zero measurements from a meter

[Rafik Fainti]

Dear all,

I have connected a meter with a node. Below you can see the code for both the meter and the parent node.

object node {
name 632;
phases ABCN;
voltage_A 2401.7771;
voltage_B -1200.8886-2080.000j;
voltage_C -1200.8886+2080.000j;
nominal_voltage 2401.7771;
}

object meter {
name m632;
parent 632;
phases ABCN;
voltage_A +2401.777+0.000j;
voltage_B -1200.889-2080.000j;
voltage_C -1200.889+2080.000j;

        nominal_voltage 2401.7771;//14376.02;

        object multi_recorder {
                        file "meter632.csv";
                        property measured_power, measured_real_power, measured_reactive_power,    measured_voltage_A, measured_voltage_B, measured_voltage_C, measured_current_A, measured_current_B, measured_current_C, measured_demand, measured_power_A, measured_power_B, measured_power_C;
                    interval 60;
                    limit 10000000000000000000;
    };

}

I have to mention here that I am using the IEEE 13 bus distribution feeder and that node 632 has no residencies connected to him.

My problem is that I am taking measurements only for the measured_voltage_A, B and C, while I am taking zero measurements for all the other parameters. Is that correct or I am doing something wrong?

Thank you very much in advance

[Jason Fuller]

Rafik,

From what you've shown here, I can't tell you whether you have a problem. This meter should measure any load flow below it (i.e., anything that is attached to it). If there is no load, then it should measure zero for everything else.

Potentially, you may need to replace the node with the meter, rather than childing the meter. As it is now, the meter is a "branch" of the circuit, at least logically. Only things attached to it (and not the node) will be measured. Depends on what you are trying to do and how you have your system configured.

[Rafik Fainti]

Thank you very much for your reply. I will try to replace the node with the meter.

[Peter Evans]

Jason, can you clarify your response? I am having the same problem - a recorder in a meter childed to a node showing zero values for flow. If I make the node a meter and embed the recorder object it works.

Is it always the case that a child is topologically a branch off a parent node? Would I have the same problem childing a meter to a load object? Could I child a meter to a line and get the values I want?

[Jason Fuller]

Peter,

The meter needs to be "inline" for the measurement you want to capture. If the load is a topological child of the meter, the load will be picked up.

So, here's a really simple picture that tries to explain it. All four of the topologies shown will give you the same power flow solution. However, 1 does not have a meter, while 3 will not see the load. Both 2 and 4 will see the load as part of the solution.

Hope that helps.

[Peter Evans]

The diagram is really helpful.

1. Could I go from #1 to #2 by defining a meter object within the middle node object?
2. Could I always define loads as meter objects so I can record flow to the load without changing the dataset topology to add a meter?

[Jason Fuller]

Peter,

(1) Yes, with no change in solution.

(2) Loads, meters, etc. are just nodes with specific logic associated with them. So, you can replace a node with any of the other objects without changing the solution. However, if you change a load to a meter, then you lose the functionality of the load. That said, if you create a meter and load with the meter as a parent, the solution is equivalent.

[Peter Evans]

Thanks. Re #2 but going the other way, are there any limitations to defining meters and recorders within nodes or loads?

[Frank Tuffner]

Hello Peter,

Limitations on #2 depend mostly on which solver you're using. If you're using the Forward-Backward Sweep method (FBS), you can put a very large number (near limitless) number of childed objects and levels of hierarchy (e.g., children, grand-children, great-grand-children, etc.). If you use the Newton-Raphson solver (NR), it restricts you to only children (no third level). You can have a very large number of children, but those objects can't have another layer of parent/child nodes. Both solvers let you connect lines to those childed/deeper-hierarchy nodes and record flows that way, if you're trying to change what specifically you're measuring (but overall electrical solution-wise, they are still the same).

For recorders, there is no real limitation. Recorders can be parented to basically any object, and will not affect the powerflow solution (and will work). The only main exception is there is a file-handle limit for most operating systems (too many open players/recorders does weird things, which is why we have collectors, group_recorder, and multirecorder objects). You can occasionally run into "ranking issues" associated with the object execution order, but these are pretty specialized cases and typically just mean your recorder is a timestep off.

Hopefully that covers what you were asking. Is there a specific scenario of #2 you are wondering about?

-Frank

[Peter Evans]

If I have a node or load object, can I construct a meter within it (as opposed to changing the node to a meter object)?

Edit: Said differently, can I construct a meter as a "nested object" within a node or load, and if yes, will that meter be in-line, or will it be treated as a branch like a parent-child relationship?

The specific scenario is a feeder model made up of a) node objects and b) load objects childed to node objects. I'm wondering if I can add meter/recorders at specific points in the model just by constructing them within the existing objects.

[Frank Tuffner]

Hello Peter,

If I follow your question correctly, you're basically trying to do Scenario 3 in the PDF Jason posted earlier. If that assumption is correct, you can just add a meter to the main node as a childed object. However, it will only provide flow measurements on devices attached to the meter. So if it is identical to the layout in Scenario 3, it will give you zero values (measure nothing, since nothing is flowing through it).

So for your specific scenario, I'm assuming you want to be able to explicitly measure the load values connected at each node. Unfortunately, the only way to do that would be to have the load "flowing" through the meter, which would require you to parent the load to a meter, suggesting you'd need to swap the nodes in your system for meters.

Alternatively, if you didn't want to modify your topology, you could put recorder objects (likely a group_recorder or multirecorder) on all of the power_in and power_out values of your lines. Then you could post-process the data to get the load portions (since it should be whatever the net power difference at a node is).

-Frank

[Peter Evans]

OK, so I understand I can't simply nest a meter inside a node object or a load object; that is topologically the same as childing the meter to the node object or load object.

So one last question. Is it correct that a load object and a meter object are different, such that while I can re-define a node as a meter, I cannot re-define a load as a meter (it would no longer function as a load)?

[Jason Fuller]

Peter,

That is correct. node is the parent class, while meter and load are both derived classes of node. So, while meter and load contain all of the properties of node, node and load do not contain all the properties of meter (same if you reverse meter and load).

[Peter Evans]

Very helplful, thanks. FWIW, the nuances among substituting, childing, and nesting nodes and their derivatives are pretty important, and I think not explained as well in the documentation as you all have here.

Also, it would be nice if loads had more of the properties of meters since there is an obvious relationship. Maybe for the future...