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Please send me some links, documentation with MV measurement . I am kind of confused when i see 2 ct-s, 3 ct-s, with 2 secondaries, 3 secondaries. Or 2 VT-s, 3 VT-s , in star, delta, etc... Thx.

Hi Can you give me some technical description of fuse supervision -(some relay or other method to monitorize fuse melting)? Also some models and manufacturers? Thanks.

Hi . For a multiple earthed network(the neutral wire is earthed at the powerhouse, at the point of supply to each consumer and at other points along the line between powerhouse and consumer), I have to use 3 p ACB, that's clear. But designer wants Ground fault. And CT on neutral. I know ground...

Do you know the standard value of illuminance inside an auto repair workhouse? And which IEC standard shows illuminance values? Thx.

Hi Does anyone know what is the short time withstand current of the bars fed by 2, 3, or 4 transformers, let's say 630 KVA Uk=6%? If the Icw(1 sec)= 15 KA for bars fed by 1 transformer, for 2 transformers Icw(1 sec)= 2x15KA , for 3 transformers is 3x 15=45 KA? Is this the rule? Thanks.

Hi I am disputing with a colleague: I say : Phase "A" exists. every 3-phase system has a phase "A" He says: Phase "A" is random. Important is just the rotation ABC, or BAC. You cant determine which is A. I believe: every circuit has a phase A, that can be measured, and labeled as A. If there...

Hi If we have 3x capacitor banls 300 KVAR in a LV switchgear, we got 3 power factor regulators. How do this Power factor regulators take the informations about currents- i need 1 CT on main bus bar/each regulator ? Or (maybe)if i have on main incomer 1 converter 5A - 4-20 mA, can this be...

Hi Does anyone know a good material to insulate the bolts from the bar joints in a 400V switchboard? Thanks!

I want to learn what is a lockout relay-86. Is just equivalent to a reset button? Thank U.

Hi. Can anyone give me the cheapest solution for a digital motor protection relay, with connection possibility for 5 PT 100 sensors ? I have checked some relays like MM200, MM300 from Multilin, General Electric , but only 1 thermistor imput available. Motors are 400V AC.

Hi Short one: What is the L in circle(same as A in circle is ammeter, V in circle is Voltmeter)? The L thing is conected in paralel with the voltmeter. Thanks

Hi IT systems are systems conected to earth through an impedance. To lower short circuit curent, right ? I have a situation, 380 V, 50 HZ, transformer 2MVA, where i have to choose circuit breakers for an IT system, and in CB catalog , the values for "single phase breaking capacity Iit " are...

Hi I learned at school and never met since then with this problem: for differential protection of transformers 3 CT-s are needed on LV and 3 CT-s on HV side. I recently saw a diagram with 6 CT-s for LV side. No info-s about HV side, anyway i am concerned only about LV switchboard. So, why 6...

Hello I want to ask you about Auto chageover systems-ACO(called also auto transfer switches- ATS), made on PLC-s not on relays. Power system: 400 V, 50 HZ, Europe How many ACB-s(Air circuit breakers) can you pun in such a system? For example if you have a system of 4 switchboards, 2 supplied...

Hi Got a question, for those who use European standards. Question is at quotation level. I got to protect VFD, with MCCB. Designer asked for 50 KA, coordination type 2, and both thermal(0.8-1 In) and magnetic protection. After u, can i use class 10 of thermal protection, with MCCB for motor...