A Tigo system is comprised of Energy Intelligent Module Level Power Electronics (MLPEs) with Rapid Shutdown solution. Since these MLPE units are intelligent, it's like having a tiny in-line computer attached to each PV module. For this reason, there are certain consideration on what affects the electronics of the units and whether a traditional testing method is considered applicable.
Tigo MLPE Systems are separated into 2 families, with their possible testing methods:
| Radio - Smart / Optimized | PLC - Fire Safety TS4-F |
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Energy Intelligent MLPE family that uses Radio Communications to transfer data and to deliver a Rapid Shutdown (RSD) response |
Fire Safety MLPE family that uses Power Line Communication (PLC) to deliver an RSD response. No Data is captured or transferred. |
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Testing Methods: ✅ Voc Test ✅ Vmp Test ❌ Isc Test ✅ Imp Test ✅ Insulation Test ❌ IV Curve Tracing |
Testing Methods: ✅ Safety Voltage ❌ Voc Test ✅ Vmp Test ✅ Isc Test ✅ Imp Test ❌ Insulation Test ❌ IV Curve Tracing |
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Before testing, always refer to the following:
- Know which MLPE family you are working with (and the proper testing methods that apply)
- Follow all safety and operation instructions of the insulation tester you are using
- Follow general electrical safety practices
- Have a certified electrician perform the test
- Make sure that all wires and conductors being testing are rated to the same voltage (or higher) than the test requires. (voltage rating of the PV cables on Tigo products are printed on them).
Smart / Optimized Systems
Tigo Smart / Optimizer MLPE units are sold in open position (passing full voltage / no RSD response). They are packaged in this state for ease of assembly and testing during the system build process. Once commissioned, these systems require Radio Communications to stay in active 'non-Rapid Shutdown (RSD) mode.
This is important to know, because the MLPE Units' state (commissioned vs not commissioned), dictates what conditions need to be present in order for the MLPE units to pass voltage.
- Non-Commissioned - MLPE units can be tested without any special consideration.
- Commissioned - CCA & TAP signal must be present for MLPE Units to pass voltage to the string.
For safety reasons: Tigo strongly suggests enacting RSD / AC Loss, before and after the test. This way, the system can be safely accessed by the installer, to prepare the conditions for the test. Once the installer is ready to proceed with the test, the system must be re-energized (deactivate RSD / AC Loss), so the units are able to pass voltage and/or current, throughout the testing period.
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✅ Open Circuit Voltage Test (Voc):
As long as the Tigo Smart / Optimizer system is active (not in RSD), an MLPE Unit or string can be DC Voltage tested for Voc results, using the standard methods.
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✅ Maximum Power Circuit Voltage Test (Vmp):
As long as the Tigo Smart / Optimizer system is active (not in RSD), an MLPE Unit or string can be DC Voltage tested for Vmp results, using the standard methods.
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❌ Short Circuit Current (Isc):
The radio family of optimizers have built-in Short Circuit protection. If a unit is placed in a short circuit condition, the unit or string automatically goes into RSD, and the test shows zero current.
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✅ Operating Current (Imp):
As long as the Tigo Smart / Optimizer system is active (not in RSD), an MLPE or string can be DC Amperage tested for Imp results, using the standard methods.
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✅ Insulation (megger) Testing:
As long as the Tigo Smart / Optimizer system is active (not in RSD), an MLPE or String can be insulation tested up to 1000 V, using the standard methods.
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❌ IV Curve Tracing:
Unfortunately, IV Curve tracing will not work for any Tigo devices (whether RSD is activated, or not). The Tigo MLPE units receive their functional power from the PV Module, and the IV Curve test will present conditions that range from Isc to Voc. This effectively starves the MLPE from it's running power and (if sustained) the unit will shut down.
Fire Safety Systems
TS4-F Fire Safety system require a constant PLC signal to stay in an active state (passing voltage / non-RSD). These systems must have a completed circuit in order for units to receive the signal and continue passing voltage. For this reason, standard testing procedures like Voc, Isc, Insulation (megger) and IV Curve Tracing are not possible.
For safety reasons: Tigo strongly suggests enacting RSD / AC Loss, before and after any test. This way, the system can be safely accessed by the installer, to prepare the conditions for the test. Once the installer is ready to proceed with the test, the system must be re-energized (deactivate RSD / AC Loss), so the units are able to pass voltage and/or current, throughout the testing period.
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❌ Open Circuit Voltage Test (Voc):
Testing for Voc is not possible with PLC signaling, as the MLPEs require an closed circuit to receive signal.
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✅ Maximum Power Circuit Voltage Test (Vmp):
Testing for Vmp is possible with PLC signaling, since the Vmp condition requires the MLPEs to be connected to an MPPT of a Charge Controller or Inverter. Since this is a completed circuit the MPLEs will be receiving the PLC signal. -
✅ Short circuit current (Isc):
Testing for Isc is technically possible with an inline ammeter, but cumbersome. Since the circuit will be complete (shorted into itself), the MLPE will no longer be in RSD. However, accomplishing this, requires that one of the leads is passing through the CT Core of the RSS Transmitter. This may require extremely long leads or jumpers to complete.
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✅ Operating Current (Imp): Clamp Meter
Testing for Imp is possible with PLC signaling, because the Clamp Meter can be applied to the completed circuit.
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❌ Insulation (megger) Testing:
Testing for Insulation is not possible with PLC signaling, as the MLPEs require an closed circuit to receive signal.
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❌ IV Curve Tracing:
Unfortunately, IV Curve tracing will not work for any Tigo devices (whether RSD is activated, or not). The Tigo MLPE units receive their functional power from the PV Module, and the IV Curve test will present conditions that range from Isc to Voc. This effectively starves the MLPE from it's running power and (if sustained) the unit will shut down.