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The OptiX Metro 1000 Equipment Stops Running Because the Voltage Difference Between Its Working Ground and Protection Ground Is too Large

Publication Date:  2012-07-25 Views:  31 Downloads:  0
Issue Description
One day, a customer provided feedback that one piece of the OptiX Metro 1000 equipment of earlier versions restarted frequently and then stopped running. The OptiX Metro 1000 equipment was displayed as grey on the T2000 and three 2M services connected to the equipment were interrupted. In addition, it was found on site that all indicators on the panel of the equipment were off. 
Alarm Information
The peer equipment reports R_LOS and TU-AIS alarms. The local equipment is displayed as grey on the T2000. 
Handling Process
1. Check the power cable on site. The power cable is correctly connected. Therefore, this fault may not be caused by power cable connection.
2. Measure the input voltage on site. The input voltage is -50 V and meets the equipment requirement. In addition, the power input is stable. Therefore, this fault may not be caused by power input.
3. Replace the power module of the equipment and then turn on the power supply switch. The equipment still fails to be powered on. Therefore, it is suspected that the connection of the power module to the backplane is faulty.
4. Replace the OptiX Metro 1000 equipment with the new one. The equipment still fails to be powered on. Therefore, this fault may not be caused by the equipment itself. The running environment of the equipment may be abnormal.
5. Measure the voltage difference between the working ground and protection group of the equipment. The measured voltage difference is 2.5 V. The OptiX Metro 1000 equipment of earlier versions can be correctly powered on when the voltage difference between the working ground and the protection ground is less than 1 V and cannot be correctly powered on when the voltage difference exceeds 1 V.
6. Check the protection grounding bar. It is connected to a ground wire of the environment monitoring equipment. The environment monitoring equipment has a signal wire. The signal wire sometimes is short circuited because the connection of the environment monitoring equipment to its own protection ground is faulty. During the check on site, the signal wire is short circuited for two times. Remove the ground wire from the environment monitoring equipment and then measure the voltage difference between the working ground and protection ground of the OptiX Metro 1000 equipment. The measured voltage difference is 0.3 V.
7. Restart the OptiX Metro 1000 equipment. It is started correctly and the services are restored. 
Root Cause
The possible causes are as follows:
1 The power cable is incorrectly connected.
2 The -48 V power input in the telecommunications room is faulty. For example, the power input is unstable or exceeds the thresholds.
3 The power module of the equipment is faulty.
4 The equipment is incorrectly grounded. 
Suggestions
All the equipment in the telecommunications room must be grounded according to the requirements. 

END