Specifications

Page 14–6
FOCUS System Manual
break in the loop is detected it would then
switch to operating as a Pass Unit.
• PRI-MP - Multi-drop Pass Unit, the
opposite end of the Gap Unit module and
all other modules must be configured as a
"Pass Unit". The Pass Unit receives on
channel A and transmits on channel B or
vice versa to pass the trip/data information
on.
Figure 14–6.
PRI with Contact Bounce Override (3ms setting).
14.2.2 Contact Bounce Override
The first setting on the configuration screen is the
“Contact Bounce” setting. which applies to the
transmit portion of the module. This setting deter-
mines how long an input is stretched at the
transmit end. The choices are 0, 1, 3, or 10
milliseconds for each of the four functions. With a
setting of 0 milliseconds, the input is not inten-
tionally stretched. By default, up to
125-microsecond delay is inherent to the system.
Settings of 1, 3, or 10 milliseconds continues
keying for the specified time after the input
stimulus is removed. This lets you override the
contact bounce by effectively bridging the gaps in
keying stimulus, as shown in Figure 14-6.
A setting of 1 or 3 milliseconds is normal for this
option and probably will not affect the perfor-
mance of any connected scheme. Note that
shortening the contact bounce override timer
increases system security, whereas lengthening
this time slightly increases system dependability.
A 10ms setting should never be used for direc-
tional comparison schemes.
14.2.3 Trip Hold Timer
The first of these receive settings is the “Trip Hold
Time” setting. It has four possible values — 0, 10,
30, or 100 milliseconds — for each output
function. The trip hold timer determines how long
the trip output remains closed after the received
trip signal goes away.
If you are using the channel for pilot relaying, a
normal setting for this function would be 0
milliseconds. The connected protective relaying
system should provide the appropriate channel
logic, if it is required, for functions such as
transient blocking and carrier continuation. In
some blocking schemes it may be appropriate to
use the 10 millisecond setting for carrier continu-
ation, to ensure that the local end pilot tripping
relays remain blocked until the remote end carrier
start relays have time to reset after the clearing of
an external remote fault. Note that this applies to
blocking schemes, not to permissive overreaching
type schemes. In either case, be sure to carefully
coordinate the addition of this time delay with the
connected protective relay scheme to ensure
compatibility with transient block and pilot
tripping logic.
If you are using the channel in a direct transfer trip
mode, it may be appropriate to use a 10, 30, or 100
millisecond trip hold timer to ensure that the
connected auxiliary tripping relay has sufficient
time to energize and seal in. Note that the FOCUS
PRI outputs are not designed to interrupt or carry
large magnitude trip currents. The maximum
current rating is one amp. Use of any trip hold
time delay increases overall system dependability
and decreases security.
012345678901234567890ms
Keying Stimulus
PRI Input Response
When Using Multi-drop Redundant systems,
the PRI/PRS that initiates a trip will see and
trip for its own trip key unless a security
setting of 2ms or greater is applied.
NOTE