JP3333753B2 - Ground potential suppression device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-to-low voltage transformer, such as when a high- voltage is applied to a low-voltage winding of a high-to-low voltage transformer.
The specified ground point of the low-voltage winding of the switch exceeds the specified ground voltage.
The present invention relates to a device for lowering the ground potential of a low-voltage side electric circuit when rising .

[0002]

2. Description of the Related Art
As a private electric facility such as a building or a factory, for example, a three-phase three-wire high / low voltage transformer having a high voltage side of 6.6 kv and a low voltage side of 200 v, a high voltage side of 6.6 kv and a low voltage side of 200 kv are used.
A v-100v single-phase three-wire high-low voltage transformer and the like are installed. In the case of the above-described three-phase three-wire high-low voltage transformer or single-phase three-wire high-low voltage transformer, according to Article 24 of the Technical Standards for Electrical Equipment, the neutral point of the low-voltage winding or the low-voltage winding It is obligatory that one of the terminals is provided with a Class B grounding work.
FIG. 2 shows that the neutral point N of the low-voltage side winding of the single-phase three-wire high-low-voltage transformer Tr1 and one of the low-voltage side winding terminals TE of the three-phase three-wire high-low-voltage transformer Tr2 are: FIG. 4 is an electric circuit diagram schematically showing that the power supply device is typically connected to a common type B ground electrode EB provided for only one pole per customer.

The cables connected to the low-voltage side electric circuit of the single-phase three-wire high-low voltage transformer Tr1 and the three-phase three-wire high-low voltage transformer Tr2 have recently become long, and furthermore, capacitors are used as constituent elements. In many cases, an electronic device having a built-in line filter or the like is connected as a load. Therefore, in general,
The apparent ground capacitance (floating capacitance) C of the low-voltage side electric circuit,
C is getting bigger.

In the above-described low-voltage side electric circuit, as shown in FIG. 2, a cable connected to the low-voltage side electric circuit of the three-phase three-wire high-low voltage transformer Tr2 is, for example, a class D grounded electric wire (not shown). When a ground fault occurs in a pipe, a ground fault current from a ground fault point is represented by a ground fault resistance R, a D-type ground wire EDL connected to the conduit, and a ground capacitance (floating capacitance) as shown by a broken line.
C, C, low-voltage side electric circuit of single-phase three-wire high-low voltage transformer Tr1,
The low-voltage side of the single-phase three-wire high-low-voltage transformer Tr1 that is not directly related to the ground fault because it flows in a closed circuit formed by the class B ground line EBL and the three-phase three-wire high-low-voltage transformer Tr2 There is a problem that the ground fault circuit breaker ELB of the electric circuit unnecessarily trips.

[0005] In normal times, a high-frequency current from an inverter or the like connected as a load to the low-voltage side electric circuit of the three-phase three-wire high / low voltage transformer Tr2 is supplied to the D-class ground line EDL and the ground capacitance (floating). Capacity) C, C, the low-voltage side electric circuit of the single-phase three-wire high-low voltage transformer Tr1 and the closed circuit of the class B ground line EBL and the three-phase three-wire high-low voltage transformer Tr2. An electronic device connected to the low-voltage side electric circuit of the low-voltage transformer Tr1 may malfunction.

Thus, a single-phase three-wire high / low voltage transformer Tr1
And the neutral point N and the low voltage side winding terminal TE of the low voltage side winding of each transformer are connected to the class B grounding pole EB which is a common grounding pole of the three-phase three-wire high / low voltage transformer Tr2. The above-described problem occurs due to the formation of the closed circuit as described above.

Therefore, in the present invention, when the high voltage is applied to the low voltage winding of the high voltage transformer, the high voltage transformer is used.
The specified ground point of the low-voltage side winding rises above the specified ground voltage.
If the conduction of the predetermined ground point of the low-voltage side winding and the common ground electrode
It is lowered to ground potential of the low-pressure side path to a safe potential in the state
The low-voltage side winding of the high-low voltage transformer
If the voltage is lower than the ground voltage , a non-conductive state is established between the predetermined ground point of the low-voltage side winding and the common grounding pole, so that a ground fault from the low-voltage circuit of the transformer to the low-voltage circuit of another transformer is performed. An object of the present invention is to provide a ground potential suppressing device that prevents a current or a high-frequency current from flowing around.

[0008]

Means for solving the above problem is to configure the ground potential suppressing device as described in claim 1 or 2 . According to claim 1 or 2 ground potential suppression device, for example a high-low pressure transformer high-voltage side winding of the low-voltage side winding is incompatible high side voltage mark low-voltage side winding
Predetermined grounding of the low-voltage winding of the high-low voltage transformer, if applied
When the point rises above a predetermined ground voltage, a circuit connected between a predetermined ground point of the low-voltage side winding of the high-low voltage transformer and the common ground electrode (ground potential formed by a semiconductor switch or the like)
The suppression device) is turned on, and the ground potential of the low-voltage side winding and the low-voltage side electric circuit connected to the low-voltage side winding is reduced. In addition to the high-voltage transformation, except that the high-voltage is applied to the low- voltage winding,
If the specified ground point of the low-voltage winding of the
If during the predetermined ground point of the low-voltage side winding of the high-low pressure transformer and the common ground electrode, the ground electrostatic constituted by a semiconductor switch or the like
Since the low-voltage side winding and the low-voltage side electric circuit of each high-and-low-voltage transformer are insulated from the low-voltage side winding and the low-voltage-side electric circuit of other high and low-voltage transformers because they are kept in a non-conducting state by the position suppressing device . Therefore, the sneak of the ground fault current and the sneak of the high-frequency current from the low-voltage circuit of the high-low voltage transformer to the low-voltage circuit of the other high-voltage transformer are cut off and connected to the low-voltage circuit of the other high-low voltage transformer. It is possible to prevent the failure of the set electric device or electronic device.

[0009]

Next, an embodiment of the present invention will be described. FIG. 1 shows a neutral point N of a low-voltage side winding of a single-phase three-wire high-low-voltage transformer Tr1 and a low-voltage side winding of a three-phase three-wire high-low-voltage transformer Tr2 of a private electrical installation installed in a certain building. FIG. 3 is an electric circuit diagram in which one of the terminals TE is set as a predetermined ground point and ground potential suppressing devices 1A and 1B described later are connected between the predetermined ground point and a common type B ground electrode EB. The single-phase three-wire high / low voltage transformer Tr1 has a high voltage side of 6.6 kv,
The low-voltage side is a 200v-100v high-low voltage transformer,
The phase 3-wire high / low voltage transformer Tr2 has a high voltage side of 6.6 kv,
The low voltage side is a 200v high / low voltage transformer.

[0010] As shown in FIG.
A and 1B are low pressure arrester Zn and TRIAC T
, A varistor Znt, and a capacitor Co. In the ground potential suppressing device 1A, a low-voltage arrester Zn and a capacitor Co are connected in series between a neutral point N of a low-voltage side winding of a single-phase three-wire high-low voltage transformer Tr1 and a class B ground electrode EB. In addition, a triac T is connected in parallel to a series circuit of the low-voltage arrester Zn and the capacitor Co, and the gate terminal of the triac T and the capacitor C
A varistor Znt is connected between the varistor Zt and the varistor Z. Also, 3
Low-voltage side winding terminals TE and B of phase 3-wire high-low voltage transformer Tr2
Ground potential suppressing device 1B connected between seed ground electrode EB
Is also configured with a similar circuit.

Next, the operation of the ground potential suppressing devices 1A and 1B will be described. First, the operation of the ground potential suppressing device 1A connected between the neutral point N of the low-voltage side winding of the single-phase three-wire high-low voltage transformer Tr1 and the B-type ground electrode EB will be described. In normal times, the low-voltage arrester Zn is in a non-conductive state because the ground potential at the point (A) is lower than the operating potential of the low-voltage arrester Zn, and the triac T is also in a non-conductive state because the gate voltage of the triac T is lower than the trigger voltage. It is. Therefore, the ground potential suppression device 1A is normally non-conductive,
Neutral point N of low-voltage side winding of single-phase three-wire high-low voltage transformer Tr1
And the class B ground electrode EB are in an insulated state.

Next, even if a ground fault occurs in the low-voltage side electric circuit of the single-phase three-wire high-low voltage transformer Tr1, the ground potential at the point (a) does not exceed the operating potential of the low-voltage arrester Zn. Therefore, the low-voltage arrester Zn remains non-conductive,
The triac T is also non-conductive. Therefore, the ground potential suppressing device 1A remains non-conductive, and the neutral point N and the class B grounding electrode E of the low-voltage side winding of the single-phase three-wire high-low voltage transformer Tr1.
The insulation state is maintained between B and B.

As described above, the neutral points N and B of the low-voltage side winding of the single-phase three-wire high-low-voltage transformer Tr1 during normal times and ground faults.
Since the seed ground electrode EB is in an insulated state (non-conducting state), the ground fault current or the high frequency current from the inverter as described in the section of the prior art is used to transmit the three-phase three-wire high-low voltage transformer Tr2. 3 phase 3 without going around the low voltage side electric circuit
Unnecessary trips of an electric device (not shown) connected to the low-voltage side electric circuit of the linear high-low voltage transformer Tr2 and troubles such as malfunction of the electronic device are prevented.

The ground potential suppressing device 1B connected between the low voltage side winding terminal TE of the three-phase three-wire type high / low voltage transformer Tr2 and the class B grounding electrode EB also has a ground potential and a ground fault as described above. Because of the non-conduction state, the single-phase three-wire high-low voltage transformer Tr1
The electric equipment and the electronic equipment (not shown) connected to the low-voltage side electric circuit are prevented from being damaged.

Next, a case in which the low-voltage side winding and the high-voltage side winding of the single-phase three-wire type high-low voltage transformer Tr1 are in contact with each other due to dielectric breakdown or the like and a high-voltage high voltage is applied to the low-voltage side winding. , High and low pressure change
When the specified ground point of the low-voltage winding of the
The operation of the ground potential suppressing device 1A when the voltage rises will be described. As described above, the single-phase three-wire high-low voltage transformer Tr1
When the high-voltage high voltage is applied to the low-voltage winding when the low-voltage winding and the high-voltage winding contact each other due to dielectric breakdown, etc.
, The voltage applied to the low-voltage arrester Zn exceeds the operating voltage. In this state, the low-voltage arrester Zn becomes conductive, so that a charging current flows through the capacitor Co, and the potential of (c) rises. When the potential of (c) rises to the operating voltage of the varistor Znt, the varistor Zn
Since t is turned on and the current discharged from the capacitor Co flows to the gate of the triac T, the triac T is triggered and turned on. As a result, the neutral point N of the low-voltage side winding of the single-phase three-wire high-low voltage transformer Tr1 is conducted to the B-type grounding pole EB, and the high voltage applied to the low-voltage side winding of the transformer is B-type. Since the low-voltage side winding and the low-voltage side electric circuit are grounded to the ground electrode EB, the ground potential is reduced. The above-described ground potential suppressing operation by the ground potential suppressing device 1A is repeated every half cycle of the commercial power supply frequency until the protection relay provided on the high-voltage side electric circuit operates and the upper circuit breaker trips to cause a power failure.

The ground potential suppressing device 1B connected between the low voltage side winding terminal TE of the three-phase three-wire type high / low voltage transformer Tr2 and the class B ground electrode EB basically has the ground potential suppressing effect. This is the same as the potential suppression device 1A. That is, the low-voltage winding and the high-voltage winding of the three-phase three-wire high-low voltage transformer Tr2 are in contact with each other due to dielectric breakdown or the like, and a high voltage is applied to the low-voltage winding.
The low-voltage side winding of the high-low voltage transformer
If the voltage rises above a certain level, the low-voltage side winding terminal TE
Since a high voltage is applied to the low-voltage arrester Zn connected to the low-voltage arrester Zn, the low-voltage arrester Zn is conducted and the capacitor Co
Is charged and the triac T is triggered, so that the low-voltage side winding terminal TE of the three-phase three-wire high-low voltage transformer Tr2 and the B-type ground electrode EB are conducted similarly to the ground potential suppressing device 1A. You. As a result, the high voltage applied to the low-voltage side winding of the transformer is grounded to the B-type ground electrode EB, and the ground potential of the low-voltage side winding and the low-voltage side electric circuit is reduced.

As described above, the ground potential suppressing devices 1A, 1
B is when the connected high-low voltage transformers Tr1 and Tr2 are in a normal state, when the low-voltage winding and the low-voltage electric circuit are grounded,
Grounding point of low-voltage side winding of high-low voltage transformer Tr1, Tr2 and B
Since it is insulated (non-conductive) from the seed ground electrode EB,
It is possible to prevent a high-frequency current or a ground fault current from flowing from the inverter from the low-voltage side electric circuit of the transformer to the low-voltage side electric circuit of another transformer. As a result, it is possible to solve the problems that the electronic device connected to the low-voltage side electric circuit malfunctions and the ground fault circuit breaker ELB unnecessarily trips. When the low voltage side winding and the high voltage side winding of each transformer touch each other due to insulation breakdown and a high voltage is applied to the low voltage side winding, the low voltage side winding of the high / low voltage transformer
When the predetermined ground point rises above a predetermined ground voltage , conduction is established between the ground point of the low voltage side winding and the class B ground electrode EB, so that the ground potential of the low voltage side winding can be reliably reduced. it can.

In the embodiment described above, the ground potential suppressing devices 1A and 1B are constituted by the low-voltage arrester Zn, the triac T, the varistor Znt, and the capacitor Co, but are limited to these constituent elements. is not.

[0019]

According to the first aspect of the present invention, when the high-voltage is applied to the low-voltage winding of the high-low voltage transformer, the high-low voltage is applied.
The specified ground point of the low voltage side winding of the transformer is higher than the specified ground voltage
In this case , the predetermined ground point of the low-voltage side winding is brought into a conductive state with the common ground electrode, and the ground potential of the low-voltage side winding and the low-voltage side electric circuit can be reduced to a safe potential. In addition, high and low voltage during normal and low voltage side winding or low voltage side electric circuit ground fault etc.
The specified ground point of the low-voltage side winding of the transformer is less than the specified ground voltage
In the case of the above , since the conduction between the predetermined ground point of the low-voltage side winding and the predetermined ground electrode can be made non-conductive, the high-frequency current from the low-voltage side electric circuit of the transformer to the low-voltage side electric path of another transformer can be obtained. The sneak current of the ground fault current can be prevented, and malfunctions of electronic devices and electric devices connected to the low-voltage side electric circuit of another transformer can be prevented.

[Brief description of the drawings]

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

FIG. 2 is an electric circuit diagram for explaining a conventional problem.

[Explanation of symbols]

 1A, 1B Ground potential suppressor Zn Low voltage arrester Znt Varistor T Triac Co capacitor EB Class B ground electrode Tr1 Single-phase three-wire high-low-voltage transformer Tr2 Three-phase three-wire high-low-voltage transformer N Neutral point TE Low-voltage side winding Wire terminal

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02H 3/14 H02H ⁷ /04-7/055 H02H 9/04 H02H 9/08

Claims (2)

(57) [Claims] A low voltage side winding in a high / low voltage transformer.
And one of the low voltage side winding terminals as a predetermined ground point,
Ground potential connected between the predetermined ground point and the common ground pole
The suppression device, wherein the potential of the predetermined ground point has risen to a predetermined ground voltage or more.
In this case, conduction is established between the predetermined ground point and the common ground electrode.
And when the potential of the predetermined ground point is lower than a predetermined ground voltage,
Non-conduction between the predetermined ground point and the common ground electrode
A potential-to-ground potential suppressor. 2. In a low-voltage side winding in a high-low voltage transformer.
And one of the low voltage side winding terminals as a predetermined ground point,
A semiconductor switch is connected between the predetermined ground point and the common ground pole.
Is a ground potential suppression device that is made conductive or non-conductive through
Thus, the potential of the predetermined ground point has risen to a predetermined ground voltage or more.
In this case, set the semiconductor switch to the conductive state and
Conducting between the point and the common ground electrode, and when the potential of the predetermined ground point is less than a predetermined ground voltage,
Make the semiconductor switch non-conducting and place it before the specified ground point.
A ground potential suppressing device, characterized in that the common ground electrode and the common ground electrode are non-conductive .