JPS6251061B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to contact signal insulation for insulating disconnection contact signal circuits at remote substations in electrical systems including cold energy generation equipment at LNG terminals, etc. It's about systems.

[Technical background of the invention]

Cold energy power generation equipment installed at LNG terminals usually generates more power than the electricity consumed within the LNG terminal, and the surplus power is transmitted externally. If the terminal or disconnection of the external power transmission line were to be opened for some reason, the LNG terminal would have to operate the cold energy generation equipment internally, and the power disturbance within the LNG terminal would be large enough to overwhelm various equipment. will be applied.
There is also the possibility that LNG terminals may experience problems with the stable supply of gas. Therefore, in many cases, the auxiliary contacts of power transmission terminals and disconnectors are received regardless of the remote location, and used as interlock signals in power plants that utilize cold energy.

Figure 1 shows the electrical system diagram of the LNG terminal and substation. In the figure, 1 is the substation that is the power transmission side, 2 is the LNG terminal that is the receiving measurement, 3 is the breaker on the substation 1 side, 3a and 3b are the auxiliary normally open contacts of the breaker 3, and the auxiliary Normally closed contact (hereinafter, both are simply referred to as auxiliary contact), 4 is
4a and 4b are the auxiliary contacts of the LNG terminal 2 side, 5 is the transformer on the LNG terminal side, 6 is the power receiving switch for the bus of the LNG terminal, 7 is the bus of the LNG terminal,
Reference numeral 8 indicates a generator shield and disconnector of the cold energy power generation equipment, and 9 indicates a generator of the cold energy power generation equipment, and the area surrounded by the dotted line in the figure represents the so-called cold energy power generation plant.

Figure 2 shows the power switch 3 of substation 1 located in a remote location.
This shows a circuit configuration in which live contacts of auxiliary contacts 3a and 3b are incorporated into the control circuit on the LNG terminal 2 side. In the figure, 11 represents a keep relay type auxiliary relay, OC represents its operating coil, and RC similarly represents its reset coil.

By the way, when incorporating a contact signal from a remote location into a control circuit signal, the following problems arise.

(1) Due to the remote location, long-distance control circuit cables are susceptible to induced voltages from other high-voltage transmission lines, surges in the opening and closing of various circuit breakers, and abnormal voltages during ground faults, which may damage the control circuit itself. It will put you at risk.

(2) Due to the remote location, the impedance of long-distance control circuit cables becomes large, making it difficult to directly conduct current to operating coils such as auxiliary relays.

[Problems with background technology]

Therefore, as a means for insulating contact signals and transmitting them to remote locations, carrier waves and microwaves have conventionally been used to transmit contact signals and other signals. Although these means are highly accurate and reliable, they require large scale and expensive equipment. Moreover, it is extremely uneconomical to simply use it only for exchanging the auxiliary contact signal of the disconnector. Further, it is complicated, such as requiring an auxiliary power source on both the transmitting side and the receiving side.

[Purpose of the invention]

The present invention was made to solve the above-mentioned problems, and its purpose is to prepare a normal commercial frequency power supply only on the receiving side without using carrier waves or microwaves, and on the transmitting side. Only an auxiliary disconnect contact is provided, and a control cable is used to communicate between the transmitting and receiving sides.The control circuit on the receiving side and the contact circuit on the transmitting side are electrically connected via an isolation transformer. It is an object of the present invention to provide a contact signal insulation system that can completely insulate the contact signal and transmit only the contact signal to the control circuit without delay.

[Summary of the invention]

In order to achieve the above object, the present invention receives a contact signal from a transmitting side contact circuit located at a remote location, and provides the received contact signal to a receiving side control circuit as its control condition signal. The output of the AC auxiliary power supply is applied to a primary winding having an intermediate tap, and a normally open contact of a contact circuit is provided between one terminal of the secondary winding having an intermediate tap and the intermediate tap, and two An insulating transformer in which a normally closed contact of a contact circuit is provided between the other terminal of the next winding and an intermediate tap, and a normally open contact, a secondary circuit of an insulating transformer depending on the open/closed state of the normally closed contact. The present invention is characterized in that it includes at least one voltage relay that responds to potential changes at the intermediate tap of the primary winding of the isolation transformer due to flowing current and sends its operational output as a control condition signal.

[Embodiments of the invention]

An embodiment of the present invention shown in the drawings will be described below. FIG. 3 shows a connection configuration of a contact circuit and a control circuit to which the contact signal insulation system of the present invention is applied. In other words, in this figure, a contact signal from a contact circuit on the substation side in a remote location is received by the contact signal insulation system 12 on the LNG base side, and the output contacts 12a and 12b are used to connect the auxiliary relay 1 of the control circuit.
1 is configured to operate.

FIG. 4 shows an example of the configuration of a contact signal isolation system according to the present invention. That is, in the contact signal insulation system of this embodiment, the output of an AC auxiliary power supply (hereinafter simply referred to as auxiliary power supply) is applied to a primary winding having an intermediate tap, and one of the secondary windings having an intermediate tap. An auxiliary contact 3a of the breaker 3 of the contact circuit is provided between the terminal u of the secondary winding and the intermediate tap, and an auxiliary contact 3a of the breaker 3 of the contact circuit is provided between the other terminal v of the secondary winding and the intermediate tap. Auxiliary contact 3b
An isolation transformer 13 provided with this auxiliary contact 3
2 of the isolation transformer 13 depending on the open/closed state of a and 3b.
It is equipped with two single-phase undervoltage relays 21a and 21b that respond to potential changes at the intermediate tap of the primary winding of the isolation transformer 13 due to the current flowing in the next circuit, and send out the operating output as a control condition signal. It is composed of In addition, 19a and 19b are isolation transformers 1
This is the impedance of the secondary circuit of No. 3.

FIG. 5 shows an equivalent circuit of the circuit shown in FIG. 4. In the figure, for convenience of explanation, the leakage reactance, primary winding resistance, and excitation conductance of the isolation transformer 13 are ignored, and the excitation susceptance is converted into reactance X ₁ , X ₂ , and the impedance of the secondary circuit of the isolation transformer 13.
A simple equivalent circuit is shown in which R ₁ and R ₂ are simply converted to the primary side.

6a and 6b show vector diagrams of the primary voltage and primary current in FIG.
This shows where in the vector diagram the potential of the intermediate tap "O" point of the next winding is located.

In FIG. 4, when the rated AC voltage is applied from the auxiliary power source, between the primary windings U and V of the isolation transformer 13 and the single-phase undervoltage relays 21a and 21b,
A voltage is applied to each. As a result, a voltage proportional to the transformation ratio a is induced in the secondary winding of the isolation transformer 13, and an impedance 19a or 1 is generated in the circuit where the remote contact 3a or 3b is closed.
A current determined by 9b flows.

This will be explained based on the equivalent circuit shown in FIG. 5 as follows. When the impedance of the secondary circuit of the isolation transformer 13 is R ₁ and R ₂ and the excitation reactance is X ₁ and X ₂ , both the remote contacts 3a and 3b are in the open state (which is actually impossible). but)
, _the transformer impedance is Z = jX ₁ + jX ₂ , and if X ₁ = It happens. Since the auxiliary contact 3a at the remote location is a normally open contact and the contact 3b is a normally closed contact, there is no case where both are open or omitted at the same time; one is always closed and the other is open, so the transformer impedance Z is It is expressed as the following equation.

(a) When contact 3a is closed and contact 3b is open (shrink breaker closed state), Z=R ₁ /a ² ×jX ₁ /R ₁ /a ² +jX ₁
+jX ₂ (b) When contact 3a is open and contact 3b is closed (open circuit breaker), Z=jX ₁ +R ₂ /a ² ×jX ₂ /R ₂ /a ² +
jX ₂ Now, transformation ratio a = 1, impedance R ₁ = R ₂
=R, excitation reactance X ₁ =X ₂ =X, the ratio of impedance R and excitation reactance X is R≪X
Therefore, Z≒R+jX. Regardless of the state of the remote contacts 3a and 3b, the impedance Z seen from the power supply side of the isolation transformer 13 remains unchanged, so the primary current does not change. but,
The potential at the intermediate tap "O" point of the isolation transformer 13 is determined by whether it is located in a phase lead region or a phase delay region relative to the primary voltage, depending on the state of the secondary circuit. Therefore, the vectors of the terminal O-U voltage V ₁ and the terminal V-O voltage V ₂ are as shown in FIG.
It becomes as shown in b. That is, (c) contact 3a is closed, contact 3b is open (circuit breaker closed state) V ₁ =R/R+jX・V, V ₂ =jX/R+jX・V ∴V ₁ ≪V ₂ .

(d) Contact 3a is open, contact 3b is closed, (the breaker is open) V ₁ = jX/R+jX・V, V ₂ = R/R+jX・V ∴V ₁ ≫V ₂ .

On the other hand, the single-phase undervoltage relay 21a is connected to the terminal "O".
-U voltage _V1 is detected and monitored, and 21b is the terminal V-
Since the “O” voltage V ₂ is detected and monitored, for example,
If the setting values of the undervoltage relays 21a and 21b are selected as R/R+jX <setting value<jX/R+jX, when the remote contact 3a closes, 21a operates, and when the contact 3b closes, 21b operates. It will work. In the unlikely event that
If the auxiliary power source is lost, it can be determined that the power source has been lost by the fact that both 21a and 21b operate. In this way, the contact signal insulation system 12 shown in FIG. 3 includes the undervoltage relay 21a.
By closing the output contact 12a with the operation 21b and closing the output contact 12b with the operation 21b, it becomes possible to transmit the contact signals 3a and 3b from remote locations to the control circuit.

Next, FIG. 7 shows another embodiment of the present invention. In the figure, 22 is a three-phase undervoltage relay. Since a 3-phase undervoltage relay is used, the disadvantage is that a 3-phase power source is required as an auxiliary power source, but the advantage is that the operation is sharp as described below. Normally, the three-phase voltages are balanced, and the three-phase undervoltage relay 22 operates according to the triangular area formed by the delta voltages. In other words, FIGS. 8a and 8b show vector diagrams of three-phase voltages, which operate in response to the area of triangle RST in the diagrams when this value falls below a certain value. In this embodiment, the three-phase undervoltage relay 2
The middle tap "O" point of the primary winding of the isolation transformer 13 is connected to the T-phase input terminal of No. 2, and it is used as the 3-phase input of the 3-phase undervoltage relay 22 (Fig. 8 a, b).
It responds to the area of the triangle RSO shown in the figure, and operates when the area of this triangle becomes less than a certain value.

The ST line voltage of the three-phase voltage is applied to the primary winding of the isolation transformer 13, and the secondary circuit of the isolation transformer 13 has impedances 19a,
Remote contacts 3a and 3b are connected via 19b. The contact circuit including this isolation transformer 13 has the same operating principle as explained in FIGS. The point potential is remote contact point 3a, 3
In response to the behavior of b, it will be positioned in a leading phase or a lagging phase with respect to the ST line voltage.

That is, when the contact 3a at the remote location is closed and the contact 3b is open (the breaker closed state), the phase is delayed as shown in FIG. 8a, and the delta voltage becomes the triangular RSO shown by the hatched part Its area S ₁ has the following value.

S ₁ = V _RS × V ₂ × sin θ ₁ /2 (However, V ₂ = jX/R + _j As shown in b, it is located in the leading phase, and the delta voltage becomes a triangular RSO shown by the hatched part, and its area S ₂ has the following value.

S ₂ = V _RS × V _{2 ×} sin θ _{2 / 2} (V ₂ = R/R + _j can be found below.

Here, if V ₂ and θ ₁ and θ ₂ are eliminated, the result is as follows.

Also, since R≪X, it is clear that S ₁ ≫ _{S 2}
It can be seen that Therefore, if the setting value of the three-phase undervoltage relay 22 is set as S ₁ >setting value > S ₂ , then
When the contact 3b at the remote location closes, the three-phase undervoltage relay 22 operates, and when the contact 3a closes, it returns to normal, making it possible to transmit the contact signal at the remote location.

As described above, the contact signal isolation system of this embodiment receives a contact signal from the contact circuit on the side of the substation 1 as the transmitting side located in a remote location, and transmits the received contact signal to the LNG terminal as the receiving side. Control condition signal 12 to the auxiliary relay 11 of the control circuit on the second side
In those given as a and 12b, the output of the auxiliary power supply is applied to the primary winding having an intermediate tap, and the auxiliary contact circuit is applied between one terminal u of the secondary winding having an intermediate tap and the intermediate tap. Contact 3
a is provided, and the other terminal v of the secondary winding
an isolation transformer 13 in which an auxiliary contact 3b of a contact circuit is provided between the auxiliary contact 3b and the intermediate tap;
2 of the isolation transformer 13 depending on the open/closed state of a and 3b.
Two single-phase undervoltage relays 21a, 21b respond to potential changes at the intermediate tap of the primary winding of the isolation transformer 13 due to the current flowing in the next circuit, and send out their operating outputs as control condition signals 12a, 12b.
Alternatively, it is configured to include one three-phase undervoltage relay 22.

Therefore, it is possible to physically separate the circuit containing remote contacts from the original control circuit, and to prevent abnormal voltages such as induced voltages and switching surges that may be carried over long distance communication cables. This is very effective in protecting control circuits. Also, from the perspective of the function of transmitting contact signals to the control circuit,
There is no delay in the isolation transformer 13, and the only delay in the operation time of the single-phase undervoltage relays 21a, 21b or the three-phase undervoltage relay 22 is minimal and does not pose any problem, and is useful for the protection and operation of LNG terminals, etc. Optimal.

In the above example, alternating current is passed through the contact cable to the remote contact point, but if it is inconvenient to pass alternating current through the contact cable,
A rectifier circuit may be provided on the outlet side of the insulation system to convert the electrical current to direct current and to pass the direct current to the connecting cables and remote contacts. In this case, it goes without saying that sufficient surge protection measures must be taken for the rectifier circuit, but the principle is as described above.

The intermediate tap of the isolation transformer 13 can be easily obtained by connecting two single-phase transformers of the same specification in series and using the intermediate point. It has the advantage of being compatible.

Further, instead of the undervoltage relay, a voltage relay such as an overvoltage relay may be used.

〔Effect of the invention〕

As explained above, according to the present invention, the contact signal insulation is capable of completely electrically insulating the contact circuit on the transmitting side and the control circuit on the receiving side, and transmitting only the contact signal to the control circuit without delay. system can provide.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the electrical system of the LNG terminal and substation, Fig. 2 is a diagram showing the circuit configuration in which a remote contact signal is incorporated into the control circuit, and Fig. 3 is a block diagram showing the system to which the present invention is applied. , FIG. 4 and FIG. 7 are circuit configuration diagrams showing one embodiment and other embodiments of the present invention,
Figure 5 is a diagram showing the equivalent circuit of Figure 4, Figure 6a,
b and FIGS. 8a and 8b are vector diagrams of voltage and current. 1... Substation, 2... LNG terminal, 3a, 3b
...Contact, 11...Auxiliary relay, 12...Contact signal isolation system, 12a, 12b...12 output contacts, 13...Isolation transformer, 21a, 21b...
Single-phase undervoltage relay, 22...3-phase undervoltage relay.

Claims (1)

[Claims] 1 In a device that receives a contact signal from a contact circuit on the transmitting side in a remote location and supplies the received contact signal to a control circuit on the receiving side as its control condition signal, an AC auxiliary coil is connected to the primary winding having an intermediate tap. 2 to which the output of the power supply is applied and also has an intermediate tap.
A normally open contact of the contact circuit is provided between one terminal of the secondary winding and the intermediate tap, and a normally closed contact of the contact circuit is provided between the other terminal of the secondary winding and the intermediate tap. An isolation transformer provided with a contact, and a potential at the intermediate tap of the primary winding of the isolation transformer due to the current flowing in the secondary circuit of the isolation transformer depending on the open/closed state of the normally open contact or normally closed contact. at least one voltage relay responsive to changes and transmitting its operational output as the control condition signal.