7010C High-Voltage, Capacitance, Inductance, Tan Delta Bridge

The 7010C is a microprocessor-controlled, current comparator–based automated capacitance bridge with metrology capabilities. It measures capacitance, inductance, reactor loss, and AC resistance, and also calibrates MI CTs. A large touch screen displays relevant measuring quantities—capacitance (Cx), dissipation factor (Tan δ)—measured current through the standard capacitor, applied voltage, and frequency. 

Easy-to-use touch screen menus let operators configure measurements, including the number of readings for statistical uncertainty analysis at the 95% (2σ) level. The touch screen can display measurement data in table format. Before measurements start, users enter the reference capacitor (Cs) value through the touch screen. All measured parameters transmit over the IEEE-488 interface for computer storage; a USB slot on the front panel also saves measurement data and parameters. 

The 7010C achieves < 15 ppm accuracy in magnitude and 1% of reading ± 10 ppm in dissipation across ratios from 1:1 to 1000:1. Dissipation spans 0 to 10% with 1 ppm resolution, making it ideal for both low and high-voltage applications. A built-in lead compensation circuit reduces measurement errors from lead length. An optional shielded rack on castors provides portability on the test floor. 

The instrument measures inductance by automatically reversing the primary winding. The automatic self-balancing feature facilitates accurate load loss measurements on large high-voltage inductive loads—a major advantage over manual capacitance bridges. The 7010C also handles frequency changes by measuring frequency and updating the display. 

To extend measurement ratios beyond 1000:1, the optional two-stage range extender model 7020 increases the ratio to 2,000,000:1. Transformer manufacturers use 7010C/7020 combinations with MI high-voltage capacitors to measure inductance and reactor losses in systems up to 600 kV.

Applications for the 7010C include:

Capacitance Measurement and Calibration
The 7010C is capable of performing both two- and three-terminal capacitance measurements. Three-terminal measurements (with lead compensation) are typically used for large capacitors to remove lead impedance. The instrument operates with a standard capacitor (C_s) range of 10 pF to 10,000 pF and a maximum measurement ratio of 1000:1. 

The optional model 7020 range extender extends the ratio to 2,000,000:1 for higher capacitance ratios. High-voltage standard capacitors (50 kV to 800 kV, 50–100 pF values) are available to support calibration work. The minimum applied voltage is 100 V when measuring a 1000 pF capacitor. 

Voltage Transformer Calibration

Voltage transformers calibrate using the 7010C and two high-voltage standard capacitors. First, measure the capacitor ratio at the voltage where the transformer will be tested. Apply the high-voltage supply to both the voltage transformer and the two standard capacitors. Interchange the capacitors during calibration; the voltage ratio calculates from the measurements, and the dissipation reading on the 7010C displays the transformer’s loss.

_{Note: The same specifications for accuracy of the 7010C Capacitance Bridge apply to each of the two measurements required for voltage transformers. Any voltage coefficient of the Cs1 and Cs2 capacitor should be taken into account when calculating the voltage ratio.}

Inductance Measurement

The Capacitance Bridge measures inductors by automatically reversing the primary winding. The reactive component of current, when reversed, comes into phase with the current through the standard capacitor, allowing a bridge balance with display readings in equivalent inductance ratio.

Note: Capacitance measurement accuracy is independent of supply frequency; inductance measurement accuracy depends on stable frequency. The 7010C automatically measures frequency and updates the display to compensate for changes.

The 7010C handles frequency changes by measuring the frequency and updating the display. Several transformer manufacturers use the MI 7010C, 7020, and high-voltage capacitor combination for measuring inductance and reactor losses, including systems as high as 600 kV. For inductance measurement, extend the 7010C’s range using the 7020 Two-Stage Compensated Current Transformer, which has a single ratio up to 2000:1. The combined 7010C and 7020 ratio is 2,000,000:1. See the inductance measurement range table for a complete range of inductance measurements.

_{Note: If other Inductance Measurement Ranges are required, contact Measurements International}

Turning on the 7010C power switch automatically loads the program and performs initialization routines, including A/D converter calibration. The touch screen provides full operational control of capacitance, inductance, and reactor loss measurements.

For each measurement type, the system prompts users to enter parameter settings on a dedicated setup page: