Folks,
We're having to review Emergency DC Lube Oil Pump circuits to ensure the O/L's do not trip the motor. My schematic shows we do have O/L Relays in the circuits, but their Auxiliary contacts are only used for alarming purposes, they're not used to drop out the Main Contactor/Starter...
Folks,
I'm working on a project which is my first on a DCB scheme using Power Line Carrier equipment. We are replacing the relays, TX/RX unit, and the line tuner, but will be using the existing line trap,, and I have little information on the line trap. I do know from old records that its a GE...
We had a PVD High Impedance Bus Diff relay misop for an out of zone LG fault. Quite frankly, I'm not that knowledgeable about High Z style relaying schemes. This was installed years ago and we now use percentage current diff's on most all 87B schemes now. And of course its electromech and we...
Folks,
Got a situation that I believe is a first for our utility. On a segment of our 115kV system, we have a few long radial feeds serving distribution (115-13.2 kV) loads. Planning Dept wants 15MVAR banks installed on the far end of these radial for system voltage support. In these cases...
Recently had a tibreaker operation on a YDY transformer due to a SLG fault on the transmission line feeding this sub (the "Y"s are grounded, feeding radial load). The upstream line breaker and the local tiebreaker at the YDY primary both operated as expected. I know the primary grounded wye is...
Folks,
Sort of a newbie to this side of the forum, I lurk around the Power Eng. I'm a sys protection EE (utilities)by profession and audio/musician geek at heart. Anyhow, I'm working on an audio processing project in which I need to create a variable freq sine wave oscillator to modulate the...
Folks,
We typically protect a 3PH Delta-Wye power transformer from blown high side fuse operations with negative sequence overvoltage detection in the low side tiebreaker. In this case, a dropped phase on the high side of a Delta/Wye produces one phase at nominal and the other two at half...
To all,
What seems to be the latest and greatest scheme in Negative Sequence Protection? In our practice, we use SEL relays operate on a negative sequence overvoltage element (59Q). This method is designed to protect a power transformer from "single phasing".. or the loss of a primary phase...
Has anyone ever recorded a 3 Phase Trip with all phases having same magnitude and same phase angle? We've never seen this before.... just looking for answers or possible causes. Thanks, very nice forum here!
-rogerj1
