My initial thought, if you can’t take Waross’s suggestion, is ground the primary Ho to prevent neutral shift. Leave the secondary neutral open and install a properly sized grounding transformer - you’ll need a good sized one if you want to carry single phase loads, or a small one if you just...
SEL makes one as well, I thinks it’s the 2660S. As you probably know these are really to achieve 100% stator protection on high resistance grounded generators - the 59G voltage element can only be set to cover 95% of the winding, without a 3rd harmonic element or a injection system you can’t...
Make sure you add some droop to the AVR as well if they are on the same bus, otherwise the voltage regulators will fight each other, unless the AVRs have a reactive load share feature.
If they each have their own transformer it should be ok.
Many of my company’s generator step up transformers (US utility) came from Waukesha, which is now GE Prolec.
Other manufacturers that we have are Hico (out of Korea) and Delta Star.
PTs on the utility side would be the best and easiest to set. I’m guessing you could probably make due with gen side PTs if you had to, since the gen voltage will likely drop pretty low for a fault on the utility side, but you’d have to model it to be sure.
Perhaps this might be useful to you:
All of our large generators are high resistance grounded. Regardless, the generator enclosure and everything else in the plant is grounded to the ground grid by two 4/0 grounds minimum. This includes plants built in the last 60 years by Black and Veatch...
One thing that has also bit me is making sure I’m using the right serial cable (null modem versus straight-through). My recollection is you need to use a straight-through cable, but I’ve only worked on DECS400s.
General Electrical large gas and steam turbine generators almost exclusively use open delta PTs on the medium voltage system to address the issue of PT secondary faults tripping the NGR ground detection. I looked back and found open delta PTs as far back as 1935 on a GE hydro generator up to the...
I’ve installed resistors that way exactly once.
Using aux PTs and a broken delta connection seems much preferable as it doesn’t load the PT under normal operation and possibly reduce the measurement accuracy - the PTs would only be loaded under ground fault conditions.
Edit - as an aside I...
1) do you have transfer trip installed so your recloser trips when the utility breaker opens, or are you planning on trying to detect an island with voltage or frequency?
It seems like unless you have a communication scheme it would be wise to detect faults on the utility system to minimize the...
I’m assuming you need the 4 for redundancy but the Siemens SGT400 is 10MW and I think they might make that in a tri-fuel: hydrogen, natural gas and diesel.
I was part of this discussion in my utility for a while before I got too busy.
Many if not most utilities use an effectively grounded distribution system. Effectively grounded is defined as X0 =< 3*X1. One of the main reasons to effectively ground a system is it allows you to connect line to...
We installed several for station service applications in our generating stations over the last 5 years. All of them were basically switched molded case breaker type, and several were service entrance rated.
Voltage and Frequency are typical interconnection relay types for islanding scenarios. If there are close in faults on the utility that your relays could see you could apply directional overcurrent or distance relaying - I am doing sensitive reverse fault settings for an intentional island at...
If the machine is conventionally grounded with high resistance there is insufficient fault current near the neutral point to pickup the differential anyway. The main protection of your neutral transformer and resistor is your neutral overvoltage/overcurrent relay 59N or 50N (mostly have seen the...
My take: as noted in the thread above by bacon4life, what would determine the separate regulators are needed is the allowable voltage range of the gen, and what is the allowable voltage range of the line, and consider any VARS present or required that would boost or voltage the gen side voltage...
In SKM powertools there’s a check box in the report options to include bus/line side arc flash in the analysis, which gives the same result as you have here. I’m not sure if that’s a thing with ETAP but you might check your arc flash analysis options and see if there’s an equivalent setting.
If I were approaching this problem I would looks at
- load current between the two cases - do vars change much.
- possible saturation modeling in SKM. By lowering the HS taps the transformer would be operating farther up on the BH curve.
Just some thoughts that might help.
What does “internal flashover” mean? Arcing in the AVR rectifier? What equipment is arcing? And you can restart your machine?
Anytime we had failed equipment in the AVR cabinet (granted, most of them are static exciters with a large bridge) something fried, like a SCR “puck” and the exciter...
