The battery discharge tester handles high-current DC power—often tens or even hundreds of amps—while the tested object is the core DC power source of a substation. Without reliable protection, any abnormal condition could not only damage the instrument but also potentially harm the battery or even cause a DC system failure. The triple protection mechanism of the HZFD-200 serves as the safety baseline for such equipment.

Overvoltage protection

Overvoltage protection monitors abnormal voltage increases in the entire battery pack. During normal discharge, the battery voltage should monotonically decrease as discharge continues. If an abnormal voltage rise occurs (e.g., due to poor cable contact causing sudden voltage fluctuations in the entire pack, or when the charging voltage exceeds the set upper limit during online monitoring), the instrument immediately triggers an alarm, displays the warning reason, and prompts the operator to take action.

The manual describes it as "enhanced overvoltage protection," indicating it is not merely a simple threshold trigger but includes debouncing and decision logic to prevent false protection activation due to transient interference signals.

Overcurrent Protection (Automatic Recovery)

Overcurrent protection triggers when the discharge current exceeds the allowable range, and the instrument automatically reduces or cuts off the output current. The "auto-recovery" function means that after overcurrent is triggered, the instrument automatically returns to normal discharge mode once the overcurrent cause is eliminated (the circuit returns to normal), without requiring manual reset by the operator—this is particularly important for unattended long-duration discharge tests (e.g., 10-hour rate discharge).

overheat protection

The power section of the HZFD-200 employs a high-power electronic load (dummy load), which generates significant heat in the power components during prolonged high-current discharge. The overheat protection system monitors the temperature of critical components and reduces or cuts off the power output when the threshold is exceeded, preventing damage to the power components from overheating.

After the test, the manual requires waiting for the instrument to cool down before turning off the power—this also serves as a supplement to the overheat protection: power devices still retain residual heat after stopping operation, and the fan continues to dissipate the heat. Do not immediately cut off the power after stopping discharge; allow the cooling process to complete naturally.

Protection logic for single-unit anomalies

When the single-cell voltage falls below the set termination voltage, the default is to trigger a shutdown protection to prevent individual deteriorated batteries from being damaged by over-discharge. However, the HZFD-200 also allows setting the single-cell low-voltage condition to "alarm only without shutdown," intended for use by professionals in specific scenarios (e.g., when continued observation of the entire battery pack's characteristics is required). Note that manual judgment is required to determine the shutdown timing in this mode.