We are installing a 24 pulse 6.6kV VFD to drive a compressor motor and the input transformer to the VFD has the vector group Yd0.75d11.75d0.25d11.25. I've never seen anything like this before and wondered if anyone could shed some light on it. HV winding is star connected (6.6kV) with 4 delta...
Here in the UK we would select our cables based on BS7671 - 17th Edition. One of the things to look out for is regulation 512.1.2 which states
Switchgear, protective devices, accessories and other types of equipment shall not be connected to conductors intended to operate at a temerature...
I have attached a drawing to explain the installation in question, I am based in the UK. The UPS system is made up multiple sngle phase chargers (hence the neutral requirement)spread across the 3 phases.
There wasn't a neutral in the local DB therfore they have installed the transformer in...
There is a current project underway on the site I am currently working and the following problem has reared its head.
A 3-core cable was installed to supply a DC UPS system and when they came to commission the system it was realised they actually needed a 4-core cable , 3 phase & neutral.
To...
Hi,
We have had an insulation breakdown in an 11kV VCB. We have sent this away for investigation and the culprit was a stress shield mounted on the end of the vacuum bottles. The clear shields had black traces on them. We have been informed that Polycarbonate will sooner or later give up...
Hi All,
Please could someone answer my query.
On my current project we have installed an 11kV switchboard and a 400v switchboard/MCC. My question is regarding the orientation of the CT's.
On the 400v switchboard the P1 and P2 primary markings are in the direction of the power flow. On the...
Hi,
Can someone please assist. Do we need to tin copper earth bars when bolting tinned copper cable lugs to it. I am working on a project where we have coflicting opinions. Some bars are in a substation and some on site for plant earthing. Project is in the UK.
Best regards
