GE D90 Plus Instruction Manual page 64

ELECTRICAL INSTALLATION
Form-A and solid-state relay output contacts
DANGER:
NOTE:
Contact inputs wiring
56
Some form-A and solid-state relay (SSR) outputs include circuits to monitor the DC voltage
across the output contact when it is open, and the DC current through the output contact
when it is closed. Each of the monitors contains a level detector whose output is set to
logic 1 (on) when the current in the circuit is above the threshold setting. The voltage
monitor is intended to check the health of the overall trip circuit, and the current monitor
can be used to seal-in the output contact until an external contact has interrupted current
flow.
Figure 28: Form-A relay contact input functions
Figure 29: Solid-state relay contact input functions
The operation of voltage and current monitors is reflected with the corresponding
FlexLogic™ operands (Cont Op ###
which can be used in protection, control and alarm logic. The typical application of the
voltage monitor is breaker trip circuit integrity monitoring; a typical application of the
current monitor is seal-in of the control command.
Relay contacts must be considered unsafe to touch when the unit is energized! If the
relay contacts need to be used for low voltage accessible applications, it is the
customer's responsibility to ensure proper insulation levels!
When current monitoring is used to seal-in the form-A and solid-state relay contact
outputs, the FlexLogic™ 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 values in the region of the pickup value).
Contact inputs are not polarity sensitive. A dry contact has one side connected to terminal
A_5. This is the positive 48 V DC voltage rail supplied by the power supply module. The
other side of the dry contact is connected to either of the contact input terminals. The
other contact input terminal is connected to the DC negative terminal (A_4) of the power
supply module. When a dry contact closes, a 10 mA current will initially flow through the
associated circuit. Once the relay has validated the state change of the contact the input
current is reduced to 1 mA.
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 one of the contact input
terminals. In addition, the negative side of the external source must be connected to the
Von, Cont Op ### Voff, Cont Op ###
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 3: INSTALLATION
Ion, and
Cont Op ### Ioff)