RFL 9300 RFL Electronics Inc.
October 29, 2001 10 - 6 (973) 334-3100
10.3.5 SERIAL COMMUNICATIONS LINK WITH THE SINGLE-POLE CHASSIS
The Supervisor Controller utilizes the SV_DAT (U9-25), SP_DETECT (U9-26) and SP_CHASSIS (P1-C29) in-
puts to interface with the Single-Pole chassis. Messages from the Single-Pole chassis are received on the
SV_DAT input. SP_DETECT is used to detect the presence or absence of the Single-Pole chassis. A low signal
on this line indicates that the Single-Pole chassis is connected to the RFL 9300. In order for single-pole trip to
be active, SNGPOLE (U1-2) must be a logic low. This can only happen when jumper J5 on the 93B SV card is
in the single-pole position (G), and the Single-Pole chassis is connected to the RFL 9300 via a ribbon cable
which in turn connects SP_CHASSIS (P1-C29) to ground. If the 93B SV detects that any of these connections
have changed since the interface with the Single-Pole chassis was initialized it will declare a SINGLE-POLE
CHASSIS ALARM locally (#54) and transmit the alarm message to the Display Controller. If the Single-Pole
chassis is connected to the RFL 9300 but jumper J5 is in the H position, the Single-Pole chassis is said to be in
three-pole mode. In this mode none of the single-pole trip algorithms apply and the RFL 9300 operates as a
normal two-terminal or three-terminal relay with six additional output trip contacts per phase.
Once initialized by the Display Controller, the single-pole logic begins transmitting a 16-bit status word to the
Supervisor at 264ms intervals. The transmission is asynchronous with a start bit (active low), 16 data bits and
one stop bit (active high) The message bits are synchronized to the system clock and are in the mark, or logic 1
condition when no messages are being transmitted. The Supervisor will not accept any status changes as valid
until it receives two identical 16-bit messages in succession. If a status change is accepted as valid the Super-
visor transmits byte 2 of the status message, as received from the single-pole logic, to the Display Controller. As
long as there are no changes in single-pole logic status detected by the Supervisor, byte 2 of every 10th status
message (2.64 second interval) is transmitted to the Display Controller. This is to insure that the Display Con-
troller will not miss a change in single-pole logic status.
If the Supervisor goes 600ms without receiving a status message it will declare a SINGLE-POLE CHASSIS
ALARM locally and transmit the alarm message to the Display Controller.
10.3.6 SINGLE-POLE TRIP ALGORITHMS
Open Breaker - When the RFL 9300 is configured for single-pole operation the open breaker condition is deter-
mined on a phase-by-phase basis. Any Phase Controller sending a ZTC signal to the RFL 93B SV will wait to
declare its’ breaker to be open until the RFL 93B SV returns the open breaker signal.
Reclose Block - The RFL 93B SV monitors all trip signals originating at both the local and remote terminals. If
the RFL 9300 is configured for single-pole trip operation and a trip signal is detected, a 3-second timer is
started. If trip signals, originating either at the local or remote terminals, are detected on the remaining two
phases before the 3-second timer expires the reclose block output relay will be energized for 50ms.
Selective Pole Relaying - If Selective Pole Relaying is not enabled and multiphase trips are calculated locally, all
three single-pole breakers will be tripped and a reclose block output signal will be issued. If Selective Pole Re-
laying is enabled and multiphase trips are calculated locally, only the breakers on the faulted phases will be
tripped.
Backup Mode Trip - If the RFL 9300 is configured for single-pole trip operation and the relay is operating in
backup mode, any trip signal that is calculated locally will result in all three single-pole breakers being tripped
and a reclose block signal being issued. This is the case regardless of the status of Selective Pole Relaying
which does not apply when backup mode is active. In three-terminal systems it is very possible that during a
communications outage between two of the terminals, the third terminal may still be providing differential protec-
tion. Only the two terminals experiencing the communications problem may be in backup mode (if enabled). If
the third terminal calculates a permissive trip it will transmit trip signals to the two terminals operating in backup
mode. Since the trip was not calculated locally these terminals will trip only on the faulted phase(s).
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