waross - wuqn said negative sequence current, not zero sequence current.
Negative sequence current could be caused by unbalanced (e.g. single phase) loads on your system. I would think that a negative sequence current of 2% is actually quite low. A common limit on negative sequence voltage is...
4) The motors on your system may be supplying fault current to the fault on the utility system. During the first few cycles of the fault this could be close to the DOL starting current of the motors.
Or can you keep the GSU energized at all times;
normally using utility power, and then during generator start up and synchronisation with your 6 MW of "intertial storage".
This could depend on whether the system has enough grunt and storage to keep you 21 kV system alive while you start up and...
You might not need RMUs at each transformer. You could work out how many transformers you can safely energize without causing an unacceptable voltage dip on the utilities network. You could then install RMUs or another switching device to divide your feeders into the appropriate numbers of...
I would think that the CTs and PTs for controling the capacitor bank should be as close as practicable to the point that you need the power factor to be controled. That is, if you need to control the power factor at the tie to the utility, then install the CTs and PTs as close as you can to the...
rsherry
Modern wind turbines are often in excess of 100metres high. Something to intercept the strikes before they reach the wind turbines would have to be even higher. To provide protection using external structures would be expensive. So far it is cheaper to put a copper cable inside the...
In reference to the posts by rsherry and scottyuk - even a wind turbine with a lightning protection system can get damaged by lightning. The protection system reduces the risk of damage, but if the lightning doesn't hit right on the receptor or you get a really big strike (e.g. >200 kA) you are...
New wind turbines with blade lengths of more than about 20 metres have metallic receptors near the tips (ends) of the blades. The receptors are connected to cables that run down the length of blades. There are often also lightning rods at the back of the wind turbine nacelle (box). The...
Wind turbines often have a clutch or "mechinical fuse" between the induction generator (-ve slip motor) and gearbox. I have been told that this is to protect the gearbox in the event of an electrical fault that leads to the rapid deceleration of the generator.
It seems to me that...
Most cable manufacturers reccomend against hi-pot DC testing of XLPE cables, and suggest an AC test instead (effectively a no-load energization test). I would reccomend an insulation resistance test prior to energization though, just to pick up possible "gross" faults.
In a 0.6/1KV cable the first rating is the phase to earth rating, the second is the phase to phase. In a three phase system there is a ratio of sqrt(3) between the phase to earth and phase to phase rms voltages.
Simplicity & the slip characteristic of induction generators provides some mechanical damping. Synchronous generators are "locked" to the grid and this could cause large mechanical loads in wind turbines in turbulent wind conditions.
Some wind turbines use "variable slip"...
Why not keep the voltage control with the generators and switch the capacitors in respose to the VAr loadings on the generators in order to take the reactive loading off the generators. That way you are able to use the dynamic cabibility of your generators for voltage control. For example if...
