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Development and Application of Leakage Current Detection Technology for AC/DC Panel: Evolution from DC Panels to AC/DC Hybrid SystemPanels

With the development of power electronics technology, DC screen systems have gradually evolved into AC/DC hybrid screens (AC/DC screens) to meet more complex power supply needs. During this process, leakage current detection technology has also evolved from a single DC detection to a hybrid detection of AC and DC to ensure system safety and reliability

1. The evolution process from DC Panels to AC/DC Hybrid System Panels

1.1 Application and limitations of traditional DC panels

DC Power PanelWidely used in power systems, communication base stations, rail transit and other fields, mainly for providing stable DC operating power supply. Its core functions include:

  • Battery charging and discharging management
  • DC load power supply (such as circuit breaker operating mechanism)
  • Insulation monitoring (detecting DC leakage current)

However, with the popularization of new energy (photovoltaic, energy storage) and frequency conversion equipment, traditional DC screens are facing new challenges:

1,Demand for AC/DC hybrid power supply：Inverters, frequency converters, and other equipment introduce AC components into DC screen systems, leading to the failure of traditional DC leakage current detection methods.

2, High frequency interference problem：The high-frequency ripple generated by switching power supplies, PWM modulation, etc. affects the accuracy of leakage current detection.

3, Increased system complexity：The scenario where DC and AC coexist requires a more flexible detection scheme.

1.2 The rise of AC/DC Hybrid System Panels

AC/DC Hybrid Power PanelOn the basis of traditional DC screens, AC distribution functions have been added, and typical applications include:

  • Microgrid system: Photovoltaic inverters and DC energy storage systems operate in a mixed manner.
  • Industrial automation: DC bus+AC motor control for variable frequency drive (VFD) equipment.
  • Data center: 48V DC power supply and AC UPS hybrid architecture.

The promotion of AC/DC screens requires leakage current detection technology to adapt to the complex environment of AC/DC mixed signals. Traditional DC leakage current sensors (such as shunt resistors and isolated operational amplifiers) cannot effectively detect AC leakage, so a new detection scheme is needed.

2. he necessity of qualitative detection of AC/DC leakage current

In AC/DC hybrid systems, the main goal of leakage current detection is to quickly determine whether there is a dangerous leakage, rather than accurately measuring the leakage value (quantitative detection). The necessity of qualitative testing is reflected in the following aspects:

2.1 Priority given to security protection

  • Electric shock risk: AC leakage current (such as 30mA or above) may directly endanger personal safety, and the circuit needs to be quickly cut off.
  • Equipment damage prevention: DC leakage current may cause insulation degradation, but AC leakage current may cause more serious short circuits or arc faults.

2.2 System stability requirements

  • In AC/DC hybrid systems, high-frequency noise may cause false alarms in quantitative detection, while qualitative detection (threshold comparison) can more reliably trigger protection actions.
  • In photovoltaic inverters or frequency converters, AC leakage may affect MPPT (maximum power point tracking) or motor control, and qualitative detection can quickly isolate faulty branches.

2.3 Economy and practicality

  • Quantitative detection requires high-precision ADC and complex algorithms, which are costly; Qualitative detection only requires a comparator or logic circuit, suitable for large-scale deployment.
  • In industrial sites, maintenance personnel pay more attention to whether there is leakage rather than how much leakage is, and qualitative testing can simplify the operation and maintenance process.

3. Application of DEXIE Electronics’ switchable leakage current sensor

3.1 FEATURES

DEXIE Electronics’ switchable leakage current sensor is a sensor designed specifically for AC/DC hybrid systems, with the following advantages:

  1. AC/DC hybrid detection:
    • Using flux gate technology for digital demodulation, it can simultaneously detect DC 0-200mA and AC 50H or 60Hz leakage current.
    • Support composite signal analysis of DC offset and AC ripple, suitable for scenarios such as frequency converters and UPS.
  2. Non contact installation:
    • The structure can be opened and closed, and can be installed without disconnecting the busbar, reducing construction difficulty.。
  3. High anti-interference ability:
    • Built in digital filtering to suppress high-frequency noise (such as PWM harmonics) and ensure the reliability of periodic detection.
  4. Adjustable threshold alarm:
    • Set the alarm threshold by customizing the threshold setting (such as conventional DC 6mA/AC 30mA), and directly output a high-level signal to drive the relay.
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3.2 Typical application cases

  • Photovoltaic energy storage system: detects leakage current between the DC side (battery pack) and the AC side (inverter output) to prevent PID effect or insulation failure.
  • Industrial frequency conversion cabinet: Monitor the AC/DC leakage of the motor drive system to avoid equipment shutdown due to insulation damage.
  • Data center power supply: Provides leakage protection in a hybrid architecture of 48V DC power supply and AC UPS.

4. Conclusion

  1. The evolution from DC panels to AC/DC Hybrid System Panels reflects the growing demand for hybrid power supply in the power system, and leakage current detection technology needs to be upgraded synchronously.
  2. In AC/DC hybrid systems, qualitative detection (rather than quantitative detection) can better meet the needs of fast protection and economy.
  3. DEXIE Electronics’ switchable leakage current sensor provides an efficient and reliable leakage protection solution for modern power systems through non-contact AC/DC hybrid detection.

In the future, with the development of Internet of Things (IoT) technology, AC/DC leakage current detection will be further integrated with intelligent operation and maintenance systems to achieve real-time monitoring, warning, and self-healing closed-loop management.