Mechanism and Protection Optimization for False Loss-of-shunt Judgment in Station Approach Sections

Abstract

After the section occupancy logic check is enabled, home-signal closing information may enter the train control center judgment process before occupation of the first section inside the home signal is confirmed during normal entry across the home signal. The evidence required for normal entry may therefore be absent when the approach section clears, causing a false loss-of-shunt judgment. Maintenance records from Qiyang Station were used to reconstruct the sequence of home-signal closing, first-section occupation, and approach-section clearance and to analyze the mechanism by which the two types of status information enter the judgment process in different processing cycles. Two protection schemes were developed: a 3 s first-section occupation confirmation window in the train control center and a 2 s delayed closing of the home signal in the interlocking. Timeout exit, out-of-sequence occupation exclusion, route-condition checking, and coding-continuity constraints were incorporated. Case timing analysis and logical checks of abnormal scenarios show that both schemes eliminate the false judgment for the recorded normal-entry sequence while retaining the existing fail-safe response under timeout, out-of-sequence occupation, or invalid route conditions. Multi-station commissioning demonstrates implementability. However, the 3 s and 2 s values are only current engineering initial values; their cross-equipment applicability and long-term effectiveness in preventing false judgments still require operational data.