Conceptual Design Report on JT- · PDF fileConceptual Design Report on JT-60SA 3. ... Vacuum Circuit Breaker ... In the case of converter fault such as the element fault,

Conceptual Design Report on JT-60SA
3. Plant description Sec. 3.6 Page 1
3.6 Power Supplies One of the greatest reconfigured components in the superconducting tokamak JT-60SA project is the power supply systems for superconducting toroidal and poloidal fields coils, and additional heating devices such as NBI and RF. This chapter describes the conceptual design on the new power supply systems being composed of newly manufactured and rearranged, re-used power supplies. Quench protection circuit is the indispensable component in dealing with superconducting coils. Fast control and sector coils will be installed in the JT-60SA to conduct advanced plasma operation. DC feeders should be newly developed for connection of normal- and super-conducting devices. To adapt the new power supplies to the commercial power grid, we have estimated higher harmonic disturbances, and power factor in the operation of plasma discharge. After this investigation, we have decided the specifications on harmonic filters, and shunt capacitors.

3.6.1 TF Coil Power Supply 3.6.1.1 Outline Toroidal field (TF) coil power supply is to energize TF coil with DC current continuously, the maximum DC current being 33.52 kA, and its nominal output DC voltage is 120 V. Typical operation of TF coil power supply is that energizing TF coil starts in the morning time of every day before plasma experiment and terminating TF coil current completes after plasma experiment of the day. It is expected that it takes about 20 minutes to reach steady coil current from starting to energize TF coil. Fig. 3.6.1.1-1 shows typical pattern of TF coil current in daily operation.
Fig. 3.6.1.1-1. Typical pattern of TF coil current in daily operation.
Fig. 3.6.1.1-2. Block diagram of operation control and monitoring.
In the normal operation, the reference value of TF coil current will be set on TF coil power supply by central control system under the rating value of TF coil current. In test or commissioning operation, it will be possible to set the reference value of TF coil current locally in TF coil power

supply. Fig. 3.6.1.1-2 shows the block diagram of operation control and monitoring of TF coil power supply. 3.6.1.2 Circuit Configuration Fig. 3.6.1.2-1 shows the circuit configuration of TF coil power supply. The nominal values of continuous DC output of TF coil power supply are 33.52 kA and 120 V respectively. The quench protection circuit will be prepared with two units. The feeding line is 22 kV CVT cables via Vacuum Circuit Breaker (VCB) in JT-60 generator building. AC line ratings are 3 phase, 18 kV and 50 Hz.
Fig. 3.6.1.2-1. Single line diagram of TF coil power supply. 3.6.1.3 Main Components and their Specifications AC/DC thyristor converter is designed with six pulses commutating one. AC/DC thyristor converter can supply 33.52 kA as continuous output DC current. The water cooling is applied to the cooling system of AC/DC thyristor converter with aim for compact design of converter system. Transformer for AC/DC thyristor converter has one winding in the secondary side. The primary voltage is 18 kV. The cooling type of transformer is oil immersed one with aim for compact design of transformer. The quench protection circuit will be prepared with two units. The voltage rise at quench

protection operation should be considered and designed with sufficient margin. The components of TF coil power supply have sensor or pickup device to measure the current and/or voltage and to monitor the operational conditions including abnormal one, the signals of them being transmitted to central control system by appropriate way. Polarity changing switchgear will be used for changing TF coil voltage and current direction. This switchgear is changed by the removable link. The primary cooling water for AC/DC thyristor converter is de-mineralized circulating one, which is treated by forced air type cooling device equipped with radiator and cooling fan. 3.6.1.4 Layout Plan of Main Components The components of TF power supply are installed in JT-60 transformer yard. AC/DC thyristor converter, DC current interrupter, crowbar switch, polarity changing switchgear and local panel are settled in airtight enclosure packages. Transformer for converter, discharge resistor and cooling device are outdoor type to be settled in open air. Fig. 3.6.1.4-1 shows the brief arrangement of TF power supply components.
Fig. 3.6.1.4-1 Brief arrangement of TF power supply components.
3.6.1.5 Reuse of Existing Components and Building Existing VCB in JT-60 generator building is reused for TF coil power supply, and other components are newly constructed. 3.6.1.6 Interfaces Main circuit terminals of the component should be designed to tie easily with other component terminals with bolts. AC/DC thyristor converter should be designed to have control signals, monitoring signal/ alarm, and status signals of operation to be able to operate in local mode and in central (remote) mode. Auxiliary electric power is 3 phase/AC200V/50Hz or single phase/AC100V/50Hz.
Local panel
AC/DC thyristor converter
Cooling device Crowbar
switch
Enclosure package for electric equipment
Transformer
Settled in one side of these places
Discharge resistor
TransformerDC current interrupter
+Pyrobreaker
Polarity changing
switchgear
Transformer yard(outdoor)

3.6.1.7 Simulation for normal operation in TF coil power supply The normal operation of TF coil power supply is estimated by the simulation model using PSCAD/EMTDC. The TF coil power supply circuit model is shown in Fig.3.6.1.7-1. The TF coil power supply circuit model is composed of transformer, thyristor converter, two quench protection circuits (QPC) and crowbar switch.
Fig.3.6.1.7-1. TF coil power supply circuit model in the simulation.
(1) Simulation results of the start operation for TF coil In the case of staring TF coil power supply, IGCT for the QPC can not be on-state because the forward voltage of IGCT is zero. Therefore, the suitable gate signal ON timing of the IGCT is estimated by the simulation. Circuit currents and IGCT terminal voltage in the case of start operation for TF coil power supply are shown in Fig.3.6.1.7-2(a)(b). From the simulation results, the suitable gate signal ON timing is t=30s after the initial magnetization start time. In this case, the ON forward voltage of IGCT for QPC is assumed as 50V in the simulation.
(a) Circuit current in the start operation for QPC.
(Idc: coil current, Ic: IGCT current, Ib: discharge resistor current)
18kV / 92V%Z: 10%
5.0MVA
0.06 ohm0.06 ohm
IGCT
1000 ohm
TF19
0.06 ohm0.06 ohm
IGCT
1000 ohm
TF1018Quench Protection
CircuitQuench Protection
Circuit
Trans.
Six-phaseThyristorConverter
Crowbar switch18kV / 92V%Z: 10%
5.0MVA
0.06 ohm0.06 ohm
IGCT
1000 ohm
TF19
0.06 ohm0.06 ohm
IGCT
1000 ohm
TF1018Quench Protection
CircuitQuench Protection
Circuit
Trans.
Six-phaseThyristorConverter
Crowbar switch
-0.20
0.20.40.60.8
11.21.4
0 10 20 30 40 50
Idc(kA)Ic(kA)Ib(kA)
Cur
rent
(kA
)
Time(s)

(b) IGCT terminal voltage in the start operation of the QPC. Fig. 3.6.1.7-2. Start operation for the QPC of TF coil power supply.
(2) Initial magnetization operation for TF coil power supply The initial magnetization time of TF coil is estimated by the simulation. As the simulation result, the initial magnetization time is about 1400s to achieve the rated current of 33.5kA. The simulation result is shown in Fig.3.6.1.7-3.
Fig. 3.6.1.7-3. Initial magnetization operation for TF coil power supply. (3) De-excite operation for TF coil power supply The de-excite operation time for TF coil is estimated by the simulation. As the simulation results, the de-excite operation time is about 1000s to reduce the rated current of 33.5kA. The simulation result is shown in Fig.3.6.1.7-4. During the de-excite operation of TF coil, the operation mode to the converter is Gate Shift (GS), in which the control angle to the converter is shifting 120 degrees.
Fig. 3.6.1.7-4. De-excite operation for TF coil power supply.
-0.010
0.010.020.030.040.050.06
0 10 20 30 40 5
Vol
tage
(kV
)
Time(s)0
-505
101520253035
0 500 1000 1500
Cur
rent
(kA
)
Time(s)
Initial Magnetization Time for TF coil1400 s
-505
101520253035
200 400 600 800 1000 1200 1400
Cur
rent
(kA
)
Time(s)
Deexcite time for TF coil(Gate Shift: 120degrees)
1000 sec

3.6.1.8 Simulation for anomalous operation in TF coil power supply (1) Quench prot

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Conceptual Design Report on JT- · PDF fileConceptual Design Report on JT-60SA 3. ... Vacuum Circuit Breaker ... In the case of converter fault such as the element fault,