Contents:
- Overview
- Open Circuit Test
- Short Circuit Test
- I-V Curve Tracer
- Earth Resistance Test
- Insulation Test
Overview
There are many different methods of testing strings and PV Modules. This article is just an overview of the different methods available.
IMPORTANT: While most of these tests are commonly used in the Solar field, some cannot be performed with a Tigo MLPE inline (or attached) to the PV-Modules. Once you have familiarized yourself with the tests, please go to: Testing Methods for Tigo Flex MLPE Systems, for a more in-depth look on what tests can be performed, and cannot be performed on Tigo Products.
Open Circuit Test
An open circuit test measures the open circuit voltage of the module, or string. Compare that value to the expected open circuit of the module(s) spec sheet.
- Requires a DC voltage meter.
- Can help detect intermittent connection issues or open sub-circuits inside the panel, such as diodes or solder traces.
- Please keep in mind that you can shake or hit the PV module during this test and the results may vary due to an intermittent or loose connection in the module.
This test can only identify completely broken panel issues, but is the easiest testing method.
Please see this video on YouTube as an example:
https://www.youtube.com/watch?v=Hey1QZkYFSQ
Note: While you cannot measure for traditional Voc on the TS4-F family, you can still use this method to check for the RSD Safety Voltage, which is 0.6 V per MLPE in the string.
Short Circuit Test
A short circuit test measures the short circuit current of the module, or string. Compare that current value to the expected short circuit current of the module spec sheet, given sunlight conditions
- Requires a DC current meter.
- Can help detect an intermittent connection or weak panel that can not sustain current unload.
- Please keep in mind that you can shake or hit the PV module during this test and the results may vary due to an intermittent or loose connection in the module
This test can identify more complicated panel issues, more accurately than an Open Circuit Test.
Please see this video on YouTube as an example
https://www.youtube.com/watch?v=Hey1QZkYFSQ
I-V Curve Tracer
An I-V curve tracer will test a panel from open circuit to short circuit and all points in between under load. IMPORTANT, this will provide the most accurate indication into the health and performance of the PV module.
- Requires an I-V curve tracer
Although, this can be the most accurate method of PV-Module testing, it cannot be performed with any Tigo MLPE attached. If it is necessary to test the PV-Module, the I-V Curve Tracer can be run on the module(s), without the MLPE connected.
Please see this video on YouTube as an example
https://www.youtube.com/watch?v=69PGz7bvets
Earth Resistance Test
An Earthing Tester measures the resistance of the earth/ground by employing a constant current generator which injects current into the earth between electrode spikes in the ground.
- Requires an earth tester, spikes, hammer and a measuring tap.
- Has several different methods of testing suggested (different numbers of spikes and distances).
This test is for the general grounding of a system and does not affect the Tigo MLPE's in any way.
Insulation Test
Commonly referred to as a Megger test, it measures the resistance of the insulation around a cable or connector. This can confirm that a wire sheathing has become damaged, dried out or compressed (pinched).
- Requires an Insulation (megger) tester
- Shows megaohm values for resistance between conductors and other surfaces (grounds, conduit, racking, etc).
Note: Before running an insulation test, make sure to read the voltage rating written on the output cable of the MLPE as there are 1000V and 1500V versions. The Insulation Tester's output voltage should not exceed the rated voltage of the equipment/cables when testing.
For a more in-depth look on what tests can, and cannot be performed on Tigo Products, please proceed to: Testing Methods for Tigo Flex MLPE Systems
If you require any assistance or information regarding testing and/or system design, please contact Tigo's Sales Engineering team at: se@tigoenergy.com or you can fill out a Sales Contact Form.