Inputs - GE 845 Instruction Manual

CHAPTER 4: SETPOINTS

Inputs

Contact Inputs
NOTE:
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
Figure 4-34: Inputs Display Hierarchy
The 845 relay is equipped with a number of Contact Inputs, depending on the Order Code,
which can be used to provide a variety of functions such as for circuit breaker control,
external trips, blocking of protection elements, etc. Contact inputs accept wet and dry
input signals. A wet type contact input signal requires an external DC voltage source. A dry
type contact input signal uses an internal DC voltage source. Depending on the DC source
level, the voltage threshold (17V, 33V, 84V, 166V) can be selected. The Contact Inputs can be
located on the HV I/O and Arc Flash cards located on slots 'B' or 'C' or 'F' or 'G' or 'H' or all.
The maximum load current that can be delivered by the relay +24 V wetting voltage supply
is 100 mA. When the internal +24 V supply is used, the current limitations of the 24V supply
must be considered.
The Contact Inputs are either open or closed with a programmable debounce time to
prevent false operation from induced voltage. The debounce time is adjustable by the user
per manufacturer specifications.
A raw status is scanned for all Contact Inputs synchronously at the constant rate of one
protection pass (1/8 cycle) as shown in the figure below. The DC input voltage is compared
to a user-settable threshold. A new Contact Input state must be maintained for a user
settable debounce time in order for the relay to validate the new contact state. In the
figure below, the debounce time is set at 2.5 ms; thus the 3rd sample in a row validates the
INPUTS
4–117