Please l would like to know the factors one would have to consider in choosing the burden of instrument transformers.

 

Responding to Simon's Aug10, 11:04 am query... You have the cart before the horse:

"Burden" is the equivalent impedance of the electrical protective and measuring devices connected to the transformer(s) secondary. The
connecting leads are also included. Device impedances are furnished by the device manufacturer.

Typically, one selects a transformer having a capacity that equals or exceeds the computed burden. Burden could be expressed in Volt-Amperes @ some load angle, or resistance and reactance. All xfmr designs are required to meet specific 'Accuracy' standards. Of course there are a myriad of standards depending on the country of origin.

Advise if additional info is needed.

Regards,
Phil Corso, PE {Boca Raton, FL, USA}
[[email protected]] ([email protected])

 

Hi,

Am worker of CNFL (National Company of Light and Traction). I need to know about Burden in Current transformers. We can to speak about it ??

cesarpal [at] costarricense.cr

 

Cesar... contact me Off-List if your are unable to extract the info you need from the Control List Archives!

Regards, Phil Corso (cepsicon[at]aol[dot]com)

 

Burden is the small voltage drop across the reflected impedance of the secondary in the primary. Since the primary is normally one turn and the turns ratio is high and the secondary effectively shorted by a current instrument. it is a small but finite voltage. It would be minuscule, but for the leakage inductance of the less than optimal coupling, etc.

Regards,
cww