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NX-500 DC Switch Ampere-Second Characteristic Tester

1. Overview  

Current DC feeder networks in substations predominantly adopt a tree-like structure, with power distribution progressing through three levels from battery banks to on-site electrical equipment. Most distribution stages employ DC circuit breakers as protective devices. However, due to mismatched protection characteristics between upper and lower-level DC circuit breakers, short-circuit faults in lower-level equipment often trigger over-level tripping of higher-level circuit breakers during system operation. This can lead to power outages in feeder lines and subsequent failures of critical substation equipment such as high-voltage switches, transformers, and capacitors. To mitigate risks caused by incompatible protection characteristics, State Grid Corporation mandates ampere-second characteristic testing for newly installed and operational DC protection devices to ensure performance alignment with design specifications and accurate differential coordination in DC circuits. Article 12(8) of the 2005 "Operating Specifications for DC Power Systems" stipulates: "DC fuses and air circuit breakers must use certified products with properly calibrated fuse elements or setting values, requiring periodic verification to prevent accident escalation through improper tripping." Article 27 of the "Technical Supervision Regulations for DC Power Systems" further requires: "...Automatic air circuit breakers must undergo random sampling tests for characteristics and tripping currents prior to deployment." Similarly, Article 11 of the "Measures for Preventing DC Power System Accidents" emphasizes: "...Pre-deployment sampling inspections of ampere-second characteristics and tripping currents should be conducted."

The ampere-second characteristics of DC protection devices are typically tested in national laboratories or testing stations. These equipment require substantial floor space and specialized charging systems along with high-current load boxes, resulting in complex operational procedures. Some operational units attempt to conduct differential coordination tests using substation battery banks, but this method fails to accurately measure current-action time characteristics. Consequently, after DC systems are commissioned, on-site maintenance personnel lack the necessary testing tools and methods to verify whether the ampere-second characteristics of DC protection devices meet required specifications.

In response to practical needs for testing ampere-second characteristics of DC protection devices, our company has developed a portable, highly automated DC circuit breaker testing system designed for substation applications. This system provides operational maintenance teams with reliable testing solutions for DC protection device performance characteristics, enabling verification of both operational parameters and differential coordination. These advancements significantly enhance the operational reliability of DC systems while ensuring safe and stable grid operations.

The NX-500 DC Circuit Breaker Ampere-Second Characteristics Testing System is designed for measuring the ampere-second characteristics of DC circuit breakers with rated currents ranging from 1A to 500A, and can also be used for testing the ampere-second characteristics of DC fuses with rated currents from 6A to 150A.

2. Technical Parameters

1. The instrument can be used either independently or in conjunction with a PC.

2. 320×240 LCD display, high-speed thermal printer, full keyboard operation for human-machine interaction, and intelligent workflow management.

3.High-current output is generated using power electronic control technology, featuring fast response speed, high precision, and continuous adjustable output current.

4. Multiple high-precision sensors automatically switch current measurement ranges and utilize high-performance 14-bit AD acquisition chips.

5. Equipped with power-off storage capability, it can store 200 sets of experimental data.

6. Automatically save settings data. The last settings will be displayed after power-off and power-on.

7. Select either the second-order action test method or the flow-through non-action test method

8. During online operation, users can control instruments, import experimental data, store experimental data, generate data reports, create data curves, and produce EXCEL reports.

9. The instrument is equipped with overheat, overcurrent, and overvoltage protection functions.

10. The instrument exhibits strong anti-interference capability and excellent electromagnetic compatibility performance.

 3. Technical Specifications

1. Power input: 220V±10%, frequency: 50Hz±0.5 Hz;

2. Test current range: 0–500A;

3. Test current ripple coefficient: less than 5%;

 4. Output current stability: ≤0.5%;

5. Time recording: 0–9999 seconds, minimum time resolution: 0.001 seconds;

6. Ambient temperature range: -20°C to 50°C;

7. Dimensions: 470mm (length) × 320mm (width) × 460mm (height).；