What are the testing methods for the complete set of AC Resonant Test System
What are the test methods for the complete set of AC Resonant Test System?
The test methods for the series resonance tester are:(1)Cable test ultra-low frequency method,(2)Cable test resonance withstand voltage method,(3)Cable test oscillation voltage method,(4)Cable test and inductance resonance withstand voltage method,(5)Cable test parallel resonance method,(6)Cable test series resonance method.This article mainly introduces three methods for AC withstand voltage test of cables.
I.Ultra-low frequency method
Usually,a 0.1Hz withstand voltage test is used.Due to the large capacity of the cable and the test transformer,it is necessary to conduct a power frequency test,and provide reactive power for the cable on-site.This method is not suitable for field use.Therefore,using ultra-low frequency as the test power source can greatly increase the capacity of the test transformer.The theoretical capacity is 1/500 of the power frequency at 0.1Hz,which is easy to achieve on-site.However,this method is not very effective in detecting main insulation and auxiliary insulation defects of XLPE and other extruded insulated cables.Currently,this method has been applied to the testing of medium and low voltage cables.
II.Oscillation voltage method
DC charging line,inductance resistance discharge to generate voltage,reaching a certain gap to obtain damping oscillation voltage,for inspecting defects in the main insulation cable and accessories.This method is more effective than DC voltage test,but still has some problems.It is difficult to meet the needs of long cables when one of the oscillating voltages decays,and the damage frequency of these two types of voltage cables is higher.
III.Vibration withstand voltage method
The resonance withstand voltage test method changes the inductance and frequency in the test circuit to bring the circuit into resonance,which can meet the testing requirements of high voltage and large current.The withstand voltage method can be divided into frequency modulation and frequency modulation according to the adjustment method.According to the resonance method,it can be divided into series resonance and parallel resonance.
1.Inductive cable resonance withstand voltage is achieved by adjusting the capacitance of the cable in the reactance loop of the reactor at the resonance frequency(50 Hz)to meet the testing requirements.
2.Frequency-modulated cable resonance withstand voltage.By changing the output frequency of the test power source,the inductor with a fixed capacitance in the circuit resonates with the test product to meet the testing requirements.
3.Cable resonance series method.When the current of the test transformer meets the testing requirements but the voltage does not,the reactor is connected in series with the test piece for testing.When the circuit resonates,an output voltage Q times(Q is the circuit quality factor)of the transformer can be generated on the test piece,and the power provided by the power source is only the active power consumed in the circuit.
4.Cable-resonance parallel method.To meet the testing requirements of the resonant circuit with a reverse parallel with test parameters when the main testing requirements for testing voltage transformers and current are met,using inductive current to compensate for the capacitive current of the test reactor.
The test methods for the series resonance tester are:(1)Cable test ultra-low frequency method,(2)Cable test resonance withstand voltage method,(3)Cable test oscillation voltage method,(4)Cable test and inductance resonance withstand voltage method,(5)Cable test parallel resonance method,(6)Cable test series resonance method.This article mainly introduces three methods for AC withstand voltage test of cables.
I.Ultra-low frequency method
Usually,a 0.1Hz withstand voltage test is used.Due to the large capacity of the cable and the test transformer,it is necessary to conduct a power frequency test,and provide reactive power for the cable on-site.This method is not suitable for field use.Therefore,using ultra-low frequency as the test power source can greatly increase the capacity of the test transformer.The theoretical capacity is 1/500 of the power frequency at 0.1Hz,which is easy to achieve on-site.However,this method is not very effective in detecting main insulation and auxiliary insulation defects of XLPE and other extruded insulated cables.Currently,this method has been applied to the testing of medium and low voltage cables.
II.Oscillation voltage method
DC charging line,inductance resistance discharge to generate voltage,reaching a certain gap to obtain damping oscillation voltage,for inspecting defects in the main insulation cable and accessories.This method is more effective than DC voltage test,but still has some problems.It is difficult to meet the needs of long cables when one of the oscillating voltages decays,and the damage frequency of these two types of voltage cables is higher.
III.Vibration withstand voltage method
The resonance withstand voltage test method changes the inductance and frequency in the test circuit to bring the circuit into resonance,which can meet the testing requirements of high voltage and large current.The withstand voltage method can be divided into frequency modulation and frequency modulation according to the adjustment method.According to the resonance method,it can be divided into series resonance and parallel resonance.
1.Inductive cable resonance withstand voltage is achieved by adjusting the capacitance of the cable in the reactance loop of the reactor at the resonance frequency(50 Hz)to meet the testing requirements.
2.Frequency-modulated cable resonance withstand voltage.By changing the output frequency of the test power source,the inductor with a fixed capacitance in the circuit resonates with the test product to meet the testing requirements.
3.Cable resonance series method.When the current of the test transformer meets the testing requirements but the voltage does not,the reactor is connected in series with the test piece for testing.When the circuit resonates,an output voltage Q times(Q is the circuit quality factor)of the transformer can be generated on the test piece,and the power provided by the power source is only the active power consumed in the circuit.
4.Cable-resonance parallel method.To meet the testing requirements of the resonant circuit with a reverse parallel with test parameters when the main testing requirements for testing voltage transformers and current are met,using inductive current to compensate for the capacitive current of the test reactor.
