Transient Protection- Phtovoltaics

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gt

Member
To provide protection to a solar photovoltaic system surge protective devices are recommended. In a solar photophotaic system that is backfeeding the utility and the protective device is a surge arrestor listed under IEEE c62.1 can it be installed on the DC line from the array without any overcurrent device in series with the line connecting the DC bus to the arrestor? If the surge protective device is a TVSS will it require a overcurrent device? How does DC fault current effect the short circuit rating of the TVSS?
 

petersonra

Senior Member
Re: Transient Protection- Phtovoltaics

I am not sure just where you plan to put the TVSS or what you are trying to protect. You might get better help if you gave out more information on what you are doing or are trying to accomplish.
 

hurk27

Senior Member
Re: Transient Protection- Phtovoltaics

Installing surge protection on the DC side of this system would seem pointless since a transient is a AC event it would be shunted out by the batteries before it ever got to the array. But the electronics in the inverters and other electronics in the system might not be as lucky. so I would say the best place for surge protection would be at the utility tie in point (meter) or as close as it can be. secondary TVSS should be used at the output of the DC to AC inverter to protect against in-house surges caused by appliance's or equipment. one more place would be the high side of the AC to DC converter that charges the batteries by the utility power. the DC side only needs protection diodes across each DC relay coil that controls the system as these can produce a spike. These should be already on the relays.

I would wait to hear from a few others as I'm not up to date with some of the newer systems.
 

hurk27

Senior Member
Re: Transient Protection- Phtovoltaics

one item I forgot to mention is a shorted high side buck boost transformer will make a very good transient protector for a DC circuit when the low voltage side in placed in series with the photo array. this will short out any AC events that might try to be imposed upon the DC lines from the array in the event of a lightning strike close by.
Use one that has a 12 volt secondary and has a low voltage amperage at least higher than the output of your array. shorting the primary leads together by just capping all 4 H1, H2, H3, H4, together. then place the secondary leads in series with the photo array down leads. it will be best to X1 toward the array and X2 toward the load for the positive conductor then X3 toward the array and X4 toward the load for the negative conductor. I wish I could draw a diagram to show what I mean. But one low voltage winding will be in series with the positive cable, and one low voltage winding will be in series with the negative cable

This has the effect of shunting any AC via the shorted primary. They make special transformers for this but I haven't seen any. Placing the transformer close to the array will have the best effect.

[ January 15, 2005, 01:38 AM: Message edited by: hurk27 ]
 
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