Contents:
Introduction
Tigo's RSS Pure Signal Transmitter (RSSx) allows multiple PLC transmitters to be linked to provide a single, synchronized keep-alive signal to large arrays. This allows greater protection from signal interference (also known as crosstalk).
Crosstalk is an electromagnetic phenomenon that can cause interference between two independent signal transmission sources (wires or antennas) that are in close physical proximity to each other. Crosstalk can affect a wide variety of products, and is not limited to photovoltaic systems.
This article provides installation required practices to mitigate crosstalk when using multiple RSS Transmitters (or transmitter groups).
Wiring for Pure Signal Technology
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Pure Signal RSS Transmitters communicate through a (series or daisy-chain) wired connection. The first transmitter (RSSx Leader) communicates to the next in series (Follower) until the last transmitter receives the signal. This arrangement synchronizes the signal so every PV conductor in the conduit, raceway, or cable tray operates on the same pulse, reducing the likelihood of crosstalk. You may connect up to 10 Pure Signal transmitters to form a group. If your design requires more than 10 transmitters, you must create a second group and maintain the proper design criteria between the groups discussed below. |
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10 Transmitter comprising a group
Important: When installing multiple groups of RSS Transmitters, all groups shall be powered from the same power supply.
For complete installation instructions, refer to the Quick Start Guide
Design and Installation Requirements
To maintain signal integrity in a PLC system, required practices and product specifications must be adhered to. The following practices are required in a Tigo rapid shutdown system using power line communication.
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RSSx in the same group - All DC strings of a single group (up to 10 RSSx) may be combined in the same conduit or raceway. |
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Max Roundtrip String Length - Single Core: 300 m (985 ft.) - Dual Core: 500 m (1640 ft.) - If your project uses an inverter with more than 10 strings and a round trip distance greater than 300 meters, contact Tigo Support. |
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Max RSSx system size: - 10 transmitters - If the project has more than 10 RSSx, then separate them into groups of 10 |
Group 1 Group 2 |
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Power supply requirements: - A single breaker must power all RSSx groups' 12V power supplies to ensure they shut off and turn on simultaneously. |
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RSSx conductor limit: - A maximum of 10 conductors from the same inverter may pass through a single Core. - More than 10 conductors in a single RSSx Core may reduce PLC signal strength. |
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Signal Wiring limit: - Must not exceed 100ft (30m). |
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String conductor pairing - Do not separate the pos/neg conductors of the same string. - Keep them in the same conduit or raceway. - Notice how the black and red strings are separated in this image |
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DC conductor separation limit - Maintain at least 8" (20 cm) of separation between DC conductors of different RSSx groups. - Different RSSx groups that are too close will cause crosstalk and reduce PLC signal integrity. - This applies to conduit runs and raceways |
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Good Group separation |
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Poor Group separation - Notice how the green and blue lines for Groups 2 and 3 crossover different group colors. |
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AC/DC conductor separation - Maintain at least 8" (20 cm) of separation between AC and DC conductors. - AC interference can cause crosstalk. - Notice how the grey AC conduit line runs through the DC conductor's pigtails. |
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DC Conductor coils: -Do not coil DC conductors as this causes inductance that can interfere with PLC signal strength. |
Video: Common RSS Transmitter w/ Pure Signal technology install errors & how to avoid them
Product information: http://tigoenergy.com/product/rss-transmitter
Documentation: http://tigoenergy.com/downloads