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SEL Motor Relay Modbus Tags not updating properly on VTScada

The Modbus User Map Register Settings are correct and the frequency tag is working correctly; however, tags IA, IB, and IC are not updating properly on VTScada. Shown herein.

As the expected value is appx. '0.54' on SEL and '1' is shown on VTScada, I was looking to increase the resolution as this could resolve potentially but couldn't locate. I showed the 'Scaling' for IA tag properties if this could make an impact.

Thanks!

6182d9625901f
6182d9c02412b

The Modbus User Map Register Settings are correct and the frequency tag is working correctly; however, tags IA, IB, and IC are not updating properly on VTScada. Shown herein. As the expected value is appx. '0.54' on SEL and '1' is shown on VTScada, I was looking to increase the resolution as this could resolve potentially but couldn't locate. I showed the 'Scaling' for IA tag properties if this could make an impact. Thanks! ![6182d9625901f](serve/attachment&path=6182d9625901f) ![6182d9c02412b](serve/attachment&path=6182d9c02412b)

It's difficult to know exactly where the issue is but I discuss this with some of my team and we feel like the issue is likely that the SEL device is showing these values with some scaling.

By Default, each Modbus register should return an integer value which could be scaled in VTScada to become a decimal value. When devices using Modbus use floating-point numbers, the addresses typically go by twos (40000 40002 40004...) as the values are 32 bit. In your case, you have a decimal value but the addresses go by ones.

In VTScada, you can tell a tag to interrupt the address as a float by adding /FLOAT to the address (ie: 40002/FLOAT). While many protocols include the information on the datatype, Modbus does not.

It's difficult to know exactly where the issue is but I discuss this with some of my team and we feel like the issue is likely that the SEL device is showing these values with some scaling. By Default, each Modbus register should return an integer value which could be scaled in VTScada to become a decimal value. When devices using Modbus use floating-point numbers, the addresses typically go by twos (40000 40002 40004...) as the values are 32 bit. In your case, you have a decimal value but the addresses go by ones. In VTScada, you can tell a tag to interrupt the address as a float by adding /FLOAT to the address (ie: 40002/FLOAT). While many protocols include the information on the datatype, Modbus does not.

Trihedral Engineering Ltd.

According to the manual for the SEL-849, Table E.23, for Modbus the IA, IB & IC currents are 16 bit integers with a minimum of 0, a max. of 65535 and a scaling of 1.

This would imply that fractional values aren't available for the currents and that the scaling set in VTScada is correct, i.e. rounding up to 1. You could adjust the raw max and scaled max in the tag to 65535, but that would still be a scaling of 1.

The frequency is similarly defined as a single register, min. 1500, max. 7000, scaling of 100, so I presume you have that tag scaled correctly in VTScada as it's displaying correctly.

It would be best to confirm my reading of the SEL manual with SEL themselves.

According to the manual for the SEL-849, Table E.23, for Modbus the IA, IB & IC currents are 16 bit integers with a minimum of 0, a max. of 65535 and a scaling of 1. This would imply that fractional values aren't available for the currents and that the scaling set in VTScada is correct, i.e. rounding up to 1. You could adjust the raw max and scaled max in the tag to 65535, but that would still be a scaling of 1. The frequency is similarly defined as a single register, min. 1500, max. 7000, scaling of 100, so I presume you have that tag scaled correctly in VTScada as it's displaying correctly. It would be best to confirm my reading of the SEL manual with SEL themselves.

Software Developer with Trihedral

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