Preferential Tripping & Its Role in Marine Power Management


It is common to point out Pref Trip alarms in the control room of the ship. These alarms are part of the preferential tripping system for efficient power management in marine vessels. This cutting-edge protective arrangement in futuristic vessels is vital to prevent power failure and blackout.

In this blog post, we provide an overview of the preferential trip mechanism and why it is an integral part of marine power management.

What is Preferential Tripping in Marine Electrical System

Preferential tripping is a schematic electrical arrangement in the generator protection system. It cuts the non-essential load on the non-essential circuit from the chief busbar whenever there is a current overload or fault in the main supply. The non-essential circuit on a ship includes air conditioners, exhaust fans, onboard kitchen appliances, and ventilation units. This type of tripping allows effortless and safe connectivity after the issues are addressed.

Preferential Tripping Arrangement – An Overview

Here is a summary of the construction, components, and operation of the preferential trip circuit.

Structural Framework

The preferential trip is a type of relay trip circuit comprising a dashpot model and an electromagnetic coil. This arrangement is connected to an alarm system to raise an alert when an overload happens. Furthermore, the tripping circuit is connected to a complex mechanical infrastructure for instant operation in case of overload or emergency.

The circuit dashpot system boasts a compact cylinder containing a moving plunger (piston). There is high-viscous silicon fluid in the cylinder and an orifice to regulate the movement of the piston.

Such configuration on the electricity board can have multiple stages of tripping circuits, depending on the size of the vessel and the volume of electrical installations.

Working Principle

Under normal conditions, the flow of current occurs along the electromagnetic coil. This arrangement has a spring to prevent contact in the linkages.

When the load of the current exceeds the normal range, the plunger in the dashpot moves up. The piston has a tiny hole to allow the displacement of the silicon fluid. The viscosity of the silicon oil determines the time lag.

The movement of the piston prompts the electromagnetic coil to pull up the linkage against the force of the spring while governing the instantaneous circuit operation. As overload occurs, the electromagnetic coil stimulates the alarms to raise a warning.

The operation in preferential tripping is scheduled every five seconds to eliminate the load. If the load persists beyond 15 seconds, the alarm with sound and lighting raises an alert.

Advantages of Automated Preferential Trips

Preferential tripping is a highly beneficial safety feature in the electricity distribution module on a vessel. It protects expensive marine electrical equipment and accessories from damage due to partial current overload or critical electrical failure.

Here are a few reasons, this type of relay trip circuit design is easy to integrate into the electrical systems in modern ships.

Firstly, this form of tripping configuration eliminates the loss of power to the vital operations on a vessel. It controls the working of the main circuit breaker trip to prevent generator overload and blackout.

Secondly, preferential tripping ensures the ship receives an uninterrupted power supply from the generator for safe navigation. The generators can perform well under normal load and continue energy transmission to move the propellers. Thus, the mechanism does not affect the essential operations.

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