Author Topic: Two SPD's in parallel  (Read 89 times)

johannes33

  • Newby
  • *
  • Posts: 2
Two SPD's in parallel
« on: November 26, 2018, 02:52:36 PM »
Dear all,

I'm consulting a mini grid (PV-source) in Sierra Leone right now and they using Midnite SPD to protect their system. At the main output of the grid with three phases (230 V), there are three SPD's installed (Type 2,/ MN SPD-600).

Since there is a earth conductor quite close, I'm afraid of a back-current from the earth to the network.

I have two questions.

1. Is the MN SPD-600 really the right choice? since I have three phases with each 230 V (Wouldn't it be better to use MN SPD-300 AC)
2. Can I combine the "MN SPD-600" with a "Type 1, MN SPD 300 AC" in parallel (To have Type one and Type two protection in the system)

Thanks for the information
Best
Johnny

KyleM

  • Administrator
  • Full Member
  • *****
  • Posts: 105
Re: Two SPD's in parallel
« Reply #1 on: November 27, 2018, 01:43:23 PM »
We have a diagram to use our SPDs on a 3 phase system located here: 
http://www.midnitesolar.com/pdfs/3_Phase_SPD_wiring.pdf  and http://www.midnitesolar.com/pdfs/spd_explanation.pdf

-Kyle

FNG

  • Administrator
  • Jr. Member
  • *****
  • Posts: 95
Re: Two SPD's in parallel
« Reply #2 on: November 28, 2018, 12:33:58 PM »
Dear all,

I'm consulting a mini grid (PV-source) in Sierra Leone right now and they using Midnite SPD to protect their system. At the main output of the grid with three phases (230 V), there are three SPD's installed (Type 2,/ MN SPD-600).

Since there is a earth conductor quite close, I'm afraid of a back-current from the earth to the network.

I have two questions.

1. Is the MN SPD-600 really the right choice? since I have three phases with each 230 V (Wouldn't it be better to use MN SPD-300 AC)
2. Can I combine the "MN SPD-600" with a "Type 1, MN SPD 300 AC" in parallel (To have Type one and Type two protection in the system)

Thanks for the information
Best
Johnny

Johnny,
Yes you can combine both, Essentially we redesigned the SPD and that is why it went from Type 2 to a type 1, in all honesty both will protect just fine.

As for the 300AC vs the 600, The 300AC has a max AC voltage to ground of 250v so you are under that by 20v. If you feel comfortable that the 230v to ground will not exceed 250 than yes I would use 2 SPD300-ACs otherwise I would use 2 SPD600s

johannes33

  • Newby
  • *
  • Posts: 2
Re: Two SPD's in parallel
« Reply #3 on: November 29, 2018, 11:20:00 AM »
Hello Guys,

perfect, thanks for the information.

Best
Johnny