SEG HighTECH Line MRN3 PROTECTION TECHNOLOGY MADE SIMPLE MAINS

SEG HighTECH Line MRN3 PROTECTION TECHNOLOGY MADE SIMPLE MAINS 

Introduction and application 

The MRN3 is a universal mains decoupling device and covers the protection requirements from VDEW and most other utilities for the mains parallel operation of power stations.     Over/ and under voltage protection, over/ and under frequency protection, extremely fast decoupling of generator in case of mains failure (MRN3-1) or rate of change of frequency df/dt (MRN3-2) Because of combination of three protection functions in one device the MRN3 is a very compact mains decoupling device. Compared to the standard used single devices it has a very good price/performance ratio. For applications where the single protection functions are required SEG Electronics GmbH can offer the single MR-relays as follows:     MRU3-1 four step independent over-/ and under voltage protection (also used for  generator earth fault protection). MRU3-2 two step independent over-/ and under-voltage protection with evaluation of the  symmetrical voltage components. MRF3  four step independent over/ and under- frequency protection and two step  frequency gradient supervision df/dt. MRG2  generator mains monitor / vector surge  detection. 

Features and characteristics

Microprocessor technology with watchdog, effective analog low pass filter for suppressing harmonics when measuring frequency and  vector surge, digital filtering of the measured values by using discrete Fourier analysis to suppress  higher harmonics and d.c. components induced by faults or system operations, integrated functions for voltage, frequency and vector surge in one device as well as single voltage, frequency and vector surge devices, two parameter sets, voltage supervision each with two step under-/and overvoltage detection, frequency supervision with three step under-/or over frequency (user setting), completely independent time settings for voltage and frequency supervision, adjustable voltage threshold value for blocking frequency and vector surge measuring, display of all measuring values and setting parameters for normal operation as well as  tripping via a alphanumerical display and LEDs, display of measuring values as primary quantities Storage of trip values and switching-off time (tCBFP) of 5 fault occurrences (fail-safe of  voltage), recording of up to eight fault occurrences with time stamp for blocking the individual functions by the external blocking input, parameters can be set  according to requirement, user configurable vector surge measurement 1-of-3 or 3-of-3, reliable vector surge measuring by exact calculation algorithm, suppression of indication after an activation (LED flash), free assignment for output relays, display of date and time, in compliance with VDE 0435, part 303 and IEC 255, serial data exchange via RS485 interface possible; alternatively with RS485  Pro-Open Data Protocol or Modbus Protocol. 

3.1.1 Analog input circuits The analog input voltages are galvanically decoupled by the input transformers of the device, then filtered and finally fed to the analog digital converter. The measuring circuits can be applied in star or delta connection (refer to chapter 4.3.1). 3.1.2 Blocking input The blocking function can be set according to requirement. By applying the auxiliary voltage to D8/E8, the previously set relay functions are blocked (refer to 4.8 and 5.7.1). 3.1.3 Reset input Please refer to chapter 5.9.1. 

3.1.4 Output relays  The MRN3 is equipped with 5 output relays. Apart from the relay for self-supervision, all protective functions can be optionally assigned: Relay

1: C1, D1, E1 and C2, D2, E2 Relay 

2: C3, D3, E3 and C4, D4, E4 Relay 

3: C5, D5, E5 Relay 

4: C6, D6, E6 Relay 

5: Signal self-supervision (internal failure of the unit) C7, D7, E7 All trip and alarm relays are working current relays, the relay for self supervision is an idle current relay. 

3.1.5 Fault recorder The MRN3 has a fault value recorder which records the measured analog values as instantaneous values. The instantaneous values UL1; UL2; UL3 for star connection or U12; U23; U21 for delta connection are scanned at a raster of 1.25 ms (at 50 Hz) and 1.041 ms (at 60 Hz) and saved in a cyclic buffer. It is possible to store 1 - 8 fault occurrences with a total recording time of 16 s (with 50 Hz) and 13.33 s (with 60 Hz) per channel.  

Storage division Independent of the recording time, the entire storage capacity can be divided into several cases of disturbance with a shorter recording time each. In addition, the deletion behavior of the fault  recorder can be influenced. No writing over If 2, 4 or 8 recordings are chosen, the complete memory is divided into the relevant number of  partial segments. If this max. number of fault event has been exceeded, the fault recorder block any further recordings in order to prevent that the stored data are written over. After the data have been read and deleted, the recorder to ready again for further action. Writing over If 1, 3 or 7 recordings are chosen, the relevant number of partial segments is reserved in the complete memory. If the memory is full, a new recording will always write over the oldest one.