I. Introduction
Time is the basic element of information acquisition, transmission, fusion and application. The accurate and reliable acquisition and determination of time information by the timing system is the premise for the stable operation of important national fields such as electric power, transportation, finance, communication, national defense and so on [1]. Timing equipment relies on its own timing system to synchronize time information through external timing sources [2], or uses its internal clock to autonomously maintain time [3]. As the most popular timing source, GNSS timing is one of the main means to obtain accurate time and maintain precise time synchronization. However, GNSS signals are vulnerable to human malicious interference, resulting in timing refusal or timing deception [4]. While, the internal clock cannot keep time accurately and stably for a long time due to its own clock drift characteristics [5]. Therefore, it is necessary to analyze in real time the GNSS interference to the timing system, and moreover the type of the detected interference, in order to prompt the comprehensive utilization of reliable backup means to perform timing enhancement and anti-interference when necessary according to the actual timing requirements [6], so as to avoid the time information output by the timing system being unavailable or deceived. As a result, it can provide the necessary support for the timing system to obtain time information and maintain time synchronization accurately and reliably for a long time in a complex environment.