Round Off Load Tap Changer

Round Off Load Tap Changer

A DETC is a tap changer that cannot be moved while the transformer is energized. It often has 5 positions (A,B,C,D,E, or 1,2,3,4,5). If a DETC is not exercised on a regular basis, there is increased risk that the DETC will not make properly when next moved.    

Tap changers have historically been one of the top causes of transformer failures. Faults in OLTC’s can be classified as dielectric failures (oil quality or clearance related), thermal failures (due to coking or crimp problems), or mechanical failures (contact wear and misalignment, limit switches, sheared pins on the linkage that operates the reversing switch, lubrication problems, etc.). The following electrical field tests provide information about the integrity of a transformer tap changer. exciting current tests have the ability to detect a myriad of transformer tap changer problems (DETC and OLTC), including: misalignment, coking and wear of contacts, loose moveable contacts, improper wiring from the tap winding to the OLTC, reversed connections to the preventative autotransformer (PA) of an OLTC, open- or short-circuited turns or high resistance connections in the OLTC PA, series autotransformer or series transformer, and more.

Model Explanation 

 WDP ? - ?/?-???
    W:  off-circuit
    D :  single phase
    P :  round type tap chager
    ?:  voltage regulation model
    ?:  rated current
    ?:  rated voltage
    ?:  number of tapping heads
    ?:  number of tapping position
Voltage Regulation Model
    I  :  terminal point
    II :   central point
    III :  neutral point
   IV :  Y-? conversion