relay shunt controller

[imsmooth]

Purpose: to prevent overvoltage to grid-tie inverter

Limit: do not exceed 500v

I was thinking of using two voltage controlled relays: one to monitor the grid and diverter the power to a dump load if the grid goes down; another to switch to the dump load if the voltage exceeds 500v and to switch back if the voltage drops below 400v.

Do these relays exist? Can they handle these voltages and currents?

[Flux]

Not a simple problem. It might work but when you dump to a resistor you have a heating scheme. You may be able to get it to work with one stage near enough to do what you want but you may find that a single stage heater will either stall the mill if resistor is too low or not limit the peak volts in a high wind if too high.

For protection alone it will probably work but for synchronising in high winds it may be neurotic. You can buy or build voltage sensitive relays but you will most like;y have to switch on the ac side with 3 load resistors and 2 static switches.

Flux

[imsmooth]

Flux,

Your comments have always been helpful.  You never answered the question on another thread what you do for your real job.

[Flux]

I thought I did but it disappeared.

The way you phrased it this time is easier to answer, officially I am retired.

I spent about 35 years in the electrical laboratory of a large electrical machine manufacturer and much of that work was associated with the test department.

I also had many strange hobbies that involved me with a lot of electrical, electronic and mechanical problems.

The last 10 or so years has mostly been repairing magnetos for early vehicles with a bit of odd jobs thrown which others don't want to tackle.

Wind power has been a hobby since I was about 10.

Flux

[imsmooth]

I know wind power has been around for a long time, going back to the Middle East and Europe.  Sadly, our government and power industry has done little.  One of my collegues at work went to Block Island off of Long Island, NY several months ago.  The island's power needs are met by three large Catapillar engines.  Back in 1972 NASA was testing wind turbine designs and build a 250kw unit on the island.  There were good winds and the island could use such a device as there was no utility lines from the mainland - only what the island generated itself.

When NASA was done testing they did not need the turbine, but had to sell it.  They sold it to the island's power generation company for $1.  So what happened to this turbine?  They broke it down and sold it for scrap.

My friend told this story to me.