Operate and Restrain in Relaying 1

[Mbrooke]

What year did operate and restrain become the norm in differential relaying in power plants and substations? Or when was it realized that systems needed this? I ask out of curiosity looking at protective relaying books from the 1900s where bus, line, generator and transformer differential CTs were connected in parallel into a low impedance trip coil.

The text makes no mention of CT saturation, rather that as long as CT ratios are proportional and winding phase displacements are taken into account current will always be "zero" through the solenoid coil.

 

[sushilksk]

No stabalization provided. What of there is ratio error in CT?

 

[jghrist]

The first ABB (Sweden) harmonic restraint transformer differential relay was in 1940. See

https://library.e.abb.com/public/c1...Protection__the_Swedish_ABB_Relay_History.pdf

I'd be surprised if there weren't other differential relays with operate and restraint coils much earlier.

 

[cranky108]

Generator differentials have always been sensitive. That said, what restraint did they need?

 

[Mbrooke]

I'd imagine the coils are set to trip above the normal current produced by CT errors and tolerance.

 

[7anoter4]

Because by MikeH. you can't send a tab in excel I attach it here although it's not related to the subject. I apologize for the inconvenience.

 

[7anoter4]

I have to check the files...

 

[Mbrooke]

Thank You for the Excel file! No apologies needed.

Once editing is enabled, can it auto calculate parameters or is this fixed just for the one scenario listed?

{I just need the XL for a single circuit under the configuration shown rather than all the sets in parallel.}