Use Of Form-A And Solid-State Relay Outputs In High Impedance Circuits - GE T60 Instruction Manual

3 HARDWARE
Figure 3–14: FORM-A AND SOLID-STATE CONTACT OUTPUTS WITH VOLTAGE AND CURRENT MONITORING
The operation of voltage and current monitors is reflected with the corresponding FlexLogic operands (
, and
CONT OP # VOFF CONT OP # ION
the voltage monitor is breaker trip circuit integrity monitoring; a typical application of the current monitor is seal-in of the
control command.
See the Digital Elements section of chapter 5 for an example of how form-A and solid-state relay contacts can be applied
for breaker trip circuit integrity monitoring.
Consider relay contacts unsafe to touch when the unit is energized.

USE OF FORM-A AND SOLID-STATE RELAY OUTPUTS IN HIGH IMPEDANCE CIRCUITS

For form-A and solid-state relay output contacts internally equipped with a voltage measuring circuit across the con-
NOTE
tact, the circuit has an impedance that can cause a problem when used in conjunction with external high input
impedance monitoring equipment such as modern relay test set trigger circuits. These monitoring circuits may con-
tinue to read the form-A contact as being closed after it has closed and subsequently opened, when measured as
an impedance.
The solution is to use the voltage measuring trigger input of the relay test set, and connect the form-A contact
through a voltage-dropping resistor to a DC voltage source. If the 48 V DC output of the power supply is used as a
source, a 500 , 10 W resistor is appropriate. In this configuration, the voltage across either the form-A contact or
the resistor can be used to monitor the state of the output.
Wherever a tilde "~" symbol appears, substitute with the slot position of the module; wherever a number sign "#"
appears, substitute the contact number
NOTE
When current monitoring is used to seal-in the form-A and solid-state relay contact outputs, the Flex-
Logic operand driving the contact output should be given a reset delay of 10 ms to prevent damage
of the output contact (in situations when the element initiating the contact output is bouncing, at val-
ues in the region of the pickup value).
GE Multilin
) which can be used in protection, control, and alarm logic. The typical application of
T60 Transformer Protection System
3.2 WIRING
3
,
CONT OP # VON
3-13