JPH0622227Y2 - Dielectric strength recovery diagnostic device - Google Patents

Description

[Detailed Description of the Invention] <Industrial application field> The present invention relates to a dielectric strength recovery diagnosis device for an electric device, and more specifically, an electric device such as a bus bar which constitutes an electric station such as a substation is protected from an accident such as a ground fault. The present invention relates to a device for automatically diagnosing the recovery state of the dielectric strength of an electric device after an accident or disconnection in the case of occurrence.

<Prior Art> A case where a ground fault occurs on the bus bar 22 in an electric station having a system configuration as shown in FIG. 5 such as a substation will be considered. Generally, the ground fault detection relay 24 operates due to the occurrence of a bus bar ground fault accident (for example, point P), and the bus bar 2
All breaker CBm connected to 2, CBf ₁ ~CBfn, since CB _S is configured to block, in this case bus 22 becomes no voltage.

If the dielectric strength of the bus bar 22 is restored by removing the voltage, the circuit breaker CBm is turned on again (usually by manual operation) to operate the bus bar 22, and then the circuit breaker CBf ₁ By supplying CBfn and CB _S , it is possible to restart the power supply to the distribution line 25 and other parts. For this purpose, it is necessary to investigate and diagnose whether or not the insulation of the bus bar has been restored.

Conventionally, as a means of diagnosing this insulation recovery condition, an electric maintenance staff visits the accident site, and, for example, an insulation resistance meter (mega)
For example, the quality of insulation, that is, the insulation recovery state is diagnosed by a method such as artificially measuring the insulation resistance.

<Problems to be solved by the invention> According to such a conventional means, since the insulation resistance and the insulation diagnosis are artificially performed at the accident site, the operation of the electric equipment such as the bus bar is restarted (that is, the power is restored). Processing) requires a lot of time and labor. These result in significant losses, especially in unattended electrical stations such as substations that are remotely monitored and controlled. Furthermore, since the measurement terminal voltage of the insulation resistance tester is as low as 1,000 VDC at most, the voltage applied to electrical equipment such as the bus bar during insulation resistance measurement is low.For example, the dielectric strength is diagnosed for electrical equipment of 6.6 KV or more. This is not the case, and there is a problem in that the accident may be repeated again when the operation of the electric device is restarted even though the dielectric strength is not sufficiently recovered.

Therefore, the purpose of the present invention is to automatically diagnose whether or not the dielectric strength at the accident point of the electric device is restored after the accident point of the electric device has been cut off and there is no voltage. An object of the present invention is to provide a device for promptly determining whether or not to restart the operation (power recovery) and saving labor in the operation restart operation.

<Means for Solving Problems> In order to solve the above problems, the present invention provides a capacitor capable of storing electric charge, the capacitor, and a voltage applying portion of an electric device such as a bus bar to which a constant voltage is applied. A switch that is connected between the switch and that is turned on after there is no voltage to be applied to the electric device, and that is obtained when the charge accumulated in the capacitor is discharged by turning on the switch. A means for solving the problem is configured by a waveform diagnostic device that applies a switching surge voltage to the electric device and determines whether the waveform of the switching surge voltage is good or bad.

<Operation> According to the above configuration, when electrical equipment such as a bus bar that configures an electric station goes from normal operation to no voltage due to an accident, the switch is automatically turned on and the electric charge accumulated in the capacitor is Whether the dielectric strength of electrical equipment has been restored by applying a voltage with a switching surge characteristic due to discharge to electrical equipment and diagnosing with a waveform diagnostic device whether the waveform of that voltage is within a predetermined allowable range It can be diagnosed.

<Embodiment> An embodiment of the present invention will be described with reference to FIGS. Fig. 1 is a single-line system diagram in which the present invention is applied to a metal clad cubicle that accommodates a general power distribution system, and a bus bar 3 is charged through a main transformer 1 for power reception and a breaker 2 for power reception for power distribution. Electric power is supplied to the distribution lines 51 to 5n via the circuit breakers 41 to 4n, and to the internal load 10 via the internal power circuit breaker 6 and the internal transformer 9.

Reference numeral 14 is a metal clad vehicle (hereinafter referred to simply as "cubic vehicle"), which is a circuit breaker 2 for receiving power, a bus bar 3, and a circuit breaker for power distribution.
41 to 4n, the power supply circuit breaker 6, the station transformer 9, the injection transformer 7 for injecting a surge voltage into each of the three phases of the bus bar 3 when the bus bar 3 is unvoltage A voltage measuring transformer 8, a lightning arrester 19, and a ground fault detection relay (not shown) for detecting a ground fault, a short circuit detection relay for detecting a short circuit accident, etc. are housed.

By the way, in this embodiment, in order to extinguish the arc at the accident point when a ground fault occurs in the distribution system, the primary winding of the transformer is star-shaped (Y) connection and its neutral point is grounded. A grounding transformer, in which the secondary winding is a broken delta connection (see FIG. 2 (a)) and an arc-extinguishing reactor (not shown) is connected to the grounding transformer, is installed on the bus bar 3. Are used for.

Reference numeral 11 is an example of a dielectric strength recovery diagnostic device according to the present invention. The device is an AC / DC converter 12 for converting an AC voltage applied from a secondary side of a local transformer 9 through a breaker 20 into a DC voltage. A capacitor 13 connected to the DC side of the AC / DC converter 12 for storing electric charge; a switch 15 for supplying the electric charge stored by the capacitor 13 to the injection transformer 7 in the cubicle; A switch closing condition signal (for example, a ground fault detection signal,
Switch control device 17 for automatically turning on and off the switch 15 and issuing a neutral point reactor (not shown) disconnection command by inputting the state signal of each circuit breaker, etc., and for voltage measurement in the cubicle 14. A waveform diagnostic device 16 for determining the quality of the switching surge voltage waveform injected from the injection transformer 7 by using the signal from the transformer 8 as an input,
An output terminal 18 for outputting the quality judgment result of the waveform diagnostic device 16 is provided.

Next, the operation of the present invention will be described by taking the case where the rated voltage of the distribution system is 6.6 KV as an example.

When the power distribution system is operating normally, the switch 15 in the dielectric strength recovery diagnostic device 11 is in an open state, and the capacitor 13 has 2 of the transformers 9 in the station 14 in the cubicle 14.
A DC voltage of about DC 2,000V is constantly applied from the next side through the breaker 20 and the AC / DC converter 12, and charges corresponding to the product of the applied voltage and the capacitor capacity are stored.

Now, considering the case where a ground fault occurs at point P of the 6.6KV bus bar 3 in the cubicle 14, a ground fault detection relay (not shown) operates due to the ground fault and the power receiving circuit breaker 2
However, all the circuit breakers are cut off, and the bus bar 3 becomes non-voltage, but the electric charge accumulated in the capacitor 13 remains as it is thereafter.

After the bus bar 3 has no voltage, the switch 15 is automatically closed by the switch controller 17 according to the flow chart sequence shown in FIG. 3, for example. That is, in step, it is determined whether or not a ground fault has occurred, and if an accident has occurred, the disconnection status of all the circuit breakers is determined in step. If all circuit breakers are disconnected, the process proceeds to step. In the step, the ion annihilation time T ₁ at the accident point P (for example, 30
It is determined that about 10 seconds have passed and the arc extinguishing reactor (not shown) is cut off in the next step, and then the switch 15 is turned on. The electric charge stored in the capacitor 13 when the switch 12 is turned on is transferred to the three phases of the bus 3 through the injection transformer 5 configured as shown in FIG. 2 (a) or (b). Is applied. Fig. 2 (a) shows a three-phase injection transformer 7 that uses a grounding transformer, the capacitor side of which is connected to the broken delta, and the bus side is configured as a star (Y) connection. 1/3 of the voltage is multiplied by the number of turns and applied to each phase of the bus bar 3.
In (b), the capacitor side and the bus side of the three-phase injection transformer 7 are star-shaped (Y) -connected, so that a voltage that is a turns ratio multiple of the charging voltage of the capacitor 13 is applied to each phase of the bus 3. It is the one.

By the way, the voltage waveform applied to each phase of the bus bar 3 at this time is a damping oscillation waveform determined by the capacitance of the capacitor 13, the reactance of the injection transformer 7 and the resistance component of the discharge circuit of the capacitor 13 including the bus bar 3. That is, the waveform has a switching surge characteristic (see FIG. 4 (a)). The voltage of the switching surge waveform applied to each phase of the bus bar 3 in this manner is supplied to the waveform diagnostic device 16 by the voltage measuring transformer 8.
The voltage waveform of each phase is determined here. That is, if the voltage value of the switching surge waveform when the dielectric strength of the busbar is normal is stored in the waveform diagnostic device 16 in advance, if the fault point P of the busbar 3 is completely restored to insulation, then each phase The voltage of the value stored in advance is measured. For example, if insulation of one specific phase of the bus bar 3 is not recovered, the measured voltage value of that phase is the other two as shown by the waveform shown in Fig. 4 (b). It can be determined because the measured value is lower than the value stored in the phase and lower than the value stored in advance, and the measured values of the three phases are lower than the stored value if insulation recovery is not performed for all the three phases.

FIG. 4 (a) shows a series of operations with a voltage waveform of a specific one phase of the healthy phases of the bus bar 3. That is, the figure
A 1-line ground fault occurs at point (a), the ground voltage of the sound phase rises, and then the ground fault detection relay (not shown) operates to shut off the power receiving circuit breaker. The bus bar 3 has no voltage.

The switch 15 is automatically turned on at the point (c) after the ion annihilation time T _{1 at the} accident point, and a voltage having a switching surge characteristic is applied to each of the three phases of the bus bar 3 by the discharge of the capacitor 13.

The opening operation of the switch 15 after diagnosing the recovery state of the dielectric strength may be appropriately performed, but as an example, according to the flow chart of FIG. 3, a certain time T ₂ (for example, 1 to 5 seconds) is detected and automatically opened.

The switching surge voltage applied to the busbar is briefly described below. The switching surge voltage applied to each of the three phases of the busbar 3 is selected to be 80 to 90% of the discharge start voltage of the arrester 19. and which, for example, the discharge starting voltage V _D because the rated voltage Vn is a 8.4KV when arrester 6.6KV bus up 38K
However, the voltage value of the switching surge is as high as about 30KV, but it is sufficient to diagnose the dielectric strength against the normal operating voltage of 6.6KV / ▲ √ ▼.

In this embodiment, as a method of applying a switching surge voltage to the bus bar 3, a method of combining one capacitor 13 and a three-phase transformer 7 as shown in FIGS. 2 (a) and 2 (b) is adopted. Of course, it is also possible to use three capacitors and three single-phase transformers, and as a method of further storing the electric charge in the capacitor 13, it is installed in an electric station in addition to this embodiment. Of course, the battery can be used as a power source for charging. Furthermore, it goes without saying that the charging charge of the capacitor 13 can be applied to the bus 3 only via the switch 15 and the injection transformer 7 can be omitted.

<Effect of device> As described above, according to this device, a voltage with a switching surge characteristic is automatically applied to an electric device after the electric device has no voltage due to an accident such as a ground fault occurring in an electric device such as a busbar. However, since the quality of the waveform is judged by the waveform diagnostic device, whether or not the dielectric strength of the electrical equipment has recovered can be automatically and quickly diagnosed, and the electrical maintenance personnel can It is possible to reduce the time to go to the home, to shorten the operation stop time of the electric equipment, and to save the labor of restarting (restoring) the electric equipment.

[Brief description of drawings]

FIG. 1 is a single-line system diagram showing an embodiment of the present invention, and FIG. 2 (a) is a connection diagram showing the connection relationship between a capacitor, a switch, and an injection transformer. In the case of type (Y) -broken delta connection, FIG. 2 (b) also shows the case where the injection transformer winding connection method is star (Y) -star (Y) connection. FIG. 3 is a flow chart showing conditions for automatically operating the switch, FIG. 4 is a waveform diagram for explaining the operation of the present invention, and FIG. 5 is a single line system diagram for explaining the conventional technique. 11 ... Dielectric strength recovery diagnostic device 13 ... Capacitor 15 ... Switch 16 ... Waveform diagnostic device

Claims (1)

[Scope of utility model registration request] 1. A capacitor for storing electric charge, a capacitor, and a voltage applying portion of an electric device to which a constant voltage is applied, such as a bus bar, connected to the electric device. A switch that is turned on after the voltage has been depleted, and a switch surge voltage that is obtained when the charge stored in the capacitor is discharged by applying the switch is applied to the electric device to switch the switch. A dielectric strength recovery diagnostic device comprising: a waveform diagnostic device that determines whether a waveform of a surge voltage is good or bad.