PV Test Equipment
Filter By Challenge

Insulation Resistance

Learning & Resources
DC Safety Testing

Insulation Resistance

Insulation resistance testing is a foundational safety and quality check for every PV installation. It verifies the integrity of DC wiring insulation between live conductors and earth, detecting degraded cable jackets, water ingress, and damaged junction boxes before they become arc or ground fault events. This section covers test methodology, voltage selection, pass/fail criteria, and equipment options for both commissioning and periodic O&M testing.

Equipment Options
Sonel
PVM-1530
Professional 1500V multifunction PV meter — IV curve tracing (IEC 62446-1 Cat. 2), Voc, Isc, Riso at four test voltages (RISO+ and RISO−), bypass and blocking diode test, continuity, and STC correction per IEC 60891 via IRM-1 sensor.
Field Testing Guide
Reading IV Curves: A Field Technician's Guide
What a healthy IV curve looks like, how six common fault types deform it, and when alternative test methods can identify the same issue faster — or catch what the IV curve misses.
Emazys
Z300 HE
1500V PV tester with inrush current protection for HE and bifacial modules. Riso 0–99 MΩ, Voc, Isc, Rs, ground fault location. Bluetooth cloud-connected.
Emazys
Z300 PVT
1500V PV tester for conventional and PERC modules. Riso 0–99 MΩ, Voc, Isc, Rs, ground fault location. Bluetooth cloud-connected.
Articles
Articles Coming Soon
Content for this topic is in development. Sign up on the home page to be notified when new resources are published.
Frequently Asked Questions

IEC 62446-1 requires a DC test voltage of at least 500V for systems with system voltage above 120V DC. For 1500V systems, testing at 1000V DC is common practice and gives better sensitivity to soft insulation faults than 500V. Some instruments support 1500V Riso testing — useful for high-voltage strings where insulation is rated to system voltage and you want a margin-of-safety test.

IEC 62446-1 sets the minimum at 1 MΩ for systems up to 100 kWp and 100 kΩ for larger systems, but these are acceptance thresholds — not targets. A healthy new installation should measure well above 10 MΩ, typically 100 MΩ or more at 1000V. Values below 1 MΩ indicate a fault requiring investigation before energisation. Trending downward values over time is as important as the absolute figure.

Separate RISO+ and RISO− tests locate whether insulation degradation is on the positive or negative pole of the array. A positive pole fault and a negative pole fault have different safety implications and different root causes — positive faults are more common from cable damage, negative faults often indicate PID or grounding issues. Some instruments measure both simultaneously, halving test time.

No. Riso testing requires the array to be isolated from the inverter and all external connections. The test injects a DC voltage from the instrument and measures leakage current — doing this on a live array would compromise both the measurement and the equipment. Always isolate at the DC main switch and wait for inverter bus capacitors to discharge before connecting the Riso instrument.

Yes, significantly. Moisture on module surfaces, in cable connectors, or in junction boxes creates temporary leakage paths that dramatically lower apparent Riso values. Readings taken immediately after rain or heavy dew are unreliable and will often fail even a healthy installation. Wait for the array to dry fully — surface moisture should be visually absent — before taking acceptance-quality Riso measurements.