JPH0127643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an automatic inspection method for a frequency protection relay device, and in particular a frequency protection relay capable of detecting a one-phase disconnection fault in a voltage transformer for supplying voltage input to the protection relay device. This relates to an automatic inspection method for equipment.

Electric power systems are operated to adjust the load to match the power generated and to maintain a constant frequency. However, if a part of the power supply in the power system is cut off due to a generator failure or a system accident, for example, if the generator is overloaded, the frequency will drop and the generator will stop if the load is not quickly removed. Therefore, consideration has been given to constantly monitoring the frequency of the power system and issuing a load shedding command by detecting frequency abnormalities. FIG. 1 shows a PT voltage input circuit of a conventional frequency protection relay device. In the figure 1
is the busbar, and this voltage is applied to PT2 and cable 3
It is introduced into the frequency protection relay device 4 via R, 3S, and 3T. And in the frequency protection relay device 4,
Generally, frequency relays 5, 6 are provided, and undervoltage relays 7, 8, 9 are provided to prevent trip commands from being sent out due to malfunction of the frequency relays when the input voltage drops. FIG. 2 is a block diagram of a frequency protection relay system, which will be further explained. Here 10 is an AND circuit, 1
1 is an OR circuit, 12 is a NOT circuit, 13 is a trip condition detection circuit, and 15 is an automatic check circuit. That is, as can be seen from the circuit diagram, frequency relays 5 and 6
The output of is locked by the AND circuit 10 as long as any one of the undervoltage relays 7, 8, 9 is operating. Therefore, undervoltage relays 7, 8, 9
If all of the frequency relays 5 and 6 are inoperative and both frequency relays 5 and 6 are in operation, a trip command will be sent. The constant monitoring circuit 14 detects any malfunction of the device, and the automatic inspection circuit 15 operates in the same manner. That is, apply inspection input to each relay,
The purpose is to determine the quality of the relay based on the final stage output.

FIG. 3 is a flowchart showing the functions of this automatic inspection circuit.

As clearly shown in the block diagram shown in FIG. 2, the frequency relay is locked in an undervoltage condition when the input voltage is low because, due to its operating principle, accurate detection cannot be expected.

Now consider the case where a one-phase disconnection fault (cable 3S disconnection) occurs in the three-phase PT secondary voltage in the circuit shown in Figure 4. V _RS , V _ST , and V _TR are the line voltages of the PT secondary circuit, respectively. be. and frequency relays 5 and 6
generally have the same input impedance, and the undervoltage relays 7, 8, and 9 also have the same impedance, so the input voltage V of the undervoltage relay 7 is V _RT /2
becomes. Therefore, the setting value of the undervoltage relay is
If it is lower than V _TR /2, it is inoperable, e.g.
Even if a one-phase disconnection failure occurs in the PT input circuit, it cannot be detected by constant monitoring and automatic inspection of the device.

The present invention has been made for the purpose of solving the above-mentioned drawbacks, and is an automatic inspection of a frequency protection relay device that can detect a one-wire disconnection failure in the input voltage circuit of the frequency protection relay device by automatic inspection. The purpose is to provide a method.

Examples will be described below with reference to the drawings. Fifth
The figure is a circuit configuration diagram of an embodiment according to the present invention, Fig. 6a
7 shows the automatic inspection state when the input circuit is healthy in the embodiment, b shows the non-automatic inspection state when one phase of the input circuit is disconnected, c shows the automatic inspection state when one phase of the input circuit breaks, and FIG. FIG. 7 is a circuit configuration diagram of another embodiment.

Reference numerals 1 to 9 in FIG. 5 correspond to those in FIG. 16 is a normally closed contact of the auxiliary relay for inspection, and is used to detect whether or not the input circuit (PT2, cables 3R, 3S, 3T) of the frequency protection relay device 4 has a one-wire disconnection fault. . The normally closed contact 16 of the auxiliary inspection relay is closed, and since it is not being inspected, three-phase input line voltage is applied to the frequency relays 5 and 6 and the undervoltage relays 7, 8, and 9, respectively. There is.

Figure 6a shows the case where the normally closed contact 16 of the auxiliary inspection relay is opened for automatic inspection.
The input voltage of the undervoltage relay 7 is V _ST /2,
If the relay setting is lower than V _ST /2, it is inoperable.

FIG. 6b shows a case where the cable 3S of the voltage input circuit has a disconnection fault. In this case, the input voltage V of the undervoltage relay 7 is V _TR /2, and as above, the undervoltage relay It is inactive.

FIG. 6c shows a case where the cable 3S of the voltage input circuit is disconnected and the normally closed contact 16 of the auxiliary inspection relay is opened. In this case, it is clear that due to the impedance of the frequency relays 5, 6 and the undervoltage relays 7, 8, 9, the voltage will be lower than when the cable 3S is disconnected and not inspected (Fig. 6b), and the undervoltage The relay operates if the set value is lower than the voltage V at the time of automatic inspection. Therefore, if the integer value of the undervoltage relay is set lower than the voltage V applied during automatic inspection (the voltage applied when the normally closed contact 16 of the auxiliary inspection relay is opened in normal conditions), the cable 3S An undervoltage relay can be operated in the event of a disconnection.

That is, if a step of operating the normally closed contact 16 of the auxiliary inspection relay is added to one step of the automatic inspection flowchart of FIG. 3, and as a result, outputs from the undervoltage relays 7, 8, and 9 are present,
Alternatively, a check input may be applied to the frequency relays 5 and 6, and if there is no trip output from the device when the normally closed contact 16 is operated, each may be determined to be defective.

FIG. 7 shows another embodiment for setting a low setting value of an undervoltage relay.

That is, due to the operation of the normally closed contact 16 of the auxiliary inspection relay, the input voltage of the undervoltage relay is lower than the normal state when one phase is disconnected. However, if this reduced voltage is higher than the set value of the undervoltage relay, the undervoltage relay will not operate, and therefore a failure determination cannot be made. Therefore, when the normally closed contact 16 of the auxiliary inspection relay operates, the input voltage V of the undervoltage relay
It is necessary to add a resistor 17 such that the voltage is less than or equal to a set value.

By adopting such a configuration, the voltage applied when one phase is disconnected is lower than the voltage V applied to the undervoltage relay when the normally closed contact of the auxiliary inspection relay is opened in normal conditions. This makes it easier to discover defects.

As explained above, according to the present invention, a normally closed contact of an auxiliary inspection relay is provided on one phase of the secondary side of a three-phase input voltage circuit and connected to an undervoltage relay, and the voltage is applied to the undervoltage relay during normal times. 1 than the voltage of
Since the voltage applied at the time of line breakage is set low, it is possible to provide a frequency protection relay device inspection method that can sufficiently detect a one-phase breakage failure in the input voltage circuit.

[Brief explanation of drawings]

Figure 1 is the PT voltage input circuit of a conventional frequency protection relay, Figure 2 is a block diagram of the frequency protection relay, Figure 3 is a flowchart of the automatic inspection circuit, and Figure 4 is the inside of the frequency protection relay. A wiring diagram of each relay, FIG. 5 is a circuit configuration diagram of an embodiment according to the present invention,
6a is an automatic inspection state in the embodiment when the input circuit is healthy, FIG. 6b is a non-automatic inspection state when one phase of the input circuit is disconnected, and FIG. 6c is an automatic inspection state when one phase of the input circuit is disconnected. FIG. 7 shows another embodiment. 1...Bus bar, 2...PT, 3R, 3S, 3T...
...Cable, 4...Frequency protection relay device, 5, 6
...Frequency relay, 7,8,9...Undervoltage relay, 10...AND circuit, 11...OR circuit, 12
...NOT circuit, 13...Trip condition detection circuit,
14... Continuous monitoring circuit, 15... Automatic inspection circuit,
16...Auxiliary relay contact for automatic inspection, 17...Resistance.

Claims (1)

[Claims] 1. In a frequency protection relay device consisting of a frequency relay connected from the grid via a three-phase voltage transformer and an undervoltage relay that detects the line voltage, the three-phase voltage transformer and the undervoltage relay During a natural inspection, insert an auxiliary inspection relay contact into one phase between the two, and open the auxiliary inspection relay contact.
The voltage transformer circuit is controlled by detecting that the voltage value applied to the undervoltage relay or the frequency relay decreases in a one-phase disconnection failure state compared to a healthy state of the three-phase voltage transformer circuit. An automatic inspection method for frequency protection relay devices that detects abnormal conditions in the circuit.