Yes, it’s simply S = VI*. And thank you for the kind words about MATPOWER. I’m glad you’re finding it useful.
Ray On Dec 14, 2020, at 4:02 PM, Russ Patterson <[email protected]<mailto:[email protected]>> wrote: Hi Ray, Thank you sir. I’m working the problem by hand (for my sanity) and I’m getting very close to what MATPOWER has below shaded in green. How does MATPOWER calculate those values? Just <image001.png>? <image002.png> Here is the circuit I’m working by hand. I can share the entire slide deck (7 slides) if anyone wants it. <image003.jpg> Best regards, Russ p.s. I’m really liking MATPOWER. It is really nice package. I’ve even got it running on an RPi 400 running Ubuntu MATE on an ARM processor. ;-) From: [email protected]<mailto:[email protected]> [mailto:[email protected]] On Behalf Of Ray Daniel Zimmerman Sent: Monday, December 14, 2020 11:30 AM To: MATPOWER-L Subject: Re: circulating current (MVAR loss) Those are the VAr flows in the branches (corresponding to the circulating current) from bus 1 to bus 2 in branch 1, and vice versa in branch 2. And you are correct that the current version of MATPOWER does not include a unique branch identifier to distinguish parallel branches, so they are only distinguished by their order of appearance in the branch matrix. Ray On Dec 11, 2020, at 4:53 PM, Russ Patterson <[email protected]<mailto:[email protected]>> wrote: Hi friends, I have a simple power flow case with an infinite bus and 2 transformers (no load). The transformers have different turns ratios so I’ll get circulating current and VAr drop in the banks. #1 Transformer (100MVA) 161:13.8kV, X=0.1pu #2 Transformer (100MVA) 161:13.14kV, X=0.1pu <image001.png> The voltage difference is (13.8kV – 13.14kV)/13.8kV = 0.0478 pu which is the driving voltage for the circulating current. The circulating current will be 0.0478/0.2pu = 0.239pu A. This circulating current will produce a var drop of Q = (0.239)(0.239) x (0.2) = 0.01144 pu. This is 1.14MVAr. I ran the attached power flow case and got 1.13MVAR (nice). But, I don’t understand the big MVAr drops being reported in the branch report (see below). What is causing those big values? ================================================================================ | Branch Data | ================================================================================ Brnch From To From Bus Injection To Bus Injection Loss (I^2 * Z) # Bus Bus P (MW) Q (MVAr) P (MW) Q (MVAr) P (MW) Q (MVAr) ----- ----- ----- -------- -------- -------- -------- -------- -------- 1 1 2 0.00 23.81 0.00 -23.24 -0.000 0.57 2 1 2 0.00 -22.68 0.00 23.24 -0.000 0.57 -------- -------- Total: 0.000 1.13 I have a second minor question, how do you specify “branch 1” or “branch 2” when you have 2 branches between 2 buses? Does MATPOWER just take them in order they show up in the mpc.branch structure (e.g. the 1st occurrence as “branch 1”)? I did “help idx_brch” but didn’t see anything specifying. Thank you, Russ <circulating_current_no_load.m>
