Hi all,
do you have any suggestion for the power supply of an unmanned offshore platform:
distance from shore: 100km
load: 50kw
How about using DC with a rectifer/inverter combination?
Thanks !
Hi all,
we've been asked to investigate fuse tripping on a compressor starter:
Compressor nameplate:
RLA: 16.8A
LRA: 84 A
Fuse:
Low-Peak
class CC
current limiting
LP-CC-30 (30A)
Contactor:
Siemens
42BF35AJ
FLA:30 A
LRA:120 A
15HP 3ph
First thing we did is hook up a power recorder to the...
Hi all,
here's the situation; a 20MVA generator will be shutdown for 3 years at a papermill. This generator was providing all power factor correction needed by the plant. And about half of the load. (Total load is 12MW, 5.7MVar)
When the generator is down, pf at service entrance drops down to...
Hi all,
we are working on design and construction of ground grids for a wind farm.
For each 1.5 MW generator (80 total), GE is specifying ground grid resistance of 2 to 10 ohms.
With the data we have:
-ground resistivity : 500 to 1000 ohms, average
-projected ground grid area: 285 m^2, (about...
Hi all,
I'm looking for a neutral grounding reactance to install on a 25 kV Y transformer.
This is to reduce de phase-ground fault current. The reactance has to be 35 ohms.
I would like to know manufacturers or distributors of this kind of product, in Canada, that could help us with the...
Hi all,
when protecting a 600V alternator against ground faults (high resistance grounded, 5A); is there an advantage of using a 59N protection over using a 50G/51G with a sensitive CT?
I see common practice is 59N, but basic motor relays don't have this function. I'd use 50G/51G with...
Hi all,
in the case of 1MW hydro powered induction generator, connected to the grid.
I know we should use subtransient reactance (13.3 to 16.7 %), for first cycle contribution, and 1.5xsub. transient reactance for interrupting time contribution (2 to 8 cycles).
My question is: is it correct...
Hi all,
I was wondering what is the common practice for the grounding of induction generator (1MW, 600V in my case). The generators are ordered with the neutral out. So what should we do with it?
If it is let floating, we will need to add some kind of ground fault detection system somewhere...
Hi all,
I would like to have some advices about the replacement of breaker in an aging switchgear.
Some of you have probably been in this situation; we have two options : replacing the whole switchgear or replacing the breaker and cradle.
As usual, downtime has to be minimal.
Here is the...
Hi all,
we would like to do a qualification test on a new 15 kV switch.
We need to do a 60 HZ 36kV test for one minute, AND a partial discharge test on the insulator (14 inches).
I would like to know some manufacturers/models that can supply a good test set that can achieve that, because we...
Hi all,
I have been asked to investigate a strange noise coming out of three 3MVA 25kv/600v oil immersed transformers.
There is a small noise coming out of the transformer, like a "ting-ting-ting...", about 160 times a minute.
three out of four transformers are doing it. They are all exactly...
Hi all,
we need to connect utility's PT/CT secondary circuit to the meters (100 m away), we would like to use the same duct bank (concrete encased) we use for power cables (25kV),
Is this possible to do?
I'm worried about power cables interfering with the secondary signal from the PT/CT. I...
Hi all,
I will be involved in underground distribution (25kV,solidly grounded) in future projects.
I started reading on the subject I still have interrogations
one of them is:
How do you size the neutral cable when going underground from an overhead line?
One of our client has an...
Hi all,
I have a simple question concerning PT voltage class signification.
I want to install 3 PTs , wye-wye connected (2400-120V) on a 4160V system.
Since it is a high resistance grounded system, de line-to-ground voltage will rise to 4160V on two phases in case of a fault.
My question...
Hi all,
what i'm looking for is a guide/book/standard that explains every step of the design of an underground distribution line. Cable pulling techniques, number of manholes, choosing the right conductor etc....i'm most interested in the civil/mechanic part of the work.
Thanks in advance.
JL
"ground or not" the concentric neutral of MV cable.
I read a lot in different threads and found opposite answers, it probably depends on the setup you have.
In my situation: it is a 4160V resistance grounded (10A)system. The tranformer is outdoor and the cable run is about 300 feet. I was...
Hi all,
i'm working on the preliminary design for an outside substation ground grid. (underground incoming cables + 4 feeders and a capacitor bank). Metal-enclosed switchgear on a concrete slab.
I received the soil resistivity from the civil contractor and it is 3000 ohm-m !!
so I started...
Hi,
what conductor size should I use to connect NGR to neutral bushing of txfo.
NGR is 5A continuous.
the code (canadian) says to size the conductor to 5A (max let through current of the resistor)
But, in our installation, the resistor is in a switchgear about 250 feet away from the txfo. Is...
Hi,
when designing a new substation (industrial plant), what criterion do you base your decision on whether or not to include an On Load Tap Changer on the main power transformers.
What kind of load will require an OLTC?
OLTC are quite expensive and I wonder how often do you have to use it...
Hi,
according to IEEE 80-2000, the current split factor will decrease when the earth grid resistance increase -> more current will go in the transmission line neutral and less in the earth grid.(current split factor = Igrid/3Io)
which give us a lower touch potential.
what I understand from...
