ST-3 (2017 Edition) Intelligent Controller

Product Overview

The ST-3 series intelligent controller is the core control unit of air circuit breakers. It is mainly used in 50Hz/60Hz low-voltage distribution systems, providing comprehensive protection, measurement, monitoring and communication management for lines, distribution equipment and loads. It is widely applied in industrial distribution, power plants, petrochemical, metallurgy, infrastructure and other scenarios. The product complies with domestic and international standards including IEC60947-1, IEC60947-2, GB14048.1 and GB14048.2.

Product Models and Classification

The series includes three basic models for different frame circuit breakers:

1. ST40-3: Compatible with DW40 series circuit breakers, rated current range 200A~1600A
2. ST45-3: Compatible with DW45 series circuit breakers, rated current range 200A~3200A
3. ST450-3: Compatible with DW450 series circuit breakers, rated current range 200A~6300A

By function configuration:

• Type M: Basic version, no communication function
• Type H: Communication version, optional Modbus, Profibus-DP, DeviceNet protocols

Optional functions such as voltage measurement, demand protection, power metering, harmonic analysis and zone interlocking are available on demand.

Core Protection Functions

Three-Stage Current Protection

• Long-time Overload Protection: Supports 7 protection curves including standard inverse time, fast inverse time and extremely fast inverse time. With thermal memory function, the cooling time is configurable to prevent impact from repeated overload.
• Short-time Short-circuit Protection: Adopts inverse time + definite time dual characteristics, supports Zone Selective Interlocking (ZSI) to realize selective coordination between upstream and downstream circuit breakers.
• Instantaneous Protection: Quickly cuts off high-current short-circuit faults with action time less than 60ms. Additional MCR closing protection and HSISC ultimate breaking protection respond within 10ms to protect the breaker body.

Earth Fault and Leakage Protection

Supports two earth fault protection modes: residual current differential type and earth current type. Independent leakage protection function with adjustable operating current 0.5~30A adapts to electric shock and insulation fault protection in different scenarios. Alarm and trip thresholds are set independently for earth fault and leakage.

Voltage and Frequency Protection

Equipped with over-voltage, under-voltage, voltage unbalance, phase sequence error, over-frequency, under-frequency and reverse power protection. Action threshold, delay time and return value can be set independently, supporting two execution modes: alarm or trip.

Other Protection Functions

Including current unbalance protection, load monitoring protection, demand current protection and PT disconnection alarm, which can be enabled or disabled flexibly according to site requirements.

Measurement and Metering Functions

• Basic Electrical Parameter Measurement: Real-time acquisition of three-phase current, neutral current, three-phase line/phase voltage, active/reactive/apparent power, power factor and system frequency, with industrial-grade measurement accuracy.
• Harmonic Analysis: Supports harmonic detection up to the 31st order, displays total harmonic distortion (THD) of current and voltage, and provides amplitude spectrum analysis of each harmonic.
• Demand Measurement: Sliding window type current/power demand statistics, with adjustable window time from 5 to 60 minutes, used for load control and peak warning.
• Energy Metering: Bidirectional active and reactive energy metering, supporting separate statistics of input and output energy to meet metering and energy management requirements.

Operation and Maintenance Functions

• Event Log: Stores up to 8 trip records, 8 alarm records and 8 operation records, including fault time, action parameters and fault type, with data retained after power failure.
• Equipment Maintenance: Automatically counts circuit breaker operation times and evaluates contact wear degree, giving automatic warning when reaching the life threshold. Supports recording and resetting of historical current peak and demand peak.
• Self-diagnosis: Real-time monitors internal status such as chip, sampling, storage, communication and CT disconnection, and gives active alarm in case of abnormality.
• Zone Selective Interlocking (ZSI): Realizes interlocking coordination between upstream and downstream circuit breakers through DI/DO signals. In case of short-circuit/earth fault, the downstream breaker acts instantaneously while the upstream breaker waits with delay, ensuring selectivity and reducing the power outage scope.

Communication Capability

Supports three mainstream industrial bus protocols: Modbus-RTU, Profibus-DP and DeviceNet. It can be connected to DCS, SCADA and other monitoring systems to realize four remote functions: remote measurement, remote signaling, remote control and remote adjustment. The communication interface adopts photoelectric isolation design for stable operation in strong electromagnetic environment.

Power Supply and Environmental Parameters

• Power Supply Modes: Three modes are supported: CT self-power supply, auxiliary power supply (DC24V, AC220V, AC380V, DC110V/DC220V) and test port power supply. Core functions can be maintained under voltage loss.
• Environmental Conditions: Operating temperature -10℃~+70℃, storage temperature -25℃~+85℃, pollution degree 3, installation category Ⅲ.
• Electromagnetic Compatibility: Passes all EMC tests of GB14048.2, with level 4 immunity to surge, static electricity and burst interference.

Supporting Accessories

Optional accessories include ST201 relay output module, ST-IV power supply module, ST-I DC power supply module, T04/T05 communication connectors, ZCT1 leakage current transformer, ZT100 earth fault current transformer, etc.