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Thanks a lot for all the response. Very insightful and I beginning to appreciate the subject a lot better. Still looks like different Utilities have a "unique" way of defining "cross-country" faults. There are wide similarities; Minimum of two faults occurring either at the same time and same...

@Davidbeach, Thanks for the response.I tend to agree mostly with your definition but I would also like to know if there is any "Standard" definition or better still if yours qualifies as such. And how different is it from "simultaneous fault". I have also searched this forum and realised you...

Are there any "standard" definition for a cross-country fault? Any references? Is there any relationship between the faults ie. the occurrence of a second fault depends on the first fault? ( For eg. a phase to ground fault causing voltage rise in healthy phases which in turn may lead to some...

Need suggestions or ideas for a Ph.D. in Electrical Power Engineering.? Thanks

To trip on a voltage fluctuation of 2% would make the system less reliable. For LV/MV networks, some people go with a range of +/- 10%.

To know the CT ratio in the absence of reliable nameplate data, your best option is to do a CT primary injection; injection of current of known magnitude into the primary side.

Thanks for the response. The fixture is fairly new. These problems happened just after installation. What's the difference between a 2 terminal and 3 terminal igniter?

I have been at a lighting company not long and I have inherited a pending issue. A 2000W metal halide fixture comes on when connected but when put off and even allowed to cool, it fails to come on. My observations: During initial start up, voltage across lamp sockets gradually builds from zero...

I am on the contractor side. I have seen some people mix it up and I want to know if there are Literature or some sort of guidelines to that effect. My boss has not really given his preferences; let's just say he relies on my information and decision and I also look up to great minds. Thanks

Hi, I would like to know some few things; 1. How are final circuits referenced/ labelled? eg. Board/breaker1/breaker2..... And is there a laid out procedure for this? 2. What would be the best order of circuit protection; is it Main breaker/MCB/RCCB ? Thanks, great minds.

Thanks for the replies. The transformer trainer is a lab equipment for studies on small power transformers. On the issue of shorting of taps, the taps were properly isolated from each other.

the transformer was connected to a transformer trainer (TT179) with analogue measuring instruments. The current was measured by the trainer as well as the voltage. I only used the oscilloscope to view the waveform since the input current gave a high value.

the scope ground was connected to the neutral lead of the transformer

this is a schematic of the transformer ...(attached)http://files.engineering.com/getfile.aspx?folder=61f9179f-c46f-417c-a3a2-ba56d1363c97&file=transformer.PNG

I built a 125W transformer with input voltage of 50V and an output voltage in taps (6). When I energised the transformer and tapped the primary input voltage to a Cathode Ray Oscilloscope, and output left opened, A HIGH CURRENT WAS OBSERVED IN THE PRIMARY. I disconnected the connection to the...

Great suggestions. Thanks for the lovely ideas. I am really interested in the operation of voltage optimisation devices that employ variable transformer circuits. Looking to build one. I dont want to consider servo-tap switching due to drawbacks such as slow response.

I think for a rated field current in a separately excited dc motor is derived from the Voltage divided by the Impedance in the field winding.

Also should the supply voltage fall below the desired output, for eg 230V, mechanisms must operate to step-up the voltage. In DC-DC converters, SEPIC works exactly like that. But I am thinking of using a transformer either with taps or some other mechanism

Thanks for the responses. The idea is to keep the voltage at a fixed value of say, 230V despite changes in the supply. Ultimate goal is to save energy by keeping the voltage low instead of supply voltages that goes way high.

I want to design a voltage optimisation device using a transformer approach. Is it possible (practically) to control the taps such that the output voltage stays at a CONSTANT value irrespective of the supply voltage? Need wild Ideas. Thanks