GE B30 Instruction Manual page 72

3.2 WIRING
CONTACT INPUTS:
A dry contact has one side connected to terminal B3b. This is the positive 48 V DC voltage rail supplied by the power sup-
ply module. The other side of the dry contact is connected to the required contact input terminal. Each contact input group
has its own common (negative) terminal which must be connected to the DC negative terminal (B3a) of the power supply
module. When a dry contact closes, a current of 1 to 3 mA will flow through the associated circuit.
A wet contact has one side connected to the positive terminal of an external DC power supply. The other side of this contact
is connected to the required contact input terminal. If a wet contact is used, then the negative side of the external source
must be connected to the relay common (negative) terminal of each contact group. The maximum external source voltage
for this arrangement is 300 V DC.
The voltage threshold at which each group of four contact inputs will detect a closed contact input is programmable as
17 V DC for 24 V sources, 33 V DC for 48 V sources, 84 V DC for 110 to 125 V sources, and 166 V DC for 250 V sources.
3
Wherever a tilde "~" symbol appears, substitute with the slot position of the module.
NOTE
Contact outputs may be ordered as form-a or form-C. The form-A contacts may be connected for external circuit supervi-
sion. These contacts are provided with voltage and current monitoring circuits used to detect the loss of DC voltage in the
circuit, and the presence of DC current flowing through the contacts when the form-A contact closes. If enabled, the current
monitoring can be used as a seal-in signal to ensure that the form-A contact does not attempt to break the energized induc-
tive coil circuit and weld the output contacts.
There is no provision in the relay to detect a DC ground fault on 48 V DC control power external output. We recom-
mend using an external DC supply.
NOTE
GENERAL APPLICATION CONSIDERATIONS:
Contacts outputs of protective relays, auxiliary contacts from breakers, disconnectors and other devices, are generally con-
nected to contacts inputs of protective relays. In some situations, the contact outputs of some protective relays can have
high impedance connected across it. When such a contact output is connected across a B30 contact input, it can spuriously
operate the B30 input even when the output is open, if there is a substantial distributed capacitance (represented by C1)
present in the wiring between the output and the B30 input and the debounce time setting in the B30 relay is low enough.
This false assertion of the contact input, when there is inadvertent ground present at the DC positive terminal, can be pre-
vented by inserting a resistor across the B30 input.
3-20
(Dry)
DIGITAL I/O 6B
~ 7a + ~
CONTACT IN 7a
~ 7c + ~
CONTACT IN 7c
~ 8a + CONTACT IN ~ 8a
+
~ 8c CONTACT IN ~ 8c
-
~ 7b COMMON ~ 7b
SURGE
~ 8b
B 1b
CRITICAL
B 1a
FAILURE
2b
B
B 3a -
48 VDC
B 3b + OUTPUT
B 5b HI+
CONTROL
B 6b LO+
POWER
B 6a -
8a
B SURGE
B 8b FILTER
Figure 3–19: DRY AND WET CONTACT INPUT CONNECTIONS
B30 Bus Differential System
(Wet)
DIGITAL I/O
~ 7a +
CONTACT IN
~ 7c +
CONTACT IN
~ 8a + CONTACT IN
24-250V
+
~ 8c CONTACT IN
-
~ 7b COMMON
SURGE
~ 8b
827741A4.CDR
3 HARDWARE
6B
~
7a
~
7c
~ 8a
~ 8c
~ 7b
GE Multilin