Compared with conventional low-voltage systems, the trend toward higher voltages in photovoltaic power generation—especially high-voltage DC—significantly increases the risks faced by inspection personnel. The three major risks are as follows:

■ Electric Shock Injuries Are More Severe

The safe DC voltage for the human body is generally considered to be below 60V, while the voltage of high-voltage PV systems, such as 1500V DC, far exceeds this threshold. More importantly, PV systems commonly use high-voltage DC. DC has no zero-crossing point, so once electric shock occurs, current can continue flowing through the human body, whereas AC current is briefly interrupted as it periodically crosses zero. In addition, DC arcs contain more energy and are more difficult to extinguish, potentially causing severe consequences such as skin burns.

■ Significantly Higher Risk of Incorrectly Assuming the Circuit Is De-energized

PV systems have capacitive energy-storage characteristics. Even after the main switch is disconnected, components such as cables and combiner boxes may still retain large amounts of electrical charge, especially in high-voltage systems with greater capacitance, resulting in “residual high voltage.”

If inspection personnel mistakenly assume that the system has been de-energized—for example, if a low-voltage measuring instrument displays “zero” even though residual high voltage is actually present—direct contact with the equipment may result in an instantaneous electric shock.

■ Higher Risk of Insulation Breakdown

High voltage makes air and insulating materials more susceptible to “breakdown,” creating a conductive path. For example, in humid environments, 1500V DC may break down the air across a gap of only a few centimeters and generate an arc. If inspection personnel are holding an instrument that does not meet high-voltage requirements, insulation failure in the instrument may cause arc burns or electric shock.

According to the photovoltaic module safety qualification standard IEC 61730-1, PV modules are regarded as Overvoltage Category III and require measuring instruments rated for Measurement Category III. Using instruments that match the required measurement category can help protect personnel and equipment from serious accidents such as electric shock and burns.

■ Insulation Performance Suitable for High-Voltage Applications

The probes, cables, and enclosure of high-voltage measuring instruments must use high-voltage-resistant insulating materials and provide sufficient “creepage distance” (the current path length along an insulating surface) and “electrical clearance” (the distance through air).

For example, an instrument designed to measure 1500V DC should have insulation capable of withstanding a dielectric strength test of at least twice its rated voltage, i.e. 3000V or higher, ensuring that high voltage cannot be conducted through the instrument to the human body during normal measurement.

■ High Resistance to Electrical Hazards

Mainstream PV system voltages have already increased to 1500V DC, while some projects are exploring 2000V solutions. High-voltage systems have much higher transient overvoltage energy. For example, surge voltages in a 1500V system can reach 10,000V, far exceeding the withstand limits of ordinary low-voltage equipment.

A CAT III 2000V measuring instrument, however, is capable of withstanding high-voltage surges of this type, providing much greater protection against transient voltage shocks.

■ Effectively Reduces Residual-Voltage Risks

PV modules have a capacitive effect and may retain residual electrical charge even after the main switch is disconnected. The CM4375-93 features residual-voltage detection, helping prevent electric shock accidents caused by incorrectly assuming that no voltage is present.

■ Slim Jaw Design

PV equipment often features complex cable layouts with many narrow and confined spaces. Conventional clamp meters may be unable to access these areas because of their bulky jaws, making measurements difficult.

The slim jaw of the CM4375-93 can easily reach into these narrow cable spaces, making previously difficult measurements simple and efficient. This greatly reduces measurement time and improves work efficiency.

■ Automatic AC/DC Detection

When measuring high-voltage PV equipment, distinguishing between AC and DC is a fundamental and critical step. Conventional measuring instruments require manual switching between AC and DC modes, which is not only cumbersome but also prone to incorrect settings.

The CM4375-93 can automatically and accurately identify AC or DC, eliminating the need for manual switching and reducing the possibility of operating errors. This allows measurement personnel to focus more on data acquisition and significantly improves measurement efficiency.

■ Wide Measurement Range

With a maximum current measurement of 1000A, the CM4375-93 meets the high-current measurement requirements of high-voltage PV equipment.

When checking the open-circuit voltage of PV panels, it can measure up to DC 2000V, making it ideally suited to the voltage measurement requirements associated with the trend toward higher-voltage PV systems and providing a solid foundation for measurement accuracy and reliability.

■ Supports Wireless Data Transmission

The CM4375-93 can easily transmit measured values to a smartphone or tablet, and measurement data can also be transferred directly to spreadsheets created in Excel®, greatly simplifying the data recording and organization process.

Personnel no longer need to manually record measurement data, reducing the likelihood of human recording errors and improving data management efficiency.

In addition, with the GENNECT Cross software, 1st- to 30th-order harmonic analysis can be performed, providing comprehensive and accurate data for gaining deeper insight into PV equipment operating conditions and evaluating equipment performance.