JP3378418B2 - Leakage protection method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth leakage protection system, and more particularly, to earth leakage protection of a power receiving and transforming facility in which a secondary side of a transformer is subjected to a second type grounding work and a load device is subjected to a third type grounding work. .

[0002]

2. Description of the Related Art In a power receiving and transforming facility in which a plurality of transformers are installed and electric power is supplied from each transformer to a load device, the grounding line is used for the primary or neutral line on the secondary side of the transformer. It is connected to a common ground busbar via a common grounding electrode, and second grounding work is performed by a common grounding electrode. An earth leakage relay is provided on the ground wire of each transformer to protect against electricity leakage.

FIG. 5 shows an explanatory diagram of a circuit in the power receiving and transforming equipment and leakage detection protection.

In FIG. 5, reference numerals 1A, 1B and 1C denote transformers, only secondary windings are shown, and each secondary side has a line A, respectively.
It is connected to the load via B and C to supply electric power. And, one wire or neutral wire on the secondary side of each transformer is the ground wire 2
The second type grounding work is carried out by the common grounding electrode 4 through the grounding busbar 3 by A, 2B and 2C. R ₂ represents the grounding resistance of this type 2 grounding.

Reference numerals 5A, 5B and 5C are zero-phase current transformers for detecting zero-phase currents, and 6A, 6B and 6C are earth leakage relays connected to the output sides of the zero-phase current transformers 5A, 5B and 5C. Shows.

Reference numeral 7 denotes a load device installed in the power receiving and transforming facility which requires a third type grounding, for example, an iron stand or an outer box of a switchboard is grounded. Each device is grounded by a grounding electrode 9 via a grounding busbar (or a collective terminal) 8 and is of the third type. R ₃ represents the ground resistance of this third type ground.

CA, CB, and CC are capacitances to ground of the lines A, B, and C, and K and L are directions passing through the zero-phase current transformer, and the K side is a power source end.

FIG. 6 is an equivalent circuit of FIG. 5, and the same reference numerals as those in FIG. 5 denote the same parts.

Next, leakage protection will be described. Now, when the device on the load side of the transformer 1C has a leakage that corresponds to a complete ground fault, the leakage current iR is from the electric path of the line C to the third type grounding pole 9, the second type grounding grounding pole 4, and the grounding line. Flows through 2C and transformer 1C. The leakage current iR is detected by the zero-phase current transformer 5C and input to the leakage relay 6C. When the leakage current iR is equal to or more than the set value of the leakage relay 6C, the leakage relay 6C operates and shuts off an alarm or a circuit breaker. Performs the protective action of.

[0010]

However, each line A,
B and C have electrostatic capacitances CA and C to the ground as shown in FIG.
B and CC exist, and when a leak occurs in the line C, the other ground lines A and B also have the ground capacitances CA and CB.
Leakage currents iCA and iCB flow through.

The leakage currents iCA and iCB are
If the current value of this leakage current flows above the operation sensitivity set value of the earth leakage relays 6A and 6B, which is affected by the magnitude of the ground capacitance of the earth leakage relays 6A and 6B, the earth leakage relays are not affected even if the lines A and B are sound. 6A and 6B operate (obtaining operation) and may interrupt a healthy line.

As a countermeasure against this, the sensitivity setting of the earth leakage relay may be set to a sensitivity current commensurate with the leakage current due to the earth capacitance, but the earth capacitance depends on the length of the distribution line, the laying method and the load equipment. It will vary greatly depending on its capacitance and other factors such as noise prevention capacitors installed in various electronic devices such as computers.

For the current value of the sensitivity setting, it is necessary to predict the electrostatic capacities of these loads, calculate the current value that flows into a sound line when an accident occurs in another line, and allow some margin from this current value. However, it was extremely difficult to determine an appropriate set value.

In view of the above points, an object of the present invention is to provide a leakage protection system of this kind without considering the ground capacitance on the load side and without causing malfunction.

[0015]

Means for Solving the Problems In the present invention, the means for solving the above-mentioned problems is that, when a leakage occurs in a certain line, the leakage current is from the ground electrode of the third type ground to the ground of the second type ground. It flows in the fault circuit through the pole. At this time, due to the ground resistance of both ground electrodes, between the ground electrode of the third type and the second type,
A voltage proportional to the leakage current is generated. Therefore, the present invention detects this voltage and discriminates the faulty line.

Further, there is a constant phase relationship between the voltage between the grounding electrodes (hereinafter referred to as the voltage between the grounding electrodes) and the leakage current, and the phase of the leakage current is determined on the basis of the voltage between the grounding electrodes. , In the operation phase, the faulty line is discriminated and the protection operation is performed.

When the voltage between the ground electrodes reaches a predetermined level, the output signal is stopped, and when the voltage does not reach the predetermined level, an output signal is output to notify that the zero-phase current exceeds the predetermined level. A means for outputting to the condition is provided so that the protection operation is performed when the zero-phase current exceeds the predetermined level even when the voltage between the ground electrodes is equal to or lower than the predetermined level.

Furthermore, the leakage current flowing in the leakage fault circuit is
Since it is always larger than the leakage current flowing through other healthy lines via the ground capacitance, the zero-phase current of each line is compared, and the line in which the largest zero-phase current is flowing is determined to be the faulty line.

By doing so, it is not necessary to predict the ground capacitance of each line to change the operating current value of the earth leakage relay or the like, and the conventional problem is solved.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, when an electric leakage accident occurs in a certain line, a leakage current flows through another healthy line through the electrostatic capacitance to ground, thereby causing the earth leakage relay installed in the healthy line to operate. It is intended to prevent

According to the first aspect of the invention, when a leakage occurs in a certain line, the leakage current is from the ground electrode of the third type ground (hereinafter referred to as the third type ground electrode) to the second type ground. It flows in the fault circuit through the ground electrode (hereinafter referred to as the second type ground electrode). At this time, attention is paid to the point that a voltage corresponding to the leakage current is generated between the ground electrodes due to the ground resistance of these ground electrodes, and the voltage between the ground electrodes (hereinafter referred to as the voltage between ground electrodes) is used. This is to detect a leakage fault.

FIG. 1 shows an equivalent circuit diagram in the case where the present invention is applied to the power receiving and transforming equipment of FIG. 5, and the same or corresponding parts as in FIG.

A voltage relay 10 as a voltage detecting means is connected between the third type grounding electrode 9 and the second type grounding electrode 4, and the grounding resistance R ₃ of the grounding electrode 9 and the grounding resistance of the grounding electrode 4 are connected. R ₂
The voltage E3 + E2 generated between them is detected. Then, set the operating voltage setting value of the voltage relay 10 in advance,
It operates when the detected voltage exceeds this set value.

When a leak occurs on the line C shown in FIG. 5, leak currents iCA and iCB also flow to the other sound lines A and B through the ground capacitances CA and CB. This leakage current value is
Although affected by the capacitance to ground, the voltage E _{3 between} the ground electrodes generated when the leakage current flows through the ground resistances R ₃ and R ₂ of the ground electrodes.
Also affected by E ₂ . If the leakage current is large, this voltage E ₂ + E ₃ will be correspondingly high. Therefore, the voltage relay 10 provided in the leakage fault circuit operates reliably.

On the other hand, since no leakage current flows through the third-type grounding electrode of the sound line, the third-type grounding voltage E ₃ is not generated, so that no operation is performed.

Further, there is a constant phase relationship between the inter-electrode voltages E ₂ and E ₃ and the leakage current and the leakage current flowing through the electrostatic capacitance to the sound line. In the second embodiment, this phase is discriminated to detect an earth leakage accident line.

That is, the phase relationship between the current iR flowing through the zero-phase current transformer 5C installed in the line C where the leakage occurs and the ground electrode voltage (E ₂ + E ₃ ) is based on the ground electrode voltage. when in phase, whereas, healthy line a of this time, the current flowing through the zero-phase current transformer 5A, 5 B of B ICA, iCB becomes 90 ° lag relative to the ground inter-electrode voltage.

Reference numerals 16A, 16B and 16C denote earth leakage relays having this directivity, and input the ground inter-electrode voltage E ₂ + E ₂ and the zero phase current from the zero phase current transformers 5A, 5B and 5C of the self line. To do.

Each of the earth leakage relays 16A, 16B, 16
C is for inputting the zero-phase current and the voltage between the grounding poles, respectively, and extracting the fundamental wave component with a filter circuit, amplifying it, shaping the waveform, and grounding the grounding signal on the condition that the input signal has reached a predetermined level. Phase comparison between voltage and zero-phase current. When it is within the operating phase range, it is determined that it is a self-line leakage fault and operates, and when it is in the inactive phase range, it is determined as another line fault and is inoperative.

The above is the case of a ground fault corresponding to a complete ground fault. The ground fault (leakage) resistance Rg at the time of the ground fault is large, and the voltage Vg between the ground fault resistors is the ground fault voltage E ₂ + E ₃ Even if the leakage current becomes extremely high and the leakage current flows to about the operation setting value of the leakage relay, the inter-electrode voltage may not reach the operation setting value of the voltage relay 10. In such a case, the third embodiment is designed to operate only with a leakage current.

FIG. 2 shows a circuit diagram of an earth leakage relay having such a function. In FIG. 2, 21 is a zero-phase current input from the output terminals Z ₁ and Z ₂ of the zero-phase current transformer to generate a fundamental wave component. Filter to be taken out, 22 is an amplifier for amplifying the output of the filter 21, 23 is a level detection circuit, 24 is a waveform shaping circuit, 25
Indicates a first AND circuit, and when the detected zero-phase current exceeds a predetermined level, the output of the waveform shaping circuit 24 is output from the first AND circuit 25.

Reference numeral 31 is a filter for inputting the ground electrode voltages E ₂ and E ₃ and extracting the fundamental wave component, 32 is an amplifier, 33 is a level detection circuit, 34 is a waveform shaping circuit, and 35 is a second AND circuit. , When the voltage between the ground electrodes becomes equal to or higher than a predetermined level, the output of the waveform shaping circuit 34 is changed to the second AND circuit 35.
Output from.

Reference numeral 40 denotes a phase discriminating circuit, which inputs the outputs of the first and second AND circuits 25 and 35, compares the phases, and outputs an output signal to the OR circuit 41 when the operation phase is set, and the OR circuit 41 input to timing circuit 42 through 41, after a predetermined time period, actuating the relay contacts 4 3.

An inverter circuit 44 receives the output of the level detection circuit 33 on the side of the voltage between the ground electrodes, and outputs the third output.
Of the AND circuit 45. Further, the output of the zero-phase current side level detection circuit 23 is input to the third AND circuit 45. The output of the third AND circuit 45 is input to the OR circuit 41.

Therefore, in the normal state, the inverter 44 does not output the level detection circuit 33 on the side of the voltage between the ground electrodes (has not reached the predetermined level), so the output signal is input to the third AND circuit 45. If there is no output from the level detection circuit 23 on the zero-phase current side, no output signal is output from the third AND circuit 45.

However, even when the voltage between the ground electrodes E ₂ + E ₃ does not reach the level set by the level detection circuit 33, if the zero-phase current is higher than the level set by the level detection circuit 23, the third
An output is output from the AND circuit 45 and the relay contact 43 is operated.

As described above, even when the ground fault resistance Rg is large and the voltage between the ground electrodes does not reach the set level, the zero-phase current operates if the set level is reached and the breaker is cut off. The operation of.

In this case, since the leakage current iC flowing through the electrostatic capacitance to the healthy line is extremely small, the leakage relay provided in the healthy line will not operate properly. Therefore, it is not necessary to provide the leakage relay with directivity.

On the other hand, when the voltage between the ground electrodes exceeds the set level, the inverter circuit 44 does not output, so that the third AND circuit 45 also does not output. When the voltage between ground electrodes is equal to or higher than the set level and the zero-phase current is equal to or higher than the set level, both output signals are input to the phase determination circuit 40, the phases are determined, and the original function as an earth leakage relay is exhibited.

Although the embodiment of the present invention using the voltage between ground electrodes has been described above, it has been found that there is a means for preventing a desired operation without necessarily using the voltage between ground electrodes. 4th Embodiment concerning FIG. 3 is shown.

The leakage current flowing through the faulty leakage line is larger than the leakage current flowing through another healthy line through the ground capacitance. When a leakage fault occurs in the electric circuit of the line C in FIG. 3, the leakage current iR flows through the third type ground electrode 9, the second type ground electrode 4, the ground bus bar 3, the ground line 2C, and the transformer 1C as indicated by arrows.

On the other hand, in the sound lines A and B, leakage currents iCA and iCB flow through the ground capacitances CA and CB in the directions of the arrows through the ground lines 2A and 2B, respectively, and further through the ground bus 3. Flows into the ground wire 2C. This leakage current i
Since CA and iCB flow in the ground line 2C in the same direction as the leakage current iR, a current of iR + iCA + iCB flows in the ground line 2C. On the other hand, the ground lines 2A and 2B of the sound lines A and B have leakage currents iCA and i, respectively.
Since only CB flows, the line in which the largest zero-phase current flows is detected.

That is, as shown in FIG. 3, the outputs of the zero-phase current transformers 5A, 5B, and 5C for detecting the leakage current are input to the comparison / discrimination circuit 15, and the comparison / discrimination circuit 15 outputs the most current value. The large line is discriminated and the output signal OA, O of the corresponding line is detected.
Output one of B and OC.

The comparison / determination by the comparison / determination circuit 15 is, for example, comparing the output currents of the zero-phase current transformers 5A and 5B, comparing the larger one with the output of the zero-phase current transformer 5C, and determining the largest current. Method for discriminating the line, or zero-phase current transformers 5A, 5
The outputs of B and 5C are compared at the same time, the maximum value selection circuit that outputs the largest current is used, and the leakage fault circuit is determined from this output.

The embodiment of FIGS. 1 to 3 described above is
This is an application example in which the secondary sides of a plurality of transformers 1A to 1C are grounded by a common grounding electrode, but the secondary side of one transformer Tr as shown in FIG. Construction work,
It can also be applied to the case where the secondary side is branched into a plurality of lines A to N and the load device of each line is grounded by the third type, and the same effect can be obtained. The means for detecting the zero-phase current in this case is the zero-phase current transformer ZCT provided in each line.

[0046]

In the past, when an earth leakage fault corresponding to a complete ground fault occurred, an earth leakage relay installed in a sound line with no trouble sometimes operated. However, in the present invention, the earth leakage fault occurs. Since only the voltage relay or the earth leakage relay in which the line is installed operates, it is possible to immediately know the faulty line without requiring time to find it. Therefore, there is an effect that wasteful time for finding a failed line is eliminated and reliability is improved.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram of a power receiving and transforming facility to which the present invention is applied.

FIG. 2 is a circuit diagram of an earth leakage relay used in the present invention.

FIG. 3 is a circuit diagram of a power receiving and transforming facility to which the present invention is applied.

FIG. 4 is a circuit diagram of another substation equipment to which the present invention is applied.

FIG. 5 is a circuit diagram of a conventional power receiving and transforming facility.

6 is an equivalent circuit diagram of FIG.

[Explanation of symbols]

1A, 1B, 1C ... Transformer 2A, 2B, 2C ... Ground wire 3 ... Ground bus 4 type 2 grounding electrode 5A, 5B, 5C ... Zero-phase current transformer 6A, 6B, 6C ... earth leakage relay 7 ... Load equipment 8 ... Ground bus 9 ... Third-type grounding electrode 10 ... Voltage relay 15 ... Comparison discrimination circuit 16A, 16B, 16C ... earth leakage relay 21, 31 ... Filter 22, 32 ... Amplifier 23, 33 ... Level detection circuit 24, 33 ... Waveform shaping circuit 25, 35 ... AND circuit 40 ... Phase discriminating circuit 41 ... OR circuit 42 ... Timer circuit 43 ... Relay contact 44 ... Inverter circuit 45 ... AND circuit

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-4-19576 (JP, A) JP-A-4-1579 (JP, A) JP-A 61-45977 (JP, A) JP-A 53- 99440 (JP, A) Actual Kaihei 5-45578 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02H 3/00-3/52

Claims (4)

(57) [Claims] 1. A power supply is supplied to a load device through a plurality of lines by one or a plurality of transformers, and a secondary wire of the transformer, one wire or a neutral wire, is grounded by a grounding electrode. In the earth leakage protection method of the power receiving and transforming equipment, in which the load equipment connected to each line is grounded by the grounding electrode, the voltage between the grounding electrodes is between the grounding electrodes of the second type grounding and the third type grounding. A leakage protection method, characterized in that a detection means for detecting is provided, and a protection operation is performed when the voltage between the ground electrodes exceeds a predetermined value. 2. A means for detecting a zero-phase current flowing through each line is provided in each of the lines, and the operating phase is determined by comparing the phases of the zero-phase current detected by these means and the ground voltage. The earth leakage protection system according to claim 1, wherein a determining means is provided to perform a protection operation when the zero-phase current and the voltage between the ground electrodes are in the operating phase. 3. An output signal is stopped when the voltage between the ground electrodes reaches a predetermined level, an output signal is output when the voltage does not reach a predetermined level, and the output signal is output when the zero-phase current exceeds a predetermined level. 3. The earth leakage protection method according to claim 2, further comprising means for outputting the condition so that the protection operation is performed when the zero-phase current exceeds the predetermined level even when the voltage between the ground electrodes is below the predetermined level. 4. The electric power is supplied to the load device by a plurality of lines by one or a plurality of transformers, and the secondary side one wire or neutral wire is a second type by a common ground electrode. In a leakage protection system for power receiving and transforming equipment, in which grounding is performed and load equipment connected to each line is grounded by a grounding electrode, detection means for detecting a zero-phase current flowing through each line in each line And the zero-phase current detected by each of these detecting means is compared with each other to be inputted to the judging means for judging the leakage line.
The other means is that in the event of a line leakage accident, the leakage that flows to the faulty line.
Current and leakage current flowing through a healthy line via capacitance to ground
Current leakage is the line with the highest current value
The leakage protection method is characterized in that the protection operation is performed on the determined line.