04-02-2010, 09:53 AM
pt means Potential Transformer,ct means Current Transformer
Optical current and voltage sensors are an alternative to conventional iron-core instrument transformers (pt and ct commonly using in measuring instruments) ,and Optical current and voltage sensors having advantages include improved accuracy over a broader dynamic range, wider band-width, zero risk of explosive failure and lighter weight.
read
http://freepatentsonline5583428.html
http://library.abbGLOBAL/SCOT/scot232.ns...dustry.pdf
http://tdworldmag/power_move_cts_pts/