NRC Power Calibration Facility: Power Bridge

The NRC Power Bridge is the Canadian national standard for power and energy. It maintains among the world’s highest accuracy for power frequency calibrations, with uncertainties as low as 5 µW/VA over most of its operating range. It has a wide dynamic range, producing voltage and current conditions as low as 0.02 VA (1 mA 20 V) up to 120 kVA (200 A 600 V). The current produced can be generated at any phase angle relative to the test voltage with a magnitude resolution of 1 µA/A and a phase resolution of 1 µR. Refer to Figure 1 for a diagram of the Power Bridge. NRC’s client base consists of: • Measurement Canada • Manufacturers of high accuracy power and energy meters • Manufacturers of large transformers Measurement Canada send NRC a high accuracy power and energy meter for calibration. This meter is in turn used to realize the accuracy of all electrical billing measurements throughout Canada. Transformer manufacturers require a high accuracy power and energy meter to determine the losses of their products. With the power factor being very low during the Loss Measurement, a high-quality calibrated power meter is required even to make a 1% accurate measurement.