JP2005065368A - Digital form protection relay device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To specify a fault/defect of a polyphase analog input circuit while capable of easily dealing with the case that rates of a main current transformer to be monitored and an auxiliary current transformer of an analog input unit have a difference. <P>SOLUTION: A digital form protection relay device includes auxiliary current transformers ACT<SB>a5</SB>, ACT<SB>a1</SB>which have transformation ratios different from each other and in which their primary sides are connected in series and connected to secondary sides of a main current transformer CTa. A CT selector SW selects either one of the secondary side outputs of the auxiliary current transformers by selectively setting the secondary side outputs of the auxiliary current transformers and captures the one as the analog input current. A defect judging unit DET sets the secondary side outputs of both auxiliary current transformers to the same level and takes a difference of the secondary side outputs, and judges as that the transformation ratio of either one auxiliary current transformer is abnormal, both the transformation ratios are abnormal or a secondary side disconnection of one auxiliary current transformer when the difference exceeds a predetermined value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a digital type protective relay device, and more particularly to taking in an analog input current in an analog input unit and monitoring a fault / abnormality of a current transformer circuit.

  FIG. 2 shows a circuit configuration example of a digital type protective relay device. The analog input unit 1 removes noise components from analog signals of currents and voltages detected from input objects (auxiliary transformers) CT / PT from the object to be protected, such as transformers and distribution lines, with an analog filter AF, and samples Each sample is sampled by the hold circuit S / H, each sample value is sequentially switched by the multiplexer MPX to be input to the analog / digital converter A / D, and converted to a digital signal by the analog / digital converter A / D.

  The protection operation unit 2 is equipped with a microprocessor (or computer) CPU having a software configuration that implements a protection operation algorithm, and performs a protection operation based on measurement data acquired from the analog / digital converter A / D.

  The output unit 3 outputs a circuit breaker trip signal to the digital output circuit DO when the calculation result of the protection calculation unit 2 is an accident detection, and drives an external trip auxiliary relay Ry.

  The protection calculation unit 2 has a functional configuration in which a program corresponding to the difference in the relay system for the protection target system or device is incorporated. For example, transformer protection is configured as a differential relay that detects the current on the primary side and the secondary side, detects an abnormality of the transformer based on the ratio or difference of both current values, and obtains a protection output. The Further, the distribution line is protected by a ground fault overvoltage relay that detects and protects a ground fault based on generation of an unbalanced current / voltage of zero phase current or zero phase voltage.

  Furthermore, the digital type protective relay device is not limited to a single protective relay function, and often has a composite relay function in which a plurality of protective relay functions are combined. For example, in order to increase the reliability, a dual configuration in which the main detection relay element (M) and the accident detection relay element (FD) are combined is adopted. In this case, the analog input unit 1 is also duplicated.

  In the digital protection relay device as described above, in order to normally protect the system to be protected and the equipment, it is necessary that the device itself has no failure or abnormality. In the digital type protective relay device, failure and abnormality are likely to occur in the analog input unit 1 and the output unit 3 having a discrete configuration, and various failure / abnormality monitoring methods have been proposed. Among these, a constant monitoring method represented by zero-phase current monitoring is mainly used for failure / abnormality monitoring of the analog input unit. This method focuses on the fact that the zero-phase current, which is the combined current of each phase, becomes almost zero because the phase currents to be protected are balanced in normal times.

For example, as shown below, from the sum of the phase currents I _a , I _b , and I _c of the protection target a, b, and c, the unbalanced portion of each phase current that is always generated + a current transformer ( CT) A value obtained by subtracting an apparent zero-phase current I ₀ generated due to variation in characteristics and a value obtained by multiplying the maximum value max (I _a , I _b , I _c ) of each phase current by a coefficient α. A failure / abnormality determination of the analog input unit is obtained depending on whether or not the difference is within a certain range ε. As a result, failure / abnormality monitoring of the analog input section after the auxiliary current transformer is performed without being affected by the system.
(Equation 1)
| I _a + I _b + I _c −I ₀ | −α · max (I _a , I _b , I _c )> ε
Other monitoring methods of the analog input unit include a main current transformer CTa, CTb, CTc provided for each phase of the primary side and secondary side of the transformer to protect the transformer by a differential relay, and an auxiliary The absolute value of each phase current and the absolute value of the zero-phase current detected through current transformers (instrument transformers) ACTa, ACTb, ACTc (only the secondary side is shown in FIG. 2) are respectively compared with threshold values. Some have determined that the current detection system (current transformer) is disconnected when the absolute value of the zero-phase current is greater than a threshold value and the absolute value of each phase current is below a certain ratio. (For example, refer to Patent Document 1).
JP-A-5-38041

  In the digital type protective relay device, the current input signal of the analog input section is taken in. The secondary side of the main current transformer has an input / output rating of 5A / 0.01A or 1A according to the difference of 5A rating or 1A rating. Specification / design is made by providing an auxiliary current transformer set to /0.01A in the analog input section.

  For this reason, when entering the design / manufacturing stage after confirming the specifications, there is a problem that even if an attempt is made to change the specifications for some reason, it becomes difficult to cope with it, and the design / manufacturing needs to be repeated.

  Note that a voltage transformer such as a capacitor type is used for detecting the voltage to be protected, and the specification / design change can be handled relatively easily by changing the capacitor capacity of the analog input section.

  Next, regarding the analog input unit monitoring method of the digital type protective relay device, when the above judgment formula is used, even if failure / abnormality judgment is obtained for comparison by the sum of each phase current of the multiphase analog input. Therefore, it is impossible to specify which of the auxiliary CTs is faulty / abnormal, and it is not possible to determine the fault / abnormality for each phase.

  Similarly, Patent Document 1 has a circuit that individually compares the absolute value of each phase current with a threshold value to determine a failure / abnormal part of the current detection system. The comparison result of the threshold value also becomes a determination condition, and it is impossible to specify which part of each auxiliary CT is faulty / abnormal.

  The object of the present invention is to make it possible to easily cope with the case where there is a difference in the rating between the main current transformer to be monitored and the auxiliary current transformer of the analog input section, while the failure of the multi-phase analog current input circuit. -To provide a digital protective relay device that can identify abnormalities by phase.

  In order to solve the above-mentioned problems, the present invention provides a plurality of auxiliary current transformers having different transformation ratios for each phase, and the primary sides of both auxiliary current transformers are connected in series to each other. Connect to the secondary side, select one transformer output of both auxiliary current transformers and take it as an analog input, and flexibly handle the difference in the transformer current rating between the main current transformer and the auxiliary current transformer It is possible to determine whether the transformation ratio of one auxiliary current transformer is abnormal or both are abnormal, or the secondary side disconnection of one auxiliary current transformer Thus, it is possible to specify the failure / abnormality of the analog current input circuit for each phase, and it has the following configuration.

(1) Each phase current to be protected is transformed by the main current transformer, and each phase current from the main current transformer is transformed by the auxiliary current transformer provided in the analog input section as each phase analog input current. A digital protective relay device for capturing,
The auxiliary current transformer for each phase is provided with a plurality of auxiliary current transformers having different transformation ratios, and the primary sides of the plurality of auxiliary current transformers are connected in series, and the secondary side of the main current transformer Connect with
For each phase, there is provided a CT selection unit that takes in the transformation current output to the secondary side of the plurality of auxiliary current transformers, selects one of them according to the selection setting, and takes in it as an analog input current,
For each phase, the transformation current output to the secondary side of the plurality of auxiliary current transformers is set to the same level and the difference is taken. When this difference exceeds a certain value, the current of either one of the auxiliary current transformers is taken. The present invention is characterized in that an abnormality determining unit is provided that determines whether the metamorphosis ratio is abnormal or both of the metamorphosis ratios are abnormal or the secondary side disconnection of one auxiliary current transformer.

  As described above, according to the present invention, a plurality of auxiliary current transformers having different transformation ratios are provided for each phase, and the primary sides of both auxiliary current transformers are connected in series, and the secondary current of the main current transformer To select one transformer output of both auxiliary current transformers so that it can be taken in as an analog input, flexibly adapting to differences in the rated current rating between the main current transformer and the auxiliary current transformer it can.

  In addition, in order to determine that the transformation ratio of one of the auxiliary current transformers is abnormal or both of the transformation ratios are abnormal, or the secondary side disconnection of one of the auxiliary current transformers, by comparing the transformation current of the auxiliary current transformer, Faults and abnormalities can be identified by phase.

  FIG. 1 is a main part configuration diagram of a digital protection relay device showing an embodiment of the present invention, and shows only a part for taking in an a-phase current into an analog input part.

The analog input unit is equipped with an auxiliary current transformer ACT _a5 rated at 5A / 0.01A and an auxiliary current transformer ACT _a1 rated at 1A / 0.01A as the auxiliary current transformer for phase a. side are connected in series is set to the terminal lead structure that can be connected to the secondary side of the main current transformer CT _a.

One of the transformation currents output to the secondary side of both auxiliary current transformers ACT _a1 and ACT _a5 is selected and output by the CT selection unit SW and taken into the analog filter AF or the like of FIG. The CT selection unit SW is shown in a logical configuration in the drawing, and the input selection signal generation units SEL ₁ and SEL ₅ are selected and set by a hardware tap or software. For these selection settings, as with the set value of the relay, enter a numerical value from the panel (for example, 1 for 1A rating, 2 for 5A rating), “1A rating”, “5A rating” on the PC screen. This is realized by a method of making a key and selecting it with a cursor, or a method of selecting a position of “1A rating” or “5A rating” with a screw by means of a selection tap and taking in the CPU with DI.

When the digital type protective relay device configured as described above is installed, that is, connected to the main current transformer CTa, depending on whether the secondary output of the main current transformer CTa is 5A rated or 1A rated, Complementary switching is performed to enable one output of the input selection signal generators SEL ₁ and SEL ₅ . Thereby, one of the secondary outputs of both auxiliary current transformers ACT _a1 and ACT _a5 can be taken in from the CT selector SW. With the same configuration, one of the secondary outputs of the b-phase and c-phase pair of auxiliary current transformers can be taken in from the CT selector SW.

  Therefore, regardless of whether the output of the main current transformer CTa is 5 A rated or 1 A rated, or has been changed to any after the device is manufactured, the analog input unit does not change the specification, design, and mounting circuit. It can be connected as is, eliminating the need for design and manufacturing.

Next, the abnormality determination unit DET takes in the secondary outputs of both auxiliary current transformers ACT _a1 and ACT _a5 and determines the presence or absence of abnormality in the a-phase detection current system according to the following determination formula.
(Equation 2)
| 5 × I _a5 −I _a1 |> ε
Where I _a5 is the secondary output current of the auxiliary current transformer ACT _a5 , and I _a1 is the secondary output current of the auxiliary current transformer ACT _a1 .

Here, the secondary output of the main current transformers CTa is the subsidiary current transformers ACT _a1, for supplying the same current to the ACT _a5, the subsidiary current transformers ACT _a1, secondary output of the ACT _a5 is always 5 pairs 1 relationship. Utilizing this relationship, the above-described judgment formula is obtained by taking the difference between the secondary output current values of the auxiliary current transformers ACT _a1 and ACT _a5 at the same level, and this difference is a constant value ε (for example, 20% ) Is detected as an abnormal transformation ratio of one of the auxiliary current transformers, or both of the transformation ratios are abnormal, or detected as a secondary disconnection of one of the auxiliary current transformers. These detections can identify an abnormality in the a-phase current detection system regardless of other phases. With the same configuration, abnormalities of the b phase and the c phase can be specified for each phase.

  This abnormality detection is not affected by the current change of the main current transformer CTa. In addition, the disconnection of the primary winding of the auxiliary current transformer and the disconnection of the connection line with the main current transformer can be determined and the phase can be specified when the output of the CT selection unit SW becomes zero.

The principal part block diagram which shows embodiment of this invention. Configuration example of digital type protective relay device.

Explanation of symbols

1 analog input unit 2 protection calculation section 3 outputs unit CTa, CTb, CTc main current transformer ACTa, ACTb, ACTc auxiliary current transformer ACT _a5, ACT _a1 auxiliary current transformer SW CT selection unit DET abnormality determination unit SEL _1, SEL ₅ Input selection signal generator

Claims (1)

Each phase current to be protected is transformed by the main current transformer, and each phase current from the main current transformer is transformed by the auxiliary current transformer provided in the analog input section and taken as each phase analog input current. A protective relay device,
The auxiliary current transformer for each phase is provided with a plurality of auxiliary current transformers having different transformation ratios, and the primary sides of the plurality of auxiliary current transformers are connected in series, and the secondary side of the main current transformer Connect with
For each phase, there is provided a CT selection unit that takes in the transformation current output to the secondary side of the plurality of auxiliary current transformers, selects one of them according to the selection setting, and takes in it as an analog input current,
For each phase, the transformation current output to the secondary side of the plurality of auxiliary current transformers is set to the same level and the difference is taken. When this difference exceeds a certain value, the current of either one of the auxiliary current transformers is taken. A digital type protective relay device comprising an abnormality determining section for determining whether the transformation ratio is abnormal or both of the transformation ratios are abnormal or the secondary side disconnection of one of the auxiliary current transformers.

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