kV Vacuum Interrupter Research Articles

Optimal Design of Insulation of 3.6kV Vacuum Interrupter

This paper compares and analyzes the insulation structure of the vacuum interrupter, focusing on the influence of the mechanical characteristics and the structure of the shield on the insulation, and establishes an electric field calculation model for the axisymmetric structure of the vacuum interrupter. Finally, the radius of the conductive rod and the thickness of the contact are compared and optimized, and then the thickness of the shield is compared and calculated, and then simulated and analyzed with ANSYS software to verify the optimization direction.

Design and short‐circuit current breaking test verification of a 72.5 kV single‐break fast vacuum circuit breaker

Fast clearing of a short-circuit fault is vital to increase the transmission capacity of power grid transmission lines and improve the transient stability of a power system. A fast vacuum circuit breaker (FVCB) is a good candidate to realize quick elimination of a short-circuit fault. The original contribution of this paper is to present the design of a 72.5 kV single-break FVCB and its verification of short-circuit breaking performance. A specially designed 72.5 kV vacuum interrupter, with floating shields and reduced mass of moving components, was developed. An electromagnetic repulsion actuator was used to provide a high initial opening speed, V1, of 5 m/s over half of the full-contact gap and a relatively low average opening speed, V2, of 1.59 m/s in the full contact gap of 30 mm. The high-designed V1 and low-designed V2 were achieved with the aid of a deliberately designed oil buffer. The opening and closing time of the designed 72.5 kV FVCB was 1.2 ± 0.04 ms and 18 ± 0.20 ms respectively. The terminal fault test duty of T100s(b), carried out on the 72.5 kV FVCB, demonstrated both the 40 kArms and 80 kArms short-circuit current breaking performance. The short-circuit current breaking arcing time windows of FVCB, including the minimum arcing time, the maximum arcing time, and the middle arcing time, was verified to fulfill the requirement of the international standard, IEC 62271-100 2017, and the Chinese standard, GB/T 1984–2014, both for the 40 kArms and 80 kArms switching cases, respectively. Further development of the 72.5 kV single-break FVCB would benefit the development of ultra- or extra-high voltage FVCBs by reducing essential numbers of series-connected breaking units.

Study on Arc Evolution Behaviour of Breaking Short Circuit Current for a Fast Vacuum Circuit Breaker

Abstract A fast vacuum circuit breaker (FVCB), driven by an electromagnetic repulsion mechanism, has an extremely short opening time, and in coordination with the controlled switching technology contributes to breaking a short circuit current with the minimum arcing time. The objective of the paper is to determine the arc evolution behaviour of fast vacuum circuit breakers with a minimum arcing time. A 40.5 kV vacuum interrupter (VI) was used, which was equipped with a pair of CuCr50 (Cr 50 wt%) axial magnetic field (AMF) contacts. The diameters of the contact were Φ50mm, Φ58 mm and Φ65 mm respectively. The arc evolution behaviour in the drawn arc experiment was photographed by a high-speed camera through a glass envelope of the VI. The experiment results showed that an initial intense arc tended to evolve into a diffuse arc when the arcing time is larger than a critical arc diffusion time under a certain opening velocity. The critical arc diffusion time for the vacuum arc is defined as arc evolving from the instant of contact separation to an appearance of separated cathode spots. For a Φ50 mm cup-type AMF contact, the critical arc diffusion time decreases from 0.7 ms to 0.46 ms, with the increase of the opening velocity from 2.52 m/s to 4.65 m/s. What’s more, for a Φ58 mm cup-type AMF contact, the critical arc diffusion time decreases from 1.0 ms to 0.58 ms with the increase of the opening velocity from 2.52 m/s to 4.65 m/s. For a Φ65 mm cup-type AMF contact, the critical arc diffusion time decreases from 1.30 ms to 0.64 ms with the increase of the opening velocity from 2.52 m/s to 4.65 m/s. The critical arc diffusion time increases with the increase of the diameter of the contact under the same opening velocity.

Design, Construction, and Test of a Lightweight Thomson Coil Actuator for Medium-Voltage Vacuum Switch Operation

This paper details the design, construction, and test of a lightweight, low energy usage Thomson Coil actuator for the operation of a commercial medium-voltage vacuum switch. A novel latching design, directly linked to the actuator armature, helps to keep the actuator mass at minimum. Experimental results show that 125 J of electric energy is sufficient for operation of a commercial 27 kV vacuum interrupter in times suitable for medium-voltage dc protection applications. The use of high conductor density coils is shown to play a key role on the observed actuator performance. Finite element simulations are used to demonstrate that shorter operation times are feasible, without augmenting the consumed electrical energy, by further increasing coil conductor density.

Influence of arc-melted cathode layer depth on vacuum insulation

It is well known that after current interruptions, a fine Cu-Cr melted layer is formed on the electrode surface, and the vacuum insulation between electrodes is improved. However, the influence of the depth of the arc-melted layer on the vacuum insulation is still not clear. The objective of this paper is to determine the influence of the depth of the arc-melted layer of the cathode on the vacuum insulation. A 12 kV vacuum interrupter with a pair of rod-plane electrodes was designed. A DC current source was applied to the vacuum interrupter, and the rod electrode was chosen as the anode. A drawn vacuum arc in the anode spot mode was used to generate melted layers with different depths on the rod electrode. The arcing time was controlled to 0, 10, 46 or 73 ms. Then, the vacuum gap was adjusted to 1 mm to measure the basic lightning impulse breakdown voltage. Standard positive-polarity 1.2/50 μs lightning impulses were applied by a basic up-down method, in which the rod electrode was the cathode. Experimental results revealed that the breakdown probability followed a Weibull distribution when the breakdown voltage reached saturation. The 50% breakdown voltage U50 with arcing times of 0, 10, 46 and 73 ms was 55.6, 73.3, 75.5 and 77.9 kV, respectively. Next, a cross section of the rod electrode was analyzed using an electron microscope, and the average depths of the arc-melted layers were 0, 5, 35 and 65 μm at current arcing times of 0, 10, 46 and 73 ms, respectively. The depth of the arc-melted layer varied approximately linearly with the arcing time. The U50 values of the vacuum gaps with the arc-melted layers were significantly larger than that without a melted layer but very close to each other for all arc-melted layer depths. Thus, the melted layer did improve the breakdown voltage, but the depth of the arc-melted layer had little influence on the breakdown voltage.

Review of 72.5kV double-break vacuum circuit breaker based on rapid repulsion actuator

72.5kV double-break vacuum circuit breakers based on rapid repulsion actuator remain blank in China. Based on the theoretical analysis and experimental results from researchers, the design of 72.5kV double-break vacuum circuit breakers based on rapid repulsion actuator was presented. It takes the form of double-break, using two standard 40.5kV vacuum interrupter in series at the bottom, which adopt a permanent magnetic repulsion actuator. The permanent magnetic repulsion actuator consists of rapid repulsion actuator and magnetic retentivity actuator. On the basis above, we produced the prototype, and the superiority of the design was verified through the experiments.

Investigation on X-Radiation for 126 kV Vacuum Interrupters**supported by National Key Basic Research Program of China (973 Program) (No. 2015CB251002)

When subjected to high voltages between opened contacts, vacuum interrupters may emit X-rays. In order to ensure that these are of an acceptable level, vacuum interrupters should comply with the limits for X-ray emission and the test procedures to be carried out to verify this based on relevant standards and specifications. In this paper, a comprehensive experimental study has been performed for 126 kV vacuum interrupters used in a transmission system to understand the X-radiation level and its influence by three main parameters, namely applied power-frequency voltage, contact gap and power-frequency voltage conditioning. The radiation instrument is an FJ347 radiometer and the X-radiation dose was measured at the power-frequency test voltage. These tests demonstrated that the X-radiation emission level for a 126 kV vacuum interrupter did not exceed the following: 5 μSv per hour at a rated voltage of 126 kV and 150 μSv per hour at a power-frequency voltage of 230 kV at 1 m distance. The X-radiation dose increased with the applied power-frequency voltage increasing and decreased with the contact gap increasing. The X-radiation dose for 126 kV vacuum interrupters decreased by 57% after the conditioning procedure with a certain power-frequency voltage. During the conditioning procedure, the average value of the X-radiation dose was 4.49 mSv, which means if a professional conditions 180 interrupters per year, it will be safe at the 6.4 m distance.

Electric field optimization design of a vacuum interrupter based on the Tabu search algorithm

During interruption in the vacuum interrupter, the re-ignition between the contact and the shield is influenced by the shape of the contact and size of the shield. The design of the contact and the shield is an intricate optimization problem. In this paper, the Tabu search algorithm is applied to optimize the contacts of a 35 kV vacuum interrupter. The optimization design is based on electric field computation using the finite element method. By solving the inverse problem, the optimization of the contacts is achieved, and a reasonable distribution of the electric field is obtained. Based on the combinatorial optimization Tabu search algorithm, an improved universal algorithm for continuous variables global optimization is proposed.

Insulation characteristics of vacuum interrupter for a new 72/84 kV C-GIS

This paper describes insulation technology for 72/84 kV vacuum interrupter for a new cubicle-type gas insulated switchgear (CGIS). The insulation performance has been increased significantly by a multi-gap shield configuration around the ceramic surface, which resulted in a 40% volume reduction of the vacuum interrupter. The CGIS housing the vacuum interrupter also reduced by 40% in volume. In the paper, the authors describe the basic characteristics on surface insulation and the area effect on surface insulation and their application to an new 72/84 kV CGIS.

Prebreakdown emission current measurements in a 24 kV vacuum interrupter with butt contacts

Commercial 24-kV vacuum interrupters with butt contacts were tested under DC conditions with three different contact materials: OFHC-copper, stainless steel 304 and Cu/Cr (75/25, wt.%). The critical breakdown field was computed at contact distances of 1, 2 and 3 mm, based on the prebreakdown emission current and the breakdown voltage. While the values for the critical breakdown field for OFHC-copper and stainless steel 304 were in agreement with the values found by other authors, no previous data were found for Cu/Cr. >