JP3407133B2 - Ground fault directional relay for low voltage road - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault direction relay for a low-voltage path for determining whether or not a low-voltage side electric path of a high-voltage transformer in which a low-voltage side winding is commonly grounded has a ground fault.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
As a private electric facility such as a building or a factory, for example, a high-voltage side is 6.6 kv, a low-voltage side is a 3-phase three-wire high / low voltage transformer of 200 v, a high-voltage side is 6.6 kv, and a low-voltage side is 200 v
A v-100v single-phase three-wire high / low voltage transformer or the like is installed. In the case of the above-mentioned three-phase three-wire type high / low voltage transformer or single-phase three-wire type high / low voltage transformer, according to Article 24 of the technical standard interpretation of electrical equipment, the neutral point of the low voltage side winding or the low voltage side winding Type B grounding work for one of the terminals (usually less than the specified ground resistance value, 1
It is obligatory to carry out common grounding pole construction, where only one pole is provided for customers. FIG. 6 shows that one of the low-voltage winding terminals TE of the three-phase three-wire high / low voltage transformer Tr1 and the neutral point N of the low-voltage winding of the single-phase three-wire high / low voltage transformer Tr2 are normally Common B type grounding electrode E, which is provided only for one pole for one customer
It is the electric circuit diagram which showed typically being connected to B.

Recently, the cables used for the low-voltage side electric circuit of the three-phase three-wire type high / low voltage transformer Tr1 and the low-voltage side electric circuit of the single-phase three-wire type high / low voltage transformer Tr2 have become large in size recently, and further capacitors have been used. In many cases, an electronic device having a built-in line filter or the like as a component is connected as a load. Therefore, in general, the apparent electrostatic capacitance (stray capacitance) C of the low-voltage side electric circuit is large.

In the low voltage side electric circuit as described above, as shown in FIG. 6, the cable of the low voltage side electric circuit of the three-phase three-wire high / low voltage transformer Tr1 is, for example, a D-type ground electrode ED (usually a conduit tube or a control panel, When a conduit is grounded to the control panel etc.), the ground fault current from the ground fault point is the ground fault resistance Rg as shown by the broken line, and the D-class ground connected to the conduit. Line EDL, electrostatic capacitance (floating capacitance) C to ground, low-voltage side electric circuit of single-phase three-wire high / low voltage transformer Tr2, class B branch ground line EBL1
(Branched from the class B ground bus EBL0), and 3
Breaking the low-voltage side electric circuit of the single-phase three-wire type high / low voltage transformer Tr2 that is not directly related to the ground fault because it flows in the closed circuit configured by the low-voltage side electric circuit of the three-phase three-wire type high / low voltage transformer Tr1. Bowl E
The LCB may shut off unnecessarily.

Thus, the three-phase three-wire high / low voltage transformer Tr1
And the low-voltage side winding terminal TE and the low-voltage side winding neutral point N of each transformer are commonly connected to the class B grounding electrode EB, which is a common grounding electrode of the single-phase three-wire high-voltage transformer Tr2. However, there is a problem that the circuit breaker ELCB, which is not directly related to the low voltage side electric circuit of the grounded high / low voltage transformer, may perform a breaking operation.

Therefore, according to the present invention, when a low-voltage side electric path of any of a plurality of high- and low-voltage transformers whose low-voltage side windings are commonly grounded is ground-faulted, a high- and low-voltage transformer in which the low-voltage side electric path is ground-faulted is surely provided. It is an object to be solved to provide a ground fault direction relay for a low piezoelectric road which can be determined.

[0007]

The above-mentioned problems can be solved by the ground fault direction relay for a low piezoelectric path described in the claims. According to the ground fault direction relay for a low piezoelectric road according to claim 1 , the low voltage side windings of a plurality of high and low voltage transformers are common.
Flow through the ground busbar connected to the common ground electrode for grounding
Current is detected by the ground bus current detector.
, The predetermined ground point of each low voltage side winding and the ground bus
The current flowing through the branch ground wire connected between
When detected by the line current detector, the ground bus current effective value
The phase calculation means calculates the effective value and phase of the ground bus current.
And branched by the branch ground line current effective value phase calculation means
The effective value and phase of the ground line current are calculated. in this way
Effective value and phase of calculated ground bus current, and branch connection
The effective value and phase of the ground wire current are written in the storage means at specified intervals.
It is replaced and stored. The ground bus current vector calculation means is
The effective value and position of the latest ground bus current calculated as described below.
Phase-based current vector and connection stored in the storage means
Connection of effective value of ground bus current and current vector based on phase
Calculate the ground bus current vector difference and branch branch line current vector
The latest calculation method is branch grounding
Current vector and storage means based on effective value and phase of line current
Based on the effective value and phase of the branch ground wire current stored in
Calculate the difference between the branch ground line current vector and the current vector
It Then, the ground fault determining means determines the branch ground line current vector.
If the effective value of the difference exceeds the specified value, the ground bus current vector
To the phase of the branch ground line current vector
Is connected to the low voltage side winding of the high voltage transformer based on
It is determined whether or not the low voltage side electric circuit has a ground fault.

According to the ground fault direction relay for low-voltage road according to claim 2, when the ground fault judging means judges that the low-voltage side circuit of the high-voltage transformer is grounded, the low-voltage side circuit is cut off. Since the circuit breaker can be shut off, only the circuit breaker of the low-voltage side electric circuit that is grounded is prevented from performing a breaking operation, and the other healthy circuit breakers of the low-voltage side circuit are prevented from malfunctioning.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described. In Figure 1, the high voltage side is 6.6kv and the low voltage side is 2
One of the low-voltage side winding terminals TE of the 00v three-phase three-wire high / low voltage transformer Tr1 and the high-voltage side 6.6 kv and the low-voltage side 2
The neutral point N of the low-voltage side winding of the 00v-100v single-phase three-wire high / low voltage transformer Tr2 is set as a predetermined ground point, and the predetermined ground points TE, N and the B-type ground electrode (common ground electrode) EB are connected to each other. It is an electric circuit diagram showing that it is connected via each branch ground line EBL1, EBL2 and ground bus EBL0. As shown in FIG. 1, the current detector ZCT0 for detecting the current flowing through the ground bus EBL0, the current detector ZCT1 for detecting the current flowing through the branch ground line EBL1, and the current flowing through the branch ground line EBL2 are detected. A current detector ZCT2 is provided for this purpose. In addition, the current detector ZCT
0, the current detector ZCT1, and the output terminal of the current detector ZCT2 are three-phase three-wire high / low voltage transformer Tr1 as described later.
Alternatively, when the low-voltage side electric path connected to the low-voltage side winding of the single-phase three-wire high / low voltage transformer Tr2 has a ground fault, the circuit breaker ELCB
1, the ELCB 2 is connected to the ground fault direction relay 1 for a low-voltage path that operates to shut off.

In FIG. 1, C1 and C2 are electrostatic capacities between the low voltage side electric circuits and the ground, and Rg is a D type ground electrode ED.
On the other hand, for example, it is a ground fault resistance when the low-voltage side electric path of the three-phase three-wire high / low voltage transformer Tr1 is grounded. Also, RE is B
It is a grounding resistance between the seed grounding electrode (common grounding electrode) EB and the D type grounding electrode ED, and the EDL is usually a grounding wire for connecting a conduit tube, a control panel, an operation panel or the like to the D type grounding electrode ED. Also, 3
Current detected by the current detector ZCT0 in a state where neither the low-voltage side electric path connected to the low-voltage side winding of the three-phase three-wire type high / low voltage transformer Tr1 or the single-phase three-wire type high / low voltage transformer Tr2 is grounded. Is I0a, the current detected by the current detector ZCT1 is I1a, and the current detected by the current detector ZCT2 is I2a. In addition, 3-phase 3-wire high / low voltage transformer Tr
1. Despite the fact that each low-voltage side electric path of the single-phase three-wire type high / low voltage transformer Tr2 is in the non-ground fault state, each of the above currents I0a, I
The main reason why 1a and I2a flow is that the current from each low voltage side electric circuit is capacitance C1 and C2, ground line EDL, D type grounding electrode ED, ground, B type grounding electrode EB, ground bus EBL0, and branch grounding. This is because it flows through the route of the line EBL1, the branch ground line EBL2, and each low-voltage side electric path.

Next, in the electric circuit shown in FIG. 1, for example, the operation principle of the ground fault direction relay 1 for a low piezoelectric path when the R phase of the low voltage side electric path of the three-phase three-wire high / low voltage transformer Tr1 is grounded. explain. According to Hoh-Thevenin's theorem, as shown in FIG. 1, when one phase of the low-voltage side electric circuit of the three-phase three-wire high-low voltage transformer Tr1, for example, the R phase is grounded at the ground fault point ES,
An equivalent circuit of the electric circuit of FIG. 1 can be shown as in FIG. In addition, according to the above Hoo-Thevenin theorem, three-phase three
One phase of the low voltage side electric circuit of the wire type high and low voltage transformer Tr1, for example R
When the phase is grounded at the ground fault point ES, each current detector ZCT
The currents flowing through 0, ZCT1, ZCT2 are represented by the sum of the currents I0a, I1a, I2a before the ground fault and the currents I0b, I1b, I2b shown in FIG. 2 based on the Hoh-Thevenin theorem. That is, the current detected by the current detector ZCT0 is I0a + I0b, the current detected by the current detector ZCT1 is I1a + I1b, and the current detected by the current detector ZCT2 is I2a + I2b. The voltage V0 shown in FIG. 2 is a voltage between the R phase and the ground fault point ES when the R phase is not grounded.

Further, FIG. 3 shows the currents I0b, I1b, I
It is a vector diagram of 2b. The current I0b has the same phase as the voltage VR across the ground resistance RE, and the current I1b (I0b-I2b) flowing in the ground-faulted transformer bank is the current I0b because it flows through the ground capacitance C2. The phase is more advanced. Further, the current I2b flowing in the transformer bank which is not ground-faulted has a phase leading by 90 ° from the voltage VR because it flows through the above-mentioned capacitance C2 to ground, but in the case of the electric circuit of FIG. ZCT0 and current detector ZC
Since T2 is installed so that the current detection directions are opposite to each other, the detected current I2b has a phase lagging the current I0b by 90 °. This phase relationship is based on the type of voltage (100V, 200V, 400V, etc.), circuit method (single-phase two-wire system, single-phase three-wire system, three-phase three-wire system, three-phase four-wire system, etc.), and transformer bank. Irrespective of the number of lines, it is always established when an electric circuit to which a voltage other than the grounded line is applied has a ground fault.

As is clear from the above description, the currents I0b, I1b, I2b can be obtained by subtracting the current before the ground fault from the current after the ground fault. When the currents I1b and I2b obtained by the above calculation exceed a certain set value, that is, when the low voltage side electric paths of the high and low voltage transformers Tr1 and Tr2 are in a state of being grounded, By comparing the phases of the current I1b and the current I2b with the phase of the current I0b as a reference, the low-voltage side circuit of the high-low voltage transformer in which a ground fault has occurred and the low-voltage side circuit of the high-low voltage transformer in which no ground fault has occurred To determine.

FIG. 4 is a block diagram showing the structure of the ground fault direction relay 1 for a low piezoelectric road. The block diagram shown in FIG. 4 shows a circuit block for determining whether or not the low-voltage side electric circuit (transformer bank) of the high / low voltage transformer Tr1 described above has a ground fault. Therefore, the circuit block for determining whether or not the low-voltage side electric path of the high / low voltage transformer Tr2 described above is grounded is basically configured similarly to FIG.

As shown in FIG. 4, the aforementioned current detector ZC is used.
T0 is connected between terminals z1 and z2, and current detector ZCT
1 is connected between terminals z3 and z4. Terminals z1, z
An over-input protection / filter circuit 2a connected to 2, and
Over-input protection filter circuit 2 connected to terminals z3 and z4
Reference numeral b is a circuit for preventing excessive voltage input, electrically protecting the internal circuit, and removing high frequency noise components.

The over-input protection / filter circuit 2a, the effective-value operation circuit 3a and the effective-value operation circuit 3b connected to the over-input protection / filter circuit 2b are current detectors ZCT0, ZCT.
It is a circuit for obtaining the effective value of each current detected by CT1.

Further, the phase calculation circuit 4a and the phase calculation circuit 4
b is a circuit for obtaining the phase of the detected current with reference to the phase of the power supply voltage (AC100V commercial power supply) of the ground fault direction relay 1 for low piezoelectric roads, for example.

The timer circuit 5 includes an effective value arithmetic circuit 3b and an effective value arithmetic circuit 3b, and an effective value arithmetic circuit 3b of the current detected by the current detector ZCT0.
And the current detector ZCT output from the phase calculation circuit 4b
The effective value and phase of the detected current according to 1 are set as t1
The data is stored in the storage circuits 6a and 6b at intervals of seconds. The data (effective value and phase of the detected current) stored in the storage circuits 6a and 6b are rewritten every t1 seconds, and only the latest data is stored.

The vector operation circuit 7a is a current detector ZC.
The effective value and phase of the current detected this time by T0 and the current detector ZCT0 stored in the memory circuit 6a.
Based on the effective value and phase of the detected current of
0b is obtained by vector calculation.

The vector operation circuit 7b is a current detector ZC.
The effective value and phase of the current detected this time by T1 and the current detector ZCT1 stored in the storage circuit 6b.
Based on the effective value and phase of the detected current of
1b is obtained by vector calculation.

The level judgment circuit 8 is a vector operation circuit 7.
A logic H signal is output when the current I 1b obtained in b exceeds a preset level setting value.

The phase discrimination circuit 9 is a vector operation circuit 7a.
When the phase of the current I 1b calculated by the vector calculation circuit 7b is delayed by about 90 ° with respect to the phase of the current I0b calculated by the above, the above-mentioned single-phase three-wire high / low voltage transformer Tr2 When it is determined that a ground fault has occurred in a transformer bank (bank of another transformer) and a logical L signal is output, while the phase of the current I 1b is the same phase or the advanced phase with respect to the phase of the current I0b. Determines that the transformer bank of the high / low voltage transformer Tr1 has a ground fault, and outputs a logic H signal.

The AND circuit 10 outputs a logical H signal only when the signals output from the level determining circuit 8 and the phase determining circuit 9 are both logical H signals. That is, the current I 1
When b exceeds the preset level setting value and the phase of the current I 1b is the same phase or the advanced phase with respect to the phase of the current I0b, it is confirmed that the transformer bank of the high and low voltage transformer Tr1 is grounded. The logic H signal shown is output.

The time settling circuit 11 has a t that can be set arbitrarily.
The logic H signal is output when the logic H signal is continuously output from the AND circuit 10 for 2 hours, and erroneous determination due to noise or the like is prevented.

When the logic H signal is output from the time settling circuit 11, the output circuit 12 activates the output relay X1 and turns on the operation display lamp 13 so that the transformer bank of the high and low voltage transformer Tr1 is grounded. Display what you have done. The a contact (make contact) of the output relay X1 is connected to a trip circuit (not shown) so that the trip coil of the circuit breaker ELCB1 is actuated to perform the circuit breaking operation of the circuit breaker ELCB1. Also, output relay X1
B contact (break contact) is the high and low voltage transformer Tr1.
Is connected to an alarm circuit (not shown) for alarming that the transformer bank has a ground fault.

When the 100 volt voltage from the commercial power source input from the terminals P1 and P2 is supplied through the over-input protection filter circuit 15, the power supply circuit 14 includes each circuit of the ground fault direction relay 1 for the low piezoelectric path. Outputs the DC voltage required by.

In the above embodiment, the three-phase three-wire type high / low voltage transformer Tr1 is used as the high / low voltage transformer to be the target of the ground fault judgment.
And an example of two single-phase three-wire high / low voltage transformers Tr2 are shown, but if each circuit of the ground fault direction relay 1 for low piezoelectric path is increased according to the number of high / low voltage transformers subject to ground fault determination. Any number of high-voltage and low-voltage transformers can be the target of the ground fault determination. Fig. 5 shows three high- and low-voltage transformers that are the targets of ground fault judgment.
Ground fault direction relay 1 for low piezoelectric road and current detector ZCT0, ZCT1, ZCT2, Z of each transformer bank
It is a circuit diagram showing the connection with CT3, and is the same when a plurality of high- and low-voltage transformers are provided in the number of three or more.

[0028]

According to the present invention, when a low-voltage side electric path of any of a plurality of high- and low-voltage transformers whose low-voltage side windings are grounded in common is ground-faulted, the low-voltage side electric path is ground-faulted. Can be reliably determined.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram in the case where the low voltage side electric circuit is grounded in the electric circuit of FIG.

FIG. 3 is a vector diagram of each detected current in a state of a ground fault.

FIG. 4 is a circuit block diagram of a ground fault direction relay for a low piezoelectric path.

FIG. 5 is a system diagram for explaining a connection state of a ground fault direction relay for a low piezoelectric road.

FIG. 6 is an electric circuit diagram for explaining a conventional problem.

[Explanation of symbols]

1 Ground fault direction relay for low piezoelectric road 2a, 2b Over-input protection / filter circuit 3a, 3b RMS value calculation circuit 4a, 4b Phase calculation circuit 5 timer circuit 6a, 6b memory circuit 7a, 7b vector operation circuit 8 level judgment circuit 9 Phase discrimination circuit 10 AND circuit 11 hours settling circuit 12 Output circuit 13 Operation indicator lamp X1 output relay Tr1 3-phase 3-wire high / low voltage transformer Tr2 Single-phase 3-wire high / low voltage transformer N neutral point TE Low voltage side winding terminal ZCT0 current detector ZCT1 current detector ZCT2 current detector EB Class B grounding electrode EBL0 ground bus EBL1 Branch ground wire EBL2 Branch ground wire

Claims (2)

(57) [Claims] 1. A low voltage side winding of a plurality of high and low voltage transformers is common.
Flow through the ground busbar connected to the common ground electrode for grounding
Ground bus current detector for detecting the current
Connected between the specified grounding point of the low voltage side winding of the
Branch ground wire electric current which detects the electric current which flows through the branched ground wire
Detected by the current detector and the ground bus current detector
Ground bus current RMS value for calculating RMS value and phase of current
Detected by the phase calculation means and the branch ground wire current detector.
Branch ground wire current actual that calculates the effective value and phase of the generated current
Effective value phase calculation means and the ground bus current effective value phase calculation
The effective value and phase of the ground bus current calculated by the means, and
The amount calculated by the branch ground line current effective value phase calculating means
Rewrite the effective value and phase of the ground wire current every predetermined time.
Memorizing memory means and the ground bus current effective value phase calculator
Based on the effective value and phase of the latest ground bus current calculated at each stage
Current vector and ground stored in the storage means
Grounding of RMS value of bus current and current vector based on phase
Ground bus current vector operation to calculate bus current vector difference
Calculation means and the branch ground line current effective value phase calculation means
Based on calculated latest branch ground line current RMS value and phase
Current vector and branch ground stored in the storage means
Bifurcation connection between effective value of line current and current vector based on phase
Branch ground line current vector that calculates the ground line current vector difference
The calculation means and the effective value of the branch ground line current vector difference are
If the specified value is exceeded, the ground busbar current vector difference
Based on the phase of the branch ground line current vector difference to the phase
The low voltage side connected to the low voltage side winding of the high and low voltage transformer
A ground fault judgment means for judging whether or not the electric circuit has a ground fault.
A ground fault direction relay for low-voltage road. 2. The low-voltage road site according to claim 1, wherein the ground fault determining means causes the circuit breaker of the low-voltage side circuit to perform a breaking operation when it is determined that the low-voltage side circuit of the high-low voltage transformer is ground-faulted. Folding direction relay.