# What 'Admittance' mean in [Bus Fault] option when performing Dynamic simulation?

I want to apply bus fault in my dynamic simulation.

When I select [Bus Fault] option,I have to input [R,X] of "Admittance", the default parameter is:

|     R      |      X     |
|     0      |  -2e+009   |


My understanding is that the bus fault defaults to a three-phase short circuit fault by default. If it is not specified as a ground fault, then there is no impedance parameter to be input, because the simple short circuit fault impedance is 0.

But when I set [R,X] to [0,0], I found no change in the angle curve of my dynamic simulation result

So what does this "Admittance" mean?

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This fault admittance enables you to apply balanced and unbalanced shunt faults. In the case of three-phase faults, it is assumed that the faulted point is all three-phases to the zero potential reference (in this case, the ground). Like any other stability programs, PSS/E is based on positive-sequence network i.e. network components are represented by only one phase.

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Well, the fault admittance is always a balanced shunt connected to the bus. This balanced shunt is used to emulate the effect of a three phase fault (very big shunt). A single phase to ground fault is represented with a smaller shunt, defined by the negative and zero sequence impedance at the bus.

( 2018-06-06 03:14:18 -0500 )edit

I used to represent unbalanced shunts using this fault impedance too. I compute for the negative- and zero-sequence admittance in MVA, connect them in series (for 1LG fault) and put the resulting value as the fault impedance in the positive-sequence dynamic simulation.

( 2018-06-06 23:12:13 -0500 )edit

In dynamic simulations a bus fault is modelled as a shunt connected to the faulted bus. A solid fault is modelled in PSSE with a shunt reactor of 2 000 000 000 Mvar, .i.e. a very large shunt reactor driving the node voltage to (almost) zero.

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Is the shunt reactor connected to the A, B, C phase line of the fault bus separately? I don't know whether the bus fault under this modeling is a three-phase short circuit, a three-phase short circuit grounding, or any other fault.

( 2018-05-28 19:45:21 -0500 )edit

It is a positive sequence shunt, i.e. connected to all three phases. Only the positive sequence is modelled in PSSE in a dynamic simulation.

( 2018-05-29 06:33:32 -0500 )edit

This is a three phase to ground fault by default. Other are specified but the worst case fault being three phases to ground. If your system can withstand this type of fault, then you assume it can withstand other, lesser types.

( 2018-06-01 19:40:04 -0500 )edit