The MMCO is a microprocessor-based multiphase instantaneous and time overcurrent relay.
The MMCO greatly simplifies overcurrent relay selection and enhances the protective relay function. It can be programmed to fit virtually any overcurrent application, and provides valuable fault information not available from conventional relays. Communications options provide immediate retrieval of fault and status data, and the ability to reset or reconfigure the relay remotely.
The MMCO uses microprocessor technology to incorporate eight time curve families into one relay. Any traditional COtype curve family may be selected from the relay’s memory.
A separate version of the MMCO can be ordered with three standard IEC curve families. Each relay provides independent phase and ground trip settings and curve selections, and accepts up to four current inputs to facilitate any usual combination of phase and ground fault protection.
The MMCO can also be supplied with optically-isolated inputs for directional control by distance or directional relay contacts.
The MMCO can be programmed and interrogated manually or remotely. All trip parameters (time curve, time dial, pickup, instantaneous) are programmable, and fault data and metering current values are accessible by push button selection from a scrolling digital display. A real-time clock
option allows time-tagging of fault records, and display of present time.
Fault records for the last 16 faults are stored internally, providing greatly enhanced trouble-shooting and system analysis capability. The most recent four records are manually available on the LCD display, while all 16 are accessible via the optional communications port.
For remote communications capability, the MMCO can be equipped with a WRELCOM™ interface for RS–232C communications, modem communications, or INCOM™ networking with other relays and relay systems, accessible over a single phone circuit.
Additional features of the MMCO design include:
- instantaneous reset;
- self-checking of the dc power and programmed trip parameters;
- LED seal-in initiated by trip current flow;
- FT-22 case construction for ease of inservice testing and isolation.