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slavag, Many thanks

slavag, I used to work in IEEE world earlier and this concept is also new to me but as I mentioned earlier, I am now in UK and this is a backup protection. There is a already a combined diff biased and HV/LV REF protection (Duobias Relay) as main protection. Plain balance is a standard back up...

breaker 12 If you are in IEC world the applicable code would be IEC-287. Sometimes the clients are happy with cable sizing calculations based on current capacity for specific laying conditions and applying different de-rating factors which are clearly mentoined and explained in cable...

jghirst / slavag, Many thanks for your responses. I must confess the scheme is not correct, excuse my drafting techniques. I have uploaded another one. The relay used is P122 Micom series relay. 5:1 interposing CTs shall be used to balance 2000/1 to 2000/5 LV sides as one is existing. The only...

Hi, I am involved in protection scheme design for substation in UK. We have a plain balance scheme similar to a high impedance differential scheme for trafo protection but as a back up so thats why 5P20 CTs and interposing CTs are used. 3 Wdg trafo vector group is Yyn0yn0. It is a common O/C...

Could anyone please educate me (or refer to a book / link) about EHV Mesh Corner arrangement and protection principles? Regards

Hi, Is there any international (European, American or British)standard which describe the method of providing lightning protection for overhead oil and gas pipe lines? I have come across 800 meter long pipelines laid on 17meter height overhead pipe racks (reinforced concrete structure) carrying...

Thanks jghrist, I am using CEDEGS software by SESTECH. There are several modules with different capabilities. In a nutshell, it is not possible to model the two grids with return path in that software as there are lot of coated conductors as well. SES helpline told me that I could ignore the...

Sorry David, ECC stands for earth continuity conductor. I should also mention that I am in UK.

Hello everyone, I have a situation here regarding grounding. There is a new 2x132/11/11kV substation fed by 2x132kV cable circuits. Cable sheaths (95mm2 each) are connected at both ends, length is only 4200m. We also have 2x150mm2 ECCs connected at both ends. Cable sheaths and ECCs are within...

Does this surprise only me? I would be more surprised if in IEC world someone would ask you to do so ....

giuseppe I am not sure but I think IEC 60617(1-13) 1996, is the current British graphic symbol standard. At least the copy I am having says so.

Are you sure you are going to install CTs for O/C protection on a 200kVA transformer on 11kV side? Genarally transformers of this capacity are protected by H.V (or M.V) Fuses. However in IEC world IEC-185 and IEC-44-6 are the standards for CTs. Regards

Could anyone please educate me with the difference(s) between class PX and class X CTs? What are the related standards, if different? Regards

It is an old scheme with high impedance relays.

Well I am exactly of the same opinion. Not only it involves more CTs and more wiring in an existing switchgear but more tripping relays make it more vulnerable to failure. The main question is, do wee need to put additional check CTs around bus coupler and wire in the same manner as main (or...

Hi everyone, I have been encountered with a situation where my client wants me to put "SEPARATE CHECK CTs FOR EACH BUS SECTION" across the Bus Coupler, balanced by other check CTs in that particular bus section. The the usual bus wires stuff put into operation by isolator aux switches. Its a...

All I can say that is GREAT ... Thanks

Thanks RalphChristie, It is indeed a helpful link. SMA

stevedantonio, I believe there is a mistake in your 2nd last post (200kAIC for service switch). If is 20kAIC, then it seems OK for 13.7kA fault level. What is the cable size and no. of cables/phase from Service switch to 10kA MDP (I think it is Main Distribution Panel). If the length is more...