SINT Ingegneria

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XGSLab FAQ

 

 

 

Answers

 

Sales

Can I buy XGSLab and then have training in-house to learn how to use it?
Yes, you can. We provide courses on site on demand or Video Conferences.
Furthermore you can count on a complete and clear User’s Guide with some very useful tutorial.

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Is there a demo version?
According to our experience a web presentation is more effective than a demo in showing XGSLab features.
You can arrange a web presentation contacting our Customer Service.
By the way, you can require also a demo application to us, simply filling this form.

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How much does it cost?
It depends on the features you are interested in.
Different sizes of XGSLab are available: Light, Standard, Professional, Educational, Research.
The larger the size, the higher the potential of XGSLab.
The size depends on elements number managed.
For more information about the sizes you can ask our Customer Service.

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Software

What hardware/equipment and software are required?
XGSLab is designed to operate on personal computer (PC) having the following software and hardware requirements.

Software requirements:
- Operating system: Windows® 7, Windows® 8 or upper, 32 and 64 bit
- Microsoft ®.NET Framework 4.5 installed

Hardware requirements suggested:
- HD: 100 MB free space
- RAM: 4 GB for GSA and 16 GB for GSA_FD
- CPU: Intel Core i7 , quad-core or more
- Monitor: 24’, 1920x1200 resolution

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XGSLab works on Windows 64-bit?
XGSLab is distributed both 32bit and 64bit.
The 32bit version has better perfomance in terms of speed but it suffers some limits of memory (eg. 2GB).
While 64bit version is fast in calculation and it can manages all available memory.

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What software apart from XGSLab is required?
XGSLab comes with Microsoft Server SQL Compact Edition, and Microsoft .NET Framework 4.5 as well.
Both these softwares are installed with XGSLab.

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Does XGSLab require any hardlock?
Yes. XGSLab has two possible versions of protection hardlock: one working on local PC, the other one working on a network.

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Technical

Which are the specific standards that XGSLab uses?

XGSLab is based on physic laws and uses standard only in some specific circumstance, for instance.
 
Touch and Spep Voltages limits:
-       IEC/TS 60479-1:2005 - IEC/TS 60479-5:2007 (international standards)
-       HD 637 1999 e EN 50522 2010 (European Standards)
-       IEEE 80-2000 e IEEE 80-2013 (USA Standard)
 
 Conductor Sizing:
-       HD 637 1999 e EN 50522 2010 (European Standards)
-       IEEE 80-2000 e IEEE 80-2013 (USA Standard)
 
 Current to Earth evaluation:
-       HD 637 1999 e EN 50522 2010 (European Standards)
-       IEEE 80-2000 e IEEE 80-2013 (USA Standard)
 
Reference Standards considered by XGSLab are accepted in many countries in the world.

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What is the frequency range of the phenomena that may be studied by XGSLab?

XGSLab can be applied in a frequency range from DC to a few MHz.
 
A few MHz means about 10 MHz but validations indicate that in some cases, calculations are precise also at 20 MHz and more, depending on the soil resistivity.
 
In any case, the limit a few MHz is limit is conservative and should not be understood in an absolute sense.
This limit means that starting from a few MHz, calculation accuracy gradually decreases.
 
The frequency range from DC to a few MHz contains all power system frequencies and the most significant frequency spectrum of the electromagnetic transient as represented in the figure (corona effects are clearly out of the application range).
 
c02 01
Frequency spectrum of electromagnetic transient

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Does XGSLab consider multilayer soil model?

Starting from the release 8.0.1, XGSLab considers the multilayer soil model.
 
The implemented algorithm is powerful and rigorous and can considers a multilayer soil model with an arbitrary layers number without constraints (for instance on layer thickness multiple of the thinner layer).
 
The choice of the soil model is crucial in electromagnetic simulations and in particular in the grounding systems analysis.
There is much literature about the criteria to set an appropriate soil model which can be used for predict the performances of a grounding system.
XGSLab allows to use uniform, multilayer and multizone soil models.
 
A uniform soil model should be used only when there is a moderate variation in apparent measured resistivity both in vertical and horizontal direction but, for the majority of the soils, this assumption is not valid.
A uniform soil model can also be used at high frequency because in that case, the skin effect limits the penetration depth of the electromagnetic field to a few meters and so, the soil resistivity of the depth layers do not affect the results.
 
The soil structure in general changes both in vertical and horizontal direction.
The earth inhomogeneity can be considered with the Green functions.
 
The vertical changings are usually predominant on the horizontal ones, but to correctly apply this concept it is essential to consider also the grounding system size.
 
In case of small grounding systems (maximum size up to a few hundred meters), soil model is not significantly affected by horizontal changings in soil resistivity and usually a multilayer soil model is appropriate. The layer number depends on the soil resistivity variations in vertical direction and three or four layers can be sufficient for most cases.
 
In case of grounding systems of intermediate size, soil model is affected by both horizontal and vertical changings in soil resistivity and usually an equivalent double or triple layer soil model is appropriate. This is the most important case in practical applications.
In case of large grounding systems (maximum size over a few kilometres), soil model is significantly affected by horizontal changings in soil resistivity and usually a multizone soil model is appropriate. The zone number depends on the systems size and soil resistivity variations in horizontal direction. 
 


Why the double layer soil model is so important?

In case of grounding systems of intermediate size, soil model is affected by both horizontal and vertical changings in soil resistivity and usually an equivalent double layer soil model is a good approximation.
 
The choice of an equivalent double layer soil model is often important for the following simple considerations that even a unskilled user can easily understand.
 
The soil resistivity is a parameter that is difficult to know with precision due to several variables:
  1. The resistivity of the upper layer changes with temperature, rain, pollution …,
  2. The resistivity of the deep layers changes mainly with the kind of soil,
  3. In case of large sites, horizontal resistivity variations is unavoidable,
  4. In case of large sites, the soil surface often cannot be considered flat.
 
In practical cases, a single soil model is not able to represent a large site, in all places and possible environmental conditions.
Therefore it is useless to refine soil models that inevitably are correct only in some specific point of the site.
A double layer soil model represents a good approximation because touch and step voltages depend mainly on the resistivity of the upper layer, where the electrode is usually buried, and the lower layers can be represented by one equivalent layer which mainly affects the equivalent resistance of the electrode.
 
In few words, in general, a double layer soil model is not a compromise but the only possible alternative to a uniform soil model.
 
In the following a true double layer soil model case.
The measurements at different sites indicate about the same model.
 
c04 01 
Soil analysis – Measured resistivities and equivalent double layer model
 
In the following some false double layer soil model cases.
The measurements at different sites indicate different models.
XGSLab finds the general equivalent double layer soil model.
In these cases, a multilayer soil model does not improve the calculation.
 
c04 02 

Soil analysis – Measured resistivities and equivalent double layer model

c04 03 

Soil analysis – Measured resistivities and equivalent double layer model

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Why is so important to consider soil parameters frequency dependence?

When frequency is over some kHz soil permittivity effects are not negligible and is important to take into account this soil parameter.
 
Moreover, when frequency grows, resistivity and permittivity change substantially with frequency and is fundamental to consider these effects in order to avoid large calculation errors.
 
There is not a general consensus about the soil parameter frequency dependence model.
XGSLab consider the following models:
-       Messier
-       Visacro – Portela
-       Visacro – Alipio
 
In time domain calculation involving high frequency spectrum signals, if the soil parameters frequency dependence is neglected, calculation errors could be unacceptable.

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Why is so important a model that considers both self and mutual impedances?

As described in the previous FAQ about soil modeling it is clear is not possible to improve the soil model over a given limit.
 
In order to increase the calculation precision, is important to improve also the electric model taking into account both self and mutual impedances.
 
Self and mutual impedances can be known with high precision, rather than looking for a more detailed soil model, which is always an approximation of the real soil.  Moreover self and mutual impedances weakly depend on the soil properties.
 
In general, neglecting self and mutual impedances can lead to very large errors.
Anyway, a parametric study showed that is not sufficient consider only self impedances.
The effect of mutual impedances can be significant and neglecting this parameter, the calculation error can be more than 25%.
 
In general, effects of self and mutual impedances grow with the grounding system size, with soil conductivity (inverse of resistivity) and with frequency.
 
More details in the web site and in the brochure.

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Use of the software

What do “too short element” error and warning message mean?

First of all you have to consider this general principle: XGSLab works with “thin” elements. With the adjective “thin” we mean that the length of the element must be much greater than its diameter. We remind you of the fact that the element length depends on the number of divisions of the span that generates that element and on the possible crossing by the span of the soil layers surface division. The element diameter is obviously the same of the span’s.
In Debug session, among all the controls, there is also the control that elements are thin enough. To judge this we have chosen the following:
  • In case of bare element,
    • no message means that the diameter of the element is lower than 1/12 of the element length
    • warning message means that the diameter of the element is higher than 1/12 but also lower than 1/6 of the element length
    • Error message means that that the diameter of the element is higher than 1/6 of the element length
  • In case of covered element,
    • no message means that the diameter of the element added to 2 × covering thickness is lower than 1/6 of the element length
    • warning message means that the diameter of the element added to 2 × covering thickness is higher than 1/6 but also lower than 1/3 of the element length
    • Error message means that that the diameter of the element added to 2 × covering thickness is higher than 1/3 of the element length
Warning message does not stop you because it is just an advice. Consider that this does not affect the calculation very much in all cases but especially if the number of the spans found with this warning is low in comparison to the total amount of spans.
You can easily understand that if you want to solve this warning you have to choose one of these alternatives:
  • modify the number of elements (lowering it) which the span is divided into
  • delete the span where the too short element is when the span itself is too short. After deleting the faulted span the User has obviously to simplify the model (see following picture). This happens when the span is divide into 1 element in GSA or into 2 elements in GSA_FD and in victims of XGSA_FD

d01 01

  • more seldom, act on the diameter of the span or on the thicknesses of the soil layers. These last solutions can be taken into consideration if you are in a case in which this problem cannot be solved by lowering the number of elements. For example, if you have a rod with these properties:
  • Diameter = 20 mm
  • Length = 2 m
  • Zs = 0 m
  • Ze = 2 m
  • Elements = 3
And at the same time you have a double layer soil model with h = 1.9 m. In this case you have 2 elements 0.95 m long in the top layer and 1 element 0.1 m (=100 mm) long in the deep layer. This last element generates a too short element error because 20/100 > 1/6 and in this case you obtain nothing by lowering the number of elements to 2. So, in cases like these you have to force the diameter to a lower value (< 10mm) or force a slight modification in the soil model by setting h >= 2 m.

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What is the value that I have to input for Re in earthing currents tool?

The preliminary calculation necessary to calculate Re is a proper calculation that has to be held with the soil model and with the layout that have been input for your project. The only arbitrary data is IE because in this case you have to choose an arbitrary value (usually 1 A) just to be able to obtain a value for RE. Once you have obtained RE you can use it to re-evaluate (in the tool Earthing Currents) the value for IE. Finally use the value that you obtain to set definitively the current and start the right calculation.
this is the procedure:
  • Set the arbitrary current (usually 1 A) in the faulted electrode (remember to confirm it by clicking on the green tick). See following picture

d02 01

  • Debug
  • Run the calculation
  • Results obtained in following picture, Re circled in red. This value has to be used in Earthing Currents tool

d02 02


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How can I read the elements table?

The table can be exported in .csv format by clicking on “Export” in Results page of the panel

When you read the element table consider the meaning of the following headers:

  • cs_d_m: diameter
  • cs_deq_m: equivalent diameter (≠cs_d_m in case of bundle conductors)
  • cs_tc_m: covering thickness
  • dv_l: length of the element
  • el_dKsr, el_dKur, el_dKsi and el_dKui: reduction factors
  • el_E_Re and el_E_Im: electromotive force, real and imaginary part
  • el_Ee_Re and el_Ee_Im: external electromotive force, real and imaginary part
  • el_I_Re and el_I_Im: longitudinal current, real and imaginary part
  • el_J_Re and el_J_Im: leakage current, real and imaginary part
  • el_Je_Re and el_Je_Im: injected current, real and imaginary part
  • el_V_Re and el_V_Im: potential, real and imaginary part
  • el_Z_Re and el_Z_Im: element impedance, real and imaginary part
  • el_Zl_Re and el_Zl_Im: element longitudinal additional impedance, real and imaginary part
  • el_Zt_Re and el_Zt_Im: element transverse additional impedance, real and imaginary part
  • ID: id number (internal to the code)
  • IDElectrode: number of electrode
  • ID: id of the project (always the same)
  • IDRef: Reference point identifier
  • idx: identifier of the element
  • ly_xs, ly_ys, ly_zs, ly_xe, ly_ye and ly_ze: coordinates
  • S: span to which the element belongs
  • S_Source: 1 if source, 0 if victim
  • se: 1 for the first element of a span, 0 for a central element, -1 for final element
  • SiteName: name of the external impedances or of the reference point set in the element
  • Tag: Tag of the element

w: 0 for horizontal elements, 1 for vertical


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Question4?
Answer 4
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Question5?
Answer 5
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