waross - in this case the open corner delta windings are built in, it will not be completely missing phase in this open corner delta even the primary has one phase missing.
Veritas, you brought a very interesting discussion, thank you!
By the way, I call it open corner delta, to me it is more clear on the concept.
Well, missing one healthy phase under unfaulted balanced conditions is different than single phase fault conditions.
If just sum two phase VT secondary...
Any type of transformer can be use as the utility-DG interconnection transformer. Grounded Wye as the primary on utility side cause desensitize L-G protection if the utility source is weak. Delta on utility side will cause TOV concern on unfaulted phases. Either high current contribution or...
My thought is this:
It depends on the secondary burdens. CTs are transformers but special ones. Let us assume two extreme cases:
1) B and C secondary windings are open (of course induced high voltage, but let us park it aside)
- no secondary current, open circuit voltage is Vc +(-Vb) = Vcb<90°...
Transformer is inductive and the your cable in capacitive, I was wondering if it reached a "sweet" point of resonance!
Another thing is the poor workmanship on the cable terminations, it happens quite often!
You need to have a specification. Other than the resistivity test you may consider aggregates gradation test either by the quarry or by a third party.
There are always some smalls and fines, the gradation test will confirm whether the test samples meet your specification.
Specify clear crushed...
Isolation transformer will not fix your problem. The voltage difference between the hot and the neutral matters only, while the difference between the hot or neutral to a third reference point is relative. If your V(L-N) is applied to the isolation transformer varies, the secondary voltage...
Do you mean ungrounded system has a neutral wire brought out to customer location?
Ungrounded system is mostly for industrial 3-phase load customers not a very good practice for single phase load customers. A Delta-Wye transformer should be installed at the demarcation to create a new system...
cranky108 and waross hit the nail. It is traditional railway signalling system before the digital world. There are many zones to sectionalize the tracks, and low voltage DC is applied to the tracks. A small leakage current is measured when When no train is passing the zone or section, a large...
Dracula7, the heater nameplate rating information voltage and wattage wise, it may provide you the answer you are looking for. For example the heater could be single phase type but the designer wanted to gang them and connect them wye? Or perhaps the designer wanted to indicate heaters are not...
Hi Dracula7, you are correct that 277 is the phase to neutral voltage. 480 is the phase-phase voltage and the relationship is root 3, 1.732. So 480/1.732=277VAC.
Technically you can but is not a good practice if there is another option. In our case we have two different protections sharing the same CT circuit. But make sure the CT was rated for your application and the burdens are okay and be aware that you will lose the diversity.
Hi prc, I couldn't agree that the impedance will not change. I don't have transformer manufacturing experience but ABB Transformer Handbook, Page 3-23 and 24, gives calculation of reactance, it is based on the geometric dimensions and the number of turns of the winding.
Hello prc, the impedance is dominated by the structure of the transformer. In this case, the primary winding structure is not changed but the secondary winding will be changed depending on the parallel or series connection. So I think the impedance will not be the same. A simple way to find...
