In my opinion, the art.250.30 A(1) System Bonding Jumper requests a single SSBJ at the source enclosure, and Art.250.30 A(1) exception 2, permits 2 SSBJ: one at the source and the second at the disconnector side. In this case, we may not connect these two SSJBs with a bonding wire in order to...
In my opinion all the symbols except Ursd and df/dt are IEC 60617 protection graphical symbols.
Ursd may be Residual Voltage Relay and df/dt it has to be rate of change ROCOF relay .
My edition of IEC 60364-5-52 standard it is from 2001 In this edition Annex B is for information, only.
Also, in the last edition [of 2024?] as I saw, Annex B it is informative only.
So, the actually normative part is still A.
On A 20 it is written:
NOTE 3 Values are given for vertical spacings...
See:
EPRI AC Transmission Line Reference Book—200 kV and Above, Third Edition
Chapter 2: Electrical Characteristics of Conductor Configurations and Circuits
First, I calculated the primary phase-to-phase angle and I took for secondary phase-to-neutral the same angle[see the sketch].
Then I calculated the secondary phase-to-phase voltage using these phase-to-neutral secondary voltages, changing the absolute value -only-in order to create a...
If we recalculate the Delta phase-to-phase voltages using voltages phase-to-neutral the absolute value is not 400 V but 402.7 AB, 411.4 BC and 407 CA. That means the phase-to-neutral voltages are different.
If Powerfactory software may approximate these different phasor values in order to reach...
If the cable run in trefoil formation -as per IEEE 575-for a rated load -up 1000 A the built-up voltage it will be less than 3 V .
In case of short-circuit up to 90 kA- the voltage will be 250-300 V
In flat formation-one feet distance, not cross bonding-for rated load may be 10 V, but for 90 kA...
If there are 2 single phase transformers 240/120 you'll get only 120 V between X1,X2,Xo ,if instead of H1 and H2 connected in the middle [short-circuit!] you'll put H3.
In order to get "high point" you need 3 transformers, but for only 104 V. For 208 you need 240 V secondary [not primary!]
In order to protect the cable, from cable tray up to connected equipment, you have to keep the minimum required in NEC Art.300.
In a power station -mainly in a machine room-it is recommended to run the cable from cable tray up to maximum 6 feet from the equipment in a rigid conduit-usually rigid...
Three-phase short-circuit current I"k3=Un/sqrt(3)/Z1
Phase-to-ground short-circuit current I"k1=Un*sqrt(3)/(Z1+Z2+Zo)
That means:
Un/sqrt(3)/Z1<sqrt(3)*Un/(Z1+Z2+Zo) or:
1/Z1<3/(Z1+Z2+Zo)
3*Z1>Z1+Z2+Zo
Usually, Z2=Z1 then Zo<Z1 in transformer
Neglecting the resistance Xo<X1
See ABB attachment.
If the process area it is an open site and your panels are also in open air it is not a hazardous area for this equipment. The hazardous area border if it is enclosed it is 5 m more or less [in outgoing conduits].
First, the IEC standards use elevated earth resistivity -see IEC 60364-5-52 [2.5 K.m/W] or IEC 60502-2 [ 1.5 K.m/W].
However, directly buried power cable produces a soil heating and then the soil around stays dry. The standard IEC 60287-1-1 presents a way to overcome the actual change in earth...
