Five methods for judging the fault of the explosion-proof distribution box circuit

1. Check the control power supply air switch or insurance for faults: Use a multimeter to measure whether the voltage of the control power supply is normal. If it is determined that there is no problem with the control power supply, continue to check whether the TWJ or HWJ light of the operation box is on. If the light is on, The control loop is intact.

2. Check whether the terminal block of the switch terminal box and the switch mechanism box control circuit is corroded, loose or broken. Under normal circumstances, the control circuit wiring should be tightened without looseness, and the loop is well connected.

3. Check if the opening and closing coils are burnt out. Whether the opening and closing coil is burnt out is also the most common phenomenon in which the control circuit is broken. Since the coil generally withstands a current of about 2A at the moment of splitting, the wire diameter of our opening and closing coil is relatively small and cannot pass a large current for a long time.

4. Check if the spring does not store energy or if the energy storage is not in place. If the spring is not stored or the energy storage is not in place, the control circuit disconnection alarm signal will be sent because the contact is not conducting. If there is a problem with the auxiliary contact, it should be that the energy storage motor has failed and a new energy storage motor needs to be replaced.

1. Control circuit disconnection principle

The control loop disconnection alarm signal loop is a series connection of the normally closed contact of the closing position relay HWJ inside the protection device and the normally closed contact of the trip position relay TWJ. The advantage of this configuration method is that the trip circuit and the joint can be simultaneously monitored. The integrity of the gate circuit. It can be known from the above configuration that the condition that the protection device sends the control circuit disconnection signal is that the closing position relay HWJ and the trip position relay TWJ are simultaneously depressurized, so that the normally closed contacts are simultaneously closed. Obviously, this anomaly occurs only when the integrity of the switch trip or closing circuit is broken.

If the switch in the open state is broken, it indicates that the integrity of the closed circuit is broken and cannot be electrically closed; if the switch in the closed state is disconnected, the trip is indicated. The integrity of the circuit is destroyed and the electric trip and protection device cannot be automatically tripped. When the circuit breaker is in the closing position, the closing position relay HWJ is energized; when the circuit breaker is in the trip position, the trip position relay TWJ is energized. When the control loop is normal, regardless of whether the circuit breaker is in the merging or displacing position, one of the normally closed contacts of the two position relays is always open, and the "control circuit disconnection" signal is not reported. When the trip position relay TWJ and the closing position relay HWJ are simultaneously de-energized for some reason, the state is all 0, the two normally-closed contacts in series are closed, and the protection circuit is turned on, the device screen Immediately display the “control loop disconnection”, the panel alarm light is on, and the information is transmitted to the background machine through the network cable.

It must be pointed out that when the switch is in the closed state, the integrity of the closing circuit is broken, or the switch is in the trip state, and the integrity of the trip circuit is destroyed, the control circuit disconnection signal cannot be reported.

2. Circuit breaker common control circuit diagram

As shown in Fig. 1, the virtual circuit is an operation loop provided inside the microcomputer protection device. The jumper relay TWJ and the combination relay HWJ are connected in parallel in the closing and closing circuit, and the two position relay states are automatically detected after the device is powered on. When the control loop is normal, the normally closed point of the two position relays is always open regardless of whether the switch is in the engaged or divided position. When the two position contacts are closed at the same time, the device screen immediately displays “control loop disconnection”, the panel alarm light is on, and the information is transmitted to the background machine through the network cable. At the same time, the device also provides telecontrol signal contacts for the user to use.

3. Reasons for control loop disconnection

According to experience, the main reasons for the disconnection of the circuit breaker control loop are:

(1) The control circuit power fuse is blown or the air switch is not given (suitable for the protection device power supply and the control circuit power supply discrete setting). (2) The handrail switch power plug is not plugged in. (3) The handcart switch is not pushed to the preparatory position or the working position (the closing circuit string has the switch position contact). (4) The energy storage power switch is not given (the switch circuit has a switch energy storage contact). (5) The remote/near control switch in the circuit breaker control cabinet is hit in the local position due to maintenance and other reasons, and forget to recover when power is delivered. (6) SF6 low air pressure blocking action. (7) The mother-linked isolation handcart is not pushed to the working position (the bus-coupled switch-closing circuit is connected to the isolated hand-cranked work position contact). (8) The interlocking conditions in series in the combined circuit are not satisfied due to the process. (9) The auxiliary contact of the series connected in the switch itself is in poor contact. (10) The opening and closing coil is burned out. (11) The secondary wiring plug inside the switch operating mechanism is loosened due to vibration.

4. Control loop disconnection processing steps

When the control loop disconnection fault occurs, generally follow the steps below:

(1) Check the control power supply air switch or insurance for faults: Use a multimeter to measure whether the voltage of the control power supply is normal. If it is determined that there is no problem with the control power supply, continue to check to see if the TWJ or HWJ light of the operation box is on, if the light is on. , indicating that the control loop is intact; if the light is not bright, use a multimeter to measure the voltage of the terminal 37 or 137 of the closing circuit. If the measured voltage is negative, it means that the closing circuit is normal; if the measurement is positive If it is electric, the problem lies in the closing circuit of the terminal block to the mechanism box.

(2) Check whether the terminal block of the switch terminal box and the switch mechanism box control circuit is corroded, loose or broken. Under normal circumstances, the control circuit wiring should be tightened without looseness, and the loop is well connected.

(3) Check if the opening and closing coil is burnt out. Whether the opening and closing coil is burnt out is also the most common phenomenon in which the control circuit is broken. Since the coil generally withstands a current of about 2A at the moment of splitting, the wire diameter of our opening and closing coil is relatively small and cannot pass a large current for a long time. Causes of burnout of the coil include: mechanical failure of the closing and closing, unreliable switching of the auxiliary switch, poor quality of the coil or aging. Normally, a new opening and closing coil should be replaced. The current microcomputer protection control loops all have a self-holding circuit for switching, whether manual or automatic. As long as the closing command is issued, the closing circuit will remain in the self-holding state until the switch is closed, and the closing circuit closing current is disconnected by the switching of the auxiliary contact of the circuit breaker. If the switch is not closed for other reasons, or if the circuit breaker auxiliary contact does not switch into position after closing, the closing hold circuit will remain in the hold state, and this will continue to burn out the closing coil.

(4) Check if the spring is not storing energy or if the energy storage is not in place. If the spring is not stored or the energy storage is not in place, the control circuit disconnection alarm signal will be sent because the contact is not conducting. Since the spring energy storage contact is directly used to control whether the motor is running, it is usually checked whether the energy storage indicator light is bright. If the motor cannot store energy normally, you can manually store energy and measure the energy storage auxiliary touch with a multimeter. Whether the point is connected. If there is a problem with the auxiliary contact contact, you should find a spare contact. If there is no spare auxiliary contact, you should replace the new spring energy storage auxiliary switch. If there is a problem with the auxiliary contact, it should be that the energy storage motor has failed and a new energy storage motor needs to be replaced.

(5) Check if the remote/local switch is faulty. When the remote/local switch is faulty, a “control loop disconnection” alarm signal will be issued. A common problem with the remote/local switch is that the switch contact is poorly connected or disconnected, so that the closing monitoring circuit is disconnected from the operation box TWJ and the "control circuit disconnection" alarm signal is issued. The remote/local switch should be replaced when this problem occurs.

Other issues to be aware of:

(1) The switch cannot return too fast during operation, otherwise the switch is not closed.

(2) The switch of the electromagnetic operating mechanism should not be cut frequently in a short time, otherwise the electromagnetic closing coil will heat up, the resistance will increase, and the suction will decrease.

(3) The selection of the anti-jump circuit should be considered together with the resistance value of the trip coil. It should be ensured that the anti-jump relay current starting coil sensitivity is ≥2.

(4) Only one set of anti-jump circuit should be reserved in the control loop. It is recommended to use the anti-jump circuit in the microcomputer protection device, which is reliable and easy to maintain.