Selective Insulation Monitoring for Disconnectable Power Subsystems
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Solution Overview
Problem
Existing insulation monitoring systems in large, extensive power supply systems and high-voltage systems are inadequate in sensitivity and resource-intensive, failing to detect insulation degradation in individual subsystems until it is advanced, and are costly due to the need for additional components like isolation transformers and residual current transformers.
Innovation Solution
A method involving cyclical disconnection of subsystems using semiconductor disconnect switches with integrated energy storage, allowing insulation resistance measurement during brief intervals while the subsystem continues to operate, using standard insulation monitoring devices to determine individual subsystem insulation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If insulation monitoring is performed on the overall system with parallel connection of all subsystems, then the total insulation resistance can be determined, but the sensitivity to detect individual subsystem insulation degradation is reduced due to the parallel resistance effect
Solution Approach 1:
The patent segments the overall power supply system into individual subsystems, each equipped with its own insulation monitoring device. This allows each subsystem to be monitored independently, avoiding the parallel resistance effect that reduces sensitivity in overall system monitoring. The segmentation enables precise detection of insulation degradation in individual subsystems without being masked by other parallel-connected subsystems.
Solution Approach 2:
The patent introduces a temporal dimension by cyclically disconnecting and reconnecting subsystems. During the disconnection phase, insulation resistance measurements are performed on individual subsystems that are electrically isolated from the parallel network. This dimensional change from spatial parallel connection to temporal sequential measurement resolves the sensitivity issue while maintaining system operational continuity.
2Reliability
If localization current is injected into the overall system for fault detection, then insulation faults can be identified, but the localization current is distributed across many subsystems reducing detection sensitivity
Solution Approach 1:
Instead of injecting localization current into the entire parallel-connected system where it gets distributed and diluted, the patent segments the monitoring approach by isolating individual subsystems. Each subsystem receives the full localization current during its measurement window, maximizing the current available for fault detection and maintaining high sensitivity even in extensive systems with many subsystems.
Solution Approach 2:
The patent implements periodic disconnection and measurement cycles for each subsystem. During each cycle, a subsystem is temporarily disconnected from the parallel network, allowing concentrated localization current injection specifically into that subsystem. This periodic action ensures that the full localization current is available for fault detection in each subsystem without being distributed across the entire system, thereby maintaining high detection sensitivity.
3Power
If differential current sensors are used in high load current systems, then load monitoring is achieved, but saturation effects in soft magnetic material reduce sensor sensitivity
Solution Approach 1:
The patent segments the measurement approach by isolating individual subsystems during measurement cycles. This allows insulation and localization current measurements to be performed on small, isolated circuits rather than attempting to measure through the entire high-load parallel system. The segmentation eliminates the need for high-current-capable sensors, as measurements occur in low-current measurement modes during subsystem disconnection, avoiding saturation effects entirely.
Solution Approach 2:
The patent employs periodic measurement cycles where subsystems are temporarily disconnected from the high-load power network. During these measurement windows, the subsystems operate in a low-current state, allowing standard sensors to accurately measure insulation resistance and localization currents without experiencing saturation. This periodic switching between power delivery mode and measurement mode enables both high power handling and high measurement sensitivity.
4Measurement precision
If subsystems are cyclically disconnected for measurement, then individual subsystem insulation resistance can be accurately determined, but operational continuity is temporarily interrupted
Solution Approach 1:
The patent implements periodic measurement cycles where subsystems are temporarily disconnected for brief measurement intervals and then quickly reconnected. These disconnection periods are kept sufficiently short to minimize operational impact while long enough to complete accurate insulation resistance measurements. The cyclical nature ensures that each subsystem receives regular monitoring without requiring prolonged interruption of service.
Solution Approach 2:
The patent performs measurements during predetermined measurement windows that are scheduled in advance. Subsystems are disconnected during these pre-planned intervals when the impact on operations is minimized. By anticipating and scheduling measurement times beforehand, the system can coordinate measurements with operational requirements, ensuring that critical operations are not disrupted while still maintaining regular monitoring schedules.
Data Source
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AI summary
The invention relates to a method (1) and an electrical circuit arrangement (2) for selective insulation monitoring in a power supply system (10) with detachable subsystems (20), each of which has an integrated energy storage device (22). In this process, a cyclic, short-term disconnection (S1) of the subsystem (20) to be monitored is performed for the duration of a measurement time interval (ΔT) using all-pole semiconductor disconnect switches (SW), continued operation (S2) of the disconnected subsystem (20) to be monitored by means of its integrated energy storage device (22) during the measurement time interval (ΔT), and a measurement (S3) of an insulation resistance (Rf) of the subsystem (20) during the measurement time interval (ΔT) using a standard insulation monitoring device (IMD).