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Hi Mike, thanks for the practical insights, its a bit of a tricky one, intuitively i can see all sorts of issues. I just need to frame some sort of report with a bit of empirical data and outputs from ETAP or Digsilent to justify the position.

Hi Mike, the project is in 'concept' stage so a lot of some details are a bit sketchy, what i am trying to do is get a sense of how viable the approach is, what the gas engines are caapble of and what they are not of, and then put some mitigation in place for the electrical design, so that what...

Hi Freddy, the ultimate aim of the information is to get an accurate representation of the engine capability so we can look at motor starting and stability, in one of the other generating sets trips, so we can identify how much load we can shed. I have a load step capability curve for the...

Hi Bill, thanks - but i think we are talking at cross-purposes slightly. To my understanding a DEGOV model, is a speed control / isochronous governor with a fixed droop setting of 0%. The DEGOV1 model, specifically has an additional control loop / mode to allow it to run in droop mode, and has...

Hi All, bit of a how long is a piece of string question... but i have been tasked with looking into some gas engine generators and doing some preliminary stability studies to see what they are capable for in terms of motor starting etc. In terms of project background, there are 2x 2MW sets...

Hi All, I have what is hopefully a simple problem - but just having a bit of brain fog and cant see the way through it. We have a 2MWe rated gas engine, which is driving a 2481kVA @0.8PF alternator set, equivalent to 1984.8kW (its IEC world so alternators are rated on kVA) The alternator...

Hi All, I have carried out various system studies over the years, and while I understand power system stability and the general concepts of exciters and governors, I lack much in depth knowledge of the specifics of them. So I have a few general questions, I was hoping people could help with...

Hi, ELECEE8 is correct that it is mainly used in Oil and Gas - developed by Shell I believe. The idea is to use the intermittent and standby, instead of simple diversity factors. It’s generally a fairly robust system, but does tend to oversize things a bit. The idea with standby loads, is that...

Hi All, i am trying to size some surge arresters for a buried 33kV underground cable system using the IEC 60071 and 60099 standards, and i am getting a little lost - can anyone help shed some light / check my working. The system is a 33kV network, which is impedance earthed through zig/zag...

Hi mgtrp - interesting. I swapped the calculation method to ANSI and found that i got the same results as you, regardless of the Z1 value of the grounding Tx. However, when i use the IEC method, the problems start appearing.. I am not fully aware of the differences between the two short circuit...

Thanks mgtrp A key difference i spotted, was that you had set the earthing transformer positive / negative sequence impedance to 10%, where i had set it to 9999%, and this appears to be causing the difference. I am not sure why, as surely with a grounding transformer the pos/neg impedance...

Hi mgtrp, thanks - Yes i can see the positive and negative sequence of the grounding tx is not relevant... my rough estimation is similar to yours... its just that ETAP is telling me something different.. I have been staring at the model i have for the last few hours and cant see anything...

Hi JuanBC, thanks - but i that is a different scenario, where there is a resistor / reactor connected to the star point of the zig-zsg. In this case we just have a directly connected zig-zag.

Hi, see attached for a word document with some screengrabs from the power transformer case i set up. The first image is showing the calculated earth fault current and the second is showing the sequence current flows - the third is the model i have of the earthing transformer. Waross - you may...

Hi, I can't seem to find the Cooper book (can someone give me a link to amazon so i know what i am looking for).. I had a quick trawl through my library and see the figures that stevenal came up with, so they seem to be valid.. just surprising as i had not heard of the 25x at 0.01s before...

Hi, I am from IEC world, so things are a little different. the general inrush multipliers i use are 12x for small transformers <500kVA and then dropping down steadily to around 6x for larger say 10MVA transformers. in your case i would use a figure of around 8xIn. I am not sure stevenal /...

All, I have an 11kV site that when in island mode has a handful of EDGs that run unearthed, with an 11kV system earth provided by a zig-zag grounding transformer. the grounding transformer is rated at 131A (142ohms) for 30s. My understanding of these units is that the grounding transformer...

Hi All, i have come across some Alstom METI relays installed in conjunction with the Alstom MCGG relays to give a directional control. The METI's are set at PhA = +30deg, PhB =-45deg and PhC =+30deg. PhB being set as an earth fault. My question is does this mean the PhA and PhC elements are...

Thanks - much appreciated

Hi All, I have a project where the existing transformer protection relays are old Reyrolle TJM10 induction disc relays. My issue, is i have no idea how these work, and how to go about finding the existing settings and then changing them to something new. Does anyone have any documentation for...