Recent content by cos90

Read through this:  pencil and paper section.  Don't lose out to a technicality.

Where did you get this Kaplan? Kaplan changed their name to Brightwood and the book I purchased from them looks nothing like this.

You could also see a wye-delta used as a grounding bank, used like a zigzag transformer.

A GSU is a delta-wye. I misspoke. The LV winding is the primary on a GSU transformer.

My apologies for starting this discussion. Here's how you would solve this problem before microprocessor relays came onto the scene: @TNPE  you would see a wye-delta transformer applied for Generator Step Up (GSU), the tertiary of a large autotransformer, and at interconnection sites where...

Here is the text: In our example, the transformer has the Δ-Y connection. Traditionally, CTs on the Wye connected transformer winding (winding 2) are connected in a delta arrangement, which compensates for the phase angle lag introduced in the Delta connected winding (winding 1), so that line...

what if you lose feed from the utility and they close back in before you have someone at the station to turn the differential off? lockout differential on inrush ? genuinely curious 

page 372  5.5.4.6 Phase and zero sequence compensation 

Just beware it's not perfect and inspired my forum username  cos(180) = 0 ??????

It's in the code: the nameplate rating is used for overloads only. Everything else is in those motor tables. Also the PPI exams were really tough.

oh i forgot to mention a major source of CT error as mentioned by rg1: variation from the load tap changer!!  also if you are not tnpe or rg1 this discussion is way out of scope for the pe exam

@rg1 you have done a good job explaining the details of transformer differential protection @TNPE I am curious what your plan is for the second energization of your transformers if you don't enable differential protection during the first energization?? especially since the next time you...

thank you for finding these.

Its a really straightforward question: You need to connect 3000kVAR to correct the power factor and you have 100kVAR cans How many cans per phase do you need to connect? 3000/3 = 1000 kVar per phase  1000kVAR/100kVAR = 10 cans per phase Where the questions get strange he draws out networks...

I am glad to see you got it. I was worried for you when I saw this question. I was afraid to do anything out of the ordinary for my application.