Calculate the impedance from one bus to all others

asked 2013-04-07 20:36:07 -0600

Eli Pack

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updated 2013-04-08 22:04:32 -0600

JervisW
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I've got a concept in my mind of plotting bus voltages for a large network in one graph. For this, I'd like the x-axis to show the electrical distance between buses, and the y-axis to be voltage. A node on the graph would represent a bus voltage at some point. The nodes on the graph would be connected with thin lines to other buses that it is directly connected to in the network. It might be worthwhile only plotting buses above a certain voltage.

The first step is to come up with the x-axis values for each bus. So, if I pick a bus at one far end of the network, these x-axis values should be the resistance between each bus in the network and the selected bus at the end of the network. I was wondering if anyone had a quick way to calculate this. I'm hoping that I don't have to set my bus at the end of the network to the slack bus and run a load flow after adding some load to each node.

Eventually, I'd like to generate an animated graph that shows a system-wide voltage response to a disturbance.

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Hey, can you sketch out in MS paint how this might look? I've done some simple work on electrical distance with automatically laying out 2D for a SLD.

JervisW ( 2013-04-08 02:36:37 -0600 )edit

I should add my work on the electrical distance probably won't help your situation. Because it sounds like you are turning a long skinny network into an approximate 1D equivalent on the X-axis?

JervisW ( 2013-04-08 02:39:13 -0600 )edit

That's exactly what I'm doing (1D equivalent). Here's the drawing: http://i.imgur.com/yjc2qfu.jpg

Eli Pack ( 2013-04-08 07:50:58 -0600 )edit

@Eli - I'm liking your idea of adding some load to each node and measuring the response at the slack bus. I think that's pretty clever.

JervisW ( 2013-04-09 03:58:00 -0600 )edit

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answered 2013-04-09 04:08:09 -0600

JervisW
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updated 2013-04-09 04:12:03 -0600

Picking up on the thread in your question, here is how I'd add load to a bunch of buses and measure the response at the slack bus:

electrical_distance = {}

buses = subsystem_info('bus', ["NUMBER", "TYPE", "AREA"])
buses_in_qld = filter(qld_only, buses)

for busno, type, area in buses_in_qld:

  # rolls back to original saved case on each for-loop iteration.
  with transaction():

    # add one MW load to this bus
    add_load_to(busno, {"pl": 1}) 

    # solve probably with fixed taps, shunts, fixed everything
    psspy.fnsl(**options)

    # difference at slack bus
    slack_diff = get_p(slack_busno) - original_slack 

    electrical_distance[busno] = slack_diff

I've tied some code up into helpful functions. You'd have to write add_load_to, define some options for fnsl and write a function get_p.

The transaction function has already been written: http://www.whit.com.au/blog/2011/09/turn-back-time-using-python-and-psse/

and subsystem_info has been written too: http://www.whit.com.au/blog/2011/08/designing-easier-subsystem-data/

Here is what I'd expect electrical_distance to look like after running through the buses:

{101: 1.10, 102: 1.14, 104: 1.15, ... }

It's just a dictionary listing the increase in slack MW due to your 1MW of load added.

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As a point of interest, how is this any different than kind of a poor man's way of calculating a distribution factor? Maybe that would be more applicable?

jsexauer ( 2013-04-09 11:05:19 -0600 )edit

Distribution factors may be a good way to do this (this was actually my first though). I believe the calculation achieves the increase in flow on a line for power increases at buses in your network, so I'd just need to use a line near the end of the network rather than a bus (or perhaps create one).

Eli Pack ( 2013-04-09 19:27:48 -0600 )edit

@jsexauer and @eli I'd love to see the distribution factor method in action. I might ask a question for it.

JervisW ( 2013-04-10 20:03:45 -0600 )edit

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Calculate the impedance from one bus to all others

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