Recent content by bspace123

I agree, they are useless. What’s even more annoying is the manufacturer species an alternative “engineered solution”, called a “fast fix” screw. Link: https://pryda.com.au/for-builders/pryda-fastfix/ Of course they sell this for triple the price of a batten (bugle) screw, which I find hard...

Apologies here is the link again https://www.mitek.com.au/wp-content/uploads/2021/06/MiTek-Guide-for-Roof-Truss-Installation.pdf The bracket shown in the previous post is the correct one. I’m not concerned about the truss shaking, the trusses are braced with hoop iron, speed brace, roof...

Hello I have just installed roof trusses which are designed to hold a metal roof. The installation manual from the truss manufacturer states to secure internal non load bearing walls using L Brackets, where the bracket is attached to the wall top plate and to the truss bottom chord. The manual...

Hello I am trying to understand fundamentally how generators operated in parallel with a solar PV facility are able to regulate their power output. I understand the concept of synchronous generation. Basically, for a stand-alone synchronous generator, the rotor induces a voltage into the...

I’m also still puzzled by the floating neutral on the primary leading to no earth fault current in the secondary. If we have a Wye connected motor with no neutral connected and we increase voltage on one of the phases, the increased current will flow back through the other two phases? There’s...

Makes perfect sense, thanks!

Hi All I have been reading for hours and still confused about the grounding concepts for wye-wye transformers. 1. Say we have a wye-wye transfrormer and the primary side neutral is not connected to ground but the secondary side neutral is connected to ground, if we have a phase-ground fault on...

Hi With fault analysis using iec60909 Ik” is used to determine the thermal withstand of switchboards, cables etc. But Ik” does not consider the dc offset present for asymmetrical faults. So if Ik” is calculated as say 20kA, but the fault is asymmetrical with peak of 60kA, does this not imply...

But where is the fault path? The second transformer is now acting as a step up transformer to what is generated current from the motors. There is no ground fault current path back to the delta side?

Consider a delta/Wye 66kv/22kv transformer supplying a bus then from the bus a feeder supplying another delta/eye 22kv/6.6kv transformer. From this second transformer a bunch of DOL motors are powered. The delta sides of the transformers are not earthed. The Wye sides are at their star points...

Balanced 3 phase fault

Hello all I have a model setup in SKM with a bus which has a single incomer and supplies a bunch of DOL motors. Attached to the bus are also some generators. When I simulate a fault at the bus and open all the feeders, the fault leave at the bus is 3kA which is showing as being supplied purely...

Thanks for the response CT’s are both wired in star and appear correct on the schematics. If they were transposed wouldn’t we see either 120 or 180 deg phase shift? I’m not sure how you would wire them differently to get 60 and 30deg. I guess the next step is to physically verify them by...

Hello We have two line differential relays on two parallel cables supplying a 6.6kv switchboard. The diff relays are linked by fiber communication. The cable run lengths are 100m and 200m. The switchboard supplies a bunch of DOL started 1Mw motors. Whenever we start one of the motors, the...

Thank you for all the responses! Turns out it was a poor earthing connection on the STAR point causing capacitive voltages to build up and discharge.