Building a macrovoltage simulation

[bjjohns]

I am trying to build a macro level voltage simultaion for a classroom. I will have two 3-phase AC power sources at two different voltage levels, two 3-phase loads (3 phase motors), a 3-phase transformer, and a interconnecting coil driven 3pst switch that connect the two generator/motor circuits.

I want to implement current transformers & voltage transformers , and add a modern style protection relay. I want to automate the protection relay for phase comparison, voltage comparison, phase differential, voltage differential, ground fault, diode failure..... for those that are reading this and know power gen I am trying to build a simple generator protection circuit that I can connect DMM's and oscilliscopes to show what is happening.

My problem is three fold that I see. Problem 1 - How do I build a box in multisim that emulates a 86 style protection relay? Where do I build my logic?. Problem 2 - is there a easy way to "build in" faults rather than change the properties of the generators and the transformers? Can I build a indicator into the box showing it is in fault like a led or a light?

Thanks in advance. I realize parts of this are complex and others are easy - I only have about 60 days with multisim so far, and I just don't see how to do these things yet.

[_user32]

bjjohns ,

First you'll need to build up a simulation in Multisim.   We have most of the components/models that you may need.  Can you give us some additional detail for an 86 style relay, maybe a rough draft of the schematic as? a start?   Also you can use the TIL logic models to build up your logic simulation, these can be found here... Master DB -> Misc Digital -> TIL...

Regarding faults, some types of components have a 'Fault' tab if you double click...

Regards,

Patrick Noonan
Business Development Manager
National Instruments - Electronics Workbench Group
50 Market St. 1-A
S. Portland, ME 04106
Email: patrick.noonan@ni.com
Tel. (207) 892-9130
Fax. (207) 892-9508 

[bjjohns]

Yes, quite a bit of it is already there. I have the CT's in the attached sim (but not the PT's).

An "86 relay" is a generator proection relay system. In older power generation it would consist of a large number of different relays each performing a special function. In modern relats (Such as a GE model SR489 protection relay) they are all bundled into one relay.

The "protection" is designed to open the 3PST relay based on any one of a number of "bad generation" problems. The would include frequency comparison, voltage comparision, bad ground, bad excitor diode, motoring (in some situations), bad powerfactor, etc.

I really only need to model over-voltage, under voltage, over curent, under current, over freq (+.05%), Under Freq. for the protection relay.

I also need to model a synchronization relay (complete with lights if possible).

I'll try and get some schematics up by the weekend.

Thanks for replying!

[_user32]

bjjohns ,

Some of the functions you specify in the '86' style relay may be difficult to design in a SPICE model and may be more easily designed as measurements that are built into a custom LabVIEW VI for Multisim.  In Multisim v10.1 we now support in/out LabVIEW instruments, therefore a custom Multisim VI could be generated such that when set limits are exceeded on these measurements an output is generated to throw a switch in Multisim.

This might be a good proof of concept to showcase doing these more complex algorithms/control functions in a LV instrument.   Let me see what I can put together to start this.   If I generate the initial code, do you have LabVIEW to complete it?

Patrick Noonan
Business Development Manager
National Instruments - Electronics Workbench Group
50 Market St. 1-A
S. Portland, ME 04106
Email: patrick.noonan@ni.com
Tel. (207) 892-9130
Fax. (207) 892-9508

[lorylaci]

I am starting a design of a three phase AC/DC circuit with power factor correction.

First I wanted to simulate the three phase rectification. I built a simple three phase rectifier, with full wave rectifier circuit. When simulating the output, the oscilloscpoe showed a half wave rectification waveform. I chekced the circuit and simulated it on paper, and found that multisim 10 has problem simulating it.

Are there any special components to add? Or do I need to set analisys options?

[yyao]

Hi there,

Could you post your schematic for us to take a look at?

Thanks!

[lorylaci]

Here is the schematic.

Im also having convergence issues all the way. When i restarted Multisim, the oscilloscope image changed to fac=300Hz at output (first it was 150Hz). I'm measureing waveforms of the currents in the phase lines too.

[yyao]

Hi there,

We have been working on improving the quality of Multisim's simulation a lot recently, particularly when it comes to its treatment of diodes. Here's a few tips that I found to improve the reliability of your simulation:
1 - Change the integration method to gear (click Simulate>>Interactive Simulation Settings>>Analysis Options>>Customize>>Transient>>[METHOD]>>gear)
2 - Decrease RSHUNT - I tried 1e9 (click Simulate>>Interactive Simulation Settings>>Analysis Options>>Customize>>Global>>[RSHUNT])
3 - Decrease the size of your capacitor
4 - Attach a more power hungry load

Unfortunately, there's no silver bullet in guaranteeing simulation success. You kind of have to fiddle with different settings until you get your circuit simulating.

Hope that helped.

[saifi]

hi,

I am also facing same problem.while running same simulation in psim output voltage is coming ok.I am getting 6pulse output but using multisim 3pulse is missing.my circuit is similiar to that of yours.can you pls suggest how you have resolved this problem .thanks

[saifi]

 hi,

my circuit is same as lorylaci's circuit.it is 3phase full bridge rectifier,6pulse rectifier.I am not getting 6pulse output.I am getting only 3pulse but rest 3pulse are  inverted.in actual we should get pulsating dc output with 6 pulse output.can you please reply how should we get coreect output.