Operating Shunt Trip Coil

Been a long time since dealing with that stuff and I think that your coil specification has some flaws in the % tolerances, but those concerns aside:-

I think that you have some unresolved problems.

• You will need to calculate the time constant of your coil to determine its response time. While you have measured/nominated the coil resistance (at DC) but not the time constant of the inductive circuit to change in state.
• At your 1000Vdc (Or really 850V), your coil will have steady state current of 4 amps. Will the 40AWG wire even sustain that, or will it turn into a "fusible link"?
• Your magnetic circuit will need to provide the required force at the LOWEST supply voltage. You need to realise that at some point the magnetic circuit will saturate (Regardless of higher current you will not get additional magnetic flux and thus no additional force.) This MIGHT permanently magnetise the core and leave you with "ON" condition after voltage removed, or even have a decaying magnetisation that holds circuit closed for some time after voltage removed.
• In that configuration, almost every device could be exposed to the 1000Vdc source/potential and would need to be selected for appropriate rating. Local code in Aus would require significant safety interlocks to be able to work on those items.
• Have you successfully "switched off" a 1000Vdc line? What is the potential arc length to extinguish a 1000Vdc arc?

I would suggest that you add a simple voltage supply regulation to the front end so that regardless of system condition, the coil will see a constant supply voltage. This also means that component ratings and clearances can be designed for.

STAY SAFE!

Why not just step down the voltage?

I tested it with lower voltages, and the coil starts to actuate after about 40V. Not sure if it does reliably. As I'm designing a flyback SMPS, I may consider then having a output winding ~50V.

https://www.nxp.com/products/power-management/ac-dc-solutions/ac-dc-controllers/flyback-smps-design-tool:TEA1733-DST

If you insist on putting yourself in a vulnerable liability position:

Use the DC supply to charge an appropriate sized capacitor,and discharge it at the proper time across the coil.

Use a shunt trip rated circuit breaker,with built in shunt trip coil.

I suggest that this,or similar brand is what you need:

I have used these type in fire protection circuits.

https://www.electricalonline4u.com/2019/03/shunt-trip-breaker-wiring-diagram.html

I strongly suggest using a factory designed and tested/certified method to prevent liability in case of failure of your ad-hoc device.

Well, I would contact an Electrical Engineer and ask that individual instead of posting on here, Mildred. If you do what you suggest, then putting it right is at your expense and so is the delay that you've caused by doing it wrong. What a way to run a railway!

I cannot recommend this due to the very large voltage range (and other complexity and safety reasons), you are far better off using the 12VDC to control the solenoid coil (which is standard industry practice).

It's a hell of a lot easier and safer, AND takes the voltage range issues totally out of the equation.

yes, this is the industry standard (or 24 vdc for shunt trips controlled by fire alarm systems)

The ‘industry’ standard for power distribution and transmission protective equipment is 125 volts dc. Voltage drop and current requirements make low voltage such as 12 volts or 24 volts unsuitable for wide application.

You cannot be assured of a control voltage with one two or three phases available. A fault can take the voltage of any or all phases away. The industry designed a capacitive trip device for these situations, present on many common low voltage circuit breakers 600A to 3000A frame size. The capacitor is sized to be able to operate the trip latch one time.

The industry standard for switchgear control circuits is 125V dc usually from a battery. The high speed latching trip relays have 125Vdc applied, but self clear the current in milliseconds, to assure fast operation. I believe those coils might be rated 12Vdc, so your idea is similar to what is in practice.