Multifunctional Relay Block MCX912

Features and technical specifications:

1. Measuring connections phase by phase to the main c.t. to form the maximum value of the phase currents and the neutral current (I0 internal)
2. Alternative: Measuring connections to two main c.t. (phase R and T) and a separate current input (I0 external) to a neutral c.t. (phase S or I0)
3. The measured values are digitally processed by a microprocessor
4. Ability to combine a large number of protective functions in one unit
5. The various protective functions can be freely selected and allocated to the various auxiliary relays by means of the software tripping matrix (blocked, start signal, tripping, tripping with latching)
6. Wide setting ranges for the various protective functions
7. Exact quartz-controlled timers
8. Thermal replica with two separately adjustable time constants and two independently adjustable pickup values (warning and trip)
9. If the supply voltage fails, the state of the thermal replica is memorized
10. Memory for tripping value and time run
11. Setting by keyboard
12. Two four-figure LED displays, showing: all settings, momentary value of the measured values, number of motor starts, trips, elapsed times, etc.
13. Comprehensive self-monitoring, indication of readiness to operate
14. Supply from battery 36 – 312 V DC (or 18 – 36 V DC) or from single-phase mains 80 – 242 V, 50/60 Hz

APPLICATIONS :-

The relay type MCX is designed for
following protection purposes:
– Rotating AC machines, specially for asynchronous motors
– Large power transformers and distribution transformers
– Line- and cable feeders

This Multifunctional Relay Block is easily insert in your schematic diagram and connect as you like way.                                                                                                                                                                                                                           Three phase microprocessor based multifuncional protection relay, with freely selectable combinations of protection functions. The function types and setting ranges shall be applicable for detection of most common faults in medium – and high voltage networks. Special attention is to be given to the protection of asynchronous motors. The sensitive earth fault function shall allow use in isolated and compensated networks via one of the c.t. inputs. The setting ranges shall be very large and set values have high accuracy and long time stability. All settings shall be made with a keyboard in conjunction with numerical LED indications. The relay shall be designed so that a continuous display of service – and tripping values can be selected. Tripping and signalling contactors shall be programmable by means of a software tripping matrix. All contactors shall be blocked selectively from outside with a remote signal to design different schemes (e.g. directional protection or for motors). A comprehensive self-supervision, capable of detecting hardware and software failures with local and remote alarm facilities shall also be included. The auxiliary power supply can fluctuate in a wide tolerance range and shall not affect the reliability. The relay shall be fully withdrawable,
to simplify commissioning and service.

1. Earth fault protection :-
   The measured signal for earth fault protection is detected by either internal formation when three phases are connected or by use of an external neutral current transformer. With this arrangement a very sensitive earth fault detection can be obtained
2. Negative phase sequence protection :-
   Asymmetrical main voltages, unbalanced loads or phase failures cause a negativesequence current. This signal can be derived from three phases. If the relay is wired to only two phase currents, the neutral current is
   taken into account. For I0 more than 0,25 x set value the negative-sequence protection is blocked.
3. Motor starting protection :-
   Motor starting procedures are protected by the following functions:
   – Istart with I2 Tstart measurement The product will be built as long as the set value of Istart is exceeded. A tripping takes place when I2T exceeds the set value I2Tstart. The advantage of this feature is that motor starts can be completed with different starting times. They come up by unstable system voltages.
   – Locked rotor protection When the stalling time of a motor is shorter than the normal starting time, a speed governor is necessary and will release a trip signal only when the rotor is not moving.
   – Counter for motor starts This function consists of counters, one for cold starts and one for warm starts and a setting level for the warm condition (∆ϑ3). A timer tN-1 is adjustable for the required cooling time to permit
   another start. The function trips when the accepted number of starts has exceeded the set number Nwarm or
   Ncold.