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For industrial and distribution MV grids, we commonly use Resistance grounding (NGR), but what I've seen in Renewable generation projects (wind & solar) is that they're using reactance grounding (neutral point coil). Can anyone please clarify what are the reasons/advantages of reactor grounding...

Thank you LittleInch and JezNZ for the valuable information

Hi All I have a case with an underground pipeline (equipped with cathodic protection) that I need to cross with a MV cables underground trench and couldn't find some reference or litterature regarding the possible impacts of the MV lines on the cathodic protection, minimum clearance...

@dpc Z Base: This value is used as the base MVA for the transformer impedance and depends on the standard selection. ANSI: Base MVA = Class1 MVA. IEC: Base MVA = the largest available class MVA.

I have a tansformer as follows: Voltage: 60kV / 10kV Rated power: 45/60/75 MVA (ONAN/ONAF/ONAF) Impedance voltage at rated power and rated voltage at 75°C: 10% +/- 7.5% tol.(at 45 MVA) ETAP does not allow to change base MVA (it is always the biggest rating). Please how to specify on ETAP the...

Thank you for your answer. Do you know any standard where I can find some indications? Regarding this and also regarding protection issues..

Hello everyone I need advise regarding the proposal attached, to derive the power supply to a new 11kV/415V transformer from a PFC feeder. Are there any restrictions in the international standards (preferably IEC)? constraints in term of protection, availability... Thank you for...

Bonjour We have an HV Neutral directly grounded using an insulated cable and a disconnecting switch (normally close). The question is regarding the insulation level of this grounding material (cable+switch) per IEC standards? should it be phase voltage 60kV (72,5) or 60kV/sqrt(3) or an LV cable...

Regarding the 40kA, this high s.c level is due to 'powerful' network (composed of many power plants turbogenerators) connected to this substation throught a 50MVA trafo, and to an important number of motor loads. 2/for the feeders between the two substations, these are laid overhead in cable...

thank you all. as we are located in morocco we are using french standards (NF) and recently more and more IEC. The type of cables we commonly use are single core, non armoured, with metallic screen/shield (wire or tape) conforming to french standard NFC 33-226 (or IEC 60502-2). Cable...

Dear all I need your help for 2 issues : 1/ To order MV cables, please advise how to specify short circuit withstand capacity on cable metallic screen. What I have at this stage, is the preliminary calculation of max short circuit value (for example 40kA @ 10kV level) which I use in equipement...

thanks for your reply. Can I understand that if I have surge arrestors on transformer side and on MV switchgear (on main incomer), I do not need to use the higher value 95kv

I have a question regarding rated impulse test voltage (BIL) selection for an MV switchgear (IEC): -operatin voltage 10kv 50hz -rated insulation: 17.5kv -rated Power-Frequency Withstand voltage (1min)38kv. Per IEC for this case, both 75kv and 95kv are possible for rated Impulse Test Voltage...

I think undervoltage is more a protection for the power source side (grid/generators). For consumer side, essential protections are current based. Undervoltage is mainly used for load schedding issues.

French standard NF C15-100 / Section 533.3.1 requires this verification. This standard states for IT systems (isolated neutral): Additionaly, protective devices shall be able to interrupt under single pole, under composed voltage Ph-Ph, double fault current.> Few manufacturers give information...

French standard NFC 13-200 712.3.5 Ventilation des locaux contenant des matériels isolés au SF6 Dans les locaux situés au-dessus du sol naturel où se trouvent des matériels isolés au SF6, une ventilation naturelle est suffisante selon les conditions du sous-paragraphe 712.3.2. En cas...

Exactly, but in practice it is not obvious to keep a good sealing and in case of abnormal condition (belt sway, maintenance work..) An then with a large fault energy/overheating how to be sure of not having ignition of sulphur inside gallery.

Thank you very much. I think also that considering the high reliability of HV protections for earth faults, this can protect enough the conveyor line. I was considering also that the hazardous area is contained inside the conveyor gallery and if a regular cleaning is done, then probability to...

Thanks waross Could you please give me more detail/example about these enclosures (types, material)? Regarding the possibility of accident on the HV line, this is what I need: is there any standard describing similar case? Is there any benchmark? I can't find any IEC or European standard for...

Thanks for your answer. I want just to clarify: the ATEX area is only the conveyor galery. So in normal operation, the HV line is in safe area. You are right: the hazardous area classification was done by a Client & competent agency. All electrical equipments along conveyor are chosen for ATEX...