JPS62166734A - Private power source changer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an in-station power supply switching device for a liquefied gas fuel base that automatically switches the power supply in a short time and supplies fuel safely and stably. .

[Conventional technology]

In recent years, the demand for electricity has continued to increase, and power generation units have also increased in capacity.6Furthermore, reflecting the global energy situation, the fuel used has changed from conventional petroleum to liquefied natural gas (LNG), Liquid propane gas (LPG)
, coal or COM (coal/oil mixed fuel). Along with this, large-scale fuel receiving bases for these power generation units have also been constructed.

Among these, at liquefied gas fuel terminals such as LNG and LPG, the receiving terminal vaporizes the fuel such as LNG and LPG at the receiving terminal and supplies it directly to the power generation plant.

For this reason, if a problem occurs at the receiving terminal, it may lead to the shutdown of the power plant.

High reliability is sometimes required when operating bases.

For this reason, the on-site power supply configuration of liquefied gas fuel bases generally adopts a two-system power receiving system consisting of two systems as shown in Figure 3, and if an accident occurs in one system or there is a power outage without warning, a power outage occurs. Even if this occurs, the power supply can be switched automatically and quickly by simply disconnecting the faulty power supply and turning on the busbar connection breaker. Methods for automatically switching the power supply in a short period of time include the instantaneous switching method, which shuts off the faulty system when a failure occurs in the system, and switches the system to another healthy power source in a short period of time, and the healthy side power supply voltage. The phase detection switching method switches to another healthy power supply when the phase difference between the residual voltage on the faulty side and the faulty side falls within a certain allowable range (e.g., phase difference within 20°), and the residual voltage on the faulty side is a specified value, e.g. 30°. A low voltage switching method in which a low voltage detection relay detects that the voltage has dropped below % and switches to the healthy power supply.

Specified value 5 with residual voltage on the faulty side For example, rated voltage value 3
A timed power outage switching method is adopted in which the optimal time for the power to reach 0% or less is measured in advance, a timed relay is used to wait for that time plus a margin time, and then the power is switched to the healthy power source.

On the other hand, in the case of liquefied gas fuel bases, there are many auxiliary equipment such as pump loads with small moment of inertia GO, so if a failure occurs in the power receiving system, changes in the residual voltage of the bus bar and changes in phase will occur as usual. Compared to thermal power plants, etc., they have the characteristic of changing at an extremely rapid speed. Therefore, in order to safely switch to a healthy power source without damaging the pump, motor, etc., it has been found that the instantaneous switching method and the phase detection switching method using phase confirmation are impossible.

In addition, the timed power outage switching method requires longer power outages than the low voltage switching method, and the residual voltage characteristics vary significantly depending on the load configuration and the nature of the system accident (failure), so it is not always possible to obtain effective results. Since it is not always possible to obtain the following, it is not likely to be adopted. Therefore, it is no exaggeration to say that in the case of liquefied gas fuel bases, switching to a healthy power source using a low voltage switching method is the mainstream.

[Problem that the invention seeks to solve]

However, in the case of liquefied gas fuel bases, etc., as mentioned above, the fuel is vaporized at the receiving base and directly supplied to the power generation plant, etc., so it is necessary to quickly restore power in the event of a failure. is required. Needless to say, if power is not restored promptly, seawater pumps for the vaporizer, etc. will stop working. The fuel cannot be vaporized.

This may lead to a serious accident in which the fuel station or even the power plant that is supplied with these vaporized fuels is tripped. Although it is said that the low voltage switching method is the mainstream power supply switching method in the case of liquid gas fuel bases.

This low voltage switching method also has problems. Namely.

As mentioned above, in the case of a fault in the power grid, the low voltage switching method uses a low voltage detection relay to detect when the residual voltage on the faulty side has fallen below a specified value, for example 30%, and communicates with the healthy power supply bus. The system attempts to restore power by turning on the bus line breaker, but when the bus line line breaker is turned on, the IP and U motors for auxiliary equipment connected to the faulty bus line are activated.

Voltages will be applied before and after the bus, and a large inrush current will flow through the system components such as the transformer of the healthy power supply connected to the busbar connection breaker and the station busbar, and in some cases, the liquefied gas fuel base This may result in a system trip. Therefore, in the case of a liquefied gas fuel base, the minimum auxiliary equipment necessary to continue operating the system, such as the electric motor for the vaporizer seawater pump, is forcibly disconnected from the bus line at the same time as the accident system is disconnected. It is necessary to prevent excessive inrush current from flowing to the system components on the healthy side.

On the other hand, power to the seawater pumps for fuel vaporization at the liquefied gas fuel base needed to be restored as soon as possible, that is, before the rotational speed dropped and the flow rate stopped, so power was lost due to the accident. Immediately after this is detected by the low voltage detection relay, other auxiliary equipment must be configured to selectively cut off the load.

In view of the above-mentioned problems, the present invention has been developed to promptly remove the faulty system without affecting the healthy system power supply even in the event of a power system failure, automatically switch the power supply to the healthy system power supply in a short time, and to The purpose of the present invention is to provide an in-station power supply switching device that allows a fuel base to continue operating stably and safely.

[Means for solving problems]

Power is received through a common bus, and this power supply is divided into two systems within the plant. When one system's power supply fails, the faulty load is selectively cut off, and the power is disconnected from the healthy bus via a busbar connection breaker. An in-station power supply switching device configured to receive power supply is characterized in that a timer is added for selective load cutoff, and the busbar is automatically and quickly switched to a healthy system power supply.

[For production]

For this reason, in the present invention, the selective load is not cut off by the operation of the low voltage detection relay alone, but a timer is added which has a shorter standby time than when the busbar connection breaker is turned on, and the operation of this timer and the low voltage Selective load cutoff is performed only when the detection relay operates, quickly removes the faulty system without affecting the healthy power supply as much as possible, automatically switches the power supply to the healthy power supply in a short time, and removes the liquefied gas. The fuel base is configured so that it can continue to operate stably and safely.

〔Example〕

An embodiment of the present invention will be described using FIGS. 1 and 2. Figure 1 shows the connection between the low voltage detection relay and the busbar breaker.
This is a control block diagram with a timer added that has a shorter standby time than the "closing" operation, and Figure 2 shows the voltage behavior over time when bus bar switching is actually performed in the block diagram of Figure 1. This is a description of the operating characteristics of various component devices. TB means a timer which is one component of the present invention.

The configurations of these conventional techniques will be explained using FIGS. 3, 4, and 5. FIG. 3 is a diagram showing the internal power supply configuration of the liquefied gas fuel base, where 1 is the power supply, 2 is the common bus, 3 is the A system bus, and 4 is the B system bus. 52BT is a busbar communication breaker that opens the respective power receiving circuit breaker 52AL or 52BL in the event of an accident in the A system or the B system so that power can be received from the healthy side. 11 is a common bus breaker for the A system, 12 is a lifting transformer for the A system, 21 is a common bus breaker for the B system, and 22 is a lifting transformer for the B system. 14 and 24 are the loads of the liquefied gas fuel base;
is the load of the A system, and 24 is the load of the B system. 13 and 23 are load breakers for starting and stopping these loads.
4 and 24 are connected to the bus 3 or 4 of the A system and B system, respectively. 15 and 25 are transformers for transforming the voltages of the buses 3 and 4, and 27A and 27B are low voltage detection relays for the A system and B system buses 3 and 4. FIG. 4 is a block diagram explaining, as an example, the busbar connection breaker 52BT and the conditions for selective load cutoff associated with busbar switching in the event that an accident occurs on the upstream side of the transformer 12 of the A system. It is. Moreover, FIG. 5 shows the voltage behavior over time in the case where busbar switching is actually performed in the above-mentioned block diagram.

This explains the operating characteristics of various component devices.

As shown in Figure 3, a power source 1 is received through a common bus 2, and within the station, this power source is divided into two systems, A system and B system, to constitute the power source of the liquefied gas fuel base, and to ensure stable operation of the base. A case in which a power supply failure such as a 31G (three-wire ground 18) accident occurs at the A-system transformer 12 or its upstream side will be described in detail. If a failure like 3LG occurs in transformer 12 of system A or its upstream side, the 5th
As shown in the figure, the station bus voltages 3 and 4 of the A system and B system drop to zero at the same time as the failure occurs (to), and remain until the common bus breaker 11 of the A system opens (until t□). ) is the duration of the failure, and the station bus voltage remains at zero and does not recover.

On the other hand, when the 5 common bus breaker 11 is opened and the fault is cleared, the bus voltage 4 of the B system, which is a healthy system, is
Return to the value before the failure. However, the faulty system A recovers to a certain value due to the residual voltage of the load, but
When the common bus circuit breaker 11 is opened, the power is lost, and the residual voltage of the load attenuates as the load rotation speed changes.Also, the low voltage detection relay 27A of the A system malfunctions. As shown in FIG.

The load breaker 13 of the A system, which is the own system, is selectively cut off, and the AN with the condition that the common bus breaker is opened is set.
According to condition D, power is supplied from the B system, which is the power source from the healthy side, after a certain period of time and the timer TA is activated. That is, by operating the common bus breaker 11 and the low voltage detection relay 27A, the load is selectively cut off, and the bus connection breaker 52BT is "closed" via the timer T^, so that B is in a healthy system. When the selective load cutoff is performed and the busbar communication breaker 52BT is "closed", the voltage of the busbar 3 of the A system, which is the faulty system, also returns to the value before the fault.

Although the power reception breaker 52AL of the failure system (A system) is not explained from FIGS. 4 and 5 and the explanation, in such a system, the bus common breaker 11
At the same time as "opening", this power receiving breaker 52AL is also "opening".
', so it is omitted.

However, when the fault occurs at time t6, as shown in Figure 5, the voltage of the I3 system, which is a healthy system in the current system, becomes zero until the fault is cleared (at time t), and the B Low voltage detection relay 2 connected to the grid bus
7B operates, and even the loads connected to the healthy bus 4 are immediately and selectively cut off. In the case of a liquefied gas fuel base, most of the load will be disconnected, paralyzing the base's functions, causing the base to trip, and causing vaporized gas to be removed from the base. There is a risk that even the power plants that receive the supply will trip.

As mentioned above, the failure will continue until a failure occurs in the A-system transformer 12 or its upstream side and the common bus breaker 11 is opened.However, if the common bus breaker 11 is opened. Then, the B system, which is a healthy system, returns to its original state. However, even if the common bus breaker 11 is open and the receiving circuit breaker 52AL is open, the voltage on the bus 3 remains unchanged even if the bus breaker 52BT is open. The original voltage will not be restored until the operation is completed.On the other hand, as explained in the conventional technology when switching the bus, if the full load is left connected, a large inrush current will flow through the healthy system, damaging the equipment. In addition, it is possible that the plant may trip, so it is necessary to select the load as much as possible and perform selective load shedding at the same time as the failure system is disconnected.Therefore, in the present invention, the bus It is shorter in time than it takes for the operation of the communication breaker 52BT to be completed.

Furthermore, a timer TB is added which is longer than the accident clearing time. In this case, the voltage becomes zero when the accident occurs 1a, so the low voltage detection relay 27A is activated.

Both 27B operate, but when the fault system is cleared (disconnected), the low voltage detection relay in the B series, which is a healthy system, automatically returns to its original non-operational state. Therefore, by adding the timer TB as described above, as shown in Fig. 2, the faulty system will complete selective load shedding by t2, when the busbar connection breaker is completed, but the healthy system B will There is no need to perform selective load shedding. Therefore, although it is a single branch, the operation of the base can be continued.

In the explanation of the prior art and the embodiment of the invention, a failure on the A system side has been described, but the same applies to a transformer failure in another duplexed system (B system).

In addition, a timer TA is inserted as a condition for turning on the busbar connection breaker, but this is to confirm that the voltage does not return again, and as shown in Figure 6, the TA is inserted after the low voltage detection relay. Even in a circuit that issues a power-on command to a busbar communication breaker via a timer with a standby time, as in the present invention,
It goes without saying that the same effect can be expected by adding a timer with a standby time of T8 to the operation of the low voltage detection relay.

〔Effect of the invention〕

As explained above, according to the present invention, even if a serious accident such as a 3LG (3-wire ground fault) occurs in one line of a duplicated AC power supply, it will not affect the healthy system power supply as much as possible. This makes it possible to automatically and quickly switch from a faulty system to a healthy system power supply without any problems, and it is possible to provide an in-station power supply switching device that prevents serious accidents such as plant trips at liquefied gas fuel bases.

[Brief explanation of drawings]

1 and 2 are configuration diagrams and time charts for explaining one embodiment of the present invention, FIG. 3 is a diagram showing the internal power supply configuration of a liquefied gas fuel base, and FIGS. 4 and 5 are conventional FIG. 6 is a block diagram and a time chart for explaining the low voltage bus switching method according to the method, and FIG. 6 is a block diagram for explaining the conventional method. 1...Power supply 2...Common busbar 3.4.
...A, B system transformer 11.21...A, B system common bus breaker 12, 2
2...A, B system transformers 52AL, 52BL...Power receiving circuit breaker 52BT...
Busbar connection breaker i: +, z3...Load breaker 14.24...Load 27A, 27B...A, B system low voltage detection relay TA, TB...Timer agent Nori Chika, patent attorney Yudo Hirofumi Mitsumata Figure 1 Figure 4 Figure 6

Claims (1)

[Claims] Power is received through a common bus, and this power supply is divided into two systems within the plant. When one system's power supply fails, the faulty load is selectively cut off, and the power is disconnected from the healthy bus via a busbar connection breaker. An in-station power supply switching device configured to receive power supply, characterized in that a timer is added for selective load cutoff, and the busbar is automatically and quickly switched to a healthy power source.