Safe DC option with SolarEdge power optimizers

Safe DC option is an integrated feature in SolarEdge power optimizers and inverters. Safety of installers, maintenance personnel and firefighters is ensured with this option. This option shuts down DC current and voltage in strings when inverter is off or disconnected or in safety mode.

High string voltages are de-energized automatically to 1 Vdc per Power Optimizer and max. 50 Vdc per string in any of the above cases. Electrocution and unsafe high voltage risks are eliminated with this Trade Mark option.

Safe DC option can be triggered from SolarEdge fire fighter gateway aswell, providing centralised safety management.

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Working of Safe DC

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The SolarEdge Solution consists of a Inverter which communicates to Power Optimizers over Power line communication (PLC).
Safe DC is a mechanism which is build into the software of the Inverter and the Power Optimizer.

The Power Optimizers only harvest full power from the panels if the PLC signal is constantly renewed. If it fails the Power Optimizers initiates the Safe DC mechanism, which lowers the DC voltage to 1 Vdc per Optimizer. This feature works even when more than one panel is connected to it.

The 1 Vdc is necessary during installation and maintenance stage to check the proper working of the Power Optimizers.

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Advantages of SolarEdge Safe DC mechanism

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Installation

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During installation, panels are connected with Power Optimizers in strings. Safe DC is activated by default, lowering the operational voltage of the Power Optimizer to safe 1 Vdc, if the sun shines.

The maximum number of Power Optimizers in one String of panels is 50, therefore max. string voltage is 50 Vdc if all Power Optimizers are working properly.

Full power harvest can be safely activated when the Power Optimizers are connected and communicate with an SolarEdge inverter.

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[mk_button url=”https://www.solaredge.com/sites/default/files/solaredge_case_study_fire_safety_tasmasia_australia.pdf”]Case study on Safe DC[/mk_button]
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Emergency

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In case of a fire firefighters, mostly the AC wires of the house were cut to terminate the grid connection. Safe DC is automatically activated by the inverter if the grid connection is lost. This reduces the per power optimizers voltage to 1 Vdc. Eventually, max. 50 Vdc per String, lowering the risk for firefighters tremendously.

If properly educated, firefighters can also manually activate Safe DC by switching off the Inverter, the AC breaker or the AC/DC safety switch.

The Power Optimizers will also activate Safe DC by themselves if their thermal sensor senses a temperature above 85 °C, because such high temperatures typically indicate a fire near the PV System.

To activate Safe DC manually, inverter should be turned off so that it stops sending PLC signals to the Power Optimizers. Safe DC can also be activated if the connection to the AC side is interrupted by switching off the main AC breaker or AC/DC safety switch.

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Maintenance

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Maintaining PV system should be done regularly. Safe DC should be activated in order to reduce the high DC string voltages to a safe level. Maintenance like cleaning the panels, checking for defects, replacing panels or power optimizers should be considered only after activating the Safe DC mechanism.

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Sri Sarada Ashram, Ulundurpet

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Sri Sarada Ashram, Ulundurpet

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[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]About Kalasalingam University[/mk_fancy_title]

Sri Sarada Ashram was established with the core objectives of promoting and developing the poor and the backward villages by means of quality education, affordable healthcare, cultural and socio-economic development activities, agricultural development and providing much needy and timely relief during natural disasters.

Located at Uludurpet, on the Chennai Trichy Highway in Tamilnadu, the Ashram houses 45 Sanyasin Sisters and services the remotest villages in and around the place. Over 1000 students and 500 women are given schooling, vocational training and job-oriented career coaching annually.

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Contributing towards the sustainable future with various initiatives in ashram, they had decided to add more to it. With regular training to the women in ashram, kids in the school there is a need of energy demand. Inorder to reduce the electricity bills and promote renewable energy, ashram decided to go ahead and install solar on its rooftops.

[mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]About the project[/mk_fancy_title]

A total of 63.28kWp of Solar rooftop system was installed on five different buildings using SolarEdge power optimizer technology. These buildings include main ashram building, boys hostel, pump house.

A 10kW solar rooftop system was installed earlier on one of the buildings by another vendor. Due to performance issues, revamp of the system was needed. Sunlit future had revamped the system and extended the system to 17kW with SolarEdge power optimizers technology. Existing 240Watt panels for 10kW and 7kW of 360Watt panels under one inverter were connected. This gives an affirmation that the system could be extended in future with no extra investment on inverter.

Satisfied with the performance of the revamped system, ashram authorities had reached us for solar on other buildings as well, extending it to 63.2kW

SolarEdge Power optimizer technology enhances the generation of each of these systems. They have module level MPPT which enhances the generation. Overall performance of the system is not compromised with shade on one module due to the trees or dust or bird droppings.

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Project Details

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Location Ulundurpet, Tamil Nadu
Owner Sri Sarada Ashram
Capacity 63.28kW
Number of panels (240 Watts) 42
Number of panels (310 Watts) 32
Number of panels (330 Watts) 50
Number of panels (340 Watts) 25
Number of panels (360 Watts) 51
Type of panels Mono-crystalline
Orientation ~South at angle 10°
Structure Pre fabricated
Inverter 17kVA SolarEdge (3 units)

10kVA SolarEdge (2 units)

Average units per day 265 kWh
Average units per year 97,008 kWh
Date of commissioning (Building-1) 24th March, 2018
Date of commissioning (Building-2) 19th July, 2018
Date of commissioning (Building-3) 20th July, 2018
Date of commissioning (Building-4) 25th July, 2018
Date of commissioning (Building-5) 24th April, 2019
[/mk_table][mk_fancy_title color=”#464646″ size=”20″ font_weight=”500″ margin_bottom=”0″ font_family=”none”]Generation & Savings[/mk_fancy_title]

This system was installed with Modbus meter enabling Net Zero option. All the generation of each of the systems is being utilized in the building and there is no excess generation that gets exported to the grid.

It saves about Rupees 52,000/month at an average with the generation. All the systems together takes about 5 years for the return of the investment.

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Installation specifications

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Solar on all the five buildings was installed on the flat roof with the help of pre fabricated cement ballast structure made of Aluminium. This structure helps in corrossion free and long durability of the system.

Safe walkways were provided ensuring seamless maintenance of the system. Cables were routed through UPVC pipes providing safety from external factors like weather, insects etc.

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Project Gallery

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