Recent content by bozzah

Hello, I would like to learn the basis of calculation principles when it comes to design of substation bus structures. In particular, when it comes to the forces (kN) applies to the steel structure, equipment, cables with the respect to forces due to short circuit currents. Structural engineer...

waross, it is 3ph system;

Hello, I'd like to know the method of calculating a combiner inrush current for transformer connected in parallel. In my case there are ten (10) 10kVA transformers connected in parallel, i.e. one 600V circuit (125A breaker) is feeding all 10 transformers (separation between transformers is...

I am trying to understand how to control power factor for grid tie-in inverters for ground mounted solar system (10MW). The solar site consists of ten 1MW inverter stations (2x500kW inverers). The AC output of the inverter is 480V at which point it transforms to intermediate voltage 27.6kV...

The site is 8MW and it consists of 4 clusters (each cluster is 2MW package (2MW transformer and 4-500kW inverters)). Transformer secondary side is 480V (inverter input) and primary is 44kV. I am trying to see a benefit of transformer configuration (pri:Wye-grounded/sec:Wye). The other option...

thank you

I am modelling a system with 5 medium voltage transformers feed to the common bus. On seconday side of each transformer are PV solar panels connected to DC/AC inverter. The inverter is connected to the secondary side of MV transformer. The inverter generates voltage harmonics (at the moment I...

Scott, I had a similar concerns about CT excitation curve and knee point. Would you please explain/correct my understanding. Here the CT is C200, 1200:5A at 4.16kV. Let's say that total CT burden (including wire, relay, winding resistance) is 1 OHM. According explanation from one course I...

understood. thanks a lot!

So, in this application, the determining factor for the size of the CT is resistance grounded transfomer(25A) or this sizing is just a standard practice at this voltage? If transformer grounding resistor is, for example, 100A, an appropriate size would be say 200:5 for zero sequence CT?

Referring to a single line diagram, I'd like to confirm the size of the Zero sequence current transfromer. Full load amps for this 4.16kV motor is about 800A. In addtion to 1600:5 CT(3), motor protection relay has a set of zero sequence CTs . Zero sequence current transforer (a set with single...

A lot of good responses. thanks all!

Rbulsara, yes, I am referring to magnetic door holders mounted close to the top of door. What about Electrical Code requirements with electric strikes? I guess it there is none, because for most of the egress doors one needs just to push the door to exit. There is nothing holding the door...

Even though I understand the principles of operation, when do we use magnetic locks, i.e. electric strikes. Contractors generally run away from maglocks due to the facts there is more labour involved and they need to be interconnected with Fire Alarm pull station (if present at the door), so...

the current when passed through a wire creates magnetic field arount the wire. When wire is wrapped around the iron core, magentic vector does not cancel but is parallel, hence the power of the field. maglocks operate on 12 to 24 V DC. They need constant source of current to remain locked. If...