Cases-GoLead Intelligent

A New Materials Company in Inner Mongolia

Overview

A 10 kV substation of a new materials company in Inner Mongolia experienced frequent transformer energization failures during standby switching due to excessive inrush current triggering instantaneous overcurrent protection.

By deploying the GLSV-ZNH1-12 Smart Phase-Controlled Circuit Breaker, the transformer closing inrush current was successfully suppressed to 0.29 p.u., completely resolving the long-standing commissioning issue.

The breaker integrates zero-flux closing and dynamic residual magnetism compensation technologies to precisely control phase-by-phase closing and eliminate magnetizing inrush at its source. Combined with an independent direct-drive permanent-magnet operating mechanism, it achieves a closing time accuracy of ±0.5 ms and supports direct retrofit in existing switchgear.

Field results show that conventional random closing produced inrush currents up to 4.80 p.u.. After applying intelligent phase control, the inrush was reduced to 1.06 p.u. on first operation and further stabilized at 0.29 p.u. after optimization—representing a 90% reduction below protection thresholds and achieving an industry-leading performance.

Pain Points & Solutions

Pain Point 1: Uncontrolled Inrush Current Causing Frequent Protection Trips

During random closing of conventional circuit breakers, transformer core saturation generates magnetizing inrush currents of 4–8 p.u., far exceeding instantaneous overcurrent protection thresholds (typically 3–4 p.u.), leading to tripping and cascading protection actions.
Solution 1

The solution applies high-precision magnetic flux sensing and smart phase-controlled closing to accurately detect transformer residual magnetism and select the optimal closing phase for residual flux cancellation. By eliminating core saturation at the source, the magnetizing inrush current is reduced from 4.80 p.u. under random closing to a stable 0.29 p.u., remaining significantly below instantaneous overcurrent protection thresholds and effectively preventing nuisance tripping.
Pain Point 2: Complex Retrofit of Aging Substations

Conventional substation upgrades require switchgear replacement and civil modifications, with outages lasting 2–3 weeks.
Solution 2

A fully compatible structural design maintains identical mounting dimensions, busbar interfaces, and secondary terminal definitions as existing VSI / VD4 switchgear, enabling direct in-place replacement without cabinet modification. Combined with a plug-and-play control module featuring adaptive protocol conversion, the solution integrates seamlessly with conventional numerical protection relays without logic changes, allowing installation and commissioning to be completed within days while maintaining uninterrupted power supply.
Pain Point 3: Insufficient Reliability Under Frequent Switching

In industries such as chemicals, transformers are switched 4–6 times per day. Conventional spring mechanisms offer a mechanical life of only 10,000 operations, with high failure rates.
Solution 3

The solution adopts a direct-drive permanent-magnet operating mechanism that eliminates cams, springs, and mechanical linkages, with contacts driven directly by a permanent-magnet motor, significantly improving operational stability. Together with a fully sealed vacuum interrupter resistant to dust and corrosion, the system has been validated through 30,000 mechanical operations, ensuring high reliability under frequent switching conditions and supporting long-term, maintenance-free operation.

Values

Client Comments

GoLead Intelligent provided a professional solution centered on a smart phase-controlled circuit breaker to address the long-standing issue of transformer inrush current tripping during standby switching at our 10 kV substation. Without altering the existing system architecture, the solution effectively suppressed transformer energization inrush and completely eliminated frequent trips caused by overcurrent protection.

Since commissioning, standby transformer switching has been smooth and reliable, significantly improving the continuity of our production processes. Our on-site power supply and energy-saving operating strategies have been successfully implemented, with overall operational risks substantially reduced. This project has provided strong support for the safe and stable operation of our production system and offers a replicable technical reference for similar applications.

──────────── Project Manager, New Materials Company

Case Gallery