Unusual Voltage Measurements with ION9000

[JoseCarlosUP]

Hello,

We are currently facing an unusual situation with our ION9000 meter. The equipment is being used for voltage measurement in the 11.8kV (3-phase delta) PCC using a PT-CT set as per the diagram in the image. The instrument voltage mode is configured for 3W-WYE. Yes, we are aware that this is not the appropriate voltage mode for the wiring diagram. However, the strange aspect is that, with the mentioned configuration, the voltage measurements only show a 4% voltage imbalance on phase A (L1) and exhibit high stability.

To delve further into this issue, we have removed the ION for laboratory testing. During the testing with a low-voltage grid (without PT) using the same wiring diagram (noting that VN is not connected), we observed unbalanced voltages These were considerably worse than the field measurement, with all phases displaying pronounced oscillations. Even more peculiar is the that with another meter in the PCC (configured according to the wiring diagram), voltage measurements show no unbalance. It appears that the PT-CT set is functioning correctly.

Do you have any insights into what might be causing this slight unbalanced voltage measurement with the ION?

Best regards.

[Charles_Murison · Accepted solution]

Hello @JoseCarlosUP ,

3W-wye is very much not the correct volts mode to use. The 3W-wye has a very, very specific use case and will not work with the configuration you are using. Is there a reason why customer does not want to connect VN to VE? 

While the meter can be 4W-wye volts mode, many features can still be configured to use the VLL values. To use 4W-wye, the VN connection will need to be connected.

With Meter in 3W-wye mode, the meter is measuring V1 to VN where VN is floating. I am not surprised that using a floating reference could cause strange readings.

Regards,

Charles