We use earth fault passage indicators (EFPI) or fault passage indicators (FPI) on the secondary substations on underground open ring distribution circuits. EFPI or FPI indicate the passage and path of fault current. Based on their indication the faulty cable section between two secondary...
I don't know what are you testing?
However, from readings given above 81A is the highest among the three phase currents; so we can say that the highest 3-phase current was 81A at time when you performed measurements and corresponding 3-phase kVA is (assuming balanced load) 1.732 x 208/1000 x 81...
Have you got cable capacitance (charging current) and power loss?
Using these parameters you can calculate the admittance (Y). In PI model you can use 2Y in each leg.
Y=2 * Pi * f * C
M.A.Sh.
Elect. Engr.
Most of the friends above already explained the process, however to simplify I will add that power flow in any power system depends upon:
1. Frequency
2. Voltage
3. Power Factor
Controlling these parameters we control power flow in power system.
Usually in distribution system, power...
I agree with odlanor that in majority of cases the intertie protection will disconnect the dist generation and will not permit island operation, but I know instances where island operation is permitted after detailed studies have indicated that power quality can be maintained during island...
I can add that if the utility circuit is rated 9 MVA or more and provided that all other criteria for connection of distributed generation is met (voltage profile, power quality, etc); then your Dist Gen can be accepted, no matter what the load is on that circuit.
The only concern could be the...
djr3203; can your customer's load be assumed balanced 3-phase?
Are there 8 cables per phase or 2 cables per phase + 2 cables for neutral between the transformer & the customer's intake?
M.A.Sh.
Elect. Engr.
7anoter4 much appreciated response. Your calculations match mine.
I will ask for more explanation for: "Then Sf [ the fault current division factor] will be 0.76/(10+.76)= 0.07"
How 10+.76 is used in calculations?
Also if you could comment on the presence of a PME supply + TN-c-s supply in...
I = approx. 2700A per phase is ok 480V Y secondary
rcwilson is right that volt drop is dependant on both the resistance & reactance; so you should use the cable impedance per foot or per metre instead of just using resistance in volt drop calculations.
To elaborate more you should explain...
Isn't in calculations by Odlanor, the ground current given by:
Ig = E (phase-neutral) / (NGR + Z zig zag transf.)
Do we ignore Z zig zag transf. due to some codes? if yes what code?
M.A.Sh.
Elect. Engr.
Many thanks to all who shared their valuable experiences.
Can I ask what systems are in use in US utilities where both single phase and three phase loads are to be supplied (that is distribution systems)? Is it HRG or solidly grounded?
I understand that in past (and still at few places) in US...
