Does anyboody have the characteristics of the old B&S 12OQFRN fuses? I am particularly interested in getting the TCCs and the minimum breaking current figures as given on test certificates. Apparently the minimum breaking currents are NOT the same as the data published in the catalogues in the...
We have a bit of a debate going at the moment about the temperature "gradient" between oil temp indicator settings (OTI) and winding temp indicator settings (WTI) on power transformers using oil pockets and load current driven heaters to emulate the winding temperature. We have a number of...
Quick easy question - it's quicker for me to ask than to dig out a buzzer and bell it out.
Does a standard parallel printer ("Centronics") cable have any sort of 'cross' in it? I want to plug a dongle into the back of my PC, and I'm getting a bit sick of ratting around the back of the box...
I have a whole lot of data derived from old FORTRAN punch cards. I have imported this into Excel, but I would like to convert the numbers from the Fortran F5.2 format into "proper" numbers. Some numbers have explicit decimal points given some don't - it's a bit of a mixture.
Does anybody have...
Does anybody else share my reservations about the effect of IEC61850 on bread-and-butter protection systems? It sounds great for hi-tech transmission grids, but what about the run-of-the-mill distribution systems in small(ish) utilities, industrial plants etc?
Relay manufacturers seem to be so...
This one is driving me bananas! I have a test in a program loop that goes like this:
while (Test<1)^(t1<tm)
etc. Test is unitless. t1, tm are in seconds,and the ^ is the AND symbol from the Boolean toolbar.
As a standalone line (Test<1)^(t1<tm)= it works fine.
But in the program segment...
How do I test for the existence of a folder from a VBA module in Excel? GetAttr only works if the folder exists. There appear to be a whole heap of ways for testing for the existence of a file, but I can't figure out how to do it for a folder. The help on my MSDN disk I got with VB6 says to...
Interesting little problem cropped up during the commissioning of some instantaneous overcurrent check relays. Because the relays were not performing as expected (they were OK on the bench with a clean 50Hz injection) we were recording the current waveform as supplied to the relay by the CT...
I am interested in hearing others experiences with single vented drop-out fuses (cutouts in US parlance, I believe). There is a perception in our organisation that the failure rates (number of non-fault related element breakages as a proportion of total operations) is too high, and that the...
Does field forcing in generators (50-100MW size) act to increase the fault currents? I have had somebody tell me that it can push the fault current contribution by a generator well above (2pu)the subtransient value. A search around the web has give me lots of interesting stuff on generator...
Does anybody have any thoughts / data or anthing on the reliability of components in modern day digital technology power system protection relays?
I'm particularly interested in flash memory (EEPROM) reliability and electrolytic capacitor reliability.
We have already seen EEPROM problems in...
We have had a number of spurious operations of line differential protection at 33kV on through-faults. The general situation is as follows. This has happened at a number of different points in the system.
System voltage: 33kV
Protection: HO2, HO4 "Translay" schemes. Setting minimum...
What is the experience out there with the failure rate of drop-out fuses? Around half of the drop-out fuse operations in the distribution area I work in are not due to electrical faults - the things just drop open seemingly of their own accord. I have a few ideas, mostly concerned with thermal...
I'm interested in hearing about how people out there deal with the problem of controllong fault levels in 11kV distribution substations. Our nominal maximum (design) fault level is 13kA (250MVA). Recent plans to augment some substations by adding another transformer means that the fault level...
Does anybody have any information or suggestions on the high frequency ratings of fault current limiting fuses? I have a 1200V application where we are using standard 50Hz fuses at fequency of 1050Hz (ripple control frequency injection for hot water heater control). Points that my gut feel...
I'm looking for a method of examining the nodes in an electric circuit and modifying some parameters associated with nodes which meet certain criteria. Can anyone help? I will have to do it via a little program obviously. (I use Mathcad 2000 Professional).
The specific problem I have is to...
We use sensitive earth fault protection set at around 8A pickup on our 400A (CT primary) 11kV feeders supplying overhead lines. The idea is to detect and trip downed conductors. The time setting is 10 second definite time.
The problem is that in the past the relays used have an instantaneous...
I am having problems with a particular model of auto-recloser failing to operate under fault conditions, and instead the upstream protection operating. The picture is this: Single transformer 33/11kV substation, 5MVA, Dyn. Single incoming 33kV line, 33kV CB with overcurrent protection (IDMT...
