JPH0159819B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting a ground fault in an ungrounded high voltage distribution system.

Ungrounded high-voltage distribution lines have ground capacitance, so even if a ground fault occurs in any one feeder, zero-sequence current will also flow to the zero-sequence current transformers installed on other feeders. flows. Since this current is alternating current, either the fault occurs on the load side of the zero-phase current transformer, that is, the own feeder, or the fault occurs on the power supply side of the zero-phase current transformer, that is, it occurs on another feeder. It cannot be determined by itself.

For this reason, at present, as shown in the outline of the ground fault protection system for current distribution substations in Figure 1, one grounding transformer 1 is installed in each bank, and one is installed at each feeder 2... A zero-phase current transformer 4... is installed near the disconnector 3..., and the zero-phase voltage detected by the grounding transformer 1 and the zero-phase current detected by each zero-phase current transformer 4... are The input is made to the ground fault direction relay 5 installed at each feeder 2, and when a ground fault occurs, the preset zero-sequence current and zero-sequence voltage threshold, The feeder 2 where the accident occurred is determined based on the AND condition of comparing the phases of the phase voltages.

As urbanization progresses in recent years, high-voltage cables are increasingly used in high-voltage power distribution lines, and the capacitance between power distribution lines and the ground is gradually increasing.

Therefore, when a ground fault occurs in a high-voltage distribution line, the value of the zero-sequence voltage that occurs for the same ground fault becomes smaller, the lower limit of the ground fault impedance that can be detected becomes higher, and the direction of the ground fault increases. A problem has arisen in that this works to reduce the sensitivity of the relay, making it only possible to detect low-resistance faults, that is, faults with large ground fault currents, and therefore faults that cause relatively large damage.

Therefore, when a ground fault occurs, as in the device described in Japanese Utility Model Application Publication No. 54-74230, the direction of the fault current is directed toward the load side at the feeder where the fault occurred.
In other feeders, the current phase is different by π (rad), so that it flows toward the power source.
The problem can be solved by detecting the feeder where the accident occurred by comparing the current phases.

However, in the above ground fault detection device using only phase comparison, the residual current that greatly affects the output of the zero-phase current transformer is mostly harmonics, and if the ground fault is a high voltage intermittent ground fault, Contains multi-order harmonic components such as needle currents, increasing the risk of malfunction, requiring the addition of a compensation circuit, making the electronic circuit complex, and making the device relatively expensive. become. Furthermore, in the case of a different-phase ground fault, there is a drawback that the fault cannot be detected by phase comparison alone.

As a solution to this drawback, in Fig. 2, the fault ground fault current I' _g is I' _g = I' _g1 + I' _g ′ ₁ I _{' g1} ≒ I' _g2 + I' _g3 +... + I _{' go} Therefore, the phase difference between I´ _g1 , I´ _g2 , I´ _g3 , ...I´ _go is π
[rad] In addition to being different, it _is always _| I _g1 |>|I _g2 | |I _g1 |>|I _g3 | Using the fact that the current values are different, detect the zero-sequence current with a highly sensitive and high-performance zero-sequence current transformer without using a zero-sequence transformer, and compare the absolute values above a certain level. There is a plan to identify the feeder where the accident occurred.

One of them is to install a sheath disconnector 8 on each feeder 7 connected to the high voltage bus 6 as shown in Figure 3, and install a high-sensitivity, high-performance zero-phase current transformer near each sheath disconnector 8. A zero-sequence current transformer 9 is installed, and the zero-sequence current detected for each zero-sequence current transformer 9 is input to a comparator 10 consisting of a binary tree circuit and the like and a display section 11 to generate the maximum value of the zero-sequence current. However, the hardware of the circuit described above is quite complex and expensive.

The other method is to input the detected current from the zero-phase current transformer 9 of each feeder 7 to each corresponding display 11 as shown in FIG.
When an alarm device 13 such as a buzzer connected in parallel with a contact circuit 12 set at the lowest level of fault current in each display device 11 is activated, each digital display is visually checked to determine the maximum value, or each The output of the zero-phase current transformer 9 installed for each feeder 7 is transmitted, for example, to eight relays R ₁ to 8 as shown in Figure 5.
Lamp _L1 that displays 30A or more through _R8 , Lamp L2 that displays _10A or more, Lamp _L3 that displays 3A or more, Lamp _L4 that displays 1A or more, Lamp _L5 that displays 300mA or more, The indicator 16 for one feeder is formed by connecting a lamp L ₆ indicating 100 mA or more, a lamp L ₇ indicating 60 mA or more, a buzzer 14, and an alarm contact 15 for several feeders as shown in the sixth figure. This input is input to the display 17, and the feeder with the most lit lamps is determined to be the feeder where the accident occurred.These feeders are inexpensive, but the final selection of the accident feeder is done by humans. This must be done visually, and therefore the accident feeder cannot be cut off automatically.

In view of the above points, the present invention reduces the price and
The present invention also aims to provide a device that automatically selects and determines accident feeders.

Embodiments of the present invention will be described below based on FIG. 5 and FIGS. 7 to 18. Contact elements R ₁ to _{R 8} in the circuit of FIG. 5 are connected to two a as shown in FIG. 7. Consists of contacts a ₁ and a ₂ and two b contacts b ₁ and b ₂ , of which the a ₁ contact is connected to contact elements R ₁ to R ₈
operation display, for example, used to turn on lamps L ₁ to L ₇ ,
Pull out the other _A2 contacts, _B1 contacts, and _B2 contacts to the outside. Set 1 including the following contact elements R ₁ to R ₈
The set is called a relay unit, and the explanation of the fault feeder selection function is shown using only the contacts. In order to simplify the explanation, only three sets of relay units A, B, and C and three contact elements R ₁ , R ₂ , and R ₃ are shown, but these are the same no matter how many are added. .

In FIG. 8, the contact elements R ₁ , R ₂ , R ₃ of each relay unit A, B, C operate according to the level of the zero-sequence current value flowing through each feeder, and the contact elements R ₁ , R ₂ ,
The detection level decreases in the order of _R3 , for example, _R1 operates at 2 amperes, _R2 operates at 500 milliamps, and _R3 operates at 200 milliamps.
That is, when contact element R ₁ operates, all contact elements R ₂ and below operate.

The b ₂ contacts of each of the above relay units A, B, and C are connected to the 1st stage, 2nd stage, and 3rd stage in series from the highest level.
Connect all the steps as you go down, and connect the _A2 contacts to the alarm or break signal and mechanical indicator 18 (hereinafter abbreviated as alarm 18) for each relay unit A, B, and C. Then, a battery 19 is connected between the _b2 contact of relay unit A and each alarm 18.

In addition, in the present invention, many high-voltage cables are used in each feeder, and due to their capacitance, even in the event of a ground fault on the power supply side of the feeder or other feeders, the zero-sequence current flows backward (this reverse current (The value is always small compared to the fault current.) This is to prevent a healthy feeder from malfunctioning and being cut off.In the relay unit shown in Figure 5, the 6th stage and below will malfunction when reverse current occurs. However, in FIG. 8, the third row is the malfunction level range.

Next, the operation of the circuit shown in FIG. 8 will be explained in the following cases.

I. When a ground fault occurs on only one feeder If a ground fault occurs on the feeder corresponding to relay unit B, and a level 1 fault occurs, as shown in Figure 9, the contacts of relay unit B Elements R ₁ , R ₂ , and R ₃ all operate, and the zero-sequence current flows back to the substation bank in the other feeders, and each contact element in the third stage of relay units A and C is activated by the zero-sequence current. _R3 works. The alarm circuit is
Current from battery 19 flows to relay unit B.
The current flows through the a ₂ contacts and the b ₂ contacts of relay unit A to the battery 19 and sounds the alarm 18 of relay unit B, but the second stage of the current branched at the outlet of the alarm 18 of relay unit B The current passing through _{the a2} contact of the second contact element R2 stops at the inlet of the _b2 contact of relay unit B, and the current passing through the _a2 contact of the third stage contact element _R3 reaches relay unit A. The signal stops at the entrance of the _b2 contact of the third stage contact element _R3 , and does not flow to the alarms 18 of the other relay units A and C.

This is the same regardless of whether the fault occurs in relay units A or C, the second stage contact element _R2 , or the third stage contact element _R3 ; only the feeder where the fault occurred is selected. become. For example, if a ground fault occurs at the feeder corresponding to relay unit C and a level 2 accident occurs, as shown in Figure 10, contact element _R2 of relay unit C,
All contact elements _R3 of relay units A, B, and C operate, and the alarm circuit is connected to battery 1.
9 flows to the alarm 18 of relay unit C as shown by the arrow in FIG.
The alarm 18 is not activated, and those alarms do not sound. Figure 11 shows the third stage of relay unit B, that is, the contact element R ₃ at the malfunction level.
The operation of each contact and the path of the operating current of the alarm circuit when only the alarm circuit operates are shown. In the case of FIG. 11, there is a high resistance ground fault, and the reverse current in the feeder corresponding to each relay unit A, C is much smaller, and the value is such that contact element _R3 does not operate.

If a ground fault occurs on two or more feeders, in this case, relay unit A near battery 19 of the alarm circuit operates first, and when the high voltage circuit is interrupted, relay unit A is also restored. If this is done, when one unit returns to normal operation, the relay unit of the next failed feeder will operate. For example, if a ground fault occurs simultaneously in the feeders corresponding to relay units B and C, all contact elements R ₁ , R ₂ , and R ₃ of relay units B and C will be damaged as shown in Figure 12. However, only the alarm circuit is activated, when the alarm 18 of relay unit B is activated, the feeder corresponding to relay unit B is cut off, and the fault current disappears, the relay is activated as shown in Figure 13. Alarm 18 of unit C is activated.

If a ground fault occurs on the power supply side of the zero-phase current transformer of each feeder, this power supply side includes the main transformer/bus,
Cases of other feeders are included.

In the case of other feeders: If all high voltage feeders in the same transformer bank are located in the same electrical station, that is, only one circuit is required for alarm and breakage circuits.In this case, there will always be a faulty circuit, so all Even if the contact element _R3 of the relay units A, B, and C operates at the malfunction level, the above I
As in the case of , only the fault line is alarmed or disconnected.

When a high voltage feeder within the same transformer bank spans two or more electrical stations, and the alarm and breakage circuits are separate. This case can be further divided into the following two types.

a. In the case of a system in which the fault feeder is interrupted, a timer or delay circuit 20 is installed as shown in Figure 14 to the contact element _R3 at the malfunction level of each relay unit A, B, and C, and the start time of the interruption signal is Shift it slightly. When a ground fault occurs in the feeder of another substation, the relay units A, B, and C of this substation all operate with reverse current as shown in Figure 15, and all contact elements _R3 operate in the circuit that goes to the alarm. is stopped by the timer 20, and if the fault line is eventually disconnected, the backflow will disappear, so each contact element _R3 will automatically return to its normal state.

b When the accident feeder is not shut off only by the alarm In this case, as shown in Figure 16, use the remaining contact B ₁ of each contact element R ₃ and temporarily connect the exit of contact A ₂ going to the alarm 18 to the adjacent one. Pass through another contact b ₁ of the relay unit before outputting, and the final one uses the first contact b ₁ , that is, connect it in a loop.

In this way, if there is an accident on the power supply side (feeder of another electric station) and all contact elements _R3 of malfunction level operate,
As shown in Figure 17, in the circuit going to the alarm 18, all the contacts _b1 of the adjacent relay units are open, so none of the alarms 18 will operate.

When ground faults at the malfunction level occur simultaneously on the load side, (adjacent contact B ₁ is not operating)
The alarm of the relay unit of the feeder is activated first, and when it is restored, the alarms of the other feeders are activated. This circuit can also be applied to the case of sudden disconnection, that is, when a high resistance ground fault actually occurs in each feeder corresponding to relay units B and C, instead of a reverse current in Fig. 16, as shown in Fig. 18. relay unit B,
Each contact element _R3 of C operates, and relay unit A
Since contact element _R3 is not operating, its contact _b1 is ON, so when the feeder corresponding to relay unit C is cut off and relay unit C is restored, relay unit C Contact element R ₃
Configure the circuit so that contact b ₁ of the relay unit turns ON and immediately disconnects the feeder corresponding to the relay unit.

There remains the problem that this system will not operate if a malfunction-level accident occurs simultaneously on the load side of all feeders. The probability that a high resistance ground fault will occur is very small and can be ignored.

In the case of a ground fault accident in the main transformer/high voltage bus: Regarding the malfunction level, it can be prevented in case b among the other feeder cases, and ground fault protection is not included in the present invention.

Since the present invention is configured as described above, it is possible to provide an ungrounded system high voltage distribution line ground fault fault feeder selection detection device that is inexpensive and can automatically select and discriminate fault feeders.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the ground fault protection method for ungrounded power lines in current distribution substations, Figure 2 is a conceptual diagram showing the magnitude of fault current in the event of a ground fault in one wire of a high voltage feeder, and Figure 3 The figure is an explanatory diagram of the zero-sequence current absolute value comparison method and ground fault protection circuit. Figure 4 is an explanatory diagram of a display device that digitally displays the zero-sequence current of multiple feeders at one place. Figure 5 is an explanatory diagram of the display device. Internal connection diagram, Figure 6 is a schematic diagram of a display device made up of several feeders of the above display devices, Figure 7 is an internal connection diagram of each relay in Figure 5, and Figure 8 shows the contact elements in Figure 7. The combination of 3 relay units is considered to be 1 relay unit. Figure 9 is an explanatory diagram of the connection of each contact and alarm circuit when 3 sets of these are assembled. Fig. 10 is an explanatory diagram in which contact elements R ₁ , R ₂ , and R ₃ operate, only contact element R ₃ of relay units A and C operates, and only relay unit B constitutes the alarm circuit. When a moderate ground fault occurs in the C circuit, contact elements R ₂ and R ₃ of relay unit C operate, contact elements R ₃ of relay units A and B each operate, and the alarm circuit is activated by the relay unit. Explanatory diagram where only C constitutes a circuit, 1st
Figure 1 is an explanatory diagram in which a slight ground fault occurs in the B circuit, and only contact element _R3 of relay unit B operates, all others do not operate, and only relay unit B constitutes the alarm circuit. , Fig. 12 shows that when a ground fault occurs simultaneously in the B and C circuits, all contact elements of relay units B and C operate, and relay unit A operates only when the contact elements of relay unit A operate.
An explanatory diagram showing that only R ₃ is operating and the alarm circuit is close to running out of battery. Figure 13 shows that in Figure 12, relay unit B has been restored and the alarm circuit of relay unit C is operating. Explanatory diagram,
Figure 14 is an explanatory diagram showing a timer installed at the outlet of contact element _R3 of each relay unit to the alarm circuit.
Figure 15 is an explanatory diagram showing that contact element R ₃ of each relay unit operates due to reverse current in the high-voltage circuit, but the circuit to the alarm is blocked by a timer. Figure 16 shows only contact element R ₃ in the malfunction range. Figure 17 is an explanatory diagram in which relay units A and C are connected in series with the adjacent b contact and connected to form a loop. Figure 17 shows that, similar to Figure 15, reverse current flows through the high voltage circuit and all contact elements operate. , an explanatory diagram in which the alarm circuit is blocked by the adjacent B contact, and Fig. 18 shows that a slight ground fault has occurred in the B and C circuits, and the contact element _R3 of the relay unit is operating, but the relay unit A This is an explanatory diagram in which the alarm of the relay unit C, which is closer to the alarm power source, is activated first because the contact element _R3 is not operating, that is, this _b1 contact is in contact. A, B, C...Relay unit, _R1 , _R2 , _R3 ...
...Contact element, 18...Alarm, 19...Battery, 20...Timer.

Claims (1)

[Scope of Claims] 1. In an ungrounded system high-voltage distribution line, zero-sequence current detected by highly sensitive and high-performance zero-sequence current transformers installed in all feeders of multiple lines belonging to the same bank is input for each feeder. The relay unit is composed of several switching elements that operate in several stages depending on the magnitude of the fault current, and each switching element has one A contact and two B contacts.
Connect the contact and the 1B contact in series, connect that connection point and the output terminal via the 1B contact above in series, and connect one pole of the single-phase power supply to one end of this series circuit. The output terminal of the a-contact point is connected in parallel to each relay unit and connected to the other pole of the single-phase power supply through a circuit for alarm, break signal, etc. Distribution line ground fault feeder selection detection device. 2. The high voltage non-grounded system according to claim 1, which is connected from the output terminal of one A contact of adjacent relay units to a circuit for alarm, failure signal, etc. via the other 2B contact. Distribution line ground fault feeder selection detection device.