JP2010039797A - Overcurrent protection system of dc feeding power source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the detection sensitivity for an overcurrent to allow sure protection. <P>SOLUTION: An overcurrent protection system of a DC feeding power source has a power storage device as a constant voltage source installed in parallel with a DC feeding substation and includes feeding breakers 2 and 5 capable of individually cutting off output currents of the power storage device and the DC feeding substation and protective relays 6 and 7, and a converter 10 determines a current resulting from adding output currents of current detectors 8 and 9 which individually detect output currents of the power storage device and the DC feeding substation, and the protective relays individually perform protective operations on the basis of the conversion output of the converter to individually trip the feeding breakers. The converter performs scale conversion of an addition value of output currents of the current detectors into an input range of both of the protective relays. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a DC feeding power source in which a power storage device or the like is installed in parallel to a DC feeding substation, and more particularly to an overcurrent protection device for a DC feeding system.

  DC power system accidents include feeder ground faults, overvoltages, etc., and protective devices are provided that can handle each type of accident. For example, in a ground fault, there is a protection device that identifies an accident point by overcurrent detection and an overcurrent direction and opens a feeder breaker in a section including the fault point (see, for example, Patent Document 1).

  A DC power supply with a power storage device as a constant voltage source installed in parallel to the DC power substation can be used to level the load on the AC power supply of the power substation or regenerate from the electric vehicle. By storing the power as the charging power of the power storage device, the power can be effectively used.

As an overcurrent protection device for a DC feeder power source installed in parallel with this DC storage substation, an overcurrent protection device based on output feeder current detection of the feeder substation and an output current detection of power storage device There is an overcurrent protection device.
JP 2000-333359 A

  As described above, in the case of a DC feeding power source in which a power storage device as a constant voltage source is installed in parallel to the DC feeding substation, the fault current supply feeder substation and the power storage for an accident occurring in the feeding system Shunt to device. For this reason, since the ratio of the accident current which both sides differ according to the charge condition etc. of an electric power storage apparatus each time, the reduction of the current detection sensitivity for accident determination, and also an accident cannot be detected.

  This will be described in detail. FIG. 2 shows a configuration of a main part of a conventional DC power supply, in which a silicon rectifier 1 having no voltage control function and a power circuit breaker (54F) 2 are connected in parallel to a DC power substation constituting a main circuit. The storage medium 3, the voltage control chopper 4 and the feeder circuit breaker (54CP) 5 are provided with a power storage device constituting a main circuit. The power storage medium 3 is, for example, an electric double layer capacitor or a secondary battery. Further, the voltage control chopper 4 is configured as a step-up / step-down chopper, for example, using a semiconductor power element, and enables charging / discharging of the power storage medium 3.

  In the configuration of FIG. 2, when the output voltage of the power storage device is controlled to be constant by the voltage control chopper 4, the power storage device is individually operated (the DC feeder substation is stopped and only the power storage device is operated, or vice versa. In order to protect each device, the feeder circuit breakers 2 and 5 are provided individually, and protective relays (50F) 6 and (50CP) 7 are also provided. Provide separately. Reference numerals 8 and 9 denote current detectors, which are constituted by Hall elements, for example, and detect the currents Is and Icp by voltage signals, respectively.

  However, if the DC feeder substation and the power storage device are operated simultaneously, the fault current is shared between the DC feeder substation and the power storage device when an accident occurs in the feeder system, and each protective relay does not operate. A condition occurs. In FIG. 2, the current Is flows from the DC feeder substation, the current Icp flows from the power storage device, and the current (Is + Icp) flows to the failure point. At this time, the current Is is determined by the internal resistance of the feeder substation, and the current Icp is determined by the performance of the power storage device and the remaining capacity of the power storage medium.

  However, since the remaining capacity of the power storage device decreases with the discharge, Icp also decreases. When the remaining capacity of the power storage device is equal to or less than the capacity for discharging, the power storage device stops outputting and only the DC feeding substation output current is obtained.

  As described above, the accident current is shared during operation of the power storage device, and the current Is of the feeder substation is reduced. Therefore, the protective relay (50F) 6 cannot detect the accident, and similarly The relay (50CP) 7 side also cannot detect the accident, and the protection is performed after the power storage device is stopped, a detection delay occurs, and the protection may not be possible depending on the case.

  The case where the protective relays (50F) 6 and (50CP) 7 do not operate together will be specifically described with reference to the example of the electric circuit constant shown in FIG. In the circuit constant shown in FIG.

(A) The primary side power and the secondary side power of the voltage control chopper 4 are equal. Therefore, Vc × Ic = Vcp × Icp (1)
(B) The voltage and current when the failure point is seen from the DC feeder substation is 1620V = Is × 0.06 + 0.465 × (Is + Icp) + 300V (2)
(C) The voltage and current when the failure point is seen from the power storage device are Vcp = 0.465 × (Is + Icp) + 300V (3)
(D) The voltage control chopper 4 of the power storage device has a limiter function for limiting the power storage medium 3 to 2000 A when the discharge current of the power storage medium 3 exceeds 2000 A so that the device does not become excessive.

  From the relationship of the above formulas (1) to (3), when Is, Icp, Vcp, Vc, and Ic are obtained, Ic is 2000 A or more. Therefore, the limiter function of the voltage control chopper 4 is 2000 A. Ic = 2000A, Is = 1565A, Icp = 1716A, Vs = Vcp = 1526V, and fault current = 3282A.

  Here, when the operating current of the protective relay (50F, 50CP) is set to 2200A and the power storage medium 3 is not installed, the fault current = (1620−300) / (0.06 + 0.465) = 2514A. In order to exceed 2200A, the protective relay (50F) 6 operates to protect against a fault current. On the other hand, when the power storage devices are installed in parallel, since the failure current 3282A is shared by Is and Icp, both Is and Icp are 2200A or less, and the protective relays (50F and 50CP) do not operate.

  In the latter case, the protective relay (50F) 6 operates when the substation output current and the short-circuit current become equal after the fault current continues, the remaining capacity of the power storage medium decreases and the power storage device is stopped. To do. The discharge time of the power storage device is several tens of seconds depending on the capacity of the storage medium, and this becomes the detection delay time.

  FIG. 3 shows a case where a current limiter is provided on the secondary side of the chopper from the voltage control chopper capacity of the power storage device, but there is a similar problem even in a configuration in which no limiter is provided on the secondary side.

  The same applies when a feeder substation comprising a main circuit with a silicon rectifier having no voltage control function and a feeder substation comprising a main circuit with a forward converter having a constant voltage control function are installed in parallel. There's a problem.

  An object of the present invention is to provide an overcurrent protection device for a DC feeding power source capable of increasing the sensitivity of overcurrent detection and performing reliable protection.

  In order to solve the above-mentioned problems, the present invention has conventionally performed overcurrent detection and protection individually in a DC feeder substation and a constant voltage source (power storage device or feeder substation having a constant voltage control function). Instead of the protection device, the DC power substation protection operation and the constant voltage source protection operation are separately performed based on the sum of the output current of the DC power substation and the output current of the constant voltage source. And is characterized by the following configuration.

(1) A DC power supply with a constant voltage source installed in parallel to the DC feeder substation, and equipped with a feeder breaker and a protective relay that can cut off the output current of the constant voltage source and the DC feeder substation individually. An overcurrent protection device,
Obtain a current that is the sum of the output currents of both current detectors that individually detect the output current of the constant voltage source and the DC feeder substation, and provide a converter that performs conversion output based on this added current,
The protective relay of the constant voltage source and the DC feeder substation is configured to individually perform a protection operation based on the conversion output of the converter and to trip the feeder breaker individually. .

  (2) The converter is configured to perform scale conversion of an added value of the output current of the current detector to an input range of the two protective relays.

  As described above, according to the present invention, based on the sum of the output current of the DC feeder substation and the output current of the constant voltage source, the protection operation of the protective relay of the DC feeder substation and the constant voltage source Since the protection operation of the protection relay is performed individually, it is possible to increase the sensitivity of detection of overcurrent and perform reliable protection.

  Further, the converter scales the added value of the output current of the current detector into the input range of both protective relays, so that it is not necessary to change or replace an existing protective relay current detector or protective relay.

  FIG. 1 is a configuration diagram of a main part of a DC power supply showing an embodiment of the present invention, which is an example of a power storage device as a constant voltage source connected in parallel to a DC power substation. Based on the sum of the output current and the output current of the power storage device, the protection calculation of the protection relay of the DC feeder substation and the protection calculation of the protection relay of the power storage device are performed separately, respectively. Increase detection sensitivity and ensure reliable protection.

  FIG. 1 differs from FIG. 2 in that a converter 10 is provided which adds both current detection signals of the current detectors 8 and 9 to a common current detection signal for the protective relays 6 and 7.

  FIG. 1 shows an example in which the current detection outputs of the current detectors 8 and 9 are DC 0 to 10 V, respectively. By connecting the outputs of the current detectors 8 and 9 in series, the output current and power storage of the DC feeder substation are shown. An addition value of the output current of the apparatus is created, and the range DC0-20V of this addition voltage is scale-converted by the converter 10 to the input range DC0-10V of the protection relay, and the overcurrent protection operation signal of each protection relay 6,6 And

  For example, when the current ratio of the current detectors 8 and 9 is 20 kA / 10 V, the converter 10 has an input of 40 kA / 20 V and an output of 40 kA / 10 V, so that the protective relays 6 and 7 can be used as they are. Available.

  In the above example, as the output current detector, a current detector having a Hall element configuration is taken as an example, but a current detector (eg, a shunt and an isolator) by other methods may be used.

  According to the present embodiment, whether the DC feeding substation is operated alone or the DC feeding substation and the power storage device are operated in parallel, the input side of the converter 10 corresponds to the fault current. Since the signal of the current transformation ratio is input, the protective relay operates reliably.

  Specifically, in the device configuration having the electric circuit constant shown in FIG. 3, Ic = 2000A due to the relationship of the above-described formulas (1) to (3) and the limiter function of the voltage control chopper 4. = 2000 A, Is = 1566 A, Icp = 1716 A, Vs = Vcp = 1526 V, and fault current = 3282 A. When the operating current of the protective relay (50F, 50CP) is set to 2200A, when the power storage medium 3 is not installed, the fault current = (1620−300) / (0.06 + 0.465) = 2514A. In order to exceed 2200A, the protective relay (50F) 6 operates to protect against a fault current. Further, when the power storage devices are installed in parallel, the fault current 3282A is shared by Is and Icp, but the current 3282A obtained by adding the respective currents Is and Icp becomes the input of the protection relays 6 and 7, so that the protection The relays 6 and 7 are both acted upon immediately, and the feeder circuit breakers 2 and 5 are both tripped without delay. Further, the detection sensitivity of the protective relays 6 and 7 is increased.

  Although a current limiter is provided on the secondary side of the chopper from the voltage control chopper capacity of the power storage device, a reliable protection operation can be obtained even in a configuration in which no limiter is provided on the secondary side.

  The same applies when a feeder substation comprising a main circuit with a silicon rectifier having no voltage control function and a feeder substation comprising a main circuit with a forward converter having a constant voltage control function are installed in parallel. A protective operation can be obtained.

The principal part block diagram of the DC feeding power source which shows embodiment of this invention. The principal part block diagram of the conventional DC feeding power supply. An example of the electric circuit constant of a DC feeder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rectifier 2, 5 Feeder circuit breaker 3 Power storage medium 4 Voltage control chopper 6, 7 Protection relay 8, 9 Current detector 10 Converter

Claims (2)

Overcurrent protection of a DC feeder power supply with a constant voltage source installed in parallel to the DC feeder substation and a feeder breaker and protective relay that can cut off the output current of the constant voltage source and the DC feeder substation individually. A device,
Obtain a current that is the sum of the output currents of both current detectors that individually detect the output current of the constant voltage source and the DC feeder substation, and provide a converter that performs conversion output based on this added current,
The protective relay of the constant voltage source and the DC feeder substation is configured to individually perform a protection operation based on the conversion output of the converter and to trip the feeder breaker individually. Overcurrent protection device for DC feeding power supply.   2. The overcurrent protection of a DC feeding power source according to claim 1, wherein the converter is configured to scale-convert an added value of an output current of the current detector to an input range of the two protection relays. apparatus.

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