The safety protection mechanisms of a transformer tester are the core design to ensure the safety of operators and equipment. They mainly include four categories: electrical safety, operational protection, environmental adaptability, and intelligent early warning, ensuring stable and reliable operation under complex working conditions.
Intrinsically Electrical Safety Design (Hardware-Level Protection)
Forced Grounding and Three-Point Common Ground
The tester casing, operating box, and high-voltage tail terminal (X terminal) must achieve "three-point common ground." The grounding resistance requirement is <4Ω, verified by actual measurement using a ground resistance meter.
This prevents the casing from becoming energized due to potential floating, avoiding the risk of electric shock.
Dual Overvoltage Protection
Discharge Gap: The preset discharge voltage is 1.1 times the test voltage (e.g., for a 100kV test, the gap is adjusted to 11cm). In case of overvoltage, air breakdown is prioritized for pressure relief.
Intelligent Overcurrent Protection: Built-in electronic trip unit automatically cuts off the power supply within 0.1 seconds when the current suddenly increases by >30% (e.g., flashover of capacitive test objects). Forced Series Connection of Protective Resistors
A water resistor or silicon carbide resistor (Rb≥100Ω/kV) must be connected in series at the high-voltage output terminal to limit the short-circuit current to <1A and prevent arc burns caused by test sample breakdown.
Behavioral Protection During Operation
Five-Step Safe Start-up Procedure
① Check grounding → ② Zero the voltage regulator → ③ Perform a 10% no-load voltage increase for verification → ④ Connect the test sample → ⑤ Increase the voltage in stages (faster before 75%, 2%/second after 75%) to prevent misoperation.
Anti-Accidental Touch and Mechanical Interlock
The voltage regulator knob is equipped with a "zero lock" setting; the circuit breaker cannot be closed if it is not zeroed. This is combined with mechanical limit switches and electronic interlocks for double protection.
High-voltage bushings are equipped with insulating covers (diameter>15cm) to prevent accidental contact.
Moving Wiring During Testing is Prohibited
During the measurement process, it is strictly forbidden to disconnect or connect the test cable. Operation is only permitted after the instrument has reset and the discharge alarm has ended to prevent injury from residual charge.
Intelligent System Active Protection
Automatic Discharge and Arc Suppression Mechanism
After the test, the instrument automatically activates the discharge circuit, and a buzzer alarm sounds. Test leads must be disconnected only after the alarm stops to avoid electric shock.
For inductive loads (such as transformer windings), the discharge time must be at least 5 minutes.
Multiple Alarms and Emergency Braking
Equipped with multiple alarm functions including overcurrent, overvoltage, IGBT protection, and discharge protection. Once triggered, the control circuit power must be disconnected and restarted.
Red mushroom-shaped emergency stop buttons are located on both sides of the instrument. Pressing them cuts off the power and triggers the discharge circuit within 0.05 seconds.
Automatic Discharge Upon Power Loss
In the event of a sudden AC220V power outage, the tester automatically enters discharge mode. Disconnection is prohibited for 5 minutes to ensure safety.
