GENERATOR PREFERENTIAL AND REVERSE POWER TRIP | MARINE ELECTRICIAN

Summary

In this video, Lucky Jake explains two critical safety systems in a power management system: the reverse power trip and preferential trip. He walks through how each system works to protect the generator and essential equipment, with a focus on practical testing and troubleshooting steps. Jake demonstrates how to test the reverse power trip by lowering the generator load, and how to diagnose and repair issues with the preferential trip, particularly when breakers fail to trip. The video provides a hands-on guide to maintaining these safety systems and ensuring smooth operation in critical environments.

Takeaways

• 😀 The reverse power trip (RPT) is a safety feature designed to prevent the generator from becoming a motor if power flow reverses.
• 😀 RPT is set to activate if the generator’s load drops below a specific threshold (10% of nominal load, i.e., -220 kW for a 2200 kW generator).
• 😀 The reverse power trip circuit activates the breaker when the load decreases below the set point, isolating the generator from the system.
• 😀 Preferential trip (PT) ensures that non-essential loads (e.g., fans, reefers) are disconnected during overloads without affecting critical systems like propulsion or navigation.
• 😀 The preferential trip works to reduce load and prevent a complete system blackout by disconnecting non-critical breakers.
• 😀 The testing procedure for reverse power trip involves gradually reducing the generator’s load to trigger the trip mechanism.
• 😀 For preferential trip testing, the power management system is manipulated to simulate an overload and trigger alarms.
• 😀 A malfunction was identified when the preferential trip did not activate the breaker as expected during testing, despite the alarm being triggered.
• 😀 The issue with the preferential trip was traced to a faulty timer (57x1) that failed to activate the contactors and trip the breaker.
• 😀 After replacing the faulty timer with a spare, the preferential trip system functioned correctly, and the breaker tripped as intended.

Q & A

What is the reverse power trip and why is it important?

The reverse power trip is a protection system designed to prevent a generator from acting as a motor. It ensures that the generator doesn't become a load when power flow reverses, thus avoiding damage. This system activates when the generator load drops below a specific threshold, which is typically 10% of the nominal load.

How does the reverse power trip work in relation to the generator's nominal load?

For a generator with a nominal load of 2200 kilowatts, the reverse power trip setting is 10%. This means that if the generator's output falls below 220 kilowatts in negative power, the reverse power trip circuit will activate and trip the breaker.

What is the purpose of the preferential trip in the power management system?

The preferential trip is designed to protect essential systems like the propulsion and navigational equipment on a vessel. It will trip non-essential loads (e.g., fans, reefers) if the busbar cannot handle the total load, ensuring that the main engine continues to operate without causing a blackout.

What does the preferential trip circuit involve, and how does it function?

The preferential trip circuit involves setting thresholds on load capacity. If the busbar experiences an overload, the preferential trip activates and isolates non-essential loads to protect the essential systems. It operates by using a timer and monitoring system to control when to trip the breakers for non-essential loads.

What issues were observed during the testing of the preferential trip?

During the preferential trip test, the breakers on the main switchboard did not trip even after activating the preferential trip circuit. This issue was traced to a faulty timer (57x1), preventing the system from properly activating the breakers.

What role does the timer 57t1 play in the preferential trip system?

The timer 57t1 plays a crucial role in activating the preferential trip system. It triggers the breaker to trip when an abnormal condition is detected in the busbar. Without a properly functioning timer, the preferential trip will fail to activate.

What was identified as the cause of the malfunction in the preferential trip system?

The malfunction was caused by a defective timer (57x1). The contacts in the timer remained open, preventing the system from sending the correct signal to the breakers, thus failing to activate the preferential trip circuit.

How was the defective timer in the preferential trip system fixed?

The defective timer was replaced with a spare, and its settings were copied from the faulty timer to the new one. After installation, the preferential trip system worked correctly, and the breaker tripped as expected.

Why is it important to understand the system settings when performing tests like the reverse power trip?

Understanding the system settings is crucial for performing tests safely and accurately. It helps avoid confusion when the load values reach negative or abnormal levels, ensuring the proper operation of safety systems like the reverse power trip.

What are the steps involved in performing a reverse power trip test?

The reverse power trip test involves lowering the load on the generator slowly until it reaches the set threshold (e.g., negative 220 kilowatts). Once this point is reached, the reverse power trip circuit will activate, and the breaker will trip. It's essential to monitor the load and ensure the system is functioning correctly.