Komprehensibong Solusyon sa Proteksyon Batas Microprocessor para sa Malalaking Generator

1. Overview

Kinahanglan ang pagkakaron sa maong sistema sa pag-usbong sa mas mataas nga mga parametro, mas dako nga kapasidad, ug mas komplikado nga grid nga struktura, ang ligid ug matumong operasyon sa mga generator unit usa ka kritikal nga bahin sa kabuok nga grid nga pagkakumpiyansa. Ang tradisyonal nga relay protection devices adunay mga hamubo sama sa blind zones ug insuficiente nga sensitibidad sa pag-atiman sa komplikado nga internal generator faults. Kini nga solusyon gigamit ang advanced microprocessor-based protection technology, nag-integrate sa multi-source information ug intelligent algorithms aron mobuntag og mabilis, reliable, ug comprehensive nga protection system alang sa dako nga mga generator (e.g., thermal, nuclear, ug hydroelectric units). Ang layo niini mao ang pagtukod sa protection blind spots ug pag-aseguro sa seguridad sa power generation assets.

2. Core Challenges

Ang dako nga mga generator nakaadto sa daghang internal fault threats sa panahon sa operasyon, kasama ania:

• ​Stator Winding Faults: Phase-to-phase short circuits, inter-turn short circuits, ug ground faults. Ang inter-turn short circuits, partikular, adunay gamay nga initial fault currents, nagpakita sa sila mahirap mogamit sa tradisyonal nga transverse differential protection tungod sa inherent blind zones.
• ​Rotor Circuit Faults: Single-point ground faults, double-point ground faults, ug open o short circuits sa excitation circuit. Bagama may single-point ground fault makapahimulos sa operasyon, ang iyang pagpatuloy isip double-point ground fault makapadaog og magnetic asymmetry ug severe unit vibration.
• ​Abnormal Operating Conditions: Reverse power, loss of excitation, over-excitation, overvoltage, ug frequency abnormalities. Bagama dili instantaneous faults, kini nga kondisyon makapabati sa generator o mapanganos sa grid stability.

3. Detailed Solution

Ang aming microprocessor-based protection solution nag-adopt og hierarchical distributed architecture. Ang core protection relay nag-integrate og robust hardware processing platform sa mature protection algorithms, as detailed below:

3.1 For Stator Inter-Turn Short Circuits: Multi-Criteria Composite Protection

Arong tubagon sa insensitivity sa tradisyonal nga transverse differential protection sa inter-turn short circuits sa samang phase, kini nga solusyon gigamit ang multi-criteria fusion decision algorithm, significant improvement sa detection reliability ug sensitivity.

• ​Technical Principles:
• Negative-Sequence Power Direction Criterion: Nag-monitor sa negative-sequence current ug voltage sa generator terminals aron magkuha sa direction sa negative-sequence power. Ang internal asymmetric faults (e.g., inter-turn short circuits) makapag-generate og negative-sequence source, ang power direction flowing gikan sa generator padung sa system, enabling accurate internal fault detection.
• Third Harmonic Voltage Variation Criterion: Nag-track sa amplitude ratio ug phase difference tali sa neutral ug terminal third harmonic voltages. Ang inter-turn short circuits makapabati sa inherent distribution pattern sa third harmonic voltages, to which this criterion is highly sensitive.
• Neutral Point Displacement Voltage Criterion: Nag-serve isip auxiliary enhancement aron mapataas ang reliability.
• ​Performance Advantages:
• High Sensitivity: Capable of detecting minor inter-turn short circuits as low as 0.5%.
• Rapid Operation: Full operation time under 20 ms, significantly limiting fault damage.
• High Reliability: Multiple criteria interlock or operate in parallel to prevent maloperation and avoid failure to operate.
• ​Case Study: After implementation in a 500MW coal-fired generator, the solution achieved 98% sensitivity in detecting inter-turn short circuits, successfully preventing major burn-out accidents caused by minor insulation defects.

3.2 For 100% Stator Ground Fault Protection: Dual-Technology Fusion Positioning

Ang traditional fundamental zero-sequence voltage protection adunay blind zones near the neutral point. Kini nga solusyon nag-combine og duha ka mature technologies aron makamit ang 100% protection coverage from the terminals to the neutral point.

• ​Technical Principles:
• Conventional Zone (85–95%): Uses the third harmonic voltage ratio method to protect most of the stator winding from the neutral point toward the terminals.
• Blind Zone Compensation (Near Neutral Point, 5–15%): Employs injection-based stator ground fault protection. A low-frequency (20Hz or 12.5Hz) voltage signal is injected into the rotor circuit, and changes in the injection current are monitored to accurately calculate insulation resistance and fault location, completely eliminating blind zones near the neutral point.
• ​Performance Advantages:
• 100% Coverage: No blind zones, ensuring full stator winding protection.
• Precise Localization: Accurately pinpoints ground fault locations for targeted maintenance.
• ​Case Study: At a nuclear power plant, the solution successfully located a ground fault at only 3% from the neutral point, with less than 1% error, enabling planned maintenance and avoiding unplanned outages.

3.3 For Rotor Circuit Health: Dynamic Monitoring and Early Warning

Rotor circuit faults, particularly open rotating diodes, are common hidden dangers. This solution shifts from "post-fault protection" to "pre-fault warning" through real-time monitoring.

• ​Technical Principles:
• High-frequency current transformers (CTs) or dedicated monitoring modules installed at slip rings collect real-time excitation current waveforms.
• Built-in algorithms perform Fast Fourier Transform (FFT) harmonic analysis on the current.
• Open rotating diodes cause severe distortion of the excitation current waveform, significantly increasing characteristic harmonics (e.g., the fifth harmonic).
• ​Performance Advantages:
• Early Warning: Issues alerts based on harmonic content exceeding thresholds (e.g., fifth harmonic exceeding 8%), prompting maintenance checks on the rotating rectifier bridge before faults occur.
• Prevention of Escalation: Timely warnings prevent serious accidents such as insulation damage due to excitation current loss and rotor overheating.
• Condition-Based Maintenance: Provides critical data for predictive maintenance.

4. Summary and Value

This microprocessor-based protection solution integrates advanced sensing technology, signal processing algorithms, and multi-criteria intelligent decision-making to address traditional pain points in generator protection:

• Eliminates protection blind zones, achieving 100% coverage for stator inter-turn short circuits and ground faults.
• Transforms post-fault protection into pre-fault warning, effectively preventing faults through dynamic rotor monitoring.
• Validated by real-world cases, the solution offers high sensitivity, speed, and reliability, meeting the safety requirements of large and mega generators (500MW and above).