Leakage current

ID: fm:leakage-current
IRI: https://solarlattice.org/kb/fm/leakage-current
Status: active
Also known as: current leakage, LC

Leakage current is unwanted current flowing between the cell circuit and the grounded frame or surroundings, driven by the voltage between cells and ground. It increases with higher system voltage, humidity and module temperature, and soiling or conductive surface layers can speed it up. Its main path runs through the front glass and encapsulant, carrying sodium ions into the cells, where they cause the shunting form of PID. Leakage current can also follow a bypass diode failure that burns through the junction box or backsheet, which makes it a safety issue. In the field the current is usually tiny, in the microamp range, so it is measured in lab or wet leakage tests by applying voltage between the shorted leads and the frame. Leakage current has not been clearly linked to the amount of power lost, so confirm PID damage with IV curves, EL and thermography as well. To reduce it, change the system grounding or use offset strategies, and choose PID-resistant modules.

<!-- review notes

sentence 2: support check: partial - Voltage, humidity, temperature and soiling are supported, but 'conductive surface layers' speeding it up is not stated (glass conductivity is lowered by rain/pollutants).
sentence 5: support check: partial - Microamp order of leakage and voltage applied via shorted leads are stated, but 'in the field' usually tiny and wet-leakage-test method details are not explicit. -->

Claims

`leads_to`

c1 verified · fact Potential Induced Degradation (PID)

Leakage current between cells and grounded frame drives Na+ migration into cell stacking faults, shunting the cell (PID-s).

potential induced degradation sec=h5 h=0ba88c724cf4
Assessment of Photovoltaic Module Failures in the Field sec=2.3.4 h=c8ae742a163e
potential induced degradation sec=h4 h=21df64fc133e

verified by: joshuahamsaverified on: 2026-10-20

`caused_by`

c2 verified · fact Bypass Diode Failure

Heat from a failed diode can burn through the junction box or backsheet, after which leakage current may follow as a safety issue.

Quantification of Technical Risks in PV Power Systems tbl=38.r6 h=c1a079fd37d5
Degradation and Failure Modes in New PV Technologies – Annex tbl=19.r5 h=7604ad2cfcc4
bypass diode failure sec=h6 h=bfcbbd1f5824

verified by: joshuahamsaverified on: 2026-10-20

c3 verified · fact High voltage to ground

Potential difference between cells and frame grows with modules in series; higher voltage gives more leakage.

potential induced degradation sec=h5 h=0ba88c724cf4
Review of Failures of Photovoltaic Modules sec=6.2.5 h=c440122cb9d9
potential induced degradation sec=h4 h=21df64fc133e
Review of Failures of Photovoltaic Modules tbl=26.r2 h=1223ddfd18c3

verified by: joshuahamsaverified on: 2026-10-20

c4 verified · fact Humid climate

High humidity raises conductivity of the leakage path.

potential induced degradation sec=h5 h=0ba88c724cf4
Review of Failures of Photovoltaic Modules sec=6.2.5 h=c440122cb9d9

verified by: joshuahamsaverified on: 2026-10-20

c5 drafted · lead High operating temperature

Elevated module temperature increases leakage current.

potential induced degradation sec=h5 h=0ba88c724cf4
Review of Failures of Photovoltaic Modules sec=6.2.5 h=c440122cb9d9

c6 drafted · lead Surface soiling

Positive charges from soiling can accelerate the process.

potential induced degradation sec=h5 h=0ba88c724cf4

review note: support check: partial - u9 says positive charges from soiling can accelerate the degradation process, not explicitly leakage current itself.

c7 drafted · lead Sodium ion migration

Na+ accumulating in stacking faults creates a self-reinforcing path that further eases leakage toward the frame.

potential induced degradation sec=h5 h=0ba88c724cf4
Assessment of Photovoltaic Module Failures in the Field sec=2.3.4 h=c8ae742a163e

`affects`

c8 drafted · lead Module front glass

Main leakage path runs through the front glass; soda-lime glass supplies sodium ions.

potential induced degradation sec=h5 h=0ba88c724cf4
Review of Failures of Photovoltaic Modules sec=6.2.5 h=c440122cb9d9

review note: support check: partial - Passages say the main leakage path 1 forms Na+ in the glass and soda-lime glass accelerates PID, but not explicitly that the main path runs through the front glass.

c9 drafted · lead Encapsulant

Low-resistivity EVA facilitates leakage.

potential induced degradation sec=h5 h=0ba88c724cf4
Assessment of Photovoltaic Module Failures in the Field sec=2.3.4 h=c8ae742a163e

c10 drafted · lead Solar cell

potential induced degradation sec=h5 h=0ba88c724cf4
Assessment of Photovoltaic Module Failures in the Field sec=2.3.4 h=c8ae742a163e
Review of Failures of Photovoltaic Modules sec=6.2.5 h=c440122cb9d9

c11 verified · fact Junction box

A burnt-through junction box can open a leakage path.

Quantification of Technical Risks in PV Power Systems tbl=38.r6 h=c1a079fd37d5
Degradation and Failure Modes in New PV Technologies – Annex tbl=19.r5 h=7604ad2cfcc4

verified by: joshuahamsaverified on: 2026-10-20

c12 drafted · lead Backsheet

A burnt-through backsheet can open a leakage path.

Quantification of Technical Risks in PV Power Systems tbl=38.r6 h=c1a079fd37d5
Degradation and Failure Modes in New PV Technologies – Annex tbl=19.r5 h=7604ad2cfcc4

`detected_by`

c13 drafted · lead Wet leakage current test

Review of Failures of Photovoltaic Modules fig=39 h=48fafd3c7c1e
Assessment of Photovoltaic Module Failures in the Field fig=82 h=e86c421aecf2

c14 drafted · lead PID susceptibility lab test

High voltage is applied between shorted leads and frame and the leakage current is metered, e.g. via a resistor to ground; leakage has not been clearly linked to power loss in c-Si.