When attempting to update a transformer, you get the error "Object cannot be cast from DBNull to other types" and the update does not happen.
The Transformer Bank feature has a "NULL" value for its KVA, and it likely already has a unit created.
Normally the relationship AU "ArcFM Update Rated kVA" on the Bank to Unit relationship syncs the UNIT KVA to the BANK KVA. In some cases where this AU was not assigned, some of your transformer bank features may have a "NULL" KVA value, even if you have unit KVAs assigned.
Make sure that you have the ArcFM Update Rated kVA AU assigned to the TransformerUnit_Transformer relationship class.
- Select the Transformer Bank feature and verify that its KVA is Null
- Right-click on the Transformer Bank layer in the Table of Contents and click "Open Attribute Table"
- Find the selected Transformer Bank feature (you can click the "show selected" button on the bottom of this window) and find the "Rated KVA" field.
- Change the field from "Null" to any other value, 0 works fine here, and hit Enter.
- Now, in the ArcFM Attribute Editor, go to the Transformer Unit record and change the KVA to what it should be. If the desired KVA is already there, change the KVA to something else, then back to the one that you want.
If you need to do this on a large number of records, you can use the "Field Calculator" ESRI feature to mass-update all transformer KVA fields of "Null" to any other number.