Development Of 150kV High Voltage Solid-state Switch Based On Direct Light-triggered Thyristor

Damped AC Voltage(DAC)is a new method for the detection and evaluation of XLPE cable insulation condition.It has many advantages such as simple operation,small equipment size,good equivalence with the power frequency tests and low damages to the cables.In current domestic power system,DAC method has been widely used in the cable systems that have a voltage under 35kV for the partial discharge test.However,for the cable system with voltages higher than 110kV,imported equipment is needed when the ultrahigh voltage cables are going to be tested,which is quite expensive and limiting the moreover development.So it is very important for the power system to develop high voltage DAC equipment.A high voltage solid-state switch is the main part of the oscillating wave test system(OWTS).In this paper,direct light triggered thyristor(LTT)was chosen as the basic component to develop the switch,and the following parts of studies have been done:a)Testing several electrical performances of LTT,then the characteristics of the trigger device oscillating were tested according to the opening time and synchronization requirement of the switch,several disciplines of driving characteristics about laser diodes have been achieved;b)The voltage distribution in steady state for different total voltages and series with different assisting voltage sharing current were measured,characteristics of the series connection of devices about voltage distribution in steady state have been achieved;c)Opening synchronization testing of thyristors in series connection with high voltage capacitor voltage divider and optical signal transformer,and the opening synchronization of thyristors in series connection has been verified;d)Doing consequent opening tests with the set-up switch and the possible factors which may cause the interferences in PD detection test were discovered.The generation mechanism and controlling method of the interferences were testified by the simulation and experiment verification.Through the above research work,the conclusions that can be achieved include the following ones:a)According to the study of the performances of LTT,a pulse that has wavelength of 850nm,rising edge time of 50ns,peak of 150mA will get the best driving effect for the switch in this paper;b)Among the voltage sharing current,a resistor of 2M? will make the voltage balancing best;c)Differences between the transient parameters of the thyristor and the diode reversing parallel to the thyristor are the main cause of the transient interferences.In connection with the parameters of the switch in this paper,on-state voltage drop of the diode is 1.8V and the capacitor is 0.4?F,which can remove all the interferences.The results of final experiments are:The voltage resistance of the switch reaches 160kV;the opening time reaches 1.1 ?s;There are no interferences from the switch which may affect the PD measuring.Which indicate that the switch can be used for the 150kV OWTS and conform all the criterion requirements.