By David Wren
While MEPworx’s Wiring is primarily an LV electrical distribution design program, it can also be used to carry out a HV-LV discrimination study. This can be performed between the last breaker on the HV Supply side of the HV/LV supply transformer and the first LV breaker on the Consumer’s side of the distribution, plus any additional downstream LV breakers/fuses.
The HV breaker is set up on the supply side of the Wiring project’s Supply Transformer.
In the standard MEPworx Installation folder, typically:
C:\Users\Public\Documents\Cadline\MEPworx 2021\DB\CPDCPD DBs.
There is a HVCPD2010_17 breaker database containing samples of various HV breakers. HV fuses, HV relays & HV static relays.
Because Wiring is an LV program, the HV breaker will be expressed in scaled LV terms. e.g. For a typical 11kV/400V transformer, the primary and secondary voltages are in the ratio of 27.5:1. Therefore a 100A HV breaker expressed in LV terms will be calculated using a rating of 100A x 27.5 = 2,750A
You can use HV breakers in your project, by following the steps below:
- First, use the CPD DB (database) program to open the Wiring project’s default CPD DB and then perform a, “Save As” to create a copy of the CPD DB for use with HV breakers.
- Change the name the new version of you project CPD DB, by adding ‘HV_’ at the start or the end of the name.
e.g. “HV_ Schneider Electric UK 2021a”.
- Working with the new ‘HV’ version of your CPD DB, use the ‘Import’ function to select and import HV breakers from the, “HVCPD2010_17” CPD DB.
In the example screen shot below, the HV Fuses have been grouped by Type for selection & import. - Open your Wiring project and in the Edit/General dialog, change the project’s default CPD DB to the new ‘HV’ version, then you can select the HV breaker for the HV side of the supply transformer.
Once the above steps are completed you will then be able to use HV protection in your electrical distribution schematic and carry out an HV to LV discrimination study in the Wiring project (or in the CPD program as a ‘New DCR Study’), between the last HV breaker and the first LV breaker, where the HV breaker’s curve will be shown in Blue.