Current measuring method and measuring device

Abstract

The invention discloses a current measuring method and belongs to the technical field of electrical measurement. According to the current measuring method, a Rogowski coil is adopted to sample the current to be measured, an integral circuit is utilized to carry out integral reduction on a sample signal of the Rogowski coil, the current to be measured is figured out according to the amplitude of the integral reduction signal, the amplitude of the integral reduction signal for figuring out the measured current is the product of the amplitude of a signal outputted by the integral circuit and a compensation factor A, and the compensation factor A is figured out according to the frequency of the current to be measured and the cut-off angular frequency of the integral circuit. The invention also discloses a current measuring device. The current measuring method and the measuring device can be used for accurately measuring current with frequency being as low as a few hertz in a similar wind power generation system, and the safety of a power system is improved; and according to the current measuring method and the current measuring device, an existing measuring device does not need to be modified greatly, and the low cost is realized.

Description

technical field [0001] The invention relates to an electrical measurement method, in particular to a current measurement method and a measurement device, which are suitable for occasions such as wind power generation systems where the current frequency varies in a large range. Background technique [0002] Intelligent controller is the key component of low-voltage intelligent circuit breaker, generally applicable to 50 / 60Hz power grid, mainly used for power distribution, feeding or power generation protection. With the increasingly prominent environmental and energy issues, renewable energy power generation is developing rapidly around the world, among which wind power generation is the fastest growing and the technology is the most mature. In order to protect the normal use of wind turbines from damage and facilitate the maintenance of wind turbines Or service, the fan system must be equipped with some electrical protection products such as circuit breakers. However, when ...

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Problems solved by technology

When designing an integral circuit, many manufacturers will choose a suitable integral time constant, such as T=R*C=0.01, and the cut-off frequency can be obtained according to formula (1), which can not only ensure the sensitivity of circuit protection, but also ensure The measured signal (frequency 50 / 60Hz) will not be attenuated but will be truly restored, but when the current measuring device with the above-mentioned integrating circuit is applied to the generator side of wind power generation, for example, it is applied to the smart circuit breaker on the wind turbine side , since the frequency of the primary large current flowing into the circuit breaker may be too low (even as low as a few Hz), then the secondary output voltage signal e(t) of the Rogowski coil must be greatly attenuated after passing through the integrating circuit, thus affecting the correctness of the primary current Measurement, especially when a short-circuit fault occurs in the primary current, the measurement of the circuit breaker is distorted and refuses to move, which is very dangerous

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