Industry Testing Methods for PV Modules and Strings – Tigo Help Center

Contents:

Overview
Open Circuit Test
Short Circuit Test
I-V Curve Tracer
Earth Resistance Test
Insulation Test

Overview

This article provides an overview of the various techniques available to test PV modules and string homeruns to the inverter. It does not cover TS4-specific testing. Some of these tests cannot be performed with a Tigo MLPE inline (or attached) to the PV-Modules. Once you have familiarized yourself with the tests, go to: Supported Testing Methods for TS4 MLPE Systems, for a more in-depth look at what tests can and cannot be performed with Tigo MLPE.

Open Circuit Test

An open circuit test can be performed to measure the open circuit voltage of the module or the string.

The test requires a DC voltage meter, and it helps to detect intermittent connection issues or open sub-circuits inside the module (such as diodes or solder traces). The results usually identify issues of completely broken modules, but is the easiest testing method to perform.

Compare the results to the expected open circuit values for the module(s), as per the spec sheet.

🏆 Pro-Tip: Shaking or hitting the PV module during this test can expose intermittent or loose connections within the module.

Please see this video on YouTube as an example:

Note: While you cannot measure traditional Voc on the TS4-F family, you can still use this method to check for the RSD Safety Voltage (0.6 V per MLPE).

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 clamp meter.
Detect an intermittent connection or a weak module that can not sustain the current load.
Shaking or hitting the PV module during this test may reveal an intermittent or loose connection in the module.

This test can more accurately identify complicated module issues than an Open Circuit Test.

Please see this video on YouTube as an example:

I-V Curve Tracer

An I-V curve tracer will test a module from open circuit to short circuit and all points in between under load. IMPORTANT, this will give you the most accurate indication of 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:

Earth Resistance Test

A ground resistance 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 spikes, a hammer, and a measuring tape.
There are 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.

Insulation Test

An insulation test with a megohmmeter is commonly referred to as a Megger test. This 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).

This requires an Insulation (megger) tester that 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.