High Voltage Measuring Techniques

Various industrial and commercial environments require high voltages of electrical energy. Techniques for measuring high voltage are varied. They include direct measurement using an electrostatic voltmeter, reduced level measurement using dividers or transformers, and gap measurement. Workers must adhere to appropriate safety procedures when they deal with high voltages.

Direct Measurement

• Several types of electrostatic voltmeters have been developed that attach to high voltage circuits for direct measurement. Electrostatic voltmeters are capable of measuring voltages of around 200 kV. Common voltmeters are the attracted disc type, which measures voltage above 10 kV, and the Abraham voltmeter, which covers a range between 3 kV and 500 kV. Above 200 kV, however, some recording errors do occur.

Gap Measurement

• The sphere gap technique is used as a calibration method for voltmeters and other devices owing to its high degree of reliability. Sphere gaps essentially measure the drop in voltage as it passes over uniform gaps along the voltage circuit. The device consists of two metal spheres with a gas gap between them, the density of which must be considered when calculating voltage.

Reduced Level Measurement

• On some occasions, the actual high voltage is not measured but rather a secondary voltage at a lower level is recorded. Devices used for this technique include voltage dividers and transformers. Owing to the small amount of current measured, the risk of error is increased. Examples of dividers are resistive and capacitive potential dividers, which are used predominantly in a laboratory setting. Transformers are attached to substations in the power distribution system.

Measuring Lightning

• There is little data available on lighting, as it cannot be artificially induced. This lack of information also applies to its measurement, which is investigated using a Klydonograph. The Klydonograph consists of a dielectric sheet covered by a photographic film layer. This film is attached to a high-voltage electrode, while the other electrode is grounded. In the event of a lightning surge reaching the high-voltage electrode, a photograph is recorded and analyzed. This image is called a Litchenberg pattern.