JPH0214281Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inspection circuit for a protective relay device applied to bus bar protection in a power transmission system.

As a conventional inspection circuit for a protective relay device in this type of power transmission system, an inspection circuit shown in FIG. 1 is known. In FIG. 1, 1 is the bus of the power transmission system, 2-1 to 2-n are current transformers (hereinafter abbreviated as CT) provided in each of the plurality of branch systems of the bus 1 to detect the transmission current. 3 is a varistor for overvoltage protection of the voltage differential relay 5 which will be described later; 4 is a current limiting resistor of the voltage differential relay 5; 6 is a reactor; 7
8 is a monitoring relay for the bus 1, 8 is a power transformer for inspection, and 9 is an inspection command contact for opening and closing the power supply 10 for inspection.

The operation of the conventional inspection circuit having such a configuration will be explained below. First, in order to detect a fault on bus 1, it is necessary to use multiple branch system current detection CTs.
The secondary circuits 2-1 to 2-n are all connected in parallel to the differential circuit 20, and the combined amount of detection signals obtained here (generally referred to as a differential circuit) is connected to the current limiting resistor 4.
The differential voltage is introduced into the voltage differential relay 5 via the voltage differential relay 5, and it is detected by the voltage differential method whether or not this differential voltage is larger than a preset specified value.

Here, the varistor 3 and the reactor 6 are overvoltage protection elements having saturation characteristics in an overvoltage range, and are provided for the purpose of preventing an overvoltage from occurring in the event of an internal bus-bar fault.

Further, the monitoring relay 7 is a highly sensitive detection relay that operates when the secondary voltage of the reactor 6 reaches a certain value or more, and under normal conditions, the CT 2-1 to 2-2
When a disconnection or the like occurs in the -n secondary circuit, the monitoring relay 7 detects an error differential voltage commensurate with the power flow generated by the disconnected CT.

In order to inspect the protective relay device as described above, conventionally a transformer 8 is installed between one end of the differential circuit 20.
Connect the secondary side of the transformer 8, and connect the inspection power supply 10 to the primary side of the transformer 8 via the inspection command contact 9.
By closing this inspection command contact 9,
An inspection input was applied from the inspection power source 10 via the transformer 8 to check whether the voltage differential relay 5 and the monitoring relay 7 were operating normally.

In addition, as mentioned above, the inspection voltage is connected to the voltage differential relay 5 and the monitoring relay 7 as well as CT2-1 to CT2-2-n.
The purpose of applying the voltage to the next circuit is not only to check the operation of each relay, but also to check for short circuits in the secondary circuits of CT2-1 to CT2-n, and for disconnections in the differential circuit 20 or the current limiting resistor 4. The points where inspection input is applied are configured to enable circuit checks as wide as possible.

However, as is well known, the conventional inspection circuit requires a high voltage of several hundred volts as the inspection voltage to operate the voltage differential relay 5, and voltage is also applied to CT2-1 to CT2-2-n, resulting in a considerable amount of excitation current. Therefore, the transformer 8 needed to have a very large capacity. In addition, the inspection command contact 9 must have a large contact capacity, and CT2-1 to CT2-2
If the -n secondary circuit is inspected for a short circuit, there is a risk that the inspection power supply 10 will be short-circuited.

The present invention was made to eliminate the above-mentioned drawbacks of the conventional technology.The input terminal for inspection applies voltage through a high impedance, and the inspection voltage is as low as possible, and the inspection power supply and It is an object of the present invention to provide an inspection circuit for a protective relay device in which the current carrying capacity of an inspection command contact is kept small and there is no fear of an inspection short circuit.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, the same parts as in FIG. 1 are indicated by the same reference numerals. In FIG.
A reactor to which a secondary coil is connected and which is provided with an intermediate outlet having the b contact 11, 4
Reference numerals 1 and 42 are voltage dividing resistors obtained by dividing the conventional resistor 4 into appropriate values, and between the voltage dividing resistors 41 and 42, an inspection power source 10 is connected to the transformer 8 and a contact 9 that is closed during inspection. In addition to applying an input voltage, the transformation ratio of the reactor 12 can be automatically switched by tap at the time of inspection using a contact 9 that is closed during inspection and a contact 11 that is opened during inspection provided on the secondary coil of the reactor 12. It is the composition.

Next, the operation of the present invention will be explained below. In FIG. 2, the operation of the voltage differential relay 5 is the same as the conventional example shown in FIG. The contact is opened, and the contact is operated in the opposite state to that described above so as to have high sensitivity during inspection.

Therefore, the transformation ratio of the reactor 12 is normally large and becomes small during inspection, and the circuit is configured so that the monitoring relay 7 can operate at a voltage lower than normal during inspection.

The detection sensitivity of this monitoring relay 7 is
It is necessary to set the CT and the CT's secondary circuit to a value that does not detect the error voltage generated by the power flow when the CT is normal, so it is not possible to set the sensitivity higher than a certain value during normal times.

Although not shown in the drawings, since the monitoring relay 7 is of course activated in the event of an accident or inspection, appropriate circuit processing is applied to prevent monitoring failure detection at that time from being erroneously detected.

At the time of inspection, an inspection input voltage is applied between the voltage dividing resistors 41 and 42 from the inspection power supply 10, and the voltage differential relay 5 and the monitoring relay 7 are operated to check the operation of these relays.
Secondary circuit of CT2-1 to 2-n and varistor 3,
Check the voltage dividing resistors 41 and 42 for abnormalities.

In this case, even if there is a short circuit in either of the circuits, the inspection power supply 10 will not be shorted by the voltage dividing resistors 41 and 42, and circuit abnormalities can be reliably detected.

In addition, in Fig. 2, the output voltage value of the inspection power supply 10 is constant, but in reality, with respect to the tap voltage value of the monitoring relay 7, the voltage at which operation is possible is approximately 120%, and the voltage at which the relay is inoperable is approximately 80%. In order to carry out a tap check of the input voltage to check the operation and non-operation of the relay by applying each voltage individually,
Reliably performs abnormality detection operations for short circuits or disconnections in CT secondary circuits, varistors, resistors, etc.

In addition, the operating voltage value of the voltage differential relay 5 is CT2-
Although the voltage is several 100 V in the secondary circuit of 1 to 2-n, there is a significant voltage drop at the point where it passes through the resistor 41. Therefore, the input impedance of the voltage differential relay 5 itself and the voltage dividing resistors 41 and 42 should be By setting the value, the inspection voltage required to operate the voltage differential relay 5 can be arbitrarily set, and it becomes possible to easily reduce the inspection voltage.

In this case, if the resistance 41 is set to a large value, the inspection voltage for operating the voltage differential relay 5 can be reduced, but this is inconvenient for operating the monitoring relay 7.

That is, the voltage applied to the monitoring relay 7 is
The voltage is divided by the parallel impedance of the resistor 41, the total excitation impedance of CT2-1 to CT2-2-n, and the input impedance on the reactor 12 side, so if the number of CT lines increases, CT2 The sub-excitation impedance becomes significantly smaller, making it difficult for the inspection voltage to be transmitted; however, in this case, the detection value of the monitoring relay 7 may be made highly sensitive.

However, in normal times, as mentioned above, the sensitivity cannot be made very high, so the transformation ratio of the reactor 12 is changed so that the detected value is made highly sensitive only during inspection.

In the above embodiment, the secondary side tap of the reactor 12 is switched as a sensitivity switching means for switching the detection sensitivity of the monitoring relay 7 between normal times and inspection, but the transformation ratio of the reactor 12 is fixed. Similar effects can be obtained by changing the sensitivity of the monitoring relay 7 itself, for example by changing the bias or input resistance of the level detector.

As described above, according to the present invention, since the inspection input voltage is applied to the differential circuit via the voltage dividing resistor, there is no risk of the inspection power source being burnt out due to a short circuit when the circuit is in short circuit mode. Further, since the monitoring relay detection value during normal operation can be set to a voltage value that is sufficiently larger than the differential error voltage due to the load current, erroneous detection during monitoring is eliminated. During inspection, the inspection input is consumed on the CT side and less inspection input is transmitted to the monitoring relay, but during this inspection, the monitoring relay is switched to high sensitivity by the sensitivity switching means, so inspection can be performed reliably. Effects such as this can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an inspection method in a conventional voltage differential protection circuit, and FIG. 2 is a circuit diagram of an inspection method in a voltage differential protection circuit according to an embodiment of the present invention. 1...Bus line, 2-1 to 2-n...CT, 3...
Varistor, 41, 42...Resistor, 5...Voltage differential relay, 12...Reactor, 7...Monitoring relay, 8...Power transformer for inspection, 9...Contact that closes during inspection, 10...Inspection Power supply, 11...Contact that opens during inspection. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of utility model registration request] A plurality of branch systems connected to the bus bar of the power system, a differential circuit in which secondary circuits of current transformers provided in each of the branch systems are connected in parallel, and a primary circuit between one end of the differential circuits. A reactor connected to a coil, a monitoring relay connected to a secondary coil of the reactor, a varistor connected between the other end of the differential circuit, and a varistor connected in parallel to the varistor through a voltage dividing resistor connected in series. an inspection power supply device connected between the voltage differential relay and the voltage dividing resistor through a contact that is closed during inspection between the differential circuit;
An inspection circuit for a protective relay device, comprising: sensitivity switching means for switching the monitoring relay from low sensitivity in normal times to high sensitivity during inspection to close the contacts.