Eskom’s next step towards Solar PV standards

Rooftop minimum safety requirements

 

Contrary to popular belief, Eskom is excited about solar PV, they have a dedicated team doing research and developing solutions for grid tied PV installations in the low voltage electrical network environment.

Since the re-introduction of load shedding early in 2015, solar contractors and suppliers have experienced a significant growth in the demand for solar PV and backup energy solutions. Although hundreds of grid tied systems have already been installed, the lack of clear standards have left many electricians and contractors in the dark. This post was written in an effort to shed some light on what Eskom is doing and to add a few pointers of what could be considered during solar PV installations to ensure a safe installation.

Solar contractors expose themselves to risk by doing an installation in an environment where no clear standards have been provided. Once standards become available, contractors would technically have to go back and make the required changes in order for the system installation to comply to the newly established standard. As a result of our activities with the required departments at Eskom, we have the privilege of providing up to date information on what is being discussed and considered as solutions for grid tied installations on the LV network.

By providing this information, we would like to make it clear that although the proposed standards contained in this post have not yet been approved, it should provide guidelines on where the standards are heading and possibly contains information on what could be expected in the foreseeable future. PQRS would therefore accept no responsibility should the proposed standards in this post not be adopted. The following are being considered in future standards.

  • Type 2 surge arresters before and after the Grid-Tied inverter on both the AC & DC side of the inverter. This is being considered for all sizes of grid tied solar PV systems. Although the existing SANS10142-1 does not prescribe surge arresters as being a mandatory component in an electrical installation, this may change for solar PV installations, possibly only being excluded in installations where a risk analysis has been done and the analysis indicated that it was not necessary according to SANS62305-2.
  • Disconnecting contactors before the inverter controlled by a relay. This line diagram has been included as part of the image above. The complete Powerpoint presentation can be viewed by following the link to the PQRS website and also includes a rough cost breakdown as part of the powerpoint document.
  • A residual current device that monitors the presence of both AC & DC on larger installations. The boundaries of “Larger installations” have not yet been defined, and may be for systems exceeding 10kW in size.
  • A separate DB for control and switching circuits related to the PV generator.
  • Adequate labeling that would make it obvious which circuits are AC and which are DC.

Based on feedback received from the Linkedin Post we could add the following comment.

Although the contactors being positioned before the inverters could be seen as an amateur failsafe device; the reason for the contactors being there is to prevent the unit from re-energizing in the event of a power failure. Municipal or utility workers will therefor test the lines before maintenance and need to be assured that there wont be any systems that allow re-energizing for any reason or under any condition whatsoever.

This link will take you to the Powerpoint presentation that discusses the Disconnecting device currently being proposed for solar PV installations in grid-tied configuration in more detail.

Comments

  1. Obviously an external device?!
    Standard and state of the art grid inverters have at minimum such a device included. Common use and practice in Germany since early 1990s.
    But: The experience was, that with over 1,5 million installations (in Germany) you face a problem when you have just short grid failures (<400ms = low voltage event). If all (!) PV systems disconnect immediately you might lose GW(!) of generation capacity and it takes minutes before they start up again.
    Todays inverters (even small string inverters) manage such events by measuring the grid frequency and ramping down in a certain mannor to avoid "real" grid problems.
    And yes, they do disconnect from the grid when Eskom switches off for maintenance or what ever to avoid islanding.

    1. Author

      Hi Ralf, Yes, it was intended as an external device. However the function of the device is a little questionable as it was supposed to make installations safer and the reality is that contractors doing illegal installations would probably not fit the device either way.

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