How to deal with the instability of the battery DC system

　　1. The DC bus voltage is too high or too low

　　(1) Failure phenomenon

　　 Central audio signal'ringing' ring ; DC bus failure 'optical card' is turned on; DC bus voltage indicates deviation from the allowable value.

　　(2) Troubleshooting

　　 1. Check whether the voltage relay of the voltage monitoring device is correct.

　　 Two. Observe the output voltage of the charger and the display of the DC bus insulation monitor, or use a multimeter to measure the bus voltage, and comprehensively judge whether the DC bus voltage is abnormal.

　　3. Adjust the charger output, restore the DC bus voltage, and restore the floating charging current to normal.

　　4. If the DC bus voltage is abnormal and the charger device fails, the charger should be disabled and switched to the backup charger.

　　Second, DC system grounding

　　(1) Failure phenomenon

　　Central alarm signal'alarm ring;'DC bus failure' light board is turned on; the'insulation reduction' indicator of the DC system insulation monitoring device is turned on; the positive and negative ground voltage of the DC bus is measured, and the voltage is extremely unbalanced.

　　(2)Troubleshooting

　　 In order to prevent re-grounding and re-grounding, resulting in protection misoperation or power failure, or Leading to short circuit between poles and double battery burnout, the ground fault in the DC system must be quickly eliminated. How to find the reference point.

　　The principle and order are as follows:

　　 1. Find out the grounding method. Use the method of instantaneous power off to find the connection point, that is, immediately pull out the DC feeder switch and close it quickly (cutting time does not exceed 3 seconds). When disconnected, if the ground signal disappears and the voltage from each pole to the ground indicates normal, then it is connected to the loop.

　　2. The principle of finding the contact location:

　　(1) For a double-bus DC system, which bus should be grounded first ;

　　2. First check the DC feeder according to the important load, and then check the double battery, charging equipment and DC bus.

　　3 Use instantaneous shutdown method to find secondary DC feeders (such as emergency lighting, signal devices, power off), for important feeders that do not allow short-term power outages (such as tripping power) , The load should be transferred first, and then the instantaneous stop method should be used to determine the connection point.

　　3. Find the contact location in the following order:

　　1) Determine the grounding polarity and grounding degree. Use a DC and insulation monitoring device to measure the voltage between the positive and negative poles to ground. When the insulation is good, the voltage of the positive and negative electrodes is equal to or zero; if the voltage of the positive electrode to ground is equal to or equal to the voltage of the bus bar, and the voltage of the anode is reduced or equal to zero, then the insulation of the grounded anode is reduced; otherwise, the insulation of the cathode is reduced Or ground.

　　 2) Check whether the DC feeder or transmission equipment of the maintenance equipment is grounded.

　　 3) Check whether the DC lighting and power supply lines are grounded.

　　4) Check whether the circuits of the flash memory device and the DC insulation monitoring device are grounded.

　　5) Check the control and signal circuit grounding (disable related protection first).

　　6) Check whether the charging device and the double-layer battery are grounded.

　　(7) If no intersection is found after the above inspection, the bus has been suspended.

　　3. The common faults of the charger are as follows:

　　 1. Overvoltage and overcurrent occur at the output of the device . When the output of the device is over-voltage and over-current, the device can automatically protect and send out audible and visual alarm signals. At this time, the voltage and current adjustment knob should be rotated to zero, press the alarm twice to protect the reset button, and then adjust the voltage and current adjustment knob to make the voltage or current reach the actual value.

　　 AC input failure. When the input AC fails, the device can automatically protect and send out audible and visual alarm signals.

　　 At this time, turn on the power switch of the device to cancel the alarm of the device. After disconnecting the AC fault, turn off the power switch and restart the device according to normal operation steps.

　　3. Fuse. When the primary protection fuse (or secondary protection fuse) of the rectifier transformer T of the equipment is fuse, the equipment can automatically protect and send out an audible and visual alarm signal. At this time, the AC input power switch should be turned on to find out the cause of the fuse. After troubleshooting, replace the fuse with the same capacity as the original fuse, and restart the device according to the normal operation steps.

　　 4. The equipment does not reach the rated nominal voltage. When the equipment does not reach the rated voltage, the first step is to check whether the phase sequence of the three-phase AC input of the equipment meets the equipment requirements; the second step is to check whether the secondary voltage of the rectifier transformer meets the requirements (ie Uu003d1.35Uz. For DC output) Voltage, U2 is the output voltage of the rectifier transformer, 1.35 is the three-phase rectification coefficient). For the DC output voltage, U2 is the output voltage of the rectifier transformer, and 1.35 is the three-phase rectification coefficient); the third step is to check whether the 6 pulse waveforms are normal; the fourth step is to check whether the six thyristors of the main rectifier circuit are damaged.