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4-20mA to 110Vac

4-20mA to 110Vac

(OP)
Hello,

I need to send the secondary 110Vac/sqrt(3)of a HV metering PT, to a remote location at around 5 km. I have found analogue to digital converters and signal transmission through fiber optic. However, for the remote end, I require also a 110Vac/sqrt(3) output, and I am only able to find digital to 4-20mA or 0-10V transducers.

Anyone can tell me a solution for this?

RE: 4-20mA to 110Vac

What is on the receiving end?

xnuke
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RE: 4-20mA to 110Vac

Quote:

However, for the remote end, I require also a 110Vac/sqrt(3) output, and I am only able to find digital to 4-20mA or 0-10V transducers.

Anyone can tell me a solution for this?
You can only do this with some sort of inverter technology, and it's unlikely that whatever is looking for that 120V 3 phase PT input is going to like an inverter created output, i.e. PWM into an inductor. That's probably why xnuke was asking you what was at the receiving end; it's more likely that if you investigate it, the 3 phase 120V PT signals are being transduced to something else anyway, so it would be a lot easier to just dig into that and convert your signal into something that directly couples to that; bypass the 120V analog values altogether.


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RE: 4-20mA to 110Vac

A couple of decades ago Dowty / RFL manufactured a 'digital pilot wire' which did something similar, accepting CT inputs at one end, pushing digital data down an optical fibre, and synthesising a current output at the remote end. That used linear amplfiers, not PWM.

In principle what you're asking can be done, but is it a good solution? What are you connecting to?

RE: 4-20mA to 110Vac

(OP)
It is for tariff metering. Client Contract clearly specified to measure current at one location and voltage at substation 5 km far. Although we have explained that this is nonsense, it is clearly specified in Contract and Client does not want to accept an addenda in contract for us to install VTs in power plant side.

RE: 4-20mA to 110Vac

I doubt that you can come up with something that would meet tariff metering standards of accuracy and security operating over 5km. You need to measure the current and voltage at the same point and if necessary transmit the meter reading or a representation of it over the 5km. Normally the standards governing tariff metering arrangements are very strict.

Regards
Marmite

RE: 4-20mA to 110Vac

(OP)
I know. This I explained already to Client, giving two options: either put tariff metering at Substation where we have both CT & PT of required accuracy; or pay to us to install PTs at Plant side. No success with any of the options. That is why I am asking for any experience with this PT secondary transmission.

RE: 4-20mA to 110Vac

The closest you're probably going to get is to take synchrophasor voltages from the substation and synchrophasor currents from the plant. Those values then get mathematically combined somewhere to produce the pseudo metering values.

RE: 4-20mA to 110Vac

Accounting for losses will be very strange if you mix signals from two different locations.

Meters often have the capability to compensate for losses between the metering location and the contractual point of sale. Perhaps you can put the tariff metering at the plant and then program the compensation values to calculate the plant?

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