How can MLPE Monitoring help in Combiner Box Designs?

Tigo's Monitoring MLPE platform can provide insight into other aspects of the system.

PV Combiner Boxes can offer DC OFF switches and/or fuses that disconnect the array from the PV inverter. These help to manage the safety conditions of the array during periods of maintenance (like cleaning, inspection or repair). After the work on the strings is completed, the DC switch is usually switched back to the "ON" position and the process of power production is restored.

If you are working on a large commercial system, the reactivation of a single combiner box can be overlooked, or can experience a failure (due to blown string fuses, etc). In these cases, the difference in absolute power production (over-all), can often mask the losses of the forgotten combiner due to general PV production fluctuations and cloud conditions. If so, the switched off combiner box can remain unrecognized for a long time, maybe even until the next maintenance cycle.

The addition of Tigo TS4 MLPE monitoring devices can help to identify whether all of the combiner boxes on a system are active.

Monitoring the PV System

Tigo offers 3 different MLPE monitoring products to assure power production:

• TS4-O - Monitoring with Optimization and Safety (RSD)
• TS4-S - Monitoring with Safety (RSD)
• TS4-M - Monitoring only (for use on ground mounted systems)
  
  

The clearest solution is to install a TS4 MLPE on every module of the array (i.e., Full Deployment). This will provide an intimate view of power, voltage and current production at the module level. If there is a loss of production in either a string or even a single module, it can be easily identified and the issue can be resolved.

Note: The TS4-O and TS4-S both provide an NEC compliant Rapid Shutdown (RSD) solution for systems within USA territories. The TS4-M does not meet this criteria and should be considered for non-RSD (i.e., ground-mounted or non-USA systems), only.   

A second solution is to have only one TS4 product, installed on one PV-Module of each string of the array (i.e., Partial Deployment). This method of string level monitoring (for non-RSD required systems), will display basic production data for at least one unit, so that you can confirm if each string is producing energy. This is especially important if the combiner offers a fuse for each string. 

Note: The Partial Deployment method would provide basic data readings for that unit (only). The string production would need to be manually computed by incorporating data from the DC voltage at the inverter.

The third (and lowest) cost solution would be to install one TS4 per grouping of parallel strings in the  combiner box. This restricted method of Partial Deployment will supply a basic knowledge of electric current flow based upon the actions of the strings that are in parallel combinations. This ensures that the DC Switch of the combiner box is set to ON, the fuse inside the combiner box is operational and the strings from that combiner box are contributing to the over all power production of the system.

The following picture illustrates the monitoring setup scenarios, displaying each deployment method (per Combiner Box):

Tigo Setup for Monitoring

The TS4 system communicates wirelessly with Gateway transceiver (or Tigo Access Point (TAP)), up to a maximum distance of 50ft (15m). These communicate via RS485 cable connection with the Tigo Data Logger (Cloud Connect Advanced (CCA)).  The CCA connects to the Internet with Wifi or Ethernet cable.

The following picture illustrates a simplistic schematic or setup of the Tigo monitoring system.

The number of TAPs required, depends upon the layout of the system. A Gateway can communicate directly with up to 120 TS4 MLPE units within a range of 50ft (15m), but a Mesh system can communicate with up to 300 MLPEs per TAP, with a maximum range of 115ft (35m).

For more information, see:  TAP Placement and Layout