High-Precision Current Sensors for Large Wind Power Currents

1. Introduction

As a response to global environmental issues, wind power generation systems are being introduced in the renewable energy sector. These systems supply electricity to the grid by connecting the power generated by generator motors. Wind power generation is a mechanism that employs the force of the wind to rotate turbines, converting the rotational motion into electricity. This makes it possible to generate clean energy without consuming fossil fuels.

2. Challenges

Since the amount of renewable energy generated often fluctuates due to natural conditions, sudden increases in generation capacity can sometimes cause instability in the power grid. When this happens, waveform observation devices are needed for capturing fluctuations in large current waveforms and examining them in detail.
In addition, conducting tests that continuously monitor the grid over an extended period may be necessary to capture abnormal waveform data. However, long-term waveform monitoring generates a large amount of data, making it difficult to find noteworthy waveforms or abnormal data.

Solving this problem requires using waveform measuring instruments and sensors capable of measuring large currents to perform long-term waveform data measurements, check, and monitor abnormal data.

3. Solutions provided by DL950 and AC/DC split core current sensors

• Current accuracy (50/60 Hz): ±(0.2% of reading + 0.01% of range)
• User-friendly, high-precision current sensors that do not require cable removal
• Can measure large currents up to AC 1000 A/DC 1500 A*
  *DC 1500 A (continuous operation) at the max. operating temperature plus 40°C
• Carrier frequency measurement at a high bandwidth of 300 kHz (−3 dB)
• Accurate measurement in noisy environments due to outstanding Common Mode Rejection Ratio (CMRR) characteristics
• Real time waveform math and power math (DL950)
• Synchronized measurement with WT5000 based on IEEE1588 (DL950)

4. Waveform measurement with a large-current sensor

4.1 A high-accuracy AC/DC current sensor that is easy to connect to waveform measuring instruments for measurement

The CT1000S AC/DC split core current sensor can measure large currents up to AC 1000 A/DC 1500 A*, with current accuracy (50/60 Hz) of ±(0.2% of rdg + 0.01% of rng). Its open/close structure means you can measure large currents without having to remove the cables being measured.
Moreover, you can directly connect the current sensor not only to waveform measuring instruments but also to power meters, making it ideal for power measurement.
*DC 1500 A (continuous operation) at the max. operating temperature plus 40°C

4.2 Reduces the impact on the axial position of the cable being measured

The principle of a current sensor makes it ideal for the cable being measured to pass through the center of the sensor’s primary current hole. But in actual measuring situations passing the cable through the center of the hole is often difficult to do, and in any case the cable position affects the measurement values. This product uses a conductor position adjuster to restrict the axial position of the cable being checked, which reduces the impact of misalignment in the axial position when sensing the current with the AC/DC split core current sensor.

Figure 1. Sensor appearance (left) and conductor position adjuster (right)

4.3 Real time math and power math by the DL950

The DL950’s real time math function (/G03 option) performs various calculations on captured signals and displays the results in real time as trend graphs. This function enables you to set triggers on calculation results or perform automatic waveform parameter measurements as well as cursor measurements. You can also apply filters to both the input signals and calculation results. In addition, since the real time math function is independent of the input channels, real time calculation results for 32 input channels and additional 16 channels can be displayed and analyzed simultaneously.
The power math function (/G05 option) calculates up to 126 types of power parameters for each cycle in real time, including the RMS value, effective power, integrated power, and harmonics. It simultaneously displays both the voltage and current signals being measured, as well as the trend waveform of the computed power parameters in real time. You can also set triggers on trend waveforms for the power parameters.
*The power math option includes the real time math option.

Figure 2. Example of single-phase voltage/current waveforms and power parameter math

Moreover, when you need to measure signals even faster, you can measure the waveforms of three-phase voltages and currents of large currents using the DLM5000 Mixed Signal Oscilloscope.