Influence of Transient Characteristics of
Capacitor Voltage Transformer and Current Transformer on Distance Protection
Kang Xiaoning, Zhang Xin, Suonan Jiale, Shao Baozhu, He Lu
(School of Electrical Engineering, Xi'an Jiaotong University, Xi'an 710049, China)
Abstract: The mechanism of transient overreach in the distance relays is analyzed for
the distance protection by solving differential equations, It is revealed that if the
coincident transient characteristics remain in capactor voltage transformer (CVT) and
current transformer (CT) , and the transient overreach phenomenon does not arise, while
the difference of transient characteristics between CVT and CT leads to a transient
overreach, and the unbalanced non-period component primarily induces the transient
overreach. EMTP simulation shows that the decay time of non-period component of CVT of 10
ms is much shorter than 40 ms of CT, thus the distance relays operate by mistake.
Keywords: transient overreach; capacitor voltage transformer; current transformer;
non-periodic component