20.3 THEORY OF OPERATION
The DTT outputs on terminal block TB2 are activated when a DTT input appears at the remote terminal. The
DTT RX trip command is issued by the RFL 93B SV Supervisor Controller to the Relay I/O as the DTT TRIP
signal.
The CCS outputs on terminal block TB3 are the result of a trip decision based on the currents applied to the
relays. This trip function originates in each individual phase controller module as an X_3PT signal sent to the
test board in the display module. These signals are combined to form the TRIP signal.
When a low TRIP RELAY ENABLE signal is received from the display module's oscillography board, the RFL
9300's trip output circuits are enabled. A low trip command signal will energize the coil of the corresponding
high-speed relays. A trip confirmation signal (TRIP LATCH or DTT LATCH) derived directly from the voltage
applied to the coil is fed back to the oscillography board. On the oscillography board, a logic circuit creates a
latch condition for which the relay remains energized after the trip command signal ceases. This performs the
"make" operation of the trip function. The contact circuits are not required to "break" the trip coil (52TC) current,
because this is done by the breaker's 52a contacts. The relay will not release until it is detected that the breaker
coil current has stopped.
The current sense board detects and generates a status signal of the 52TC current. The current sense feature
exists on only two of the contact sets available in each output, so there are two sense signals per trip function.
When current is detected through the contact set, the corresponding "sense" signal goes low and is latched on
the oscillography board to be read by the Display Controller. To release the relay, the Display Controller issues
a TRIP LATCH DISABLE or DTT LATCH DISABLE signal. This squelches the latch feedback, and opens the
loop.
The customer connections for station battery are also located on the Relay I/O (TB1). It is first fused and then
distributed to the system power supply module (Section 19) and trip circuits. An RS-232 port is provided by 9-
pin D-subminiature (DB-9) connector J3 for remote programming and monitoring,
20.3.1 POWER/RS-232 BOARD
The power/RS-232 board provides connections for station battery input to the RFL 9300. It also provides a con-
nector for an RS-232 port. The components on the power/RS-232 board have circuit reference numbers be-
tween 101 and 199.
20.3.1.1 STATION BATTERY INPUT
One of the functions of the power/RS-232 board is to provide connections for station battery input. Station bat-
tery voltage is used for the tripping circuits and the power supply input. Fuses F1 and F2 disable the entire sys-
tem, not just the trip circuits, should a severe component malfunction occur. Transient filtering of the station bat-
tery voltage is provided by LC filters formed from inductors L101 and L102, and capacitors C110 and C111.
CR110 provides transient overvoltage protection, and reverse polarity protection is provided by CR108 and
CR109. After filtering, this voltage is supplied to the motherboard through connector P101.
20.3.1.2 RS-232 COMMUNICATION PORT
There are provisions for an RS-232 port at 9-pin D-subminiature (DB-9) connector J3. U101 converts input sig-
nals from 12-volt to 5-volt logic, and output signals from 5-volt to 12-volt logic. The 12-volt supplies required by
U101 are generated by Zener-regulated supplies formed by resistors R103 through R106, capacitors C102 and
C103, and Zener diodes CR101 and CR102. The communication lines are protected by RC filters formed from
resistor network RZ101, resistor R109, and capacitors C105 through C109 and C112. Transorbs CR103
through CR107 and CR111 provide transient overvoltage protection.
RFL 9300 RFL Electronics Inc.
May 5, 2002 20 - 5 (973) 334-3100
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