Abstract
Special attention is paid to high-speed relay protections’ operation in transient modes due to a number of major failure events that have occurred over the past 10 years in the power system of the Russian Federation. Operation of power transformer’s differential protection in case of internal short circuit is studied in this research. False blocking of protection is possible in such mode due to saturation of current transformers. A value of blocking time may exceed the maximum permissible short-circuit disconnection time under conditions of maintaining the dynamic stability of the power system. Primary and secondary currents in transient modes are obtained by simulation of short circuits. Windings of the modeled current transformers are connected in a star to a null wire. RMS values are calculated using a mathematical model of the Fourier filter. The current transformers were checked according to the methods declared in PNST 283-2018 and GOST R 58669-2019. The analysis carried out in this work allows to estimate possibility of long-term blocking of the differential protection of a power transformer in case of internal short circuit, especially in case of significant value of time constants.
Highlights
The problem of relay protection’s stable operation in case of deep saturation of current transformers (CT) is relevant in Russian Federation [1,2,3,4]; it has obtained exceptional topicality since 2014 [5,6,7]
In this work, such disoperation of protection is studied using the example of differential protection (DP) of a power transformer (PT)
If the protection is triggered later, such a delay is considered unacceptable, which is tantamount to a failure in operation, which means that violations of the dynamic stability of the EPS are possible
Summary
The problem of relay protection’s stable operation in case of deep saturation of current transformers (CT) is relevant in Russian Federation [1,2,3,4]; it has obtained exceptional topicality since 2014 [5,6,7]. Estimation of relay protection will be relevant for a long time in Russian Federation In this work, such disoperation of protection is studied using the example of differential protection (DP) of a power transformer (PT). Such protection may be blocked if there is special programming against incorrect operations in case of magnetizing inrush based on detection of second harmonic of fault current.
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