Handheld oil immersed non partial discharge test transformer

The core definition of oil immersed non partial discharge test transformer refers to a specialized test transformer that controls its partial discharge at an extremely low level (usually ≤ 5pC) under rated test voltage, without interfering with the partial discharge detection of the test sample. Absolute non partial discharge equipment is currently difficult to achieve, and its core value lies in providing a "interference free" high-voltage environment for high-precision testing.

1、 Core Definition and Technical Principles

Partial discharge is a local breakdown phenomenon in the insulation system of electrical equipment caused by the electric field strength in a certain area exceeding the dielectric withstand strength, which is an early signal of equipment insulation degradation. The core definition of oil immersed non partial discharge test transformer refers to a specialized test transformer that controls its partial discharge at an extremely low level (usually ≤ 5pC) under rated test voltage, without interfering with the partial discharge detection of the test sample. Absolute non partial discharge equipment is currently difficult to achieve, and its core value lies in providing a "interference free" high-voltage environment for high-precision testing.

Its technical principle is based on electromagnetic induction, while achieving low partial discharge characteristics through structural optimization: firstly, the low voltage winding is connected to a 220V/380V power supply, and through magnetic coupling of the iron core, it induces the generation of 0-1000kV AC or 0-1400kV DC high voltage in the high voltage winding; The built-in 25 # transformer oil serves as an insulation medium, with dual insulation and cooling functions, and is combined with an epoxy cylinder structure to form multiple insulation protections; The key lies in the special design of the iron core and winding to reduce its own partial discharge source, such as using DQ130-30 high permeability silicon steel sheet and 45 ° full oblique seam stacking process to reduce partial discharge caused by iron core hysteresis loss; The high-voltage winding adopts a cylindrical pagoda structure to ensure uniform distribution of electric field and avoid discharge caused by local electric field concentration. During testing, pure high voltage is applied to the test sample, and with the help of a partial discharge meter, its true partial discharge level can be accurately detected to determine insulation defects.

2、 Core Structure and Design Highlights

The structural design of oil immersed non partial discharge test transformers revolves around the core goal of low partial discharge, with key components using special processes and materials to form a complete low partial discharge guarantee system. As the core of the magnetic circuit, in addition to selecting high-quality silicon steel sheets, the iron core needs to be tightly wrapped and dried with epoxy cloth tape after stacking to avoid the risk of partial discharge caused by vibration; The high-voltage winding is made of equal resistance copper wire winding, and the interlayer insulation is made of diamond grid adhesive polyester film. The end is equipped with an oil passage compression structure to prevent electric field distortion caused by vacuum drying or loosening during testing.

The insulation system is the focus of the design, using a composite structure of "epoxy cylinder+insulation oil": the epoxy cylinder is made by constant temperature and pressure winding with untwisted roving, which has high density, low leakage current, and is not easy to absorb moisture; Transformer oil # 25 needs to undergo vacuum degassing and dehydration treatment, with a breakdown voltage of ≥ 35kV/2.5mm, to ensure insulation strength while quickly removing operating heat. In addition, the equipment is equipped with a multi-layer shielding structure, which can effectively isolate external electromagnetic interference; The high-voltage output end adopts anti corona porcelain bushing to reduce the risk of air gap discharge and further control the local discharge.

The control system has a high degree of integration, with functions such as automatic voltage boosting, voltage holding, and overcurrent/overvoltage protection. When the test current or voltage exceeds the set value, the output can be cut off in milliseconds to protect the safety of the test object and equipment; Some models are equipped with intelligent measurement and control modules, which support real-time collection of test data and curve display, simplifying the operation process.

3、 Main application scenarios

The application of oil immersed non partial discharge test transformers runs through the entire life cycle of power equipment and plays an important role in core areas. In the production process of power equipment, transformer and GIS composite electrical equipment manufacturers use them as the core equipment for factory inspection. Through partial discharge testing at 1.3 times the rated voltage, hidden defects such as winding turn to turn short circuits and insulation bubbles are checked. Mainstream transformer enterprises in China have achieved 100% coverage of factory partial discharge testing.

In the field of power grid operation and maintenance, it is a key equipment for equipment handover and preventive testing: after the construction or renovation of substations, it is used for handover testing of GIS, transformers and other equipment to ensure that the insulation performance of the equipment meets the grid connection requirements; During regular maintenance, partial discharge retesting is conducted on transformers that have been in operation for more than 10 years, and the degree of insulation aging is determined by comparing historical data. In ultra-high voltage engineering, its application is more extensive, such as in the construction of ± 800kV ultra-high voltage converter stations, used for partial discharge testing of converter transformers and wall bushings to ensure the safe and stable operation of ultra-high voltage power grids.

In the field of scientific research and testing, the Electric Power Test Research Institute uses it to conduct research on the aging mechanism of insulation materials. By simulating the partial discharge process under different voltage levels, the degradation law of materials is analyzed; Universities use it for experimental teaching in high-voltage majors to help students intuitively understand the principles and testing methods of partial discharge.