Simple Troubleshooting; Protection Function - Sungrow SG500MX Operation Manual

8 Inverter Functions
equipped with insulation resistance monitoring function to detect the system insulation
resistance in real time. If the resistance is detected to be low, it will send alarm at the first time to
remind the user and prevent potential hazards.
The insulation monitoring function can be divided into two kinds:

For inverter without the anti-PID function or inverter is equipped with this function but it is
disabled, both the negative insulation resistance and positive insulation resistance against
the ground should be detected.

For inverter with the anti-PID function and this function is enabled, the DC negative and the
ground is equipotential. Therefore, only the positive insulation resistance to the ground
needs to be detected.

8.10.2 Simple Troubleshooting

Regardless of the inverter setting, when the insulation resistance is below the threshold (settable
from the LCD display), inverter will send alarm signal and the Operation LED will turn to yellow.
After receiving the "low insulation resistance" alarm signal, user should stop the device and
check the specific insulation resistance from the LCD screen "Function/Run-information/Real
time data".

If the insulation resistance recovers to normal, the fault loop is in the AC side.

If the insulation resistance is still low, the fault loop is in the DC side.
No matter the fault is in the DC side or in the AC side, a thorough checking and troubleshooting
after the system is power down is necessary.
8.11

Protection Function

Inverter has perfect protection functions to protect itself when input voltage or grid is abnormal
until the anomaly is removed and the inverter can operate normally.
DC over-voltage protection
When the DC voltage of the PV array exceeds the max. DC voltage, inverter will stop operating,
send warning signal and display the fault type on the LCD screen.
Inverter can detect the abnormal voltage and respond quickly.
AC over/under-voltage protection
When the inverter AC output voltage exceeds the allowable range, inverter will stop feeding the
grid, send warning signal and display the fault type on the LCD screen.
Inverter can detect the abnormal voltage and respond quickly.
Frequency anomaly protection
When the grid frequency exceeds the allowable range, inverter will stop feeding the grid, send
warning signal and display the fault type on the LCD screen.
Inverter can detect the abnormal frequency and respond quickly.
Islanding protection
Islanding is a condition that can occur if the utility grid is disconnected while the inverter is
operating and the local load of the inverter is similar to the present output power.
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Operation Manual