GD-500 Automatic Capacitance & Inductance Tester

Overview: the capacitance and inductance tester is used mainly to measure the high-voltage shunt capacitor banks of reactive power compensation installations and to measure reactors. Its measurement basis conforms to the national standard for capacitance measuring instruments, SJ-255-10300. It was developed specifically to address the problems found when measuring high-voltage shunt capacitor banks in the field at substations, and it mainly solves the following problems.

Capacitors can be measured on site without removing the connecting leads, which simplifies the test procedure, improves working efficiency and avoids damage to the power equipment. The complete set of parameters is measured, making it easy to identify changes in capacitor quality and faults in the connecting conductors between components. Large-capacity data storage and USB communication remove the need to transcribe data on site and ensure the integrity of the measured data.

Performance: the instrument uses a superior measurement principle together with four-terminal measurement technology, so measurement is accurate and repeatability is good. It has a large-screen LCD of 320 x 240 dots with Chinese menu prompts, and the LCD has its own touch keys so operation is intuitive and simple. Automatic segmented current compensation linearises the current over the full range and improves measurement accuracy. The waveform and the measured data are displayed at the same time, making the test process more intuitive, and the USB communication function simplifies connection to a PC for transferring and managing measured data.

Equivalent circuit: the instrument calculates the required values from either a series or a parallel equivalent circuit. In the RC internal series or parallel equivalent circuit, Cx is the actual capacitance, Rs is the lead resistance, Lo is the lead inductance, Rp is the inter-electrode insulation resistance and Co is the inter-electrode distributed capacitance. Actual inductors, capacitors and resistors are not ideal reactances or resistances but present themselves as a complex impedance in series or parallel form, so different equivalent circuits give different results, depending on the component concerned. Generally a series equivalent circuit is used for low-impedance components, which are basically high-value capacitances and low-value inductances, whereas a parallel equivalent circuit is used for high-impedance components, which are basically low-value capacitances and high-value inductances. In field use there are only two cases: to test for a change in the internal quality of a device, select the parallel equivalent; to test for a change in the resistance of the external connecting leads, select the series equivalent.

Specifications summary: instrument operating conditions and ratings are an ambient temperature of -10 ℃ to +40 ℃, relative humidity of 90% or less, a working supply of 220 V at power frequency with a tolerance of 10%, a rated frequency of 50 Hz and a rated output of 22 V / 25 A / 500 VA. The instrument measures 360 x 190 x 260 mm (width x height x depth) and weighs approximately 8 kg. The source lists a measuring range, resolution and error section that carries no values.