Prefault current of 17 amps might be a branch/tree sitting on the line for a short duration before the fault evolves to low impedance.
Can you post the waveform recording? When the fault magnitude varies throughout the fault it is unclear to me which instant the relay uses to calculate the...
I have seen shield wires on incoming lines are intentionally isolated from the substation ground grid with a 15 kV class insulator. I too am curious about all your questions.
As I experimented with various configurations, it seemed like X0 and R0 sometimes go in opposite directions for a change in circuit configuration. I don't recall seeing anything change by a factor of 6.5 though.
Perhaps there could be current flows on the distribution circuit cased by the...
I am not sure what you mean by RYB indicator, but please consider what will happen if there is a short circuit between PT and the RYB indicator or fault inside the RYB indicator. I do not recall ever seeing the secondary of a PT directly connected to an instrument with a fuse or breaker as the...
Historically I ignored it based on advice that ground fault relays were typically less accurate than phase relays.
For a recent fault I analyzed, the distance shown by the ground relay element was much shorter than the actual fault location. Once I recalculated the line impedance to include...
There are many ways for utilities to implement power factor penalties. Can you share exactly which utility you receive power from? In my region, small loads like this would not be subject to power factor penalties.
Hopefully the OP can clarify their question.
Casey-Even when I have perfectly balanced loads, I still end up with voltage unbalance at the end of the feeder. I have some balanced circuits where the lack of distribution transposition causes at least a few percent voltage imbalance at the end of...
I had assumed the IEEE standards for arc resistant gear covers the whole package we buy from the switchgear vendor to attach a 115 kV/15 kV transformer to the outgoing 15 kV cables. Even if testing standard doesn't quite cover the cable terminations, I assume a vendor could at least employ...
Safer dissipation of arc products is unrelated to the IP rating. Here are some videos showing normal versus arc resistant design:
Arc flash that blows the door open directly at the operator:
https://videos.eaton.com/detail/video/6256039547001/arc-flash-explosion?autoStart=true&q=arc%20flash%20...
I have see some papers analyzing representative configurations as the basis for localized utility practices. The appropriate amount of surge arrestors is highly dependent upon the frequency of lighting in the area.
Running an EMTP analysis at every pole to determine if it should have an...
I am confused why they have FTB below the power cables and CBS surrounding/above the cables. I haven't ever used CBS, but I thought FTB had better thermal properties.
It is not obvious to me why you need 250 mm of non-native material below the cables. I can see a possible need for a much...
The earthing switch does not clear the fault. It instead turns an arcing fault into a solidly grounded fault, while still relying on the upstream breaker to clear. Before adding a device that intentionally creates a bolted fault, I would want to be sure it provides very clear benefits over an...
Are all three phases in same enclosure? I had assumed that for GIS with a separate pipe for each phase that induced currents could be nearly equal to the phase currents. Similar to an isophase bus duct.
I should have have said custom rating rather than custom nameplate. The device was a voltage regulator, so the nameplate doesn't actually include the short circuit rating. The IEEE standard calls for regulators to withstand 25x load current for 2.0 seconds, and the vendor was able to...
Depending on exactly how the manufacturer did their testing, they might be able to provide a customized rating. Often equipment falls between two preferred rating categories. On a recent project a manufacturer was able to provide a nameplate showing a rating about 5% higher than the preferred...
Test labs have a variety of tricks. Some tests involve switching be one source that can produce high voltages at low currents to a source that produces high currents at low voltages. Other tricks involve various capacitor bank energy storage techniques.
Often the procedure is not intending to...
Is there an ACSS conductor that meets the power transfer, maximum sag, and strength limitations of existing poles? It seems strange to have zero consideration of ACSS. However, I can imagine a situation where ACSS can be ruled out very early in the process.
Does the owner already have both...
There would be a whole lot of assumptions to come up with any kind of estimate. Given how rare and chaotic a flood event is, I would doubt anyone could have certainty over any specific outcome.
Regardless of the utility transformer choice, there is the possibility that household or streetlight...
