A transformer digital protection device and method based on total pressure information

Abstract

A transformer digital protection device and method based on full pressure information, including: a transient oil pressure characteristic quantity measurement module, a switch input module, a signal conditioning and acquisition module, and a digital core module; wherein, the transient oil pressure characteristic quantity measurement The module is connected with the signal conditioning and acquisition module, and the signal conditioning and acquisition module and the digital input module are all connected with the digital core module. The invention obtains the digital information of transient oil pressure at multiple measuring points inside the oil tank in real time, calculates and obtains the full value of the operating pressure representing the amplitude of the oil pressure, and utilizes the significant difference of the characteristic value under different operating conditions of the transformer to construct the protection criterion and the threshold value The setting method realizes reliable, rapid and sensitive screening and removal of internal faults in the transformer oil tank, and is not affected by the excitation inrush current. The principle of the invention is simple, the device is easy to implement, and it is suitable for the current and future requirements of large-capacity and high-voltage power transformers for non-electrical protection "four properties".

Description

technical field [0001] The invention belongs to the field of power systems, and relates to a transformer digital protection device and method based on full pressure information, which are used for reliable, fast and sensitive identification of internal faults in oil tanks of oil-immersed power transformers. Background technique [0002] As an important component of power transmission, the power transformer will have a serious impact on the reliability and operation stability of the power system once it fails. Especially for large power transformers installed at the hub of the system, because of their high voltage level, large capacity, complex structure, and high cost, damage due to failure will inevitably cause huge economic losses. Therefore, a relay protection device with good performance and reliable operation must be installed according to the capacity and importance of the transformer. [0003] The development of relay protection technology depends on the understandin...

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Problems solved by technology

However, there are two main defects in the principle of transformer current differential protection: first, the excitation inrush current in the excitation circuit when the transformer is closed with no load may cause differential protection to malfunction; second, in the face of single-turn or In the case of weak faults such as short circuit with small number of turns, the differential protection may refuse to operate due to insufficient sensitivity

Under the continuous injection of fault electric energy, the internal pressure of fault bubbles also continues to rise. At the same time, due to the expansion inertia of liquid insulating oil near the fault point, the gas-liquid phase interface between the fault bubble and the surrounding liquid insulating oil will inevitably produce a significant pressure increase. , and spread inside the transformer oil tank in the form of pressure waves, resulting in an overall sudden rise in the oil pressure inside the oil tank

In addition, since the transformer oil tank is not a pressure vessel, the tank is often deformed and cracked under the impact of internal pressure waves

On the other hand, when the transformer has an external short-circuit fault, the fault point is located at the outlet of the transformer, and the impact on the internal pressure of the oil tank is only reflected in the winding vibration caused by the short-circuit through current

At the same time, the change in oil pressure caused by this process is limited since the mechanical strain of the winding will consume a lot of energy

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