AFB Arc-free ultra high-speed DC circuit breaker

AFB^® is an innovative ultra high-speed DC circuit breaker based on PLUTON experience and advanced technologies. AFB^® is provided for application in tram, trolleybus, light rail and metro traction substations power distribution systems.

Application of arc-free interruption concept in DC circuit breaker provides the following significant benefits in comparison with a circuit breaker with standard switching and arc interruption:

safety and environmental friendliness. No damaging effect of arc and contaminating combustion products;
AFB applies innovative DC interruption concept, leading to high wear resistance. It allows to minimize costs on components, and maintenance is not required for a long period;
AFB^® circuit breaker is developed and manufactured according to EN 50123-2/IEC 61992-2, EN 50123-3, IEC 60947-3 standards requirements;
in contrast to standard contact circuit breaker, which requires additional work space for plasma ejection in its operation, AFB^® circuit breaker applies principle of power circuit interruption in vacuum. As a result, AFB^® circuit breaker requires half the size of work space in comparison with standard circuit breaker, and there is no need to meet special requirements to insulation gaps;
secure low current interruption. Breaker contacts damage prevention.

lowest maintenance

combination of reliability and high-speed operation in one compact unit

high wear resistance and long lifetime

operational and environmental safety

50 000 switchings to maintenance (including short circuit current interruption);
short contacts opening time (1 ms). High-speed power contacts opening and possibility of circuit breaker tripping before short-circuit current reaching by current rate of rise (di/dt);
short circuit current limitation is < 25 kA with peak calculated value 100 kA.

BENEFITS
OPERATING PRINCIPLE
MAIN COMPONENTS
CURRENT PROTECTIONS
CONTROL AND INTERNAL MONITORING SYSTEM

Benefits of AFB^® arc-free circuit breaker in comparison with a circuit breaker with standard switching and arc interruption:

adjustment of fine current interruption setting;
no need for circuit breaker tripping setting calibration;
constant opening time that does not depend on short circuit current value;
resource of emergency current interruptions is much greater in comparison with circuit breaker with standard switching and arc interruption;
no arc interruption contacts, and as a result, no need for their periodic replacement;
no main contacts wear;
no need for main contacts replacement up to the expiry of vacuum interrupter mechanical life;
no need of contacts inspection after emergency currents interruption with unlimited number of trippings;
no arc plasma emission;
no combustion products;
no combustion products deposits on circuit breaker components and switchgear units;
no arc plasma overpressure in switchgear during switching;
no arc plasma flashover during switching;
fire risk reduction;
possibility of remote resetting.

Operating principle

Before circuit breaker tripping control system tests: auxiliaries voltage, high-voltage opening and interrupting capacitors voltage, interrupting thyristors and shunt diodes proper functioning. Closing is possible with preliminary line test and without it.

Closing

Pre-charged low-voltage capacitors battery provides circuit breaker closing by closing coil actuation with closing thyristor.

Operational opening

Circuit breaker control system actuates opening thyristor on receiving opening command. When thyristor opens, the power stored in high-voltage opening capacitor is switched to opening coil. The opening coil magnetic field influences opening mechanism, which actuates vacuum interrupter moving contact, thereby vacuum interrupter power contacts open.

Arc starts between vacuum interrupter contacts upon their opening. Pre-charged capacitor with discharge current directed towards load current flow is used for the arc interruption.

Capacitor discharge current is switched in antiphase to the main current of power circuit. The arc is interrupted at the moment, when currents algebraic sum is zero. Afterwards the contacts open and interrupt power circuit.

Emergency opening

Emergency opening has similar to operational opening principle. In this case, the signal for opening is measurements from current sensor, installed in the circuit breaker main power circuit, and processed by AFB^® control system microcontroller according to specified algorithms.

Vacuum interrupter:

high switching wear resistance;
no open arc;
reduction of circuit breaker work space.

Electrodynamic tripping drive:

high-speed contacts opening system;
interruption speed does not depend on short circuit current value.

Disconnector:

high dynamic stability;
long mechanical life;
no necessity of maintenance.

Control system has built-in adjustable protection functions:

І₀instantaneous overcurrent protection;
Imax protection;
di/dt protection.

І₀INSTANTANEOUS OVERCURRENT PROTECTION

Overcurrent protection is activated upon exceeding of measured current value, setting without time delay.

Imax PROTECTION
Overcurrent protection is activated upon exceeding of measured current value setting within the specified time interval.

di/dt PROTECTION
In case of current preset rate of rise exceed, protection is activated before the instantaneous overcurrent protection or Imax protection setting is reached. Thus, total tripping time is reduced and maximum short circuit current is limited. It helps to increase significantly the circuit breaker lifetime, to reduce the number of substation equipment failures, to eliminate contact network cables burning-off, etc.

Control and internal monitoring system provides complete all-sufficient control of circuit breaker and its components, and fulfills all necessary functions, including protection, as well as remote control and measurement, etc.:

all circuit breaker components and parts operation control;
continuous diagnostics of circuit breaker units;
receipt of control signals from the upper level (via discrete signals and isolated RS-485 interface, Modbus RTU protocol);
built-in power current and voltage measurement system;
output of its own status data and measurements for the upper level;
built-in HMI (LCD display with keyboard for adjusting main system parameters);
switching overvoltages protection system control.