Yes, that is correct. The Ze is the impedance at the board, but only if DB is at origin. The boards in the training establishment will include the internal wiring in the building, so are in fact a Zdb. An estimate of Pfc between two phases, is the highest current measured between phases and neutral and multiplied by 1.732 or root 3. To estimate the current if all three phases and neutral came together would be double the current between phase and neutral. Hope that helps, and do get in touch if you need further? Thanks for the question and happy testing.
Good Vid thank you. Am I right in saying that at this distribution board the Ze is actually the Zdb and when advising about the current generally the x 1.73 is the fault for 2 phases and the x 2 is for short between all three phases ? please advise.
YOU SHOULD BE BANNED. TEACHING BARE HANDS within inches of 3 phase terminals AND EXPOSING 'CROSS CHEST SHOCK HAZARD. YOU NEED TO BE REMOVED FROM TEACHING ANYONE.
The book suggests testing Phase to neutral(single-phase) and doubling the result to obtain a 3-phase value. Since making the video, I have started also measuring the Phase to earth which as you say, could be a higher reading as it is likely to include parallel paths. In other words, you are proceeding exactly as you would with a single-phase installation but doing 3 tests; one for each phase. This is useful if you have a single-phase board fed from the three-phase board. If this is the case, you would have all the info needed for PFC on the single-phase board, and for the three-phase PFC, you simply double the highest result. Let me know if you need further.
Could someone please put me right, I thought that the test carried out was not the the PFC as he only tested phase to neutral and not phase to earth which may have given a higher fault current which then would have been the PFC, it showed on the meter that only 2 probes was in use which was the line and neutral test probes, I do stand to be corrected.
The book suggests testing Phase to neutral(single-phase) and doubling the result to obtain a 3-phase value. Since making the video, I have started also measuring the Phase to earth which as you say, could be a higher reading as it is likely to include parallel paths. In other words, you are proceeding exactly as you would with a single-phase installation but doing 3 tests; one for each phase. This is useful if you have a single-phase board fed from the three-phase board. If this is the case, you would have all the info needed for PFC on the single-phase board, and for the three-phase PFC, you simply double the highest result. Let me know if you need further.
Dear Sir, the one-phase or three-phase isolation procedure (sequence) should be in more detail, this process you are explaining should be for everyone , you should explain the sequence of testing like Broun and Black, Broun and Grey, Black and grey, or L1 and L2, L2 and L3, L2 and L3, this very important for the beginners, and I hop you accept my comment.
Dont use 500v in real life, it will fry up electrical equipment in a domestic home including loads and stuff, use 250v then do calculation as if it was a 500v test. This way you dont need to remove light bulbs and stuff
It is a radial circuit as he only disconnected one line conductor (R1) and also you can have more than one socket outlet on a radial but the R1+R2 readings will rise and fall depending on which direction you test whereas a ring circuit should be the same reading at each socket outlet.....but you've probably got this by now.
DONT AGREE. Measuring phase to neutral shortcircuit is not going to give you three phase PFC even if you multiply by 1.73 or 2. You better have a look at schneider cahier technique 158 and compare the formulas for all shortcircuit types. you will see that you need to measure between two phases and multiply x1.16. Many mft meters support measuring between phases even if you select L-N test. For example fluke 1654B. The only place you could do that aprox x2 times (no x1,73) is subject to the neutral being the same size and length as the live, all the way upstream and if you are far away fron the transformer so the transformer windong impedance is much smaller than the cable. Things that you will never be 100% sure. Hope this comment helps you. And if you dont believe what i said and dont know how to check, think about it. If it was so easy as doubling it up you would get that info from the meter when you are doing LN tests.
Sorry no explanation of why the readings differ? No mention of Max Zs to prove readings are suitable? No mention in fact relating to disconnection times?
Thank you for this Video My question is if this test is Carried out for main low voltage panel with 2500 A breaker , so the main breaker should be off ? Right ?? And we will measure for the incoming point of the breaker which is live ? We did this as a safety procedure or just to take the exact reading for pfc and ze ?
Hi thanks for the Video. Can you tell me please why you had the Main Breaker turned off when doing your PSCC test? surely the main switch and breakers should be on ?
Hi, The main switch is should in the "OFF position when carrying out a test of PFC because the we are looking for the worse case scenario: when the resistance is at it's lowest and the current will be at the highest. If the switch was on, you could theoretically get voltage drop which would change the reading. When the switch is off, you are still including parallel paths as long as the earthing conductor and all the extraneous-conductive-parts are connected to the MET via the equipotential bonding. Hope that helps..
@@gregsmith5553 No; The bottom of the switch is live at all times, so the current is measured at that point. The installation is isolated and so there is no voltage in the actual system when the switch is off!
I couldn't see what you were probing on to, in order to conduct the test and you didn't tell the viewer... ! Terrible video and a poor choice of cameraman.
Could you please answer my question below to clear up the confusion for me which is why do you not get zero ohms between neutral and earth in the consumer unit if the neutral is ultimately connected to earth back at the supply transformer?
Hi Bernard, The neutral is isolated on the single-phase, so there is no connection between N-E when the isolator is switched off. You will get a short on insulation resistance in the 3-phase board on a TN system as the neutral is bolted direct to the neutral bar and so you have to then remove it to complete the test. Let me know if you need further?
Excellent instruction but I have one question: The star side of a delta/star supply transformer has the neutral connected to the central point of the star which is earthed so why would you not show zero ohms from neutral to earth, or am I missing something? Thanks
Sir, that's a very good video, but I wish to know , how to select the applied voltage for single and 3 phase conductors. Is it that the the voltage applied must be twice the RMS value of nominal operatinal voltage??? Kindly reply
Test voltages are taken from the regs and are dependant on the circuit to be tested rather than RMS of supply. As a rule in domestic application and on standard circuits on 3 phase, that value is 500V. However to ensure you are testing IR appropriately for each circuit reference should be made to BS7671.
sorry to be off topic but does someone know of a way to log back into an Instagram account..? I somehow forgot the login password. I would appreciate any assistance you can offer me!
@@hughjadiel2999 isn't there an option of" Forget password ".there should be, I believe you can get the One Time Pass word on the registered number in Instagram. Please check, or please try
Depending on the earthing arrangement then for TN-C-S Ze must not exceed 0.35 ohms, for TN-S Ze must not exceed 0.8 ohms. For TT it can be as much as 200 ohms.
