 3200A Frame
Figure 14. Multiple Source/Multiple Ground Scheme
Source
Black
Trip
Actuator
Digitrip 520
with GF
Load
a
b
c
a
This scheme uses a large zero sequence CT to magnetically sum the currents and the output is sensed via element R
4
.
b
A jumper is required on B-6, B-7 to program the Digitrip to use element R
4
.
c
This scheme is not applicable to four-pole breakers.
R
5
R
5
R
5
φ
φ
T
M2
M1
B5
B4
I /2
G
I /2
G
I /2
G
I /2
G
I
G
I
G
i
g
i
g
i /2
g
i /2
G
i /2
g
i /2
g
i /2
g
N
in
B5
B5
B4
B4
N
N
Digitrip
Ground
Sensor
otes:N
Breaker M2 trips since this is the only breaker seeing the I
G
fault via element R
5
.
No jumper on B-6, B-7 terminals—all breakers are programmed for standard residual ground fault protection.
Auxiliary CTs not shown. Wiring needed at system level is shown as a dotted line.
Capital letters represent primary current. Lowercase letters represent secondary current.
The three breakers (M1, M2, and T) must all have the same breaker/sensor rating.
Neutral Sensors Wired
in a Loop Configuration