Kaiichirou Hirayama

Transformer overvoltage problems and countermeasures at black start

A system of Kyushu Electric Power Company Inc. or KEPCO (about 19 GW) belongs to the western Japan system (110 GW) and has a 500-kV and 220-kV transmission line in a loop configuration. Japans power system has high reliability and experienced no blackout for the past several decades. However, there is a possibility, though very slight, of a blackout in the event of a big earthquake or unforeseen accident. Considering the risk of blackout, KEPCO has been conducting studies on system restoration. This paper discusses a mechanism of an overvoltage phenomenon during a restoration period in which, about 0.2 seconds or more after a transformer is energized, a voltage becomes maximum in excess of 200% of the rated voltage. The paper also discusses countermeasures against this phenomenon.

Analytical study on generator load rejection characteristic using advanced equivalent circuit

This paper describes the analytical study on generator load rejection characteristic using the advanced equivalent circuit model. The authors have studied the synchronous machine equivalent circuit model and transient phenomena, by simulation with the electromagnetic transients program (ATP-EMTP), and compared the results with the experimental data

Effects of field mutual leakage reactance in rotor circuit of synchronous generator on the transient and dynamic behavior

This paper describes the effects of field mutual leakage reactance in rotor circuit (Canay reactance) on analysis of generator transient and dynamic behavior. The authors derived a detailed equivalent circuit model for generator, and analyzed sudden short circuit out-of-phase synchronization load rejection and sudden load application phenomena of the generator by simulations using the electromagnetic transients program (ATP-EMTP). Then, they compared the obtained results with the experimental data to verify the validity of the proposed equivalent circuit. In addition to these analyses, the influence of field mutual leakage reactance on analysis of power system dynamic stability was investigated.

Estimation of field mutual leakage reactance in synchronous machine by line-to-line sudden short circuit test

This paper describes the effect of field mutual leakage reactance in rotor circuit (Canay reactance) on analysis of small or medium capacity generator transient and dynamic behavior .The authors proposed the decision method of field mutual leakage reactance, and analyzed sudden short circuit and the power system dynamic stability characteristics affected by the rotor mutual leakage reactance

Development of a Coordinated Control System for BWR Nuclear Power Plant and HVDC Transmission System

The combined use of dc and ac transmissions or so-called hybrid transmission was under study, employing both dc and ac systems to enable stable transmission of 10,000 MW of electric power generated by the BWR nuclear plant, scheduled to be built about 800 km away from the center of load. It was thus necessary to develop a hybrid power transmission control system, the hybrid power transmission system consisting of a high voltage dc transmission system (HVDC) and an ultrahigh voltage ac transmission system (UHVAC). It was also necessary to develop a control system for HVDC transmission which protects the BWR nuclear power plant from being influenced by any change in transmission mode that occurs as a result of faults on the UHVAC side when the entire power of the BWR plant is being sent by the HVDC transmission. This paper clarifies the requirements for the HVDC system control during hybrid transmission and also during dc transmission. The control method that satisfies these requirements was studied to develop a control algorithm. The adequacy of the HVDC control for hybrid transmission and for dc transmission was examined by digital simulation. Based on this analysis a BWR simulator, coordinated control equipment and HVDC control equipment were developed to conduct a dynamic characteristic test using a power system model. It was verified that ordinary control and transient control during hybrid transmission and dc transmission have the desired control characteristics.

A study of synchronous machine modeling about synchronizing phenomena

This paper describes the study of synchronous machine modeling particularly with emphasizing on synchronizing phenomena. The authors proposed a graphical method to investigate the induced spiky voltage, examined the transient phenomena by the electromagnetic transient program (ATP-EMTP) and compared the results with the experimental data

Analytical study on synchronizing phenomena using generator model with field mutual leakage reactance

This work describes the effect of mutual leakage reactance in rotor circuit (Canay reactance) on analysis of generator transient characteristics. The authors derived a detailed equivalent circuit model for 48P-15750 kVA generator, and analyzed sodden short circuit and transient phenomena of the generator at synchronization by simulations using the electromagnetic transients program (ATP-EMTP).