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Microprocessor Relay of Protection for Electric Motor 6/10 kV
RDC-01-057-4, RDC-01-057-5


RDC-01-057-4 - microprocessor relay of protection for electric motor 6/10 kV
RDC-01-057-4

The protection relays of motor RDC-01-057-4, RDC-01-057-5 with alternating and direct operational voltage (with digital control and indication of controlled parameters) are intended for protection of asynchronous electric motors with voltage of 6/10 kV from the following situations:

  • Short-circuit (current cutoff);
  • Current overloading;
  • Asymmetry of loading (phases А and С);
  • Underrunning (phases А and С);
  • Rotor blocking;
  • Single-phase ground short circuit (GSC) for zero sequence current (3 Io);
  • Overvoltage of motor;
  • Reduction of motor supply voltage;
  • Wrong phase rotation of voltage.

There are following modifications of the relay:

Modifications Operational power supply of the relay Checking of line supply voltage of the motor Current checking of motor
RDC-01-057-4 Single-phase, AC/DC
100, 220V, 50Hz
no а) for phases А and С, checking of (3 I0) at connection of external current transformer of zero sequence current;
b)for phases А, С.
RDC-01-057-5 Single-phase, AC/DC
100, 220V, 50Hz
3x100 V, 50 Hz

The relay has an opportunity to turn off the action of the following functions:

  • Current cutoff;
  • Protection against maximum voltage (RDC-01-057-5);
  • Protection against minimum voltage (RDC-01-057-5);
  • Protection for no-load, dry course;
  • Protection for current asymmetry;
  • Protection for rotor blocking;
  • Protection against ground short circuit;
  • Protection against wrong phase rotation (RDC-01-057-5).

The relays can work in one of two modes:

  1. Current checking in the phases А and С and 3Io;
  2. Current checking in the phases А and С.

At the same time (except protective functions) the relays have a possibility of monitoring:
     - consumption current for phase (IA, IC), 3I0.
     - network frequency;
     - motor term of life;
     - line voltage in the network (UAB, UBC, UCA) (modifications with voltage checking).

The relays are manufactured:
     - in climatic modifications for deliveries to areas with a temperate and frigid climate;
     - in climatic modifications for deliveries (export) to areas with tropical climate.


SUZD - the stations of control of electric motors

At the enterprise on the basis of the protection devices of the RDC series the stations of control of electric motors are produced. These stations are intended for work with the three-phase asynchronous motors 550 W – 350 kW of various producers. The stations are made according to various schemes with a possibility of a full complete set of electric equipment and are intended for automatic and manual control, automation, scheduling and also in various systems of water supply where asynchronous motors are used. The stations automatically support the set pressure in the system of water supply or the set level in the tank, provide complex protection of the electric motor against emergency operation. Learn More...



Main technical characteristics of the relays RDC-01-057-4, RDC-057-5


Power supply
Rated (single-phase) operational supply voltage of the relay (direct, alternating), Urated op. AC/DC 100, 220 V
Rated frequency 50 Hz
Power consumption, not more than 5 VA
Rated input signals
Rated input alternating current of phases: А and С or А, В, С, Irated 5 A
Rated current Irated, 3I0 1 A
Rated input (line, three-phase) voltage of the controlled network, Urated 100 В
Average main error of voltage measurement 2,5 %
Average main error of motor current measurement ±2,5 % / 5 %
Protection settings for voltage
Setting of rated input line three-phase voltage (Urated), alternating current with frequency 50 Hz 100 V, 6 кV, 10 кV
Setting of maximum voltage Umaxс     OFF / (110...125) % Urated
Setting of minimum voltage Umin     OFF / (70...95) % Urated
Protection settings for current
Transformer ratio of external current transformer of the phases, Кtf (1...200)
Setting of rated current of the motor Irated (1...990) A
Transformer ratio of external current transformer 3I0, KT, 3I0 (1...100)
Limit of actuation of elements of off-load     OFF / (20...85) % Irated
Loading current asymmetry Iasym     OFF / (20...55) % Ioperated
Rotor blocking for current     OFF / (1,1...6,0) Irated
Current setting GSC (primary values), А     OFF / (0,02...1) Kт 3Io
Hysteresis for actuation current 5%
Setting of level of current cutoff, ICC (6...10) Irated
Settings of time parameters
Start-up time of electric motor tstart (1...99) s
Actuation delay of elements of off-load toff-load delay (0,1...30) min
Actuation delay of current element (Iasym, phase disconnection), tАС (1...255) с
Delay at short-circuit to earth tearth (0,1...99,9) s
Delay at rotor blocking tRB (0,1...99,9) s
Actuation delay of voltage element (UMAX, UMIN) (1...999) s
Delay of current cutoff (50...100) ms
Output intermediate relays
Intermediate protection relay for the current 1 change-over contact
Intermediate protection relay for the voltage 1 change-over contact
Outside and linkage dimensions of the relay, HхWхD 85 х 140 х 137 mm

The relays RDC-01-057-4 and RDC-01-057-5 provide protection of the high-voltage motors by means of formation (at emergencies ) the signal (contacting) on an open coil of the high-voltage switch switching power supply of the electric motor. Output circuit of the relay are the make contact of the relay "KI" which is connected consistently with an open coil of the high-voltage switch and also the change-over contact of the relay "KI", which is connected consistently with an open coil of the high-voltage switch and also the change-over contact of the relay "KU", which can be used for a signal formation about the excess or the decrease of the controlled voltage or for blocking of the circuit of turning on a high-voltage switch of the electric motor.

The design of the relay provides its installation by means of projection mounting with front connection of wires.

Purpose of output relays

KI - output relay - it actuates for overload current, dry course, current asymmetry.
KU - output relay - it actuates for controlled voltage (excess, decrease).

Purpose of indication elements


LED display RDC-01-057-4 RDC-01-057-5
KI Status indicator of output relay of current protection
KU Status indicator of output relay of voltage protection  
I > Indicator of current overloading
I ≠ Indicator of current asymmetry
I < Off-load indicator / indicator of relay readiness
3I0 Ground short-circuit indicator
U > Indicator of voltage excess  
U < Indicator of voltage decrease  
ABC Indicator of wrong phase rotation of voltage  

In case of excess of emergency settings on current the delay timer on shutdown and the blinking indication (red color) of the corresponding light-emitting diode are turned on. If for the determined time controlled parameters (taking into account a hysteresis) are not come back to admissible limits, then the output relay KI actuates (the command for shutdown of the high-voltage switch is given) and the constant luminescence of the corresponding LED indicator takes place.