Grid Islanding & WAMS Solutions

Process of Implementation

To constantly monitor the synchronicity of the complete grid and phase angles between key transmission points to ensure stability and dynamically adjust generation and load as needed, to maintain a safe operational range.

A Grid Island shall be formed in the following scenarios

1. When the grid frequency falls below a specific frequency (example falls below 47.9Hz).
2. When the ROCOF (df/dt) value indicates a shift in the grid frequency eventually falling below 47.9Hz.
3. When any phase angle of any zone deviates from the other zones and goes out of and exceeds a permissible threshold.
4. A malicious, hostile attack, (which would include a cyber-attack) would normally lead to the occurrence any one or all of the above events or conditions.
5. In such a scenario, unless synchro-phasors (Phasor Measurement Units) are used to monitor the phase angles and their deviations, the stability of the grid cannot be effectively ensured.
6. In the event of any one of above scenarios occurring, the tripping of the entire zone / entire feeder line tripping process must be completely automated implemented, with an option of manual intervention.

Why choose PMU based Islanding?

• The power grid in a synchronized, homogeneous structure and relying only on the detection of an under-frequency, or an over-frequency condition to detect a grid-instability condition is fraught with numerous pitfalls.
• A phase angle variation exceeding the safe threshold between any two (or more) power generation points of the grid can cause the grid to become unstable and collapse. The grid can be rendered unstable without causing an under-frequency or over-frequency condition, by simply by manipulating the phase angle at one, or more than one, power generating sites.
• In a modern, distributed grid, which consists of multiple elements of power generation and power generating locations consisting of thermal, wind and solar, the possibility of occurrence and the susceptibility to such an attack becomes even more imminent.

What is required to implement a grid islanding scheme?

• High-speed communications network
  Transport PMU data and carry protection signaling
• Reference clocks synchronized to the GPS / NavIC satellite system
  Time stamping and reading accuracy
• Phasor Measurement Unit
  Frequency, load, and generation readings
• Digital Teleprotection (DTPC) equipment
  Protection Signaling and decoupling action
• Central Control Intelligence
  Decision making based on acquired data

Key Advantages of PMU and Centralized Data Processing based Grid-Islanding Scheme:

• Real-time Monitoring and Control: PMUs provide high-speed, real-time monitoring and control capabilities, offering a more accurate and immediate understanding of grid status compared to the slower and less precise response of standalone under-frequency relays.
• Wide-Area Situational Awareness: The integration of PMUs with Tele-protection and CPU enables comprehensive situational awareness across the grid, facilitating coordinated responses. In contrast, standalone relays only monitor local frequency changes.
• Data Accuracy and Resolution: PMUs offer high-resolution data with precise time synchronization, crucial for detecting grid anomalies. Standalone under-frequency relays lack this level of precision.
• Speed of Response: The combined system's integration allows for faster response times, which is critical during grid disturbances, whereas standalone relays react slower due to their reliance on frequency changes alone.
• Dynamic Stability Assessment: PMUs can provide real-time dynamic stability assessments, giving early warnings of potential instabilities. Standalone relays are limited to frequency-based detection.
• Enhanced Protection and Control: Combining protection, control, and monitoring in a unified system improves grid reliability and security, which is not achievable with standalone under-frequency relays.
• Adaptive and Predictive Capabilities: The advanced algorithms and central processing of PMUs enable adaptive and predictive analysis, unlike the fixed, reactive approach of standalone relays.
• Integration with Modern Grid Technologies: PMUs easily integrate with other smart grid technologies, enhancing overall grid management, while standalone relays are limited in this aspect.
• Data Logging and Analytics: PMUs offer extensive data logging and advanced analytics, aiding in post-event analysis and system improvements, whereas standalone relays provide basic data logging.
• Scalability and Flexibility: PMUs are highly scalable and flexible, making them suitable for complex and evolving grid environments. Standalone relays have limited scalability.
• Reliability and Redundancy: The combined system's multiple data sources and centralized processing enhance reliability and redundancy, compared to the single-point measurement of standalone relays.

This comparison highlights the significant advantages of using PMUs with Tele-protection and a CPU over standalone under-frequency relays for grid islanding, particularly in terms of real-time monitoring, situational awareness, high coordination and advanced protection and control capabilities.