BT AND MT CIRCUIT BREAKERS

Despite some differences in built, BT and MT circuit breakers are the opening elements in load and aim at protecting electrical installations from potential damages caused by short-circuits and electrical overloads.

M&I Brazil and our experienced team of engineers and field technicians are qualified and equipped with testing instruments from various manufacturers, such as: ABB, Eaton, GE, Schneider and Siemens.

» Retrofit and modernization of obsolete equipment;
» Cleaning of drive mechanism and cable out ports;
» Lubrication of mobile parts in drive mechanism;
» Inspection of mechanical operation parts;
» Verification of drive coils and load spring motor, with electrical testing;
» Injection of primary and/or secondary current testing;
» Protection modules testing (ABB, Schneider, GE, Siemens, Eaton test boxes)
» Electrical testing:

› Housing and contacts isolation measurement (Megger);
› Ohmic resistance of contacts (Ducter);
› Oscillography (measurement of primary contacts opening and closing timing);
› Vacuum integrity testing (for circuit breakers with pole vacuum isolation).

Protection Relays & Meters

Electromechanical and microprocessor relays are protection devices whose main function, despite using of a different build method and being associated with a circuit breaker, is to assure the removal of a load in absent or abnormal operating condition.

Given the importance of such element, some hardware and software testing are crucial for adequate functioning. Within M&I Electric work scope, we may highlight:

» Multi-brands with a highlight to the main manufacturers and models:

› ABB – 500/600 REM, RET, REF families and others;
› DEIF – GPU, DPU, RM and others;
› GE – Multilin 489/469/650/750/239/G60 and others;
› Siemens – 7SJ, 7UM lines and others;
› Schneider – Sepam, Micom, Vamp and others;
› SEL – 400G / 651 / T400 series and others;
› Other manufacturers;

» Automation, digitalization and communication via IEC 61850 network;
» Retrofit and modernization of obsolete equipment;
» Current, differential, distance, voltage, directional relays etc;
» Analysis of curves and equations which define relays characteristics;
» Measurements of current/voltage injection to verify proper operation;
» Parametrization of relays in general (Numerical or Conventional);
» Comparison of compliance with selectivity study;
» Repairs and testing of active protections;
» Download & Upload of configurations used;
» Looping and operation testing in switchgears logic.

Switchgears and MCCs

Switchgears and Motor Command Centers (MCCs) are projected to distribute all the power through the circuit, usually connecting the generation and the load in the same bus.

M&I Electric relies on a full maintenance work scope, including:

» Retrofit and modernization of obsolete equipment;
» Thermographic inspection;
» General cleaning of buses and compartments;
» Inspection of isolators and buses in general;
» Verification and checking of wiring and connections;
» Torque verification in bus screws; accessible.
» Cleaning and lubrication of sliding contacts
» Contact resistance measurement in bar leads
» Isolation measurement (Hipot and Megger tests).

Workshop Service

Certain interventions to this equipment are subject to be conducted in repair workshops only due to the need of resources and testing instruments.

M&I Electric Brazil offers the necessary structure for the recovery of such equipment according to the details below:

Main characteristics:

» physical area of 600 m²
» capacity for repair of equipment from several manufacturers (ABB, GE, Schneider, Eaton etc)
» Three-phase secondary current injection set
» Primary current injection set of up to 100,000A

Service scope:

» Circuit breakers: repair/maintenance – BT e MT
» Protection relays: testing & calibration (electromechanical, microprocessor)
» Calibration of measurement instruments under the Brazilian Calibration Network standards
» Switchgears: electrical testing, modification and upgrade, retrofits
» Drives: authorized representative of Vacon Drives for workshop and field services