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Hi, Wondering if anyone is aware on if a single phase open circuit fault on an overhead line feeding the HV side of a Ynyn transformer, 33/11kV for example, can be detected by protection on the 11kV side of the transformer? Would the 11kV side current distribution be able to identify the...

Hi. Ok just to clarify, if operating in capacitive mode then the current is leading the voltage, and the generator is exporting with a leading power factor yes? Why does a leading power factor result in an increase in voltage? Thanks

Hi. Can someone explain why generators on distribution networks result in the increase of voltage on the network?

Hi, Can someone help me understand, in really basic terms how does a synchronous generator change the power factor at which it exports at? I think with inverter based generation this is done by thyristors switching the current at different angles along the voltage waveform is this correct...

Hi, Can anyone advise, for the attached circuit, is the current and voltage in the metrosil going to be in phase with that of the capacitor? Thankshttps://files.engineering.com/getfile.aspx?folder=e1ad7afc-7826-490b-bcc2-73cbd284b532&file=Circuit.JPG

Does it make a difference that the cables running from the VT through junction boxes is quite long? Could this be a factor?

Hi, In commissioning a 110V VT with an earthed neutral, if I am I getting 50V across the fuse holders with the fuses out what might be the cause of this? The cables and instruments have already had insulation tests. Could it be an interconnection via another earthed VT on site? Thanks

Hi, I am struggling to see how I can plot a vector of a current for which the load is stated to have wattful and wattless components of 87% MW export and 50% MVAr import respectively. Does anyone understand this? Thanks

To clarify, this is from the point of view that the 33kV assets are existing already. I am referring to technical issues not financial.

Hi, Does anyone know what the main issues (if any) are associated with using higher voltage (such as 33kV) lines or cables for 11kV power distribution? Thanks

Hi, I am looking at using a 1:1:3 summation transformer for a phase comparison system. For a blue-ground internal fault is it correct that if I find what the fault values are entering from each side of the circuit I can then take 33.3% of each value to see if it is above the threshold of the...

Hi, Between a L-L-G fault and a L-G fault which would you expect to give a higher MVA? I am getting a study with a higher L-G fault level, but I though that the L-L-G fault level should be higher? Thanks

Hi, I am calculating the voltage and current flowing in pilot wires in a voltage balance protection system. The literature I am reading says that for an external fault the impedance seen is half the open circuit impedance of the pilots. Does this mean that no current flows for an external fault?

Hi, I am looking at a 22/400kV 600MVA transformer. I am looking at CT sizes for the LV side of the transformer. For full load current the current is 15745A. Is it possible to use a 16000/1 CT or does this ratio of CT not exist? Thanks

Hi, I am trying to calculate what interposing CT I will require. For a delta/star transformer with the star side solidly earthed, the transformer 600MVA 22/400kV. I am proposing to have Ct ratios of 200/1 on HV side and 4000/1 on LV side assuming a 5A rated relay with the following: HV side...

Hi, Please see the current distribution I am proposing in the attached as I need to verify which relays will be tripping. Is this correct, for a phase to phase fault at F1 I am getting the attached fault current in the CTs...

Hi, I don't think I understand exactly how it works. Please see the link below https://electrical-engineering-portal.com/fuses-protecting-rural-distribution-systems They mention that in the case of transformer HV and LV fuses, the current values must be converted to a common voltage base. For...

Hi, For a restricted earth fault relay with an effective setting of 0.2A. The CT ratio is 2000:1 and the maximum earth fault current is 800A through an earthing transformer. If there is an earth fault at the end of an LV winding (so covers the entire winding) is it correct that the primary...

Hi, Can someone please comment if I have done the current distribution in the CTs at the bottom correctly? Thanks https://files.engineering.com/getfile.aspx?folder=187dbb62-8428-438b-955d-05e3a66ecd38&file=Bias_Differential.JPG

Separate Neutral Earth (SNE) and Combined Neutral Earth (CNE). So with SNE you have a neutral and an earth conductor run to the consumer property. With CNE just one combined conductor is used as the return path for the load and fault current.