A three-phase submersible pump was newly installed in a factory, and Master Li on duty sent electricity to check the water output of the pump after connecting the power cord. However, he found that the water flow at the outlet was very small, and the water pressure was also very low, Master Li took it for granted that it was a problem with the power supply or water pump, so he tested the voltage, current and even the insulation resistance of the water pump, but the results were normal, so he sent the power again to observe, but the fault was still the same. Later, he used a phase sequence tester to detect and found a problem - the three-phase asynchronous motor is connected to the reverse phase sequence, which causes the reverse operation, and if the pump is reversed for a long time, the impeller on the pump and the packing connected to the outlet pipe may fall off. Master Li was shocked into a sweat, and quickly reversed two of the three power cords leading to the pump (that is, changed the phase sequence of the pump), and the water output and water pressure reached the rated requirements after power transmission.
In fact, similar to the above, the equipment that cannot reach the rated output parameters due to the wrong phase sequence is also the air compressor (air compressor) and hydraulic pump dragged by the three-phase asynchronous motor. Once some three-phase electrical equipment reverses the phase sequence, it is often very prone to serious safety accidents. For example, when the grinding wheel, cutting saw, fan and other high-speed rotating equipment driven by the three-phase motor are running in the reverse direction of the power supply phase sequence, the grinding wheels, saw blades, and fan blades that are clamped are easy to loosen and thrown out by the strong centrifugal force, resulting in unimaginable accidents
Professional question mark?
So, what is a phase sequence tester?How does it work?What are the functions?How do they empower professionals and related fields?And how do we choose an instrument?
CEM "understands in seconds" small knowledge
Phase sequence. In a three-phase power system, phase sequence refers to the phase relationship of a three-phase voltage or current signal, and refers to the phase sequence of the three-phase voltage waveform of phase A, phase B and phase C. When the phase sequence in the power system is correct, the phase order of phase A, phase B and phase C should be arranged in the order of ABC, that is, the phase of phase A should precede phase B, and the phase of phase B should precede phase C.
If the phase sequence is wrong, that is, the ABC sequence changes to ACB or BCA, etc., it will lead to serious misalignment of the three-phase voltage waveform in the power system, which may cause damage to the power equipment and even cause accidents.
Phase Sequence Tester.
A phase sequence tester is a device used to detect whether the phase sequence of the three-phase voltage in the power system is correct, which can help us ensure the normal operation of the power system and prevent accidents caused by phase sequence errors.
Instrument structure. A phase sequence tester typically consists of a circuit board, a display, and control buttons.
How it works. The working principle of the phase sequence tester is based on the definition of the phase sequence and the phase sequence detection algorithm, which determines whether the phase sequence is correct by sampling and processing the voltage or current signal, and outputs the corresponding signal.
Sampling: The phase sequence tester obtains discrete sampled values by sampling three-phase voltage or current signals in a power system.
Processing: The phase sequence tester processes the sampled values and calculates the corresponding phase difference or positive and negative sequence components.
Judgment: The phase sequence tester judges whether the phase sequence is correct according to the value of the phase difference or the positive and negative sequence components.
Output: According to the judgment results, the phase sequence tester outputs the corresponding signal to indicate whether the phase sequence is correct.
Phase sequence detection algorithms.
In order to determine if the phase sequence is correct, the phase sequence tester needs to obtain the phase difference by sampling and processing the voltage or current signal. There are two commonly used phase sequence detection algorithms:
Algorithm based on zero-sequence detection.
The algorithm based on zero-sequence detection is to determine whether the phase sequence is correct by detecting the zero-sequence component of the three-phase voltage or current signal. Under normal circumstances, the zero-sequence component of a three-phase voltage or current should be zero;If the phase sequence is wrong, then the zero sequence component will not be zero.
An algorithm based on positive and negative ordinal components.
The algorithm based on the positive and negative sequence components is to determine whether the phase sequence is correct by decomposing the positive and negative sequence components of the three-phase voltage or current signal. The positive order component represents the component with a phase difference of 120 degrees, and the negative sequence component represents the component with a phase difference of 240 degrees. Under normal conditions, the negative sequence component of the three-phase voltage or current should be zero;If the phase order is wrong, then the negative order component will not be zero.
Performance metrics. Material properties of insulating materials.
Material properties. Insulation withstand voltage.
The length of the insulating tube and the parameters of the attenuation resistance.
Instrument selection. Can you recommend an easy-to-use and accurate phase sequence tester that is suitable for most measurement occasions?
CEM Huashengchang's phase sequence tester DT-901 902 is quite good!
Product recommendations
Phase Sequence Tester.
CEM DT-901 902
The phase sequence tester has a wide range of applications, mainly used for the installation and commissioning of power systems, equipment operation monitoring and maintenance. Through the phase sequence tester, we can find the phase sequence errors in the power system in time and take corresponding measures to repair them to ensure the safe and stable operation of the power system. The phase sequence tester DT-901 902 independently developed and produced by CEM Huashengchang is well received by the market because of its accurate measurement, clear reading, fast response speed and simple and easy to use.
Product Overview. The DT-901 phase steering indicator is specially designed to measure the direction of the rotating magnetic field in a three-phase system.
Huashengchang DT-902 Motor Steering Indicator is specially designed to measure the direction of the rotating magnetic field of the three-phase system and detect the motor steering.
Product configuration. 
Product Advantages: High-definition LCD screen, clearer display.
The high-definition LCD display screen is convenient for users to read the test data.
Responsive and fast measurements.
The average response speed of the test is as low as 1s, the measurement results are accurate, and the safety factor is high.
A variety of functions, strong applicability.
3 phase indicator configuration, can detect the direction indication of the rotating magnetic field, steering indicator, can be non-contact rotating magnetic field direction measurement, magnetic field detection, and can also detect motor connectivity.
Anti-drop and anti-slip, safe and explosion-proof.
Sturdy and durable, hard inside and outside, explosion-proof type is IP40, safe to use.
Safe and durable, meeting international standards.
Protection level, of which DT-901 electrical safety meets IEC 61010 EN61010, IEC 61557-7 EN 61557-7;
DT-902 electrical safety meets DIN VDE 0411, IEC 61010 DIN, VDE 0413-7, IEC 61557-7 EN 61557-7.
The design is small and easy to carry.
The lightweight design makes it easy to put the instrument in the kit, making it easier to work with ease.
Product Applications. Phase sequence testers have a wide range of applications in power systems, and here are some of the main application areas:
Generator protection.
In the case of multiple generators running in parallel, phase sequence consistency between generators is very important. Phase sequence testers are used to detect phase differences between generators to ensure that their output waveforms are synchronized. If the phase sequence difference between generators exceeds the safe range, the phase sequence detection will trigger a protective device to disconnect the faulty generator to avoid a greater impact on the entire power system.
Transmission line protection.
Phase sequence testers are also widely used for the protection of transmission lines. Phase sequence changes in transmission lines can lead to current imbalances and voltage waveform distortions, causing damage to line equipment and potentially causing failures. Phase sequence detection can detect phase sequence problems in transmission lines in time and trigger protection devices to ensure the safe operation of line equipment and power supply systems.
Transformer protection.
The transformer is an important equipment in the power system, and its operational stability and reliability are crucial to the normal operation of the power system. The phase sequence tester plays an important role in transformer protection, it can detect the phase sequence on the input and output sides of the transformer to ensure that the transformer works properly. If there is an anomaly in the phase sequence, the phase sequence detection will trigger the transformer protection device to protect the transformer from damage.
Generator speed control.
The phase sequence tester can also be used in generator speed control. The speed control of the generator is used to maintain the frequency stability of the power system and maintain the quality of power supply in the power grid. The phase sequence detection can detect the phase sequence difference of the generator's output waveform, and adjust the generator's speed control strategy according to the detection results to ensure the stable operation of the generator and the power system.