Background
During project delivery or maintenance, the SmartPID2000 output overcurrent alarm (alarm ID: 1914 Cause ID: 0) is often encountered. Provide some suggestions for rectifying this problem to facilitate onsite fault locating and rectification.
Handling Method
The method of locating output overcurrent alarms is based on PID functions and requirements. Understanding the functions and requirements helps you quickly locate faults.
Function: The PID module is used to prevent PV module output power attenuation caused by potential induced degradation (PID) effects in the PV power generation system. The PID module injects the voltage between the phase line and the ground line of the isolation transformer to adjust the PV+ or PV-voltage to the ground to prevent the PID effect of the PV module, thereby increasing the energy yield of the plant and increasing the revenue.
Operating requirements: The PID module injects voltage between the phase wire and the ground wire of the isolation transformer to adjust the PV+ or PV voltage to the ground. (Note: The P-type PV module adjusts the PV to the ground to be greater than 0 V. The N-type PV module adjusts the PV+ to the ground to be less than 0 V.) until the voltage of PV+ to the ground is less than or equal to zero, or the voltage of PV-to ground is greater than or equal to zero, thereby suppressing potential induced attenuation of the PV module.
Fault Locating
SmartPID2000 output overcurrent is caused by hardware faults or abnormal application scenarios.
Product hardware fault: Cross-verification can be performed with the PID that is running properly. (For details, see 5.3 Replacing the PID Module in the User Manual.) If the fault follows the module movement, it indicates that the fault is caused by a hardware fault.
Abnormal application scenarios: The insulation resistance of AC and DC cables is low in non-isolated scenarios.
1. Check the non-isolation scenario.
The neutral line/neutral point on the low-voltage side of the box-type transformer is led out and grounded, and the system is not isolated.
Note: The SmartPID2000 supports only the IT power grid. The TN-S, TN-C, TN-C-S, and TT power grids are not supported.
The low-voltage side of the box-type transformer uses a small dry transformer to supply power to the secondary system, but the neutral wire of the primary side (inverter side) of the small dry transformer is grounded.
The three-phase power of the communication box and the inverter are not the same busbars. Instead, the power is obtained from the secondary side of other transformers (the neutral wire is grounded).
2. Check whether the insulation resistance of AC and DC cables is abnormal.
The AC-side phase cable of the box-type transformer, combiner box, or inverter is insulated abnormally to the ground or is short-circuited with low impedance.
Note: Use a multimeter to test the insulation of the AC-side phase cable. In normal cases, the resistance should be greater than or equal to 2.5 kΩ. In addition, if the AC-side SPD is faulty, a PID alarm may be generated.
The PV+ or PV-PV string on the DC side of the inverter is insulated abnormally to the ground or is short-circuited with low impedance.
Note: The PV+/- ground insulation is abnormal. If the inverter generates an insulation abnormal alarm, shut down the inverter and check whether the PID can start properly.
Summary
To solve the PID output overcurrent problem caused by abnormal insulation of a single inverter, set the PID running status to debugging mode and set the debugging output voltage. (Note: The commissioning output voltage ranges from 0 V to 800 V. It is recommended that the commissioning output voltage of the 1000 V/1100 V inverter be 50 V to 400 V and the commissioning output voltage of the 1500 V inverter be 50 V to 600 V.) Log in to the SmartLogger WebUI or use the background monitoring tool to shut down the inverters in the array one by one. If the PID of an inverter is running properly after the inverter is shut down, the insulation of the inverter is abnormal, causing the PID alarm. In this case, check the AC and DC insulation.
