Isolation Relay

[peetey]

I am not familiar with the inner working of an isolation relays' input side. I have not been able to find a diagram or schematic of the circuit so I'll just ask as best I can. I have KYZ coming from a meter and Y & Z are on the input of the relay. The K is taken to a neutral reference from the meter. The K of the input of the relay is supplied with 120v with respect to the neutral reference. If I leave the relay hot and in operation and go from K of the meter to the Y & Z of the relay can I expect the relay to show me good pulses or will the circuitry of the relay give me skewed contacts such as both closed, both open or one open one closed. I'm wondering if there is any continuity or DC that may show false contacts. I realize this may vary by manufacturer, so any thoughts are good.

If I check pulses from the meter, I choose to isolate KYZ and check them or check from the output of the relay, so this is a hypothetical question.

I would like a very simple explanation of how this works. If the relay supplies a voltage of DC to the meter per convention, is Y & Z positive and negative? If 120v is supplied to the relay to heat it up is that all it does? When we remove the input fuse what does that really do to the circuit? When we take the K from the meter to a ground or neutral reference what does this do? Can anyone post a diagram or send me a diagram of what occurs with the isolation relay and how it utilizes AC and DC voltages and the path they take. I know this is a lot to ask but it will help me bunches and help me prove or disprove conventional thinking of some I know. There is no way Google has the answer to this. pete

 

[rcw retired EE]

What type of isolation relay? Manufacturer? Any nameplate data?

KYZ outputs are just a form "C" contact with the K lead common and the Y and Z leads the contacts. The first time the relay pulses, the X contact closes so there is continuity K-Y and open circuit K-Y. On the next pulse the contacts transfer and there's continuity K-Y and an open on K-X. this provides a means of verifying a pulse occurred. If you were only monitoring K-X and your sensing voltage (AC or DC) is lost it would looklike a pulse.

I am guessing that the multiple power supplies to the relay are:

120VAC from the meter is a pulse signal to operate the relay.
24 or 48 or 125VDC to the K contact is contact wetting voltage. The X&Y terminals carry this voltage back to SCADA, DCS, PLC or some other metering summation system.