Single-Phase MCR as Automatic Ground-Fault Neutralizer (Patented)
APPLICATION FIELD AND PURPOSE:
Neutralizes automatic ground-fault capacitive current in electrical networks with isolated neutral.
Prevents transition of single-phase ground faults to multi-phase short circuits.
COMPLETE EQUIPMENT:As shown in the diagram below,
PRINCIPLES OF OPERATION:
In the figure shown, an automatic adjustment and control system (1) defines the expected value of ground fault capacitive current and sends a control signal to the single-phase MCR converter (2), thus providing reactor control.
When a ground fault occurs, the reactor reduces the resulting current value at the damage point to a negligible value. The reactor switches to compensation mode without requiring intervention by maintenance personnel. The adjustment process is fully automatic.
Under normal operating conditions, the single-phase MCR is not saturated, eliminating resonance overvoltages in the neutral line.
This reactor may also be used in 3-phase electric grids and consumers. In this case, a filter (4) for connection of the reactor to the 3-phase network is supplied with the reactor.
MAIN TECHNICAL DATA:
AUTOMATIC ADJUSTMENT & CONTROL SYSTEM
EFFICIENCY OF USE
Use of the single-phase MCR results in reduction of ground faults by a factor of three and their full containment in overvoltage-caused insulation breakdown.
This device provides intact operation and increased lifetime of electric equipment.
Average cost recovery has been achieved in about 2.5 years.
TOTAL COST OF OWNERSHIP (TCO)
As a percentage of ex-works price TCO is as follows:
In other words, the TCO of an MCR is similar to that of a transformer of the same class.
MEAN TIME BETWEEN FAILURE (MTBF)
CERC guarantees its MCR's for a lifetime of not less than 25 years, with first major maintenance guaranteed not to occur within 12 years.
Each phase of the reactor, its grounding filter and current-distortion corrector (an LC filter) are guaranteed for a minimum of 3 years.
The power control system, including the transformer with its built-in thyristor subsystem is guaranteed for one year. The average practical time to failure of smaller MCR's is 5 years.