Capacitance and Inductance Tester, often referred to as "Reactive Power Compensation Device Tester" or "Capacitor and Reactor Tester" in the power industry, is a specialized instrument designed to measure the capacitance, inductance, dissipation factor (tanδ), and impedance characteristics of reactive power compensation equipment in power systems, such as shunt capacitors, series reactors, and filter capacitors. Due to the large number of reactive power compensation devices in the power grid and their relatively high failure rate (e.g., capacitor bulging, breakdown, reactor inter-turn short circuits), this instrument is an essential tool for substation operation and maintenance, commissioning tests, and preventive tests. 1. Core Test Objects and Functions Shunt/Series Capacitors: Capacitance (C): Determine whether the capacitance has increased due to internal element breakdown or decreased due to drying out or open circuits. Dissipation Factor (tanδ): Reflects dielectric losses, indicating insulation aging or moisture. Current at Rated Voltage: Estimate the actual operating current. Series/Filter Reactors: Inductance (L): Determine whether there are inter-turn short circuits (inductance decrease) or loose magnetic cores. Quality Factor (Q value): Evaluate the efficiency of the reactor. DC Resistance: Some models integrate DC resistance testing. Combined Devices (Capacitor + Reactor): Can directly measure the total impedance and resonant frequency of the series branch, and estimate C and L values separately without disconnecting wires (feature of high-end models). 2. Working Principle and Technical Advantages Traditional LCR bridges require power-off, disconnection, and discharge before testing, which is inefficient and dangerous. Modern power-specific capacitance and inductance testers adopt the following advanced technologies: Variable Frequency Sinusoidal Excitation Method: The instrument generates a high-precision, high-stability sinusoidal current (frequency typically adjustable between 45Hz~65Hz, or fixed at 50Hz equivalent) and injects it into the device under test. By synchronously sampling voltage and current signals, digital algorithms calculate the impedance magnitude and phase angle, thereby deriving C, L, and tanδ. Non-Disconnection Testing (can be performed with or without power; recommended without power but without disconnection): Key breakthrough: For shunt capacitor banks, traditional methods require removing high-voltage leads to test individual capacitors. Modern instruments use clamp-type current transformers (CT) combined with voltage sampling, allowing measurement by clamping the ground wire or neutral point wire without removing high-voltage leads (subject to specific wiring conditions, such as star connection with accessible neutral point). This greatly improves work efficiency and reduces the risk of working at heights. Automatic Protection and Discharge: Built-in overvoltage and overcurrent protection. Automatically detects residual voltage before and after testing and controls internal circuits for rapid discharge to ensure personnel safety.
- Capacitance increase: Usually indicates internal element breakdown (plate short circuit), requiring immediate replacement.
- Capacitance decrease: Usually indicates internal element open circuit or dried-out dielectric.
- Excessive tanδ: Indicates serious insulation moisture or aging, increased losses, and risk of thermal breakdown.
