AC Resonance Test System Knowledge

What is series resonance ?

Series resonance is related with circuit and series connection. It is a resonance condition that usually occurs in series circuits. Generally, A series resonance test system is classified into two types regulating the induction and regulating frequency. It is composed by an exciting transformer, variable frequency power, capacitive voltage divider and reactor.

Series Resonance Test Condition 

The connection of series resonance is mainly composed of a reactor and a capacitor. The voltage divider connected in parallel with the test object is used to measure the resonance voltage of the test object as the signal of overvoltage protection. Moreover, 

When inductive reactance is equal to capacitive reactance, the series circuit is resistive because the phase of the current and voltage in the circuit is the same, and this phenomenon is called series resonance. When series resonance arises in the circuits, the current is up to the max value and resistance will be the min value.

AC Resonance Test System Application

AC withstand voltage test involved in large power transformer, power cable, HV switch cabinet will use AC resonance test system.

AC resonance test system is to proceed AC withstand voltage test for large capacity and high voltage level power equipment such as power cable and GIS combination equipment. The capacity of AC resonance test system is decided by the capacitance of the test object. The larger capacitance of the test object, the larger output capacity of the series resonance.

With the development of power system , the capacity of a single unit thermal generator set exceeds 1000MW, and the max capacity of a hydroelectric generator set exceeds 800MW. It is hard to finish AC withstand voltage test for these large power systems by traditional AC hipot tester. AC resonance test system can just meet the test request . Adopting a flexible combination way of series resonance, the design and manufacturing of AC withstand test overcome some factors such as power supply, capacity and volume.

AC resonance test system is mainly applied in power systems.

1. 6kV-500kV HV crosslinked cable 

2. Large generator group 

3. GIS and SF6 switches

4. 6kV -500kV transformer

5. HV power equipment such as busbar, bushing, transformer

AC Resonance Test System Feature

1. It adopts color LCD to display measurement data and measurement state and has the prompt function 

2. Flexible test: segmented test voltage, test time, and frequency range setting.

3. The test results can calculate the capacitance value of the test object and print the relevant test data.

4. Compact lightweight test equipment and easy for on-site testing.

5. The test equipment has two test methods, automatic test and manual test, which are easy to operate.

6. Series resonance test device is safe and reliable, The system has overcurrent, overvoltage and discharge protection functions, which can effectively protect the safety of people and equipment.

Series Resonance Test Device Working Principle

From the perspective of circuit theory, the principle of the series resonance test device is as follows: if the loop generates resonance, the condition of the loop frequency is f=1/2π√LC. When the loop frequency f=1/2π√LC, the voltage on test object is Q times (voltage resonance multiple that is the system quality factor) of the output voltage at the HV terminal of the excitation transformer.

Therefore, Q value is generally several tens to one hundred or more. To make the voltage of the tested product reach the test value, it is necessary to adjust the output frequency of the variable frequency power supply first, which is the primary condition for making the circuit resonant in series. Then the voltage of test object reaches the test value by adjusting the output voltage of variable power. 

AC Resonant Test System Advantage :

1. Easy operation and small size, lightweight and easy for on-site use and carry.

2. High effective test 

3. Fully reliable overvoltage protection, overcurrent protection, discharge protection and overheat protection. Action time is 1ms.

4. Real-time display HV test waveform

5. Built-in micro-printer, you can print the data result at any time.

AC Resonance Test System Composition Parts.

1. Variable Frequency Power Supply

Domestic daily electricity is 220V Industry power supply is 380V, and the frequency is 50hz. Variable frequency power supply adjusts the current of these two voltages to a current whose voltage and current can be continuously adjusted. Besides, It has four functions in one and can perform operation, protection, control and monitor functions at the same time.

2.  Exciting Transformer

It has the same function as the transformer. The function of an exciting transformer is to increase the output voltage of the variable frequency power supply in the resonant circuit, and the change amount of the voltage can also be set according to the experimental process. In addition, the high pressure and low pressure can be isolated, so that the test and production can be carried out in an orderly manner.

3.HV Reactor

A High Voltage Reactor can improve the voltage waveform of a variable frequency AC resonant test system. It can greatly improve the power factor of the whole system. It is also an important component that resonates with the capacitive test object

4. HV Divider 

High Voltage Divider also plays a very important role in the entire AC Resonant Test Systems. Its main function is to measure the highest value and lowest value of the high voltage side on the regulator. The test and production process become safe and transparent displays that are by the reason of the existence of a voltage divider.