I'm working on a brushless DC motor controller. The heat sink that contains the circuit board is completely embedded in a gray rubber type substance. It seems like it must have been filled with this as a liquid.
Any ideas on how to remove this material without destroying components on the...
Thank you. For clarity, I'm only looking at the inrush seen in an unloaded transformer (not a loaded transformer with a lack of load diversity upon energization).
Will the magnetization inrush ever stretch out to the 10+ second time range?
I typically see transformer inrush plotted as a per unit value of normal transformer FLA current on a phase TCC at a specific point, such as 0.1 seconds.
I have also come across transformer inrush current curves. So, the inrush may be plotted as 10 per unit FLA at 0.1 seconds and 2 per unit FLA...
As current flows through a bus that has a window CT wrapped around it, it's stepped down by the CT ratio. 100 A through a 100:5 ratio window CT results in 5 A secondary.
If 5 A of current is applied through the secondary winding of the CT, does this cause 100 A of current to flow through the...
See attached example. If both CTs are accurately representing the fault current and have similar specs and secondary wiring, there will be no current flowing through the high impedance element and no voltage across it. Since both CTs are producing the same output at opposite polarities and have...
The logic rules out LOP even with a minor change in current (>2%). It also analyzes other characteristics such as sequence component magnitudes and angles.
cranky108 - that is correct. The desire is to use circuit switchers with pre-insertion resistors for cap banks rather than expensive sync close breakers, but also have the ability to trip the individual switchers based on input from relaying class CTs.
I'm looking for model recommendations (commonly available in USA) for stand-alone relaying CTs (C400 or higher) that can be used for protection applications with circuit switchers. Circuit switcher manufacturers never seem to provide slip on CTs as an option similar to circuit breakers. Combo...
I'm not having any luck finding a symmetrical component example for a fault between two separate transmission lines. I'm attempting to analyze a fault that occurred between a 69 kV and 138 kV line that share the same tower. One phase on the 69 kV line came into contact with a different phase on...
Is there any benefit to implementing REF protection on a transformer that is already protected by 87T protection using CTs on the high and low side bushings? I can see the ability to isolate an internal fault to the wye winding, but I don't know if there's any other benefit or if it's just...
I live in a fairly small apartment on the 1st floor of a building. The HVAC system rarely needs to run due to the insulation provided by units above and around it. The kWh usage has always seemed high compared to similar dwellings in the past, but I unfortunately never investigated further.
I...
OK, I think that's where I'm confused. I wasn't sure if the 60 samples/second was a sample rate or a rate at which data blocks (with multiple samples within) were sent.
Most microprocessor relays are capable of sampling at rates of 128 samples per cycle or more. Would it ever be possible to get this type of resolution with Phasor Measurement Units or will these always be more for longer duration event analysis such as power swings and such?
The highest sample...
I'm looking for a few drawings that clearly indicate the potential gradient along the earth during a fault to ground. I've come across a few on Google Images, but nothing that's really clear.
I hope to find something that shows a phase conductor contacting the Earth and the voltage gradient...
I'm having some trouble wrapping my head around the voltage distribution for a ground fault. If a Delta-grounded wye transformer has an A phase line-to-ground fault a mile down the secondary line with no fault resistance, the voltage is considered to be zero at the fault point. The entire...
For power transformer protection of a standard Delta-wye radially-fed transformer, is it normal to utilize negative sequence protection to gain sensitivity? What is commonly recommended for settings sensitivity to avoid inadvertent trips? As in, should it be set to pickup at 50% of expected...
I often see a "minimum fault" specified on some fault study software that seems to typically be around 30-60% of the maximum 3 phase fault current. What is this referring to?
Is there a common fault resistance value that is used for these calculations? Minimum fault current is confusing since a...
