Marine Protection Relays: Preventing Electrical Failures

Modern marine operations require robust electrical systems. They support propulsion and power generation, navigation, safety systems, and in-cabin automation. Nearly every major operation on a ship depends on a secure and reliable electrical network. The marine environment, however, is highly challenging. High humidity, constant vibration, changing load conditions, salt exposure, and continuous operation can cause electrical faults to emerge quickly and escalate into severe failures if they are not addressed immediately.

This is where marine protection relays come in handy. Protection relays are intelligent devices that serve to monitor electrical parameters continuously and act instantaneously in case abnormal conditions occur. They protect generators, switchboards, transformers, motors, and distribution systems from damage originating from faults such as overcurrent, short circuits, voltage irregularities, frequency deviations, and insulation failures.

Why Marine Electrical Protection is so important

Unlike land-based installations, marine electrical systems work in an environment that is constantly in motion and dynamic. It can face sudden changes of loads, in particular for vessels with dynamic positioning, heavy winches, or variable propulsion demands. A single electrical fault, if undetected, may cause equipment damage, operational downtime, or even safety risks to crew and cargo.

Marine protection relays respond to these issues by:

• Fault detection in an early stage
• Isolating faulty sections before damage spreads
• Compliance with marine class requirements
• Supporting reliable power generation and distribution
• Reducing maintenance costs and unplanned outages

Modern relays can do much more than just protection. They integrate protection, measurement, communication, and diagnostics into one compact device and are hence an integral part of smart marine electrical systems.

MTR 4P Protection Relay

The MTR 4P is designed as a programmable protection and measuring relay for single-phase and three-phase power networks approved for marine applications. It is well-suited for applications where fast response, flexibility, and accurate measurement are requested.

What Makes MTR 4P Unique

The MTR 4P offers up to 13 different protection functions grouped into six logical categories: voltage, current, frequency, asymmetry, load, and loss of mains. This enables a single device to handle several protection needs that otherwise would be handled by multiple individual relays.

Along with protection, the MTR 4P acts as a dedicated measuring point that is able to measure and calculate more than 50 electrical parameters, including voltage, current, active and reactive power, apparent power, power factor, frequency, energy consumption, total harmonic distortion, and demand values. This makes it very important not only for protection but also for system monitoring and energy analysis.

Overview of Features and Limits

• Supports AC voltage inputs up to 1000 V line-to-line
• Can handle up to 20 A AC input
• Accuracy class of 0.5 for reliable measurements
• Typical trip response time is under 50 milliseconds
• Two-stage trip settings with adjustable startup delay
• Wide range covered, universal power supply
• Password-protected settings for secure operation
• RS-485 Modbus communication for system integration
• USB interface for fast configuration using the M set software
• Type approval by GL and DNV (marine)

Typical Applications

The MTR 4P is suitable for generator protection, feeder protection, and general distribution monitoring. Its flexibility allows it to become an ideal solution for new builds, retrofit projects, and even as a spare part solution where quick replacement is needed.

MDR 2 Protection Relay

Generators are among the most important capital assets aboard any vessel. Overlooking internal failures like the failure of insulation of windings or leakage currents can lead to serious consequences. The MDR 2 is designed for the protection of generators against such internal short circuits through the use of differential protection.

How MDR 2 Protects Generators

The MDR 2 constantly compares present measurements between the two sides of the generator. If the difference is higher than its predetermined limits, the relay considers it an internal fault and releases a trip. What makes the MDR 2 effective is the capability to compensate for unbalanced current measurements, which minimizes unwanted tripping.

The MDR 2 provides dependable protection even during difficult conditions with adjustable tripping characteristics for stability. 

Key Features and Capabilities

• Combined differential and short-circuit protection
• Response time of about 70 milliseconds for correspondence
• Three-phase current detection at both generator sides
• Active compensation of unbalanced current measurements
• The measuring accuracy is 1 percent.
• LCD display integrated that shows all measurements
• Onboard event and alarm log, up to 150 records
• Available options for block protection and overcurrent protection
• DIN rail or base mounting, remote display option

Benefits deriving from Operations

The integrated display eliminates additional meters and wiring. Through commissioning and troubleshooting, engineers can quickly identify the locations of faults and review historical events that save much valuable time during maintenance and reduce downtime.

MVR 200 Series

The MVR 200 series addresses more complex protection, control, and measurement applications within marine and offshore electrical systems. Medium- and high-voltage applications within main switchboards, distribution systems, or critical power infrastructures can adopt this series.

Designed with Flexibility and Integration in Mind

It includes 16 different relay types in the MVR 200 series to enable the engineer to select exactly the protection functionality that is required for the application. The modular hardware design provides support for on-site replacement of spare part modules, which adds significant value in marine applications where access and downtime need to be minimized.

Advanced Communication and Safety Features

The MVR 200 series supports a wide range of communication protocols, including IEC 60870 and IEC 61850. This enables seamless integration into modern power management systems and vessel automation networks.

An optional arc flash protection function enhances switchgear safety by detecting arc faults using multiple sensor types and initiating fast isolation to minimize damage and risk to personnel.

Key Features and Capabilities

• Programmable logic for custom protection schemes
• Fast commissioning via the front communication port
• Password-protected user access levels
• Measurement of individual harmonics up to the 31st order
• Redundant Ethernet with Modbus TCP
• RS-485 Modbus RTU communication
• IEC 60870 and IEC 61850 communication support
• Precision power and energy measurement class 0.5
• Optional class 0.2S accuracy for energy metering
• Conformal coating option for a harsh environment 
• Marine type approval by major classification societies

KDU World, Your Licensed Partner for Marine Protection Solutions

Finding the right protection relay is merely part of the equation. Correct application, configuration, commissioning, and ongoing support are equally important, which is where KDU World plays a critical role.

 As an authorized distributor of marine equipment and services, KDU World supports vessel operators, shipyards, and offshore facilities across the UAE, KSA, Oman, Nigeria, and beyond. With deep technical expertise and access to globally approved marine protection solutions, KDU World ensures every installation meets operational, safety, and classification requirements. 

From compact protection relays like the MTR 4P to advanced generator protection with the MDR 2 and comprehensive medium voltage solutions through the MVR 200 series, KDU World provides reliable products with professional marine services.