I. Product Positioning

Island Protection / Grid Disconnection Relay Protection Device, compatible with gas turbines, diesel generator sets, waste heat power stations, distributed photovoltaic / biogas generators. When the generator sets are connected to the grid, it monitors grid abnormalities. In the event of grid voltage loss / frequency loss / phase offset, it instantly trips the grid connection switch of the generator set to prevent the island from asynchronous grid connection and damage to the generator set. This is a standard component of the European VDEW / German grid standard and is often used in conjunction with Woodward 505, 8440-1706D speed control boards.

Integrated Protection Functions (ANSI Standard Protection Codes) Table

Protection Type ANSI Code Explanation

Over/Under Voltage Protection 59/27 Three-stage voltage time curve, customizable inverse-time U-t characteristic

Over/Under Frequency Protection 81O/81U 3 levels of frequency setting + delay setting

Vector Surge (Phase Angle Offset) 78 Vector Surge MRN3-1 core, rapid tripping for grid disconnection phase change (millisecond level)

Frequency Rate of Change ROCOF (df/dt) 81df Optionally available, rapid decoupling for frequency ｄｒｏｐ

Three. Electrical Specification Parameters

Voltage Input: PT secondary 100V (MRN3-11D standard); optional 230V/400V three-phase voltage sampling, power consumption < 1VA

Applicable Frequency: 40～70Hz (50/60Hz units are universal)

Power Supply: AC/DC 85～265V universal auxiliary power supply

Output Contacts: Multiple passive trip dry contacts (5A/250VAC), one alarm, one grid trip

Communication: RS485 Modbus-RTU, equipped with SmartView software for parameter setting and fault recording reading

Installation: Standard DIN rail / 19-inch plug-in frame installation, plug-and-unplug with core-pulling structure

Operating Temperature: -20℃～+60℃, industrial protection inside cabinet

Four. MRN3 Model Classification

MRN3-11D (This product): Vector offset + over/under voltage + over/under frequency (Vector Surge as the main criterion, mainstream for European and American thermal power / diesel units)

MRN3-21D: ROCOF (df/dt frequency rate of change) as the main criterion, used for wind power and photovoltaic distributed power sources

MRN3-31D: Full function (vector + ROCOF + voltage/frequency) high-end model

Five. Compatible with Woodward Speed Control System

Companion: 505 speed controller, 8440-1706D, 8290-191, 8402-271 generator speed control module, forming a complete set of unit speed control + grid decoupling protection system, commonly used spare parts for power plants, refinery turbine units.

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