Current Transformer Dimensioning for Numerical Protection Relays

An analytical approach for removal of decaying DC component considering frequency deviation

“…Related to CT Time constant (20) As mentioned in [41,42], the amount of CT time constant is much larger than system time constant. The value is large enough that in t and 2 t steps, its differentiation to be considered zero.…”

CT dimensioning for transmission line protections-an investigation into increasing saturation tolerance for protection functions

“…However, to what extent the CT could be under-dimensioned, without any compromise on the basic requirements of selectivity and security, were not explicitly covered. In Reference [12], the CT dimensioning for numerical relays was considered in more detail and some examples were presented for CT dimensioning. The degree of saturation that a relay can tolerate is dependent upon the underlying algorithms.…”

“…The degree of saturation that a relay can tolerate is dependent upon the underlying algorithms. This paper tries to refine the CT dimensioning concepts proposed in Reference [12] and covers saturation tolerance of two different commonly used distance relay algorithms and based on these studies suggestions are also made to enhance the saturation tolerance of the protection devices. The effect of line length on the CT dimension and the impact of the CT saturation on the line differential protection, breaker fail and fault location is also studied.…”

“…In Reference [12], the formula for the K CF is given and it is defined as the CT remanent factor. It is given by…”

Approximation of Parameters of Fundamental Component Of Secondary Current Distorted by CT Saturation

“…CT saturation can also follow the premagnetization of the CT core or the extremely large ac current magnitude [2]- [4], [17]. As analyzed in [5] any even correctly selected CT is prone to CT magnetic core saturation. In such conditions, a secondary current is not reliable anymore and can make the protection or control systems fail to operate correctly.…”