The bias-type arc-suppression coil features a core magnetization section arranged within its AC working coil. By adjusting the magnitude of the DC bias magnetic flux in the magnetic circuit of the core magnetization section, the equivalent AC permeability can be regulated, thereby achieving continuous and adjustable inductance. The DC excitation winding is connected in reverse series, so that the power-frequency voltages induced across the entire winding cancel each other out. The excitation current of the arc-suppression coil is controlled through closed-loop regulation of the output current from a three-phase fully-controlled rectifier circuit. By continuously monitoring the neutral-point displacement voltage and the arc-suppression coil current, the controller automatically tracks and detects capacitive currents under normal grid operating conditions, provides dynamic compensation during fault conditions, and ensures automatic recovery once the fault has been cleared.

Working principle:

When the power grid is operating normally, the microcomputer controller of the arc-suppression coil calculates the ground capacitance current under the current grid configuration through real-time measurement and computation. Based on a pre-set residual current value or detuning degree, it determines the magnitude of the inductive current that the arc-suppression coil should output. After a ground fault occurs, the controller adjusts the reactance value of the arc-suppression coil to deliver the appropriate compensation current.

The residual current at the fault point can be limited within a set range, thereby extinguishing the arc and ensuring that the power supply system remains unaffected.

Performance features:

The compensation and adjustment method of the bias-magnetic arc-suppression coil complete set of equipment is a continuous, adaptive adjustment type. Specifically, before a single-phase-to-ground fault occurs, the arc-suppression coil continuously monitors and calculates the grid current. Once a single-phase-to-ground fault arises, a DC excitation current is applied to alter the magnetic reluctance of the iron core, thereby adjusting the reactance value at millisecond-level speeds and outputting compensating current.

The bias-magnetic arc-suppression coil features a fully static design, with no moving parts or contacts inside. It offers a wide adjustment range and fast response speed.

The biased magnetic arc-suppression coil employs a dynamic compensation method that avoids the resonance point, thereby eliminating the possibility of series resonance. Specifically, during normal grid operation, no excitation current is applied, and the arc-suppression coil is tuned to a state far away from the resonance point. However, the magnitude of the grid’s capacitive current is continuously monitored in real time. Once a single-phase-to-ground fault occurs in the grid, the arc-suppression coil is adjusted to achieve an ideal compensation state.

Technical specifications:

Applicable voltage levels: 6 kV, 10 kV, 35 kV, 66 kV

Rated frequency: 50 Hz

Compensation and adjustment method: On-demand adjustment

Capacitance current measurement error ≤ 2%

Adjustment steps: Stepless continuous adjustment

During a single-phase ground fault, the residual current is ≤5A.

During system operation, the displacement voltage ≤ 15%.

Grounding response time: ≤60 ms

Control method for grounding systems: real-time online monitoring and automatic compensation.

Structural components of a bias-magnetic arc-suppression coil:

A complete set of bias-magnetic arc-suppression coil devices typically consists of a grounding transformer, the main body of the bias-magnetic arc-suppression coil, a microcomputer controller, a control panel, current transformers, voltage transformers, surge arresters, and isolating switches, among other components.

The 6kV and 10kV system control cabinets do not include smoothing reactors; the 35kV and 66kV system control cabinets do include smoothing reactors.

The arc-suppression coil compensation system for generator neutral points does not require the addition of a grounding transformer.

If the 35kV or 66kV system has a neutral point, there is no need to add an additional grounding transformer.

The overall composition diagram is as follows: