Coordination Graph

Grouch1980

Grouch1980

Senior Member
Location
New York, NY
Hi all,
I put together this graph just as an example; this is from the 'E-Coord' program by Elite Software. I'm trying to do a coordination analysis between 2 devices. The 300 amp Bussmann fuses (shown in blue) are on the primary of a transformer (@480v), and the 100 amp Square D circuit breaker (in red) is on the secondary of the transformer (@208v).

The 'drawing voltage' is 480 volts as you see on the top left, which is the transformer primary. This would be the base / overall voltage of the graph.

I have to click on 'adjust to drawing's voltage' on the bottom right for the secondary fuses, where you see the instruction tab next to it. The secondary voltage would be 208 volts as I mentioned above. The red graph for the breaker would shift to the left to accommodate the adjustment for 480 volts.

My question is: if anybody is familiar with this program (or maybe it's similar to EasyPower as well)... when I click on 'adjust to drawing's voltage'... how does the program know that my voltage on the secondary is 208 volts? How do these programs know, whether E-Coord or EasyPower, the transformer ratio?

If you look on the lower left, you'll see 240 volts... but that's the voltage rating of the breaker, it's not the 208 volts on the output of the transformer secondary. I'm assuming, based on the instruction tab on the lower right... I have to adjust the voltage rating of the breaker down to 208 volts?

Graph2.jpg
 
M

Melak 22

Member
Location
Michigan
Occupation
Electrical Engineer
I'm not familiar with this program, but it should shift the device based on ratio from the upstream transformer. The 240v shown is just the device rating.
 
Grouch1980

Grouch1980

Senior Member
Location
New York, NY
Melak 22 said:
I'm not familiar with this program, but it should shift the device based on ratio from the upstream transformer. The 240v shown is just the device rating.
Click to expand...
Right... however in the tab that you see open on the lower right, it says 'based on the ratio of the device's voltage to that of the drawing'.

This seems to be implying that I have to change the device rating from 240 volts to 208 volts, so that it calculates the ratio properly and shifts the graph. This does not seem correct... the device rating should not change.
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Why do you want to coordinate two devices in series, especially when they are so relatively small?

Yes you should 'adjust the drawings voltage'. This is a typical adjustment for graphing only programs, the programs with one-lines usually do this automatically.
 
Grouch1980

Grouch1980

Senior Member
Location
New York, NY
jim dungar said:
Why do you want to coordinate two devices in series, especially when they are so relatively small?

Yes you should 'adjust the drawings voltage'. This is a typical adjustment for graphing only programs, the programs with one-lines usually do this automatically.
Click to expand...
The downstream breaker is actually in parallel with other breakers, on the secondary of the transformer. It was a client request to make sure the fuses on the primary don't melt, knocking out power to the other breakers on the transformer secondary.

My question though is... when I click 'adjust the drawings voltage', do I have to change the device rating from 240 to 208 volts (see lower left of the image in Post#1)? It seems to be the only way the program knows what the voltage is on the secondary.
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
You need to use the voltage the breaker is installed on, which is 208V.
The software will convert the current shown through the 208V breaker using the 208:480 ratio by shifting the breaker curve to the left.

The 240V shown with the breaker data is simply information only.
 
Last edited:
Grouch1980

Grouch1980

Senior Member
Location
New York, NY
jim dungar said:
You need to use the voltage the breaker is installed on, which is 208V.
The software will convert the current shown through the 208V breaker using the 208:480 ratio by shifting the breaker curve to the left.

The 240V shown with the breaker data is simply information only.
Click to expand...
RIght... but I don't know how to tell the program I'm at 208 volts on the secondary. I called customer service... and they couldn't help :mad:. If I follow that open tab on the right... it seems to imply i have to change the device rating. I know it's for information purposes only, but it seems like the programmers didn't include a place where I can specify the secondary voltage.
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Okay.
According to the note in the OP, you simply need to check the box. It may give you another pop up.

If it doesn't it is not a big deal. The difference between 208 and 240V is probably in the margin of error for your drawing resolution. I wouldn't worry about it.
 
Grouch1980

Grouch1980

Senior Member
Location
New York, NY
Yes, that is true, it's not that much of a difference (208 vs 240v).

Where it becomes an issues is if, for example, I have a 600 volt rated device on the secondary. Then I have to go into the device rating and change the device rating to 208 volts, since there's no other way it seems to tell this program what the secondary voltage is. I just have to remember to change the device rating back to 600 volts afterwards so that the value is not lost.
jim dungar said:
It may give you another pop up.
Click to expand...
No other pop up.
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Grouch1980 said:
Yes, that is true, it's not that much of a difference (208 vs 240v).

Where it becomes an issues is if, for example, I have a 600 volt rated device on the secondary. Then I have to go into the device rating and change the device rating to 208 volts, since there's no other way it seems to tell this program what the secondary voltage is. I just have to remember to change the device rating back to 600 volts afterwards so that the value is not lost.

No other pop up.
Click to expand...
Yep. A graphing only program. You don't get what you don't pay for.

The program apparently does not know there is a transformer between these two protective devices.
 
M

Melak 22

Member
Location
Michigan
Occupation
Electrical Engineer
Changing the device rating doesn't seem like a huge deal to me. If I were the customer asking for a coordination study, I want to see how well the devices are coordinated, not regurgitated information that is already shown on the device physically...
 
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