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Just to let you guys know, I disconnected the neutrals on both generators and all the third harmonics and neutral currents (in the transformer neutral) are gone. Thanks for all the inputs!

waross, firstly thanks for always providing some insight and possibilities. 1) I dont have access to the transformers (utility owns it) so Im not sure whether they are running hot. 2) I have vector shift and ROCOF protecting an island situation. Since commissioning, every time there was a grid...

Thanks for all the inputs. I think the attached drawing will get us back to my question.please have a lookhttp://files.engineering.com/getfile.aspx?folder=a61b363c-3542-4eef-851f-e9edc04c5310&file=GeneratorsNeutrals.pdf

the total N current at full load is around 80% of the phase current. very high. I'm not sure what type of avr's are in there I have tried runnin the 600kW paralleled on its own. Neutral current are definitely there.

Ceast, When you are saying they should be fine running on PF mode, does is make a difference if the PF's are set to different values? a few people seem to think that is the problem. The first thing I want to clear up is the neutral connections. Do I isolate them or not?

Hi, I have read every single thread related to generator neutral grounding and not grounding, third harmonics, circulating currents etc. I've read through Chapter 19 of Westinghouse T&D. I'm not sure if it is my inability to understand, the different regulations or simply different site setups...

waross, I did measure the harmonic distortion and it was very clear that there was a lot of 3th order harmonic distortion. could this neutral currents be circulating currents? I must say that the PF control isn't set to the same value on the 2 generators.

waross I checked the phase to neutral as well as the phase to phase voltages on the LV side. They all seem very well balanced. raghun I will check if there is any difference with the PFCC switched off. If there is, what will be the solution? The site really need the power factor correction...

waross you mean the 900A to 600A jumps in the phase current?

rbulsara As for the power factor correction gear, it was installed in the plant before the generators. When you say that it is most likely harmonics caused by the alternator winding pitch, do you expect these harmonics to be present in an islanding situation with a non-linear load as well? We...

Hello there. I have an issue that has been there for a while, but I dont think I can ignore it any more since some caps from the power factor correction gear blew up a while back. Another problem which can be related to this is the current from the generators jumping radically between 900A and...

Thanks for the comments. It turned out I need neutral voltage displacement protection. I will be using a 5 limb measurement VT that will supply zero sequence current in order to achieve this protection with a Reyrolle relay. Thanks guys.

Hi there. We have a 500kW genset connected to a 0.415kV/11kV wye/delta transformer. We operate in parallel with the grid, and at this stage due to the switchgear setup and lack of transfer switches we never operate in island mode. We have a Deif GPU 3 unit overlooking the protection of the...

rasevskii,catserveng: Sorry for insufficient info. I should have said that we are using a Woodward 2301A Electronic Load Sharing and Speed Control unit along with a ProAct 3/4 Electric Powered Actuator and Driver + Woodward Magnetic Pickups and Proximity Switches. Both the Engine and the...

I am totally new to the field, but over in Australia Schneider Sepams seems to be up there with Siemens, SEL and Areva. Not a big player in Europe/North America ?

Good day. We are in the process of commissioning a 625kVA (at 0.8 PF) natural gas reciprocating synchronous genset. The genset is connected on the LV side of a 1500kVA step up/down transformer.(11kV > 415V). For the most part our plant will be consuming the electricity but at some stages we...