Masanori Tsukushi

A Method and Applications of a Theoretical Calculation for on-load Pressure Rises in Puffer Type Gas Circuit Breakers

An on load pressure rise in a puffer chamber of puffer type gas circuit breakers (GCB) is higher than a no-load pressure rise. A method of calculation of the on-load pressure rise has been developed. The calculation results show good agreement with the on-load pressure rises measured with an experimental puffer type GCB.

Analytical prediction of transient breakdown characteristics of SF/sub 6/ gas circuit breakers

A study was conducted to estimate transient breakdown voltages (V/sub BD/s) between contacts of a puffer-type SF/sub 6/ gas circuit breaker. When contacts are opening, compressed gas is blasted between them by an insulating nozzle. The gas pressure fluctuates greatly in the contact region. The authors suggest that this pressure fluctuation causes transient V/sub BD/s. It is demonstrated that very accurate transient V/sub BD/ characteristics can be calculated by combining the gas flow and electric field analyses and breakdown probability. The numerically calculated transient V/sub BD/ characteristics agree fairly well with the transient recovery voltages during the capacitive current interruption. >

High-frequency reignition current and its influence on electrical durability of circuit breakers associated with shunt-Reactor current switching

Very-high-frequency and high-peak reignition currents were measured in shunt reactor banks rated at 33 kV 40 MVA during breaking operations of a gas circuit breaker (CB). To measure those kinds of high-frequency transients in reactor circuits in service, a noninvasive method of measuring was proposed using Rogowski coils and capacitive coupled antennas. Some combinations of metals in an electrical collector used in CBs tend to get severely eroded by the high-frequency reignition currents. The paper also proposes a test circuit that can yield high-frequency reignition currents to evaluate the electrical durability of CBs.

Interruption ability of a self extinguishing type gas circuit breaker

Interruption ability of a self-extinguishing-type gas circuit breaker has been investigated while varying several structural factors. With a thermal puffer cylinder (0.7 l volume), excellent interruption ability (9.5 to 31.5 kA at 84 kV) was obtained for the condition of a breaker-terminal fault (BTF). In the condition of a short-line fault (SLF), however, its interruptible arcing time width at the same current levels was only 0.2 to 0.3 cycles, where 0.5 cycles was proposed. The critical current, which is the minimum current which the breaker can interrupt, was several kiloamperes. >

Research on a New Type Magnetic Puffer Gas Circuit Breaker

The magnetic repulsive force which arises between a secondary short circuit ring and a primary coil through which short circuit current flows was used for a new magnetic puffer gas circuit breaker. A floating piston type magnetic puffer circuit breaker showed much success in experiments and the examples of theoretically calculated results together with a fixed piston type magnetic puffer circuit breaker are shown by the authors for the first time. It is proved that the interrupting performance of SF6 gas circuit breakers is much improved with the addition of a simple magnetic drive mechanism as shown in the following.

Measurement of hot gas exhaust characteristics in SF 6 circuit breaker with small model interrupter

High-voltage circuit breakers have continuously been developed to reduce their size and operating energy. In the current interruption process, hot gas is generated and exhausted out of the conducting exhaust tube. The hot gas causes electrical breakdown at the exit of the exhaust tube. The hot gas characteristics in the exhaust tube were measured to clarify the dielectric strength. Two measurement methods, the small gap discharge method and the extra-fine thermocouple, were used to estimate the temperature of the hot gas. In the small gap discharge method, the temperature was deduced from the breakdown voltage at the small gap by referencing the critical electric field strength. The critical electric field strength is the electric field strength where ionization coefficient is equal to electron attachment one. An extra-fine thermocouple with a 25 micron tip was also used to measure the temperature on a trial basis. The response speed of the thermocouple was slower than that of transient change of temperature in the interruption process. First-order response lag was compensated by de-convolution with fast Fourier transform (FFT). As a result, the peak value of the temperature in the conducting exhaust tube agreed well with the results estimated by the other method.

Estimation of interruption performance in high-voltage circuit breakers with a modified method for arc parameter evaluation

Interruption performance of high-voltage circuit breakers has been quantitatively evaluated through current zero measurements during interruption tests. The interruption capabilities of the circuit breakers are able to be estimated by means of an arc model calculation. The parameters of the arc model are determined through the current zero measurements. In order to simulate more precisely the success or failure of current interruption, a modified extraction method of arc parameters is proposed in this paper. The arc parameters are calculated by combining an equivalent circuit calculation and a non-linear least square fitting for current zero measurement data. The arc model calculation with the modified extraction method of arc parameters is applied to the development and design of an actual high-voltage circuit breaker. The capacitance required for 80 kA interruption can be estimated based on the current zero data measured during 50 kA interruption tests. The test results of interruption and failure agree well with the predicted performance. The proposed method consisting of the arc parameter extraction from current zero data and characterization of the parameters as the function of arc time constant can evaluate short-line fault interruption performance in high-voltage circuit breakers.