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Hi All, We have a project where we are free issued stainless steel earth (grounding) bars. The copper down-conductors from lightning terminals (in the air) are run to this earth bar, and all of the copper conductors which connect to earthing electrodes buried in the native soil are also...

Hi Guys, In summary the question is: is it ever deemed a more economical solution to parallel PV modules before the combiner box (i.e. series AND parallel connections in a 'string' of PV panels) for a large scale solar PV project? Some more detail: When designing a large scale solar...

Thanks guys, Really appreciate your input. "At 500/115kV you're probably looking at two full windings rather than an auto transformer." I have a separate line of enquiry with a transformer manufacturer, but can you please elaborate on this? I obviously assumed an auto-transformer would be...

I am working on a project which requires either 2 x 300MVA, 500kV/115kV three phase transformers or alternatively 2 x 3 x (~100MVA?) single phase 500kV/sqrt(3) / 115kV/sqrt(3) transformers. Single phase transformers are being explored as an option due to complications in transporting such a...

Hi, I have received a fault study document. Using this document, I am trying to work out the maximum fault current which actually travels through the earthing system and returns to the upstream star point. Typically I use the worst case single line to ground fault current for this purpose...

Thanks for the replies. I measured approximately 70V induced voltage on two phases (with respect to to ground at one end of the line when all earths on the line were removed), and 135V on the other phase. Unfortunately this 'noise' was too high for the modern digital insulation resistance meter...

Thanks isquaredr We don't interact with any lines unless they are locally earthed. Earths are applied via insulated live line sticks, test leads are connected while the line is earthed. Safety is of course paramount. No personnel will be within flashover proximity to the line unless it is...

I am performing some basic pre-commissioning tests on a 132kV transmission line shortly. The line is around 40km in length and is earthed at both ends with portable earths. Several medium voltage and high voltage lines run parallel or intersect this transmission line over the route. I am...

Gents, The transformer pictured and many transformers at wind installations in the states have under oil HV isolation switches. These switches are in the same oil as the transformer core and windings. If the HV isolation switches have been operated under voltage (which may form part of the...

Hi All, Recently I have had a discussion with a fellow engineer in relation to the choice of winding configuration for a 132/33kV transformer in a wind farm application. His sentiments were that a Yyn(d)0 (buried delta) should be used. I was proposing a Dyn1 transformer as I assume it will be...

I'm performing some calculations for a substation and have been presented with the following system information at the point of connection: 3ph fault (5.53kA phase & positive sequence), X1/R1=4.8, R1=0.016pu, X1=0.077pu 2ph-G fault (6.75kA, 6.99kA phase), (3.2kA, 4.4kA, 1.2KA, zero, pos...

It is interesting to note that in many distribution and medium voltage installations (even in cases where only overcurrent or distance schemes are employed) a neutral conductor is not always run and this is accepted practice. Why should low voltage installations be treated differently? It is...

Thanks for your reply MKFPE, The document you linked is a good resource but does not explain how to calculate the zero sequence mutual impedance of the screen for a cable with screens around each core, which is where I am getting stuck. Refer equation 9 and 10 from the linked document. I don't...

Hi, I have a supply substation with an earth grid, and a long cable (e.g. 10km) which supplies some equipment sitting on its own earth grid. I have a good understanding of the earth grid impedances of both the feeding substation and the remote equipment earth grid. The cable which feeds the...

Hi All, Many thanks for your comments. I have brought similar points to the attention of our consultant and their response was along the lines of the following: As for the steel potentials, the range is from extremely cathodic to extremely anodic. Copper can be considered relatively stable in...

Hi, It is typical to use copper for an earthing conductor and also to bond it to the reinforcing steel of a large concrete structure such as a power transformer foundation. Some consultants have informed me that a passivating film will form over the reinforcing steel as a result of the...

Bill, The cable screens I am referring to are HV cable screens. These are good for fault currents of up to 10kA for 120mm2 3c Aluminium XLPE cables with copper screens. ukgraduate, When calculating the EPR or current distribution via kirchoffs laws, it is also important to understand that...

A minimum grid resistance does not mean your installation is safe or functional. You need to consider what your fault scenarios are, i.e. where the current will come from and how it will return to the source/star point. As a part of your design, you will determine an earth grid resistance value...

Hi JC, I don't know much about the physical construction of conveyors, but consider the following: USE OF EQUIPOTENTIAL BONDING: I assume the conveyor is steel. What is the problem with using equipotential bonds to earth your structure? e.g. use copper braids or strand Cu with lugs where there...

stevenal / dpc: How can I verify the reduction in fault current at my location when there is no earth wire (if by verify you mean a site test)? I have the grid resistance to remote earth at both substations,and know the conductor type, so I could estimate by simple calculation the earth fault...