The 220V emergency equipment transformer was tripped. Actions of the ETO on the vessel

Greetings! Today we have switched off all 220V emergency equipment on the vessel, including 220V emergency lighting. In this article we will analyze the cause of this breakdown, as well as ways to find and fix the problem.

Service emergency transformers 440 / 220 V

In this situation, it is necessary to immediately check the emergency distribution board, which contains all the automatic switches (breakers) for emergency power sources on the ship.

First of all, we are interested in the circuit breakers of the primary and secondary windings of the emergency service transformer. On the panel we can see that the primary winding circuit breaker of the 440V transformer was tripped and the overcurrent relay was activated.

Emergency distribution board 220V

Primary winding circuit breakers 440 V (circuit breaker is on)

Secondary winding circuit breakers 220 V

A short circuit occurred in the emergency equipment circuit, and the circuit breaker of the primary winding of the 440V transformer was tripped. After further investigation and information from the captain's mate, it turned out that the blackout occurred while all the exterior lighting on the vessel was turned on.

Current protection relay

We can conclude that a short circuit occurred in the 220V emergency lighting circuit, which contributed to the operation of the current protection. Thus, as a result of checking and sequentially disconnecting all 220V emergency lighting circuits, a short circuit was discovered in the lifeboat deck lighting floodlight.

After disassembling the floodlight, it turned out that a short circuit had occurred in the contact group of the lamp socket.

Disassembling the floodlight (water inside)

Melted (burnt) lamp base

Lamp socket

Burnt out contacts of the lamp holder

Installing a new floodlight

The photos above show that the contact group of the floodlight holder burned out and the phases shortened with each other.

A natural question arises: can such a problem completely de-energize the entire service emergency transformer, why was the breaker of only secondary winding not tripped, which directly cuts off only this floodlight. Apparently the short circuit current was so large that it immediately tripped the primary winding of the transformer without any time delay. This is how the transformer protection relay works.

Emergency service transformer data

Typically, a ship has four 440/220 V service transformers. The main two (main) and emergency two (emergency) 440/220 V transformers provide power to 220 volt consumers, which usually include lighting, chargers, fire alarm systems, and various consoles in the engine room and on the bridge, and other auxiliary equipment 220 V.

Emergency consumers 220V

One main and one emergency transformer are always running, the other two are backup. If one transformer fails, you can switch to a backup one.

Overcurrent relay operating diagram

All this is done manually; in the photo of the circuit breakers you can see the mechanical blocking of the circuit breaker of one transformer, so they cannot work at the same time.

The protection relay has tripped

When the circuit being measured is overloaded, the current protection relay acts on the shunt relay of the circuit breaker and trips the circuit breaker. The circuit diagrams above show how these relays work.

A short circuit in electricity refers to a situation where an unintended low-resistance connection occurs between two points in an electric circuit. This can cause an excessive amount of current to flow through the circuit. Here’s a detailed explanation:

Key Points about Short Circuits:

1. Cause:

   • Direct Connection: A short circuit typically occurs when there is a direct connection between the positive and negative terminals of a power source, bypassing the intended path of the circuit.
   • Faulty Wiring or Insulation: Damaged or exposed wires can touch each other, leading to a short circuit.
   • Component Failure: Internal failures within electrical devices can cause a short circuit.

2. Effect:

   • High Current Flow: Because the resistance is very low, the current flow increases significantly.
   • Heat Generation: The excessive current generates a lot of heat, which can damage components, melt insulation, or even cause fires.
   • Circuit Damage: Electrical components and wiring can be permanently damaged by the high current and heat.

3. Protection Mechanisms:

   • Fuses: A fuse contains a thin wire that melts and breaks the circuit when excessive current flows through it.
   • Circuit Breakers: These automatically shut off the electrical supply when they detect a current overload or short circuit.
   • Ground Fault Circuit Interrupters (GFCIs): These detect differences in current between the hot and neutral wires and cut off the power if an imbalance is detected, which can indicate a short circuit or ground fault.

Example Scenario:

Imagine a household electrical circuit designed to power a light bulb. The normal path for electricity is through the power source, the switch, and the light bulb. If the wiring insulation wears out and the wires inside the lamp touch each other directly, it creates a short circuit. The electricity now bypasses the bulb and flows directly from one wire to the other, causing a surge of current. This surge could blow a fuse or trip a circuit breaker, preventing potential fire hazards or damage to the electrical system.

Importance of Short Circuit Protection:

• Safety: Prevents fires and electric shocks.
• Equipment Protection: Protects appliances and electrical devices from damage.
• Circuit Longevity: Ensures the longevity and reliability of electrical systems by preventing overheating and damage.

Understanding short circuits and the importance of protective measures helps in designing safer electrical systems and troubleshooting electrical problems effectively.