For the cable withstand voltage test, I believe many people are curious about what it is for, and also curious about what uses. The following ZMS cable company’s editor will take you to understand.
Cable series resonance test device uses the way to adjust the frequency of the power supply so that the reactor and the capacitor are under test to achieve resonance. The test product to obtain high voltage high current is a new method and trend of the current high voltage test, which has been widely used at home and abroad.
The cable series resonance test device adopts a special SPWM digital waveform generation chip with 16-bit frequency resolution. The frequency fineness can reach 0.1Hz at 20~300Hz. The orthogonal non-synchronous fixed carrier modulation method is adopted to ensure good output waveform in the whole frequency interval; the power part adopts the IPM module to ensure the stability and safety of the instrument under the minimum weight.
Component Parts
The cable series resonance test device is composed of frequency modulation and voltage regulation power supply, excitation transformer, reactor, and capacitor divider.
Main Uses
1. 6kV-500kV high-voltage cross-linked cable AC withstand voltage test.
2. 6kV-500kV transformer frequency withstand voltage test.
3. GIS and SF6 switch AC withstand voltage test.
4. AC voltage test for generators.
5. AC withstands voltage test of other electric high-voltage equipment such as busbar, bushing, and transformer.
Test Alias
Variable frequency series resonance withstands voltage test device, frequency modulation series resonance withstands voltage equipment, frequency resonance test device, frequency series resonance test transformer, frequency series resonance test system, frequency series resonance withstand voltage test instrument, cable AC withstands voltage test device, series resonance device, series resonance withstand voltage equipment, GIS withstand voltage test device, etc.
Technical Characteristics
Through the national authority of the electric power industry electrical equipment quality inspection and testing centers strict type test identification, quality, and reliability, to ensure the safety of test personnel, test products, and test equipment itself.
A Portable AC frequency withstand voltage meter is small in size, light in weight, simple in structure, high in reliability, and can be used conveniently in the field.
The variable frequency series resonance withstands voltage test device is composed of a variable frequency power supply, excitation transformer, reactor, and capacitor divider. Small size, lightweight, and especially suitable for on-site use. complex structure, extensive wiring, and high cost.
Over-voltage, over-current, discharge, overheat and zero-start protection are comprehensive and reliable, with an action time of 1 microsecond.
Test Method
High-voltage cable AC withstand voltage is used to generate test power by frequency resonance device, and the frequency converter cabinet is the core component of the device.
The inverter cabinet obtains the frequency required for the test through rectification and inversion of the thyristor and introduces a large number of high-frequency pulse current components in the power conversion process.
Frequency resonant system output power can not be directly applied to the test object for partial discharge test as the power supply of cable local discharge test. Effective measures must be taken to pre-treat the test power supply, through the setting of series reactance, anti-corona conductor, and voltage equalization ring to improve the quality of the test power supply.
Technical Difficulties
High Sensitivity Requirement of The Test System
The pulse signal generated by the local discharge of high-voltage cable is weak, which requires the sensor and test system to have a high detection sensitivity.
Complex Interference Factors On Site
Interference signals can seriously affect the detection and diagnosis of cable local discharge when the cable local discharge test is implemented on-site, mainly the corona or local discharge signal generated by the operating equipment near the test site, the local discharge signal of the AC withstand voltage test device itself, and the corona signal generated by the leads of the AC withstand voltage test circuit.
Therefore, it is a challenging technical problem to identify and eliminate interfering signals, extract valid information, and diagnose the insulation status of cables according to their characteristics.
High Requirements For Testers
The signal of high voltage cable local discharge is mainly concentrated in the range of 0-30MHz, the signal band is wide, coupled with the presence of certain interference signals, testers through signal suppression, identification, classification, extraction, judgment, and other technical means to accurately analyze the complex electronic signal components to achieve the state diagnosis of the cable.
This technology requires testers to be skilled in the use of oscilloscopes, spectrometers, filters, and other electronic equipment, and to have the ability to analyze and judge high-frequency electronic signals.
Local Discharge Diagnostic Criteria
1. Through a large number of laboratory simulations and field test results show that: the phase of the local discharge signal has a phase characteristic of 180 degrees or 360 degrees with the phase of the test power supply, and it occurs in a certain width of the phase at the same time.
2. If multiple signal sources are found in the test, the pulse signals of different frequency bands need to be extracted separately by using band-pass filters for individual analysis.
3. whether the waveform and spectrum of the high-frequency pulse signal collected by the local discharge sensor have typical local discharge characteristics.
4. If necessary, the repeated analogy between the actual test local discharge waveform and the waveform when the test loop is calibrated using the analog local discharge source to observe the similarity of the signals.
5. Polarity discrimination method: using the polarity of the pulse waveform to identify the location of the local discharge source.
Test Benefits
1. In the process of cable withstand voltage test, the local discharge test is carried out at the same time, because the cable withstand voltage test power supply adopts heterodyne power supply, the signal of industrial frequency does not correlate with the phase spectrum of the test power supply, only the local discharge signal inside the test system may correlate the phase spectrum of the test power supply, which can effectively exclude the interference signal generated by the operating equipment.
The local discharge signal of the test device itself is caused by the opening and closing of the thyristor, generally concentrated in a specific phase, such interference can be excluded to a certain extent through the “open phase window”.
2. High voltage state of the local discharge test sensitivity, high voltage cable AC withstand voltage applied to 2U0, conducive to the detection of defects inside the cable.
2.1 For defects that do not produce a local discharge signal at 1U0, the defects may be found only when local discharge is generated under excitation at 2U0.
2.2 For the same cable defects, the higher the voltage, the larger the local discharge signal generated, and the higher the sensitivity of detection.
2.3 The impact of early detection of local discharge on operation safety and equipment maintenance.
Through the local discharge test, defects can be found before the cable is put into operation, and the construction personnel has enough time and space to identify the causes and eliminate defects, to avoid repeated power outages after the cable is put into operation with the disease, affecting the normal operation of the power grid.
The above is some information about the cable withstand voltage test. ZMS has professional cable production standards, to protect the rights and interests of customers and provide the best quality service.
—ZMS Cable Group