Keywords: electric submersible pump protector controller 0 Preface 1 The difference between submersible electric pump protector and motor protector 2 Features of Submersible Electric Pump Protector 3 Product Composition of Submersible Electric Pump Protector Figure 1 Schematic diagram of submersible electric pump product composition 4 Design of submersible electric pump protector 5 Conclusion The article comes from: "Electrical Technology", 2013, Issue 12. references About the Author: Yu Jing, female, undergraduate, engineer of Wuhan Ankerui Electric Co., Ltd., the main research direction is intelligent power monitoring and power management system
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Submersible electric pump is a medium-pressure mechanical oil production equipment used in oil fields. With the improvement of oilfield development automation, the original submersible electric pump fixed frequency control cabinet has imperfect leaking functions, inconvenient data analysis, no waveform recording, and no communication function. The main reasons for these deficiencies are non-specific The protector of the electric pump does not support the above functions.
At present, there are few domestic manufacturers researching and developing submersible electric pumps, and the scale is small, and the products have not been serialized and scaled. In order to enhance the competitiveness of domestic submersible electric pump protectors and make up for the shortcomings of old-style protectors, it is necessary to develop a targeted submersible electric pump protector.
(1) Submersible oil pump protector is a subdivision application product of motor protector. In terms of measurement, protection, communication and other functions, submersible electric pump protectors and motor protectors are basically common, but various protections of submersible electric pumps, such as underload, current imbalance, overvoltage, and undervoltage, are often Time limit type, and these protections mostly use the time limit type in general motor protectors.
(2) The submersible electric pump protector needs to have historical data recording and exporting functions, while the conventional motor protector has fault records.
(3) In order to facilitate the maintenance and evaluation of submersible electric pumps, the submersible electric pump protector needs to have a punching function for punching and checking, which is not necessary for conventional motor protectors.
(1) The submersible electric pump protector can measure three-phase current, three-phase voltage, frequency in real time, and can display electrical parameters such as active power and electric energy at the same time; the type of process parameters that can be detected and collected, 4- Process parameters of 20mA type are sent to the system uniformly through communication.
(2) The submersible electric pump protector has protection functions such as overload, phase failure, current imbalance, stalled, blocked, undervoltage, overvoltage, voltage imbalance, etc., and can realize underload self-starting.
(3) The submersible electric pump protector can display real-time and historical curves of parameters such as three-phase current and three-phase voltage.
(4) The submersible electric pump protector can export the stored historical data to the U disk, and the exported file supports EXCEL operation. The data can be directly analyzed after the U disk is inserted into the computer, without installing additional analysis software. This function can be used to replace the current recorder.
(5) The submersible electric pump protector supports MODBUS and PROFIBUS communication protocols, and can directly transmit real-time data and send start-stop commands through the communication network.
The submersible electric pump protector consists of a protector body, a human-computer interaction module, and a switching power supply, as shown in Figure 1. The main body of the protector completes the functions of parameter collection, protection and communication; the human-computer interaction module realizes the functions of real-time parameter display, parameter setting, real-time curve display, historical curve display, historical data query and fault query; Other grades) The voltage is converted to low voltage for the main body and human-computer interaction module.
The design of submersible electric pump protector is divided into hardware and software. The hardware design includes power supply, signal acquisition, digital input and output, communication circuit and other parts; software design mainly includes software architecture, measurement algorithm, protection algorithm, control algorithm and so on.
4.1 Hardware design Because the working voltage of commonly used submersible oil pumps is from AC 200V to AC2000V, it is not suitable to use the submersible oil pump working power directly as the working power supply for submersible oil pump protection. The voltage is converted to AC 110V control voltage. In view of this situation, the power supply of the submersible electric pump protector uses a switching power supply, because the switching power supply has a wide working range and high efficiency, which is suitable for this situation.
Signal acquisition includes voltage, current and other electrical parameter acquisition. In order to ensure the collection reliability, TV and TA are usually used as isolation converters for voltage and current signals. When selecting TA, pay attention to the TA voltage level. The conventional TA voltage level is 0.66KV, and when the working voltage of the submersible electric pump reaches AC 1000V or even AC 2000V, a TA of 3.3KV level should be selected to ensure isolation safety.
The design of the switch input and output and the communication circuit is a conventional design, without too much specificity.
Reliability design includes electromagnetic compatibility and safety design. In the initial stage of EMC design, we should fully consider various possible problems and make plans for reserved measures. Commonly used anti-interference methods include: adding EMC filter to the power supply part; adding filter circuit to the signal acquisition part; adding port protection circuit at each chip input port of signal processing; adding decoupling capacitor at the chip power input.
4.2 Sampling algorithms commonly used in software design are DC sampling and AC sampling. AC sampling can measure non-sinusoidal signals, so it is widely used in electrical parameter measurement. Common measurement algorithms include algorithms based on sinusoidal signals and algorithms based on non-sinusoidal signals. Algorithms based on sinusoidal signals include the maximum absolute value algorithm in half a week, absolute integration algorithm in half a cycle, first derivative algorithm, second derivative algorithm, sampled value product algorithm, three sampled value algorithm, etc .; algorithms based on non-sinusoidal signal include Fourier Algorithm, first-order differential half-wave Fourier algorithm, true effective value algorithm, etc. Various algorithms have their advantages and disadvantages. Although the algorithm based on sinusoidal signal is simple and consumes less resources, the measurement is inaccurate when there is harmonic or waveform conversion; while the algorithm based on non-sinusoidal signal is more complicated, but it can ensure the accuracy of the measured value.
Due to the difficulty in designing the inverse time limit curve algorithm in the protection algorithm, some products are marked as inverse time limit, but the actual time limit is divided, such as: (1.2-1.5) times, 60s protection, (1.5-2) times, 40s Protection, more than 2 times, 10s protection. This violates the basic principle of the inverse time limit curve. If the signal jumps up and down at the critical point, the action time will be inaccurate. The real inverse time limit has a continuous inverse time limit curve, and it is true that large multiples and large actions are fast, and small multiples and small actions are slow.
In software design, in addition to selecting a reasonable algorithm, we must pay attention to the standardization of software design. The basic principle of software design is information hiding and module independence. Good software requires high cohesion (cohesion is a measure of module strength) and low coupling.
Software testing is an indispensable link in software design. Its purpose is to check whether the software meets the requirements. During the development process, Chinese medicine follows the principles of early testing and early correction. After unit testing is passed, integration testing, confirmation testing, and acceptance testing are conducted.
Submersible electric pumps are a new class of motor protectors derived from conventional motor protector products. They are more suitable for submersible oil pumps. They add inverse time protection such as underload, overvoltage, undervoltage, current unbalance, and voltage unbalance. At the same time with current, voltage, power, frequency, energy, residual current and other measurement functions, more in line with customer requirements.
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Abstract: Design a special submersible electric pump protector that meets the characteristics of submersible electric pumps. The submersible electric pump protector has protection functions such as overload, phase failure, unbalance, overvoltage, undervoltage, and voltage imbalance. The design principle of this kind of product is given, the difference between this product and the conventional motor protector and its hardware and software design principle are introduced.
August 29, 2020