Potential Induced Degradation (PID) Test - Solar PV Module Test

The Potential Induced Degradation (PID) test is a test method used to evaluate the power degradation phenomenon caused by potential differen...

The Potential Induced Degradation (PID) test is a test method used to evaluate the power degradation phenomenon caused by potential difference potential when photovoltaic modules are operated for a long time in high-voltage, humid, and high-temperature environments. This test is mainly used to evaluate the long-term reliability of solar cell modules, especially photovoltaic modules under electric field stress.

What is the Potential Induced Degradation (PID) Test?

PID, or Potential Induced Degradation, is a phenomenon that affects the performance of solar panels over time. It is caused by the flow of electrical current between the solar cells and the grounded frame of the panel. This electrical current creates a voltage potential that can result in degrading the solar module's output power.

How Does The Potential Induced Degradation (PID) Test Perform?

Test Conditions For PID Test :

PID tests are usually conducted under specific environmental conditions to accelerate the occurrence of PID effects. Common test conditions include:

1. High voltage: voltages ranging from several hundred volts to several thousand volts (usually negative voltages) are applied to simulate the high voltage stress that PV modules may encounter in actual operation.

2. High humidity: Usually carried out in an environment with a humidity of 85% to 95% to simulate the impact of a humid environment on the insulation performance of components.

3. High temperature: The test temperature is generally set between 60°C and 85°C to accelerate the occurrence of potential induced decay.

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Test Process For PID Test :

Module preparation: The photovoltaic modules are placed in a test chamber, where the temperature and humidity can be controlled to simulate a humid and high-temperature environment. One side of the module is grounded and a high voltage is applied to the other side.

1. Apply voltage: A negative voltage (usually -1000V to -1500V) is applied to the component and maintained for a period of time, usually several hundred hours (e.g., 96 hours).

2. Power measurement: The output power of the PV modules is measured before and after the test. The degree of power attenuation can be used to evaluate the tolerance of the PV modules under the PID effect.

3. Analysis results: Based on the change in component power after the test, determine whether the component has an obvious PID effect. The power attenuation rate is usually used as the core indicator of evaluation.

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5. Why Was The PID Test Performed on The Solar PV Module?

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7. The main purpose of the PID test is to simulate the working environment of photovoltaic modules under long-term high-voltage conditions and to induce potential power attenuation effects on photovoltaic modules by applying high voltage, humidity, and high temperature. Through this test, the tolerance of photovoltaic modules to the PID effect can be evaluated, thereby ensuring their long-term stability in different environments.

In the PID test, the following items are mainly tested: 

Power attenuation rate: By comparing the output power before and after the test, the power attenuation percentage of the component is calculated.

Insulation Resistance: Measure the insulation resistance of a component before and after the test to evaluate changes in the insulation performance of the component.

Current leakage: Detects the leakage current of a component under high voltage conditions to determine its voltage withstand capability.

In India, there are two such standards that you can check while buying solar panels. :

 IEC- 62804-1

Under this standard introduced by the International Electrotechnical Commission, a solar brand has to operate its panel for 96 hours at 60℃ temperature and 85% humidity level. It is only approved if PID is less or equal to 5% in these conditions.

 MNRE

The Indian Ministry of New and Renewable Energy has its own test in place to check the quality of panels. A panel has to be operated for 288 hours, at 85℃ temperature and 85% humidity level, and display less than or equal to 5% PID to gain MNRE certification.

Factors affecting PID effect:

Component packaging materials: The choice of packaging materials (such as EVA) has a great influence on the PID effect. EVA materials that resist the PID effect can reduce ion migration and thus improve the tolerance of components.

Glass and backsheet materials: The glass and backsheet materials of photovoltaic modules will also affect the PID effect. Using highly insulating glass or backsheet can reduce current leakage.

Cell type: Different types of photovoltaic cells have different sensitivities to the PID effect. For example, P-type cells are more susceptible to the PID effect, while N-type cells show better resistance to PID.

Through PID testing, the reliability of photovoltaic modules in long-term operation can be effectively evaluated, and it can provide an important reference for the design of photovoltaic systems and the selection of modules.

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