Monkey Business

Monkey Jumping Over the Fence May Have Covered the Monkey Business

The national grid operates on a delicate balance between power generation and consumption, and when an imbalance occurs, it can cause cascading failures leading to a total grid collapse. The recent incident in Sri Lanka raises serious concerns about grid management, especially in handling renewable energy integration.

1. Over-Generation from Solar Power & Load Imbalance

• The event occurred on a weekend with clear skies, causing solar power generation to peak.

• Weekend demand was lower than usual, meaning excess power had to be managed effectively.

• The 900 MW coal power plant continued running since shutting it down is impractical due to long restart times.

• Ideally, flexible power sources like hydro and diesel should have been reduced to maintain grid balance, but this may not have been done in time.

• Excess generation with low consumption can lead to frequency surges above 50 Hz, putting stress on the grid.

2. Panadura Substation Tripping Due to a Monkey

• Normally, an animal on a transformer or line may cause a localized trip, but it should not result in a full substation shutdown.

• If a supply line at Panadura tripped, it could have caused an unexpected load shift, affecting nearby substations.

• This event might have triggered a circuit breaker cascade, isolating Panadura while impacting adjacent areas.

• If Panadura was already stressed due to over-generation, this tripping could have created a larger voltage or frequency disturbance.

3. How This Could Have Worsened the Situation Panadura Substation Tripping Removes Load

• Panadura was likely supplying power to a significant area.

• When it tripped, the load it was serving disappeared, creating an oversupply situation in the grid.

• However, power generation (especially solar) remained unchanged, further increasing the power surplus.

Over-Supply & Frequency Surge

• The power grid operates within a tight frequency range (49.5 – 50.5 Hz in Sri Lanka).

• With excess power and reduced load, the frequency could have surged beyond 50.5 Hz.

• If immediate corrective action was not taken (such as reducing hydro/diesel generation), the imbalance could have worsened.

4. Domino Effect & System-Wide Failure

• The Panadura substation trip created a localized imbalance.

• This imbalance may have led to an overload or under-voltage situation in nearby substations.

• Excess frequency forced turbines in thermal plants (like Norochcholai) to operate beyond safe limits, activating protective shutdowns.

• The instability propagated to Biyagama, a critical grid point.

• The tripping of Biyagama, a critical grid point, triggered cascading failures, leading to Norochcholai's shutdown and a complete grid collapse.

• Once it reached Lakvijaya (Norochcholai), the system protection may have detected a severe imbalance, leading to an emergency shutdown.

• Large plants (like Norochcholai) shutting down suddenly removes a massive power source, worsening the frequency drop and leading to a complete blackout.

5. Other Possible Causes & Contributing Factors

• Grid Protection & Relay Malfunction: If protection mechanisms failed or overreacted, they may have disconnected the wrong sections of the grid.

• Weak Transmission Network: A lack of redundancy (backup lines or flexible routing) could have amplified the failure.

• Lack of Proper Load-Shedding Response: If the control center failed to quickly adjust generation after the substation trip, the frequency imbalance could have escalated.

• Voltage Collapse Due to Sudden Load Drop: The sudden disconnection of industrial zones or major load centers could have created voltage instability, accelerating the cascade of failures.

Monkey Jumping Over the Fence Over-generation from solar combined with failure to disengage flexible power sources like hydro and diesel likely created an unstable grid condition. The Panadura substation trip could have been the trigger that set off a chain reaction. However, other grid weaknesses like protection relay settings, transmission network resilience, and response time of the control center could have played a role in escalating the failure.

Key Takeaways

• When a substation trips, it removes load but doesn't automatically reduce power generation. If excess solar power continues feeding into the grid, it can push the frequency too high, forcing further shutdowns.

• This over-generation scenario is just as dangerous as under-generation, making real-time grid balancing a critical operation.

Prevention & Mitigation Measures

• Real-Time Load Balancing: The National Control Center should have immediately reduced hydro/diesel generation to counteract the loss of load. With financial interests tied to diesel power generation, some beneficiaries may be reluctant to reduce output. This raises concerns about potential ‘monkey business’ in the continued purchase of diesel power.

• Automatic Generation Control (AGC): If in place, AGC should have automatically adjusted generation in response to the frequency spike.

• Battery Storage or Curtailment: Large-scale battery storage or solar curtailment mechanisms could have absorbed the excess power. (This proposal is already in consideration)

Final Thoughts While a monkey’s actions may have triggered the initial substation failure, the real issue lies in inadequate grid balancing strategies and weaknesses in protection mechanisms. Moving forward, Sri Lanka must enhance its grid flexibility to handle high renewable penetration while ensuring robust safety measures to prevent cascading failures. Otherwise, the next blackout might not need a monkey to set it off.

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Written by-- Sanjaya Gunasiri