Automatic reclosing device program control ladder diagram

The automatic reclosing PLC control program design is based on the control analysis of the automatic reclosing device and the I/O definition of the PLC. The designed ladder
diagram
    is explained as follows:
    1) When the circuit breaker is closed, the control switch K4 is turned on and its
contact 00004 is closed. ,． The circuit breaker auxiliary contact DL Liha has its normally
closed contact 00000 open. When a line failure occurs, the circuit breaker
trips, the auxiliary contact DL is disconnected, its normally closed contact 00000 is closed,
coil 20003 is energized, its normally closed contact is closed, and the timer
TIMOOO works. After delay. 01001 coil is energized and closed.
    2) If the automatic reclosing device closes successfully, after
the delay of TIMO01, its normally closed contact TIMO01 opens, the coil
20004 is powered off, and its normally closed contact 20004 closes, realizing
the automatic reset of the automatic reclosing device.
    3) If the closing is unsuccessful, after completing the prescribed
number of times of reclosing, the coil 20003 is energized. Due to the delay effect of TIMO01
, the coil 20004 is still energized, and its normally closed contact 20004 is in
the open state, and the coil 20003 is open. electricity. At the same time, because
the normally closed contact 00000 of the circuit breaker is closed when it is tripped, it acts as a self-holding function,
so that the 20004 coil is always energized and cannot be reclosed again.
    4) Operate control switch K to turn on node K4. The 20004
coil is energized and manual reset is achieved.
    5) The counter instruction CNT is used in the ladder diagram to set
the number of reclosing specified by the automatic reclosing, and TIMOOO is
the delay time of the automatic reclosing action. TIMO01 is the reset time of automatic reclosing
. The rising edge differential and falling edge differential instructions DIFU
(13) and DIFU (14) are combined with the timer instruction TIM002
to realize the delayed reset of the counter CNT to ensure that the automatic reclosing
completes the specified number of reclosings.
    6) During the tripping process of the manually operated circuit breaker, Kl and K2 are connected, and the corresponding normally closed contacts 00001 and 00002 are opened to ensure that the coil 20003
cannot receive power and the automatic reclosing circuit is blocked.
    7) During the tripping process of the manually operated circuit breaker. K3 is connected, the normally closed contact 00003 is disconnected, and the reclosing circuit is blocked. Normally open contact 00003
is closed, energizing coil 01002, and connecting the acceleration relay protection tripping circuit.
    8) When the air pressure or hydraulic pressure of the circuit breaker is insufficient, the SQ1 and 9Q2 switches cannot be pressed, causing the normally open contact 00005 to open and lock the automatic reclosing
circuit. Normally closed contact 00006 closes, making coil 01000 energized, and the contacts connected in series in the trip circuit open , blocking the trip circuit.
    (4) Conclusion This example analyzes the shortcomings of the traditional relay-type automatic reclosing device and designs an automatic reclosing device based on PLC.
This design scheme has the advantages of simple installation and wiring and reliable operation in terms of hardware; in terms of software, it not only meets the
basic , but also uses PLC counters, timers and other instructions to realize the automatic reclosing device. Adjustment of the number of recloses, required delay time
and automatic reset improves the system control capability and flexibility, making the pump system versatile and practical.