JPS63316646A - Two-circuit supply uninterruptible transfer protector - Google Patents

Abstract

PURPOSE:To ensure a switching operation by preventing unwanted tripping due to a loop current generated at the time of twocircuit supply uninterruptible transfer. CONSTITUTION:When an uninterruptible line transfer from a normal circuit 1 to an auxiliary circuit is conducted, the circuit breaker 4 of said auxiliary circuit 2 is closed at first and the circuit breaker 3 of said normal circuit 1 is tripped thereafter. In this case, a loop current 9 flows temporarily. At the same time, always opened contacts 3A and 4A are respectively closed in the secondary circuit of a current transformer 5 so that an electric current flowing on the secondary side of said current transformer 5 flows through bypassing a time limit element coil 51 and a coil of a ground overcurrent relay 7 by the loop current 9 to lock actions of an overcurrent relay 6 time limit element and said ground overcurrent relay. Therefore, it is possible to prevent a trip due to a loop current. A momentary element coil 50 is irrelevant to said operation, because it is not so sensitive as said loop current 9.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an uninterruptible switching protection device for two-line power reception.

[Conventional technology]

Generally, during uninterruptible switching of two lines of power reception, a loop current flows between the two lines due to the difference in impedance, etc. of the customer power reception line, and if the value exceeds the setting value of the protective relay installed on each line, that protective relay will operate and trip the power receiving circuit breaker. Therefore, conventional methods have been used to prevent unnecessary tripping of the power receiving circuit breaker due to such loop current.

As shown in FIG. 3, a manual interlock changeover switch is inserted into the trip circuit of the power receiving breaker to prevent the trip circuit from operating when the line is switched (Japanese Utility Model Publication No. 53-68036). Note that Figure 3 only shows the trip circuit corresponding to one power receiving breaker.
The trip coil 11 of the power reception breaker is configured to be tripped by the manual breaker switch 12, the instantaneous element contact 50A and the time-limiting element contact 51A of the overcurrent relay 6, and the ground fault overcurrent relay contact 7A. In order to prevent tripping due to loop current when switching lines, a changeover switch 13 is inserted into a trip circuit formed by the time-limiting element contact 51A of the overcurrent relay 6 and the contact 7A of the ground fault overcurrent relay to form an interlock circuit. When switching lines, the changeover switch 13 is manually turned off (opened).

[Problem that the invention seeks to solve]

However, according to the above-mentioned conventional technology, since the operator manually operates the changeover switch 13 to perform the interlock, if the operator forgets to turn off the changeover switch 13 when switching one line, the power receiving breaker will be tripped. There is a problem.

Furthermore, if one forgets to close the changeover switch 13 after the uninterruptible switching is completed, there is a problem that the trip circuit of the power reception breaker remains locked and the power receiving circuit breaker enters operation without protection.

An object of the present invention is to provide an uninterruptible switching protection device for two-line power receiving, which can automatically prevent operation of a protective relay due to loop current during uninterruptible switching for two-line power receiving, and eliminate erroneous interlock operation by an operator. It's about doing.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a protective relay that trips the power reception breaker of the corresponding line based on the current flowing in each line of two-line power reception. In an uninterruptible switching protection device for two-line power receiving, which has a time period in which power is applied to the two power receiving circuit breakers at the same time when switching lines, the logic of the closed state signals of the two power receiving circuit breakers is The present invention is characterized in that an interlock means is provided for preventing a trip operation by a predetermined protective relay.

[Effect]

With this configuration, during the time period when two power receiving circuit breakers are turned on at the same time, the logical product of their closed state signals becomes 1, which automatically prevents the operation of a specified protective relay. Ru. As a result, even if a loop current flows between the two lines when the two power receiving circuit breakers are turned on at the same time, it is possible to prevent the power receiving circuit breaker from tripping.

In addition, when uninterruptible switching is completed and one of the circuit breakers is cut off, the above logical product becomes O, which releases the blocking of the protective relay and automatically restores the protection of the power receiving line. become.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 shows a configuration diagram of an embodiment of the present invention, and FIG. 2 shows a trip circuit diagram of the power reception breaker of the embodiment in FIG. As shown in Fig. 1, the regular line 1 and the protection line 2 are provided with power receiving circuit breakers 3 and 4, respectively, and the secondary sides of these power receiving circuit breakers 3 and 4 are commonly connected to provide power to the load. It is designed to supply Each line is provided with a current transformer 5 for current detection, and the instantaneous element coil 50 and time-limiting element coil 51 of the overcurrent relay 6 and the coil of the earth fault overcurrent relay 7 are connected in series to the current transformer 5. It is connected to the.

Series contact circuits of normally open contacts 3A and 4A are connected in parallel to the time-limiting element coil 51 of the overcurrent relay 6 and the coil of the ground fault overcurrent relay 7, respectively. There is. Note that the configuration of the protective relay circuit connected to the protection line 2 is the same as that of the regular line 1, so illustration thereof is omitted.

On the other hand, as shown in FIG. 2, the trip circuit of the power reception breaker 3 or 4 is the same as that of the conventional example shown in FIG. 3, with the changeover switch 13 removed.

In the two-line power receiving system configured as described above, in normal times, the power receiving circuit breaker 3 of the regular line 1 is turned on, and the power receiving circuit breaker 4 of the protection line 2 is turned off.

As a result, the load current 8 is supplied to the load via the regular line 1. The current flowing into the secondary circuit of the current transformer 5 due to this load current 8 is cut off by the power receiving breaker 4, so
Since the normally open contact 4A indicating the closed state is open, the current flows to the time-limiting element coil 51 of the overcurrent relay 6, the instantaneous element coil 50, and the coil of the ground fault overcurrent relay 7.

These protective relays thereby protect against recovery through normal operation.

Next, a case will be described in which line switching is performed from the regular line 1 to the protection line 2 without interruption in response to a command from an electric power company or the like. First, after the power reception breaker 4 of the protection line 2 is turned on, the power reception breaker 3 of the regular line 1 is tripped. At this time,
Since both power reception circuit breakers 3 and 4 are temporarily turned on at the same time, a loop current shown by arrow 9 flows between both lines. At the same time, the normally open contacts 3A and 4A of the secondary circuit of the current transformer 5 are closed, so that the current flowing through the secondary circuit of the current transformer 5 due to the loop current 9 is transferred between the time-limiting element coil 51 and the ground. The overcurrent will flow bypassing the coil of the relay 7. In other words, while the power receiving circuit breakers 3 and 4 are turned on at the same time, the operation of the time-limiting element of the overcurrent relay 6 and the ground fault overcurrent relay is locked, and the value of the loop current 9 becomes the setting value of those relays. It will not work even if the value is exceeded.

It is important to prevent the instantaneous element of the overcurrent relay 6 from locking so that it can be effectively protected even if a short circuit occurs on the load side during line switching. Here, since the current value of the loop current 9 is usually much smaller than the short circuit current, the instantaneous element of the overcurrent relay 4 will not operate due to the loop current 9 flowing at the time of switching.

As described above, according to this embodiment, by simply turning on the power reception breaker 4 of the backup line 2 by the switching operation during uninterruptible switching of the two-line power reception, the predetermined protective relays 6 and 7 are automatically switched on. Since the operation is locked, there is no need for the operator to manually perform an interlock operation, which eliminates trips due to operator error, and automatically prevents unnecessary trips due to loop current during switching. The effect is that it can be done.

In the embodiment shown in FIG. 1, the current flowing through the actuating coil of a predetermined protective relay is bypassed by the AND of the closed state signals of two power receiving circuit breakers. For example, in the interlock circuit shown in FIG. 2, the same result can be achieved by inserting parallel circuits of the normally closed contacts of the power receiving circuit breakers 3 and 4 into the circuits of the time-limiting element contact 51A and the ground fault relay contact 7A, respectively. It is possible to achieve the following effects.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to automatically perform an unnecessary trip operation due to the kudzu loop current without occurring during uninterrupted switching of two-line power reception, and thus it is possible to eliminate interlock errors by the operator. , it is possible to reliably perform the switching operation of two-line power reception, and the operation is simple and extremely practical.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a trip circuit diagram of the embodiment shown in FIG. 1, and FIG. 3 is a trip circuit diagram of a conventional example. 3.4...Power receiving breaker, 5...Current transformer, 6...
Overcurrent relay, 7... Earth fault overcurrent relay, 9... Loop current, 50... Instantaneous element coil, 51... Time-limited element coil, 3A, 4A... Normally open contact of power receiving breaker.

Claims (1)

[Claims] It is constructed with a protective relay that trips the power receiving circuit or disconnection switch of the corresponding line based on the current flowing in each line of the 1st and 2nd power receiving circuits, and when switching the line, the two power receiving circuits or disconnection circuits are turned on at the same time. In an uninterruptible switching protection device for two-line power reception that is switched by uninterrupted power during a time period during which the power is received, the trip operation by a predetermined protective relay is prevented by the logical product of the closed state signals of the two power receiving and disconnecting circuits. A two-line power receiving uninterruptible switching protection device characterized by being provided with an interlock means.