The fault code "30002" on Siemens drives indicates a DC link overvoltage condition. This fault occurs when the voltage level in the DC link exceeds the maximum allowable limit. Here are steps to address this issue:

1. Check Input Power: Verify that the input power to the drive is within the specified voltage range. An overvoltage condition can occur due to fluctuations or spikes in the incoming power supply. Ensure that the power supply meets the drive's requirements.

2. Inspect Braking Resistors: If your drive is equipped with braking resistors, ensure they are properly connected and functioning. Braking resistors help dissipate excess energy during deceleration, preventing overvoltage in the DC link. Check for any damaged or disconnected resistors.

3. Monitor Load Conditions: Excessive regenerative energy from the motor or the driven load can cause overvoltage. Monitor the load conditions and adjust parameters such as acceleration/deceleration ramps to reduce regenerative energy.

4. Verify Motor Parameters: Incorrect motor parameters or mismatches between the drive and motor specifications can lead to overvoltage issues. Confirm that the motor parameters are correctly configured in the drive's settings.

5. Inspect Capacitors: Capacitors in the DC link circuit can degrade over time, leading to voltage spikes or overvoltage conditions. Inspect the capacitors for signs of damage, such as bulging or leaking. Replace any faulty capacitors.

6. Review Drive Settings: Check the drive's control parameters and settings related to voltage limits, braking behavior, and DC link protection. Adjust these settings as necessary to prevent overvoltage conditions.

7. External Protection Devices: Consider installing external protection devices such as surge suppressors or voltage clamps to protect the drive from voltage spikes or transients in the power supply.

8. Firmware Update: Ensure that the drive's firmware is up-to-date. Sometimes, firmware updates include improvements or fixes related to DC link overvoltage protection.

9. Consult Technical Documentation: Refer to the drive's user manual, technical documentation, or contact Siemens technical support for specific guidance on troubleshooting and resolving DC link overvoltage faults.

By following these steps and addressing the potential causes, you can troubleshoot and resolve the DC link overvoltage fault in your Siemens drive.