JP2011133295A - Method for detecting phase interruption of motor for driving reactor coolant recirculation pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for detecting a phase interruption in the case where an RIP-MfG set is used as a variable frequency power supply for a reactor coolant recirculation pump (RIP). <P>SOLUTION: The method for detecting a phase interruption of a motor for driving the reactor coolant recirculation pump enables the detection of a phase current value of each RST phase in an electric circuit where the electric power generated by using an MG (RIP-MfG) set with hydraulic couplings as the valuable frequency power supply for an RIP is supplied to the motor for driving the RIP and emission of a phase interruption detection signal 202 showing the presence of a phase interruption on the condition that the state where a signal 200 indicating the decline in the detected phase current value and a signal 201 indicating the integrity of the RIP-MfG set coexist lasts for five seconds, by using a delay circuit 203. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a phase loss detection method for a three-phase induction motor (hereinafter referred to as a motor) for driving a reactor coolant recirculation pump.

  In a nuclear power plant using an improved boiling water reactor, ten reactor coolant recirculation pumps are used to change the reactor coolant flow rate for the purpose of controlling the thermal output of the reactor. (RIP: Reactor Internal Pump) is used. The core flow rate can be changed by the rotational speed of the RIP, and the rotational speed is controlled by so-called frequency control that changes the output frequency of the driving power source of the motor for driving the RIP.

  On the other hand, if a phase failure occurs during motor operation in the motor circuit, the motor can continue to operate, but a large current flows compared to normal operation until the motor burns or does not burn depending on the load level. However, problems such as motor vibration and noise increase.

  Here, in the case of a general motor, the overload protection for detecting that the motor is in an overload state has a set value of about 110% of the current (rated current value) when operating at the rated frequency. Thus, it is possible to detect the phase loss state with this protection circuit.

  However, in motors that control the rotational speed by frequency control, such as RIP, the motor current depends on the frequency, and depending on the operating conditions, even if the motor circuit is in a phase-open state, it cannot be detected by overload protection. There was a problem.

  A conventional variable frequency power supply for a RIP drive motor uses an ASD (Adjustable Speed Drive) composed of a rectifier, a smoothing circuit, an inverter, and an output transformer for each of ten RIP drive motors. In this configuration, when the phase is lost in the RIP motor circuit, the ASD output transformer is overexcited, resulting in an increase in the excitation current of the output transformer, and the ASD detecting the output overcurrent. An open phase could be detected.

  However, in the configuration in which a plurality of ASDs are installed as described above, there is a problem that the facility space of the variable frequency power source of the RIP drive motor increases.

  As a method of solving this problem, there is a method of using a RIP-MG with fluid coupling (RIP-MfG) set for five RIPs instead of ASD. This entire configuration is described in FIG. By this method, it is possible to rationalize the equipment space as compared with a configuration in which a plurality of ASDs are installed.

Japanese Patent Laid-Open No. 9-257980

  Since Patent Document 1 has one RIP-MfG set as a power supply for five RIPs, it is not possible to provide phase loss detection such as ASD that individually drives the RIPs. The present invention has been made in view of the above problems, and performs phase loss detection in a RIP-MfG set.

  The method for detecting a phase failure of a motor for driving a reactor coolant recirculation pump according to the present invention uses a MG (RIP-MfG) set with a fluid coupling as a variable frequency power source for a reactor coolant recirculation pump (RIP). A phase current value is detected by an electric circuit that feeds the generated power to the motor that drives the RIP, and a signal indicating a decrease in the detected phase current value and a signal indicating that the RIP-MfG set is healthy are both present. This is a method in which there is an open phase when it exists.

  Further, another phase loss detection method according to the present invention detects a difference between the detected phase current values between the phases, and at least a signal indicating the presence of the difference and a signal indicating that the RIP-MfG set is healthy This is a method in which there is an open phase when both are present.

  According to the present invention, even when the RIP-MfG set is used as the power source of the RIP drive motor, the phase loss detection can be performed.

It is a power supply block diagram of the RIP drive motor which concerns on the 1st Embodiment of this invention. It is an interlock block diagram for judging the phase failure which concerns on 1st Embodiment of this invention. 1 is a configuration diagram of a power supply in a nuclear power plant including a RIP system configuration according to each embodiment of the present invention. It is an interlock block diagram for judging the phase failure which concerns on the 2nd Embodiment of this invention.

  In the RIP phase loss detection method according to the embodiment of the present invention, there is at least a difference in the current value between the signals indicating the decrease in each phase current upstream of the RIP drive motor or between the phases, and preferably the difference is present. When a signal generated when the signal is larger than expected and a signal indicating that the RIP-MfG set is healthy are output together, it is determined that the phase is missing. Specifically, it is as follows.

  In the RIP phase loss detection method according to the first embodiment of the present invention, a signal indicating a decrease in each phase current upstream of the RIP drive motor and a signal indicating that the RIP-MfG set is healthy are both output. If it is, it will be judged as a phase failure.

  FIG. 3 shows the power supply configuration in the nuclear power plant including the RIP system configuration. This figure describes, as an example, a low-voltage synchronous plant in which the generator 304 is synchronized with the power transmission system side via a generator load switch 303 on the low-voltage side of the main transformer 302.

  During generator operation, power generated by the generator 304 is output to an external power transmission system via a generator load switch 303, a main transformer 302, and a main transformer circuit breaker 301 provided on the generator output side. In addition, an in-house transformer 305 connected to a circuit branched from between the generator load switch 303 and the main transformer 302 and an in-house transformer power receiving breaker 300 connected to the in-house transformer 305 are connected. Power is supplied to the high-voltage bus 100.

  The in-house high-voltage bus 100 is connected to an electric motor or the like necessary for operation of the power plant, and a RIP-MfG set 307. The RIP 308 has a configuration of ten units, and each of the five RIPs is connected to the RIP-MfG set 307, so that a total of two RIP-MfG sets 307 are employed as the power plant.

  The RIP-MfG set is rated up to a core flow rate equivalent to 111% (= 10 units / 9 units) so that even when one RIP unit fails, a nuclear power plant can be rated at 9 units (core flow rate: 100% operation). The specifications are such that a voltage and frequency that can be handled can be output, and the minimum frequency is a specification that allows operation up to 30% of the rated frequency.

  Therefore, the RIP-MfG set 307 controls the output frequency in the range of 30% to 100%, and the RIP-MfG set 307 operates at 80% to 90% of the rated frequency during normal operation (10 RIP operation). ing.

Since RIP is a pump load, the input current of the drive motor is proportional to the cube of the RIP input frequency. That is, assuming that the input current of the RIP drive motor at the rated frequency operation is 100%, the current at the 80% frequency is about 51% (= 0.8 ³ ), and the current at the minimum frequency (30%) operation is about 3%. % (= 0.3 ³ ).

  Therefore, in the example of the first embodiment of the present invention, when the phase current of any of the three phases becomes 0, it is determined that the phase current has decreased. Note that the value of the phase current when determining that the phase current is reduced should be adjusted in accordance with the frequency control range of the RIP-MfG set 307.

  In addition, as an example of a signal indicating that the RIP-MfG set 307 is healthy, the field breaker closed when the excitation power source of the generator (the device indicated by G) of the RIP-MfG set 307 is healthy. Or a signal for closing the RIP feeder circuit breaker 309 in which the RIP circuit is in a healthy state.

  FIG. 1 shows an example of the overall configuration of an RIP phase loss detection method according to an embodiment of the present invention. The power supply configuration of the RIP drive motor 108 includes an AC motor 101 receiving power from the in-house high voltage bus 100 via a circuit breaker, a fluid coupling 102 connected to the AC motor 101, and an AC generator connected to the fluid coupling 102. 103, the RIP drive motor high-voltage bus 104 that receives power from the AC generator 103 via the circuit breaker, the RIP drive motor 108 that receives power from the RIP drive motor high-voltage bus 104 via the circuit breaker, and RIP A RIP pump 109 driven by the drive motor 108 and a current transformer installed in the electric circuit 105 for supplying power to the RIP drive motor 108 from the high-voltage bus 104 for the RIP drive motor in order to measure the current flowing through the RIP drive motor 108 106 and an ammeter 107. The phase current detection means for measuring the current flowing through the RIP drive motor 108 may be any means that can measure the current, and may be a method other than an ammeter.

  The high-voltage bus 104 for the RIP drive motor is normally composed of two systems, and five RIP drive motors for each system are connected.

  In the configuration of FIG. 1, the rake pipe position of the fluid coupling 102 is controlled to control the output frequency of the AC generator 103 in order to set the input frequency to the RIP drive motor 108 to a predetermined frequency.

  FIG. 2 shows an interlock block diagram for detecting an open phase relating to the R phase, the S phase, and the T phase and issuing an alarm. In FIG. 1, the ammeter 107 detects that the phase current of the electric circuit 105 that supplies power to the RIP drive motor has decreased below a predetermined value, and transmits a phase current decrease signal 200 to the control circuit 110.

  Further, the RIP power supply system transmits a signal 201 indicating that RIP-MfG is healthy to the control circuit 110. When the RIP-MfG is in a healthy state and the phase current is reduced, the control circuit 110 determines that the phase is missing.

  When both the phase current drop signal 200 and the signal 201 indicating that the RIP-MfG is healthy are input together, the control circuit 110 determines that the electric circuit 105 that supplies power to the RIP drive motor 108 is out of phase. The phase loss detection signal 202 is output.

  The phase loss detection signal 202 is output when a low current state continues for 5 seconds or more using the delay circuit 203 in consideration of the possibility of malfunction at the time of startup. By doing so, a signal indicating a low current generated due to an unstable current value at start-up can be ignored, and phase loss detection with higher accuracy can be performed. The time of the delay circuit 203 is adjusted according to the RIP start condition and the like.

  As an example showing the RIP phase loss detection method according to the second embodiment of the present invention, the phase currents of three phases are compared, and if the difference is large, it is determined that RIP is phase loss. The phase loss detection method to be performed will be described.

  FIG. 4 shows an interlock block diagram according to a second embodiment for detecting an open phase and issuing an alarm. The technical matters other than those described below are the same as in the first embodiment.

  In this case, the ammeter 107 in FIG. 1 measures the phase current of the electric circuit 105 that supplies power to the RIP drive motor 108, and transmits a signal indicating the measured phase current value to the present control circuit.

  In this interlock, the phase current values between the two phases of each phase are compared by the comparator 400, and when the difference in the current values between the phases is large, the RIP-MfG is healthy as in the interlock of FIG. In this state, it is determined that the electric circuit 105 that supplies power to the RIP drive motor 108 has lost the phase, and the RIP phase loss detection signal 202 is output via the delay circuit 203.

  Although this interlock shows the comparison of the phase current value between each two phases, the structure compared between three phases may be sufficient.

  When the RIP-MfG set is used for frequency control of the power supply for the RIP drive motor, it can be used to detect a phase loss of RIP.

100 High-pressure bus 101 in the station 101 AC motor 102 Fluid coupling 103 AC generator 104 High-voltage bus for the RIP drive motor 105 Current path 106 Current transformer 107 Ammeter 108 RIP drive motor 109 RIP pump 110 Control circuit 200 Phase current drop signal 201 RIP-MfG Signal 202 indicating that the set is sound 203 Phase loss detection signal 203 Delay circuit 300 In-house transformer power receiving circuit breaker 301 Main transformer circuit breaker 302 Main transformer 303 Generator load switch 304 Generator 305 In-house transformer 307 RIP- MfG set 308 RIP
309 RIP feeder circuit breaker 400 comparator

Claims (4)

  As a variable frequency power supply for the reactor coolant recirculation pump, a phase current value is detected in an electric circuit that feeds electric power generated using an MG set with a fluid coupling to a motor that drives the reactor coolant recirculation pump, The reactor coolant recirculation pump drive motor is assumed to have a phase failure when both the signal indicating the decrease in the detected phase current value and the signal indicating that the MG set with fluid coupling is healthy. Phase loss detection method.   The reactor coolant recirculation pump drive motor according to claim 1, wherein a difference between the detected phase current values is detected between the phases, and a signal indicating a decrease in the phase current value is generated based on at least the difference. Phase loss detection method.   3. The method of detecting a phase failure of a reactor coolant recirculation pump drive motor according to claim 1 or 2, wherein the phase failure occurs when the phase current decrease signal continues for a set time or longer.   4. The method of detecting a phase failure of a reactor coolant recirculation pump drive motor according to claim 3, wherein the time is 5 seconds.

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