Loss of electrical insulation

ID: fm:insulation-loss
IRI: https://solarlattice.org/kb/fm/insulation-loss
Status: active
Also known as: insulation fault, Insulation failure, isolation fault, low insulation resistance, Electrical insulation fault

Loss of electrical insulation means current-carrying parts of the PV array are no longer properly isolated from ground or from people. It usually comes from damaged cables, faulty connectors, broken module glass or failed junction boxes. Moisture makes it worse, so the fault may only appear during rain or humid periods and can be intermittent. In the field it shows up as ground faults and inverter trips or shutdowns. Low insulation resistance on its own does not reduce output until the inverter faults. If the leakage stays below the protection device thresholds, the fault can go undetected while still causing significant power losses. Confirm it with insulation resistance testing on isolated circuits. Treat it as a shock hazard: exposed parts can carry dangerous voltages, and in the worst case damaged cables or connectors can arc and start a fire. Replace damaged cable runs or modules that can no longer guarantee insulation, then confirm insulation integrity after the repair.

Claims

`caused_by`

c1 drafted · lead Cable Defect

Damaged or undersized DC cables are named as a main source of insulation faults.

cable defect sec=front h=b8e06ac4915e
cable defect sec=h2 h=ecd061f4ac98
cable defect sec=h6 h=2f6cadabed98
Quantification of Technical Risks in PV Power Systems tbl=46.r5 h=a680b50f7520

c2 verified · fact Connector Defect

connector defect sec=front h=27362abca33f
connector defect sec=h2 h=ffc071d1e172
connector defect sec=h3 h=b866045455bd
Quantification of Technical Risks in PV Power Systems tbl=46.r5 h=a680b50f7520

verified by: joshuahamsaverified on: 2026-10-20

c3 drafted · lead Glass Breakage

Once the glass is broken, module insulation is no longer guaranteed, especially in wet conditions.

glass breakage sec=front h=fbd89f70605e
glass breakage sec=h2 h=226b4cbee592
Quantification of Technical Risks in PV Power Systems tbl=32.r5 h=21e9fd14fbde
glass breakage sec=h3 h=6dfd57c14260
glass breakage sec=h5 h=086a578b6c8a
Degradation and Failure Modes in New PV Technologies – Annex sec=h30 h=11d01e81d3cc

c4 verified · fact Junction Box Failure

junction box failure sec=h6 h=9e4d1b1adbd8

verified by: joshuahamsaverified on: 2026-10-20

c5 drafted · lead Delamination

Delamination near the junction box or module edge can let water in, causing an insulation failure as a follow-up failure.

junction box failure sec=h6 h=9e4d1b1adbd8
Quantification of Technical Risks in PV Power Systems sec=3.1.2 h=0db875b1c7c0

c6 drafted · lead Moisture exposure

The fault can come and go with humidity and is often worse on rainy days or in humid periods.

junction box failure sec=h6 h=9e4d1b1adbd8
Quantification of Technical Risks in PV Power Systems tbl=32.r5 h=21e9fd14fbde
glass breakage sec=h5 h=086a578b6c8a
cable defect sec=h6 h=2f6cadabed98

review note: support check: partial - The passages tie moisture to insulation faults that are intermittent and worse in wet or humid periods, but they don't present moisture exposure as a generic cause.