Microcomputer-Based Protection Solution: Busbar Protection Relay

1. Overview

Busbar protection is a critical component of power system protection, serving the essential mission of rapidly isolating busbar faults and preventing fault propagation. With the advancement of smart grid construction, busbar protection faces dual challenges: current transformer (CT) saturation interference and communication delays in distributed architectures. Innovative technological solutions are required to ensure the reliability and speed of protection systems.

2. Core Challenge Analysis

2.1 Risk of Maloperation Due to CT Saturation

Current transformers are prone to saturation during close-in busbar faults, causing severe distortion of secondary currents. Traditional protection algorithms may misjudge faults due to sampling distortions. Particularly in complex scenarios where external faults evolve into internal faults, anti-saturation capability directly impacts the reliability of the protection system.

2.2 Communication Delays in Distributed Architectures

Modern substations adopt distributed protection architectures, where data transmission delays between central units and bay units directly affect protection operation speed. In ultra-high voltage systems (750kV and above), millisecond-level delays can significantly impact system stability.

3. Solutions

3.1 Weighted Anti-Saturation Algorithm

A dynamic weighting technique is employed for real-time quality assessment of CT secondary currents:

• Saturation Detection: Monitors current waveform distortion rates in real time to identify saturation onset.

• Dynamic Weighting: Assigns higher weights to non-saturated segments during the initial fault stage and automatically reduces weights during saturated segments.

• Data Restoration: Uses interpolation based on non-saturated data to restore accurate fault currents.

Application Results: Practical implementation at a 220kV substation showed that the algorithm improved accurate fault zone identification to 99.8%. The busbar fault clearance time was consistently maintained at 8-12ms, effectively preventing protection maloperation due to CT saturation.

3.2 Distributed Optical Fiber Communication System

A high-performance point-to-point optical fiber communication architecture is adopted:

• Deterministic Delay: Dedicated fiber-optic links ensure stable transmission delays.

• Clock Synchronization: Precision timing mechanisms achieve sampling value synchronization accuracy within ±1μs.

• Redundant Configuration: Dual-network redundancy design enhances communication reliability.

Validation: Operational data from a 750kV smart substation showed that communication delays between central and bay units were less than 1ms, with a 100% correct operation rate, meeting the stringent requirements of ultra-high voltage systems for protection speed.

3.3 Virtual Busbar Technology

Software-defined busbar topology enables flexible configuration:

• Graphical Modeling: Visual tools define connectivity relationships of primary equipment.

• Template Library Support: Includes standard topology templates such as double-busbar segmentation, 3/2 breaker scheme, and ring busbar.

• Online Reconfiguration: Enables adaptive adjustment of protection logic without power interruption.

Efficiency Gains: Practical application at a converter station reduced protection configuration time from 48 hours (traditional methods) to 2 hours, effectively avoiding manual configuration errors and significantly improving project implementation efficiency.