Hello
I have a closet which is approx 2.7m high by 1m deep by 1.2m wide. I have l equipment in there that needs to sit at max 30degC. There are two double doors on the closet.
In order to keep it at 30degC I’ve installed 4 extraction fans on a thermostat. The fans draw air in through gaps in...
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Can anyone provide any guidance or reference material for how to correctly size (if required) the stabilizing resistor that comes with the high impedance MFAC relay in bus differential applications? I have looked everywhere and cannot find anything.
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I am trying to calculate ampacity rating of direct buried cables. The thermal resistivity used significantly impacts the rating of these cables.
I have a report where they have performed a thermal resistivity test of the soil. It appears as if they have put the soil in an oven (or...
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I have to install some large steel angle lintels above some 5-6m wide commercial style windows. They are going to be installed in a brick veneer wall.
Due to width the lintels have to be welded to PFC beams (which are located in the timber wall cavity supported by SHS posts either...
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I have two walls with floor joists running between them (refer attached diagram, walls 1 and 2).
One of the joists runs between the two walls (i.e. walls 1 and 2) and ontop of another wall (parallel to the joist, i.e. wall 3).
Diagram:
I've been assured by a structural engineer that...
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I am trying to calculate the size of some structural beams. Each beam will be supported on one side by a timber stud and on the other hung vertically with timber from timber joists.
I have a box with UDL of 85kg/m (or 0.84kn/m). Box dimensions are 1.4m (L) x 1m (W) x 0.5m (H).
My span...
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I have a 250x90PFC and a 300x90PFC that will be supported by 3x90x45 F17 KDHW tripple studs either side. The beams are used on brick veneer walls in a residential home to support upstairs internal framing and bricks.
A 200mm flat plate will be welded underneath the beams which will...
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I have two 90x90 square hollow section columns.
I need to cleat a 300x90 PFC beam between the columns, however I need the flanges of the PFC to be flush with the column face.
This means it's impossible for me to cleat the PFC to the centre of the column. I need to offset the cleat...
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Just curious, can someone tell me what the paramaters "Centres (CTS)" and "Design At" for this steel floor beam?
I'm trying my hand at some structural engineering and just need a basic explanation.
Link to calc...
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I have some 270mm (W) x 90mm (L) 10mm (thick) base plates welded onto some SHS columns which will be used to support the upper storey of my house. The slab has been poured a month ago.
Upper storey is tin roof with light weight foam board/render on the external walls.
The engineer has...
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I am trying to understand the inner workings of surge arrestors. If a surge arrestor diverts current to ground once line voltage is above a certain threshold, does that mean you will get an earth potential rise at the surge arrestor output? For example, if I measured the voltage between...
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I am trying to understand whether there's inaccuracies with earth fault currents detected with a residual scheme (i.e. CT's connected in STAR to protection relay, protection relay measures imbalance current to determine earth fault current).
Can you please confirm if my understanding is...
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With CT rated burdens, do you need to factor in the resistance of the CT itself into the load burden calculation?
If not, can am I correct with the below calculation?
If we assume the CT is 1000/1A 5P10, assume secondary cable impedance is 0.1ohms, relay burden = 0.1VA
My...
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I am trying to wrap my head around how battery storage facility import/export power.
For these scenarios, assume grid voltage is 66kV, inverter output voltage is 660V, battery facility rated capacity is 20MVA, consisting of multiple inverters (for simplicity assume all inverters are...
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I have a 33kV bus modelled in ETAP with multiple power grid sources feeding into it. All of these grid sources are connected to the bus via 3 main CB's (via downstream CB's). I've tried to complete a short circuit analysis (3phase fault) using IEC60909 simulation, but the numbers don't...
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I have the following data for a transformer in per unit which I need to convert to % impedance to enter into ETAP:
MVAbase = 55
Voltage base = 33kV
Positive & negative impedance LV-HV = 0.0030 + j0.1 per unit
Zero sequence impedance LV-HV = 0.002 + j0.06 per unit
To get this into %...
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I have read in some literature that switching surges in systems <66kV do not typically exceed equipment BIL ratings.
Is this true? If so, have you come across this conclusion in a standard or any other literature? Looking for some further references.
Thanks
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I am trying to specify BIL ratings for some equipment based on lightning strikes. In order to mitigate risk of equipment damage, I am installing surge arrestors around critical pieces of equipment. To understand the BIL rating, I need to understand the maximum 8/20uS current wave, which...
