LDK 230w Polycrystalline solar panels 1,Using high quality Motech solar cell. 2,Certificate: IEC,TUV, CE ... : more than 25 years Standard testing condition: 25, AM1.5 spectrum, 1,000W irradiance Insulation: >100M Ohms Voltage stand-off: 2 ... 25 years Standard testing condition: 25 degrees Celsius, AM1.5 spectrum, 1,000W irradiations Insulation: ≥100M Ohms Voltage stand-off: 2 ...