As the load on modern power grids continues to grow, the contradiction between surging short-circuit currents and the interrupting-capacity ceiling of circuit breakers is becoming increasingly prominent. In grids of 220 kV and above, high-impedance transformers occupy a mainstream position in power transmission thanks to their high short-circuit impedance and strong impact-resistance capability. However, the magnetizing inrush current characteristic of these transformers during energization poses a serious threat to the safe and stable operation of the grid. Deeply engaged in power technology, GoLead Intelligent has launched the SID-3YL Inrush Current Suppressor, which overcomes this industry-wide challenge with innovative technology and provides full-process safety assurance for the energization of high-impedance transformers.

The "Energization Dilemma" of High-Impedance Transformers

High-impedance transformers are widely used in EHV grids thanks to their ability to limit short-circuit current and improve grid stability. Yet their special structure (e.g., HV-side windings placed internally, small air-core inductance) gives rise to two core risks during energization:

· 1. Magnetizing inrush current exceeds limits: When the HV-side winding is built in, the self-leakage inductance is large while the mutual leakage inductance is small, resulting in higher inrush current amplitude. This triggers frequent misoperation of differential protection and zero-sequence protection, and can even cause large-scale blackouts.

· 2. Persistent zero-sequence current: High impedance causes the inrush current to decay slowly — under extreme conditions it can take 5-10 seconds — so the zero-sequence component remains over the limit for an extended period, making protection coordination difficult and greatly reducing grid dispatch efficiency.

How the SID-3YL Inrush Current Suppressor "Tames" It

Targeting the energization pain points of high-impedance transformers, GoLead Intelligent developed the SID-3YL Inrush Current Suppressor. Through a dual-engine approach of "source suppression + precise control," it achieves a revolutionary breakthrough in inrush current management:

1. Core Technology Highlights

· Intelligent Phase Control: A microcomputer-based algorithm performs phase-selective closing, suppressing the magnetizing inrush current to below 0.4x of the rated peak (<0.4 A) — an 81% reduction compared with conventional random closing.

· Zero-Sequence Component Elimination: Through phase optimization and harmonic suppression, the measured zero-sequence content of the inrush current drops by more than 80%, thoroughly eliminating the hidden danger of protection misoperation.

· Adaptive Optimization: The device controls breaker operation, calculates the transformer residual flux at opening in real time, and uses a proprietary "residual-flux algorithm" to generate a bias flux at closing that cancels it out, achieving automatic suppression of magnetizing inrush current — with no manual intervention required throughout the entire process.

2. Full-Scenario Adaptability

· Voltage levels: Covers 220 kV / 110 kV / 10 kV three-winding and two-winding high-impedance transformers.

· Equipment compatibility: Adaptable to equipment from mainstream manufacturers such as TBEA and XD (China XD Electric), supporting both new substation construction and the retrofit of aging equipment.

· Environmentally friendly: Reduces transformer closing noise and improves the working environment for O&M personnel.

A "Safety Method" Derived from Measured Data

In a 240 MVA high-impedance transformer at a 220 kV substation in Wuhu, Anhui (State Grid), the SID-3YL achieved:

· Inrush peak: With the residual-flux data unknown, the device simulated random closing; the peak inrush current of phase B dropped from 2.175 A (2.04x) to less than 0.426 A (0.4x).

· Protection maloperation: 100% elimination of zero-sequence protection maloperation.

· Operating stability: Energizing the main transformer with the SID-3YL not only thoroughly eliminated the hidden danger of protection maloperation and greatly reduced the closing impact, but also improved power quality during energization, safeguarding the reliability of both system and equipment operation.

Inrush Current Suppression Comparison

The "Product Value" of Efficient Retrofit and Broad Adaptability

The SID-3YL inrush current suppressor has been successfully applied in high-impedance transformer scenarios across multiple locations, including the State Grid Anhui Bureau, China Southern Power Grid Guangzhou Bureau, and Inner Mongolia Power Grid. Its core advantages include:

· Strong compatibility: Adaptable to transformers and non-linear loads (capacitors, reactors, etc.) from different manufacturers and at different voltage levels.

· High cost-effectiveness: A one-time investment that delivers long-term reductions in O&M cost and avoids outage losses caused by protection misoperation.

· Leading technology: A source-suppression solution based on phase-control technology — more efficient and smarter than conventional passive current-limiting.

· Easy retrofit: As a purely secondary device, the suppressor requires no modification of primary equipment and adds no high-voltage conductors or insulation structures, greatly reducing implementation complexity.

GoLead Intelligent has always taken "striving to advance the technological progress of the world's power industry" as its mission. The successful application of the SID-3YL inrush current suppressor marks the comprehensive resolution of the high-impedance transformer energization challenge. Going forward, the company will continue to cultivate the smart-grid field, empowering grids with innovative technology for simultaneous improvements in safety and efficiency, and contributing the "China Solution" to the global energy transition.