JP2682566B2 - Protective relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a protective relay device having a constant monitoring circuit for protecting a power system.

(Prior Art) A protective relay device used to protect a power system is usually
It is composed of an accident detection circuit that detects system accidents and an internal accident detection circuit that detects the accident point. This fault detection circuit enhances the fault current detection capability in the case of a distant fault without responding to the load current.Therefore, a relay that operates by detecting the magnitude of the change in current (hereinafter referred to as current change width detection relay) It is often used.

 Fig. 7 shows the current change width relay and the constant monitoring circuit.

The current transformer 2 is installed in the power system 1, and the secondary current is connected to the input transformer 11 of the current change width relay 10. Input transformer
The secondary circuit of 11 is connected to the change width detection circuit 12, and its output is configured to give a signal to the driver 14 via the off-delay timer 13 to drive the auxiliary relay 15. The constant monitoring circuit for the current change width relay 10 and the driver 14 uses the normally open contact 15a of the auxiliary relay 15 for the logic signal "1".
Is connected to the on-delay timer 31 for configuration.

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

When a system fault occurs in the power system 1, a fault current flows,
The secondary current of the current transformer 2 changes as shown in FIG. Therefore, in the current change width detection relay 10, the change width detection circuit 12 detects the change via the input transformer 11. This change is detected, for example, by comparing the current value with the current value one cycle or two cycles ago, and the difference is detected by a predetermined value or more. Therefore, the output of the change width detection circuit is output only for a short time. Therefore, the delay is delayed by the off-delay timer 13. The extended signal operates the driver 14 to drive the auxiliary relay 15. Auxiliary relay 15 normally open contact
When the 15a is closed, the on-delay timer 31 starts counting, but the on-delay timer 31 time period is sufficiently longer than the off-delay timer 13 time period.
The normally open contact 15a is opened before 31 generates an output, and the monitoring failure does not always occur. Therefore, only when the output of the relay 10 or the driver 14 malfunctions and the auxiliary relay 15 continues to operate, the on-delay timer 31 times out and generates an output to constantly detect a monitoring failure.

(Problems to be Solved by the Invention) In general, a current change of a load current of a system is small and a current change width detection relay does not generate an output, but a special load such as an arc furnace and an increase in capacity are advanced, Recently, the aspect of the load current has changed, and the current change is large as shown in Fig. 9,
Moreover, a load that changes every cycle (hereinafter, such a load is referred to as a flicker load) is not uncommon. This flicker load occurs during the daytime for several tens of minutes to several hours in a day. In this case, as shown in FIG. 9, the current change width detection relay 10 causes the change width detection circuit 12 to intermittently output an output each time the current changes, and the off-delay timer 13 repeats delaying. 15 will work for a long time,
The contact 15a continues to be closed, and the on-delay timer 31 produces an output to constantly detect a monitoring failure.

In order to prevent this, it is possible to deal with this by not performing constant monitoring, but this significantly reduces reliability. It is also possible to abolish the current change width detection relay and apply a simple overcurrent relay, but it is undeniable that the accident detection capability will decline.

The present invention has been made in view of the above circumstances, and provides a protective relay device that does not erroneously detect a faulty continuous monitoring even when a current change width detection relay is applied to a power system with a flicker load. Has an aim.

[Structure of the Invention] (Means for Solving the Problems) A structure for achieving the above-described object will be described with reference to FIG. 1. The secondary current of the current transformer 2 provided in the power system 1 is changed in current change width. Input to the change width detection circuit 12 via the input transformer 11 of the detection relay 10, and this output off-delay timer
Auxiliary relay 15 via driver 14 with signal extended in 13
In an always-on monitor circuit that configures an accident detection circuit that drives a normally closed contact 15a of the auxiliary relay 15 with an on-delay timer 31, the on-delay timer is provided on condition that there is no output from the change width detection circuit 12. It was configured to count 31.

(Operation) According to the above technical means, even if the current change width detection relay intermittently gives an output due to the flicker load, an on-delay that constantly detects a monitoring failure each time a current change occurs or for a certain period from the change detection. Since the count of the timer is reset, there is no possibility that a constant monitoring failure will be erroneously detected.

(Example) Hereinafter, an example is described with reference to drawings.

FIG. 1 is a block diagram of an embodiment of a protective relay device according to the present invention.

In FIG. 1, the same parts as those in FIG. 7 are designated by the same reference numerals and the description thereof will be omitted.

The feature of FIG. 1 is that a prohibition circuit 30 is added between the contact 15a and the on-delay timer 31, and the output of the change width detection circuit 12 is connected to the prohibition input terminal.

The response when the same input as that shown in FIG. 9 is given will be described with reference to the time chart of FIG.

Since the output of the inhibition circuit 30 is locked by the output of the change width detection circuit 12, the on-delay timer 31 does not generate an output,
It does not always cause poor monitoring.

 FIG. 2 is a block diagram of another embodiment of the present invention.

In FIG. 2, the same parts as those in FIG. 7 are designated by the same reference numerals and the description thereof will be omitted.

The feature of FIG. 2 is that another relay 20 that operates on the same principle as the current change width relay 10 is provided, and its input transformer 21 is connected in series with the input transformer 11 of the relay 10. Also, contact 15a
The prohibit circuit 30 is provided between the ON delay timer 31 and the ON delay timer 31, and the output of the OFF delay timer 23 of the relay 20 is connected to the prohibit input terminal.

In the above configuration, when the relay 10 operates due to the flicker load and the contact 15a closes, the relay 20 also operates at the same time. Therefore, since the input of the on-delay timer 31 is not given by the prohibition circuit 30, the monitoring failure does not always occur.

 FIG. 3 shows still another embodiment of the present invention.

In FIG. 3, the same parts as those in FIG. 7 are designated by the same reference numerals and the description thereof will be omitted.

The feature of FIG. 3 is that a change width detection circuit 22 different from the change width detection circuit 12 is provided in parallel and the output of the input transformer 11 is input. Further, the prohibition circuit 30 is provided between the contact 15a and the on-delay timer 31, and the output of the change width detection circuit 22 is connected to the prohibition input terminal. Here, the detection sensitivity of the change width detection circuit 22 is set to be equal to or higher than the detection sensitivity of the change width detection circuit 12.

In the above configuration, when the flicker load is input, the change width detection circuit 22 produces an output equal to or higher than that of the change width detection circuit 12. Therefore, as in FIG. 9, since the inhibition circuit 30 inhibits the input to the on-delay timer 31,
It does not always cause poor monitoring.

As is clear from the above description, according to the present invention, even if the current change width detection relay is applied to the flicker load system,
It is possible to provide a protective relay device that does not erroneously detect a constant monitoring failure, and prevent a decrease in reliability.

In each of the above-mentioned embodiments, the example in which the auxiliary relay is driven by the output of the current change width detection relay and the operation of the contact is constantly monitored has been described, but a static circuit such as a thyristor is used instead of the auxiliary relay, and the auxiliary relay contact is used. It is also possible to realize a photocoupler circuit provided at both ends of the thyristor instead of the above. Needless to say, the same effect can be obtained even if the circuit of the present invention is not configured by an analog circuit but by a program of a digital relay device.

FIG. 4 is a modification of FIG. 1, in which the inhibition input of the inhibition circuit 30 in FIG. 1 is not the output of the change width detection circuit 12 but the output of the off-delay timer 13. When the off-delay timer 13 has a sufficiently high reliability, its effect is the same as that of the embodiment shown in FIG.

FIG. 5 is a modification of FIG. 2, in which the positive logic side input of the inhibit circuit is connected to the contact 15a and the off-delay timer 23 in FIG.
The input of the output is the OR, and the inhibition input is input by the AND of the contact 15a and the off-delay timer 23. The effect is obtained in the same manner as the embodiment of FIG.
Even if the off-delay timer 23 malfunctions, the on-delay timer 31 operates to constantly detect defective monitoring.

FIG. 6 is a modification of FIG. 3, and is configured such that the input of the change width detection circuit 22 in FIG. 3 is not given from the input transformer 11 but is given from the input transformer 21 provided separately from this. is there. The effect is similar to that shown in FIG.

[Effects of the Invention] As described above, according to the present invention, there is provided a protective relay device which does not erroneously detect a constant monitoring failure even when a current change width detection relay is applied to a power system having a flicker load. Therefore, it is possible to prevent a decrease in reliability due to the exclusion of constant monitoring, and it is also possible to prevent a decrease in accident detection capability due to replacement of the application of the current change width detection relay with an overcurrent relay.

[Brief description of the drawings]

1 is a configuration diagram of an embodiment of a protective relay device according to the present invention, FIGS. 2 to 6 are configuration diagrams of other embodiments, and FIG. 7 is a diagram for explaining a conventional protective relay device, FIG. 8 is a time chart when the circuit of FIG. 7 is in an accident, FIG. 9 is a time chart of the circuit of FIG. 7 with a flicker load, and FIG. 10 is a time chart of the circuit of FIG. 1 with a flicker load. It is a chart. 1 …… Power system, 2 …… Current transformer 10,20 …… Current change width detection relay 11,21 …… Input transformer 12,22 …… Change width detection circuit 13,23 …… Off-delay timer 14 …… Driver, 15 …… Auxiliary relay 15a …… Auxiliary relay 15 normally open contact 30 …… Prohibited circuit 31 …… On-delay timer 32 …… OR circuit, 33 …… AND circuit

Claims (3)

(57) [Claims] 1. A relay for detecting that a change width of a secondary current of a current transformer provided in a power system is a predetermined value or more and extending the output for a predetermined time, and outputting the relay. In a protective relay device having a constant monitoring circuit that detects that the current continues for a certain time or longer and determines that it is defective, the constant monitoring circuit is provided on condition that the relay does not detect a current change of the predetermined value or more. A protective relay device, which is characterized by counting a certain period of time. 2. A relay which detects when the variation width of the secondary current of a current transformer provided in the power system is equal to or greater than a predetermined value, delays the output for a predetermined time, and outputs the extended relay. In a protective relay device having a constant monitoring circuit that detects that the current continues for a certain period of time or more and determines that it is defective, if the variation width of the secondary current of the current transformer is a second predetermined value or more separately from the relay. A second relay for detecting the presence of the second relay;
The protective relay device, which counts a constant time of the constant monitoring circuit on condition that the relay detects a current change of a second predetermined value or more. 3. The relay according to claim 1 or 2, wherein the relay or the second relay does not extend a predetermined time by detecting a current change of the predetermined value or a second predetermined value or more. Under the above condition, the protective relay device is characterized in that the constant monitoring circuit counts for a fixed time.