Relay CT requirement for TPY class
Relay CT requirement for TPY class
(OP)
Hi everybody
I would like to know that for protection relay CT requirement,is there any limitation for Rct in TPY class?
I would like to know that for protection relay CT requirement,is there any limitation for Rct in TPY class?






RE: Relay CT requirement for TPY class
RE: Relay CT requirement for TPY class
RE: Relay CT requirement for TPY class
Toady TPY class is not so used.
Don't design Rct, trust to CT mnf., them know what needed.
Please check requerements to TPY class in manual of relay, what do you want to use.
Good Luck.
Slava
RE: Relay CT requirement for TPY class
When defining a TPY core, Rct must be specified, as the CT manufacturer has no way of knowing the relaying performance requirement, and Rct is integral to the relay performance of the CT. Often Rct is defined as a function of the number of turns and/or the accuracy limiting voltage is defined as a function of the Rct (which is the best way to do it in my opinion).
TPY cores are very complicated to specify and to calculate/build. They shouldn't be used unless they are absolutely needed by the application. Typically, those applications are ones with multiple reclosings and a high level of DC offset, where normal relay performance classes may not be adequate.
RE: Relay CT requirement for TPY class
RE: Relay CT requirement for TPY class
Scottf, Yes, it is an integral part of determining Ual, however it is the CT design that will ultimately determine this value. In some cases it is like a dog chasing its tail when working through these designs and trying to balance the Rct to keep the Ual at a reasonable value. I have been in situations where compromises with other parameters had to be made in order to keep the Ual at a reasonable level and keep CT size so it can be manufactured. I did not say that the CT supplier will know these requirements, but has limited control on the final design size.
Slavag, you would be surprised how much TPY class is used, I know that I am. I see them more than I care to and often ask myself the questing about protection philosphies - why do you never see them in the USA market but always encounter them in Europe and Asia?? They are extensively used in China.
RE: Relay CT requirement for TPY class
Thanks a lot to you and Scottf for explanations.
I don't see TPY class in newer system.
We work for big projects with voltage level:
500, 400, 330, 220, 170, 132 KV with full range of protection relays in few parts of world. NO TPY class.
In ME and south America lot of companies request class X.
But in lot of cases is 5Pxxx.
About China..is new for me.
Best Regards.
Slava