JP2012050306A - Protection relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protection relay capable of measuring the quantity of electricity when a circuit breaker is turned on and off.SOLUTION: The protection relay includes: an analog detection circuit 3 that detects the quantity of electricity of a main circuit; an A-D conversion circuit 4 connected to an analog detection circuit 3; a central processing unit 5 that is connected to the A-D conversion circuit 4 and performs protection operations; a memory 11 connected to the central processing unit 5; and a measurement condition control circuit 12 that is connected to the central processing unit 5 and inputs an operation signal of the circuit breaker 1 connected to the main circuit. The central processing unit 5 receives a signal from the measurement condition control circuit 12 and measures the quantity of electricity when the circuit breaker 1 is turned on and off.

Description

  Embodiments described herein relate generally to a protection relay in a power distribution system.

  2. Description of the Related Art Conventionally, protection relays are used in power receiving and distribution equipment such as switch gears to protect a main circuit. In the protection relay, when an overcurrent flows through the main circuit, the circuit breaker is operated to disconnect the circuit (see, for example, Patent Document 1).

  In this case, as shown in FIG. 4, in the protection relay, when the current of the main circuit exceeds the protection set value and a predetermined time elapses, a cutoff command is issued at time tx. Simultaneously with the shut-off operation, it measures the amount of electricity such as current and voltage and saves it in the built-in memory. The measurement data is used for overcurrent analysis and the like.

JP 2008-43145 A

  In the above-described conventional protection relay, it is possible to extract measurement data of electric quantities such as current and voltage at the time of interruption from the memory, but it is not possible to obtain data when the breaker is turned on. When the power is turned on, an excessive inrush current or counter electromotive voltage may be generated, which may affect the main circuit. For this reason, a protection relay that can measure the amount of electricity when the circuit breaker is turned on has been desired.

  The present invention has been made to solve the above problem, and an object thereof is to provide a protection relay capable of measuring the amount of electricity when a circuit breaker is turned on and off.

  In order to achieve the above object, a protection relay according to an embodiment includes an analog detection circuit that detects an electrical quantity of a main circuit, an A / D conversion circuit connected to the analog detection circuit, and the A / D conversion circuit. A central processing unit that is connected and performs a protection operation, a memory that is connected to the central processing unit, and an operation signal of a circuit breaker that is connected to the central processing unit and connected to the main circuit The central processing unit receives a signal from the measurement condition control circuit and measures the amount of electricity when the circuit breaker is turned on and off.

The figure which shows the circuit structure of the protection relay which concerns on Example 1 of this invention. The figure explaining the measuring method of the electric quantity of the protection relay which concerns on Example 1 of this invention. The figure explaining the measuring method of the electric quantity of the protection relay which concerns on Example 2 of this invention. The figure explaining the measuring method of the electric quantity of the conventional protection relay.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, a protection relay according to Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating a circuit configuration of a protection relay according to the first embodiment of the present invention, and FIG. 2 is a diagram illustrating a method for measuring the electrical quantity of the protection relay according to the first embodiment of the present invention.

  As shown in FIG. 1, a circuit breaker 1 and a current transformer 2 are connected to the main circuit of the power distribution facility. At the output of the current transformer 2, an analog detection circuit 3 for detecting the current of the main circuit constituting the protection relay, an A / D conversion circuit 4 for converting the current value from an analog value to a digital value, and processing the measured current The central processing unit 5 that performs the protection operation is connected.

  Connected to the central processing unit 5 are a display 6 for displaying a current value and an operation switch 7 for setting and changing a current value to be protected. Further, a closing output contact 8 for closing the circuit breaker 1, a trip output contact 9 for breaking, and an alarm output contact 10 for outputting an abnormality to the outside are operated. Further, a memory 11 that calls and stores various measurement data and a measurement condition control circuit 12 that controls measurement conditions of electric quantities such as current and voltage in accordance with operation signals of the circuit breaker 1 are connected.

  Next, the operation will be described with reference to FIG.

  As shown in FIG. 2, when the circuit breaker 1 is turned on at time t1, the measurement condition control circuit 12 receives the signal and measures the energization current until a predetermined time t2 of several to several tens of seconds. The sampling time is a predetermined interval of several hundreds μs to several ms. This signal includes an output of the closing output contact 8 and an external control of the circuit breaker 1, and can be obtained by monitoring a signal for closing the circuit breaker 1.

  Thereby, an inrush current that is larger than a normal energization current can be measured, and the measurement data is stored in the memory 11. If voltage measurement is performed with a transformer connected to the main circuit, an overvoltage such as a counter electromotive voltage can be measured. In addition, predetermined items such as the current value and the previous current value can be displayed on the display 6.

  When the current of the main circuit exceeds the protective set value at time t3, the measurement condition control circuit 12 receives the signal and starts measuring overcurrent. The measurement is continued until a predetermined time t4 until the circuit breaker 1 performs current interruption. The current value and the like are stored in the memory 11. The measurement data stored in the memory 11 can be transmitted to the outside such as a central monitoring room through a communication circuit (not shown).

  In addition, when the current of the main circuit does not exceed the protection set value and the normal interruption is performed, the ammeter side is performed for a predetermined time from the interruption. Further, when the current exceeds the protective set value, the ammeter side may be performed from the point of interruption as in the conventional case.

  According to the protection relay of the first embodiment, when the circuit breaker 1 is turned on and off, the amount of electricity is measured at a predetermined time, so that inrush current, counter electromotive voltage, overcurrent, etc. are measured and stored. can do. These measurement data can be used for investigation of the influence on the load, countermeasures, and the like.

  Next, a protection relay according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 3 is a diagram for explaining a method of measuring the amount of electricity of the protection relay according to the second embodiment of the present invention. The second embodiment is different from the first embodiment in the sampling method on the ammeter side.

  As shown in FIG. 3, from the time t1 when the circuit breaker 1 is turned on to the predetermined time t2, the ammeter side is performed in the same manner as in the first embodiment, but after the time t14 when the inrush current converges, the sampling time interval is shortened. is doing. That is, the time t1 to t11 to t14 at which the inrush current appears is the same as that in the first embodiment, but the sampling time interval is set to several hundreds μs or less from the time t14 to t20 to t2 at which the surge appears. The change of the time interval is set by the measurement condition control circuit 12 in consideration of the surge resistance of the load.

  Here, the region where the inrush current appears is defined as immediately after the circuit breaker 1 is turned on, and the region where the surge overcurrent appears is the latter half of the turn-on.

  Thereby, it is possible to accurately measure the peak value of the surge electric quantity that is likely to occur due to a reactor load such as a motor. In addition, the capacity of the memory 11 can be made appropriate, and recording and storage can be performed for a long time.

  According to the protective relay of the second embodiment, in addition to the effect of the first embodiment, the surge amount of electricity can be measured together with the inrush current when the breaker 1 is turned on.

  According to the embodiment as described above, it is possible to measure the amount of electricity such as the inrush current and back electromotive voltage when the breaker is turned on, and the amount of electricity when the breaker is turned on, and to investigate and analyze the influence on the main circuit Will be able to.

  Several embodiments have been described above, but these embodiments are merely given as examples and are not intended to limit the scope of the present invention. Indeed, the novel circuits described herein may be embodied in various other forms, and various omissions may be made in the form of circuits described herein without departing from the spirit or spirit of the invention. Replacements and changes may be made. The appended claims and their equivalents are intended to include such forms or modifications as would fall within the scope and spirit or spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Circuit breaker 2 Current transformer 3 Analog detection circuit 4 A / D conversion circuit 5 Central processing unit 6 Display 7 Operation switch 8 Input output contact 9 Trip output contact 10 Alarm output contact 11 Memory 12 Measurement condition control circuit

Claims (4)

An analog detection circuit for detecting the amount of electricity in the main circuit;
An A / D conversion circuit connected to the analog detection circuit;
A central processing unit that is connected to the A / D conversion circuit and performs a protection operation;
A memory connected to the central processing unit;
A measurement condition control circuit that is connected to the central processing unit and inputs an operation signal of a circuit breaker connected to the main circuit;
The central processing unit receives a signal from the measurement condition control circuit and measures the amount of electricity when the circuit breaker is turned on and when the circuit breaker is turned on.   The protection relay according to claim 1, wherein the electric quantity is an inrush current.   The protection relay according to claim 1, wherein the electric quantity is a back electromotive voltage.   4. The protection relay according to claim 1, wherein a time interval for sampling the amount of electricity is set shorter in a latter half of the charging than in a time immediately after the circuit breaker is turned on.

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