JPH0530134B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a circuit breaker that detects both ground fault current and overcurrent in a main circuit.

[Technical background of the invention and its problems]

Conventionally, circuit breakers that detect both ground fault current and overcurrent in the main circuit are shown in Figures 3 and 4.
Something like the one shown in the figure is being considered.

In Fig. 3, 1 is a three-phase main circuit for supplying three-phase AC power from a three-phase AC power source to a load;
Reference numerals 2, 3, and 4 are breaker contacts interposed in each phase of the main circuit 1; 5, 6, and 7 are current transformers arranged in each phase of the main circuit 1 for detecting overcurrent; 8 is an auxiliary current transformer that detects the three-phase total vector current of current transformers 5, 6, and 7, 9, 10, 11, and 12 are full-wave rectifier circuits, 13 and 14 are detection resistors, and 15 is a ground fault current detection 16 is an overcurrent detection circuit; 17 is a tripping signal circuit to which a grounding current tripping signal and an overcurrent tripping signal from the grounding current detection circuit 15 are given; When a current tripping signal and an overcurrent tripping signal are applied, the tripping coils 18 are energized to open the shield breaker contacts 2, 3, and 4, respectively.

Further, in FIG. 4, 19, 20 and 21 are current transformers arranged in each phase of the main circuit 1 to detect overcurrent, and 22, 23 and 24 are current transformers 19, 2.
Auxiliary transformer connected to secondary side of 0 and 21, 2
Reference numeral 5 denotes an auxiliary transformer connected to the secondary sides of current transformers 19, 20 and 21 via the primary sides of auxiliary current transformers 22, 23 and 24, and for detecting ground fault current based on its neutral line current. , 26, 27, 28, and 29 are full-wave rectifier circuits, 30 and 31 are detection resistors, and 32 is a static type tripping circuit that detects ground fault current and overcurrent and energizes the tripping coil 18.

In the conventional circuit breakers shown in Figures 3 and 4, the ground fault current setting value that causes the ground fault current to open (trip) the break contact is the maximum value of the circuit breakers. Generally, it is selected between 0.2 and 1.0 times the rated current, and the operating time at ground fault current is selected between 0.1 and 0.5 seconds. On the other hand, in the overcurrent region, approximately 10% of the maximum rated current of the circuit disconnector
Up to 15 times the maximum rated current, with anti-time characteristic
At 20x, it is common to trip instantly. Therefore, in order to satisfy the operating characteristics of ground fault current and overcurrent, it is necessary to establish a DC power source as a current transformer to operate the tripping coil at 0.2 times the maximum rated current. The secondary output must be linearly proportional to the primary main circuit current up to at least 10 times the maximum rated current. However, in order to satisfy such characteristics, it is necessary to reduce the secondary side load of the current transformer, and for this purpose, in the circuit and disconnector shown in Fig. 3, the current transformer 5, The core capacity of current transformers 5, 6, and 7 must be increased, and the external dimensions of current transformers 5, 6, and 7 become large.
In the circuit breaker shown in the figure, the auxiliary transformer 22,
23 and 24 had to be provided, and in any case, there was a problem that the overall size was increased and the installation space became large.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a circuit that can be made smaller and requires less installation space while satisfying the operating characteristics of the main circuit's ground fault current and overcurrent. and provide disconnectors.

[Summary of the invention]

The present invention provides a DC power supply circuit in which a current transformer for detecting load current is disposed in each phase of a main circuit, and a DC power supply circuit is provided to obtain a DC power supply by rectifying the secondary output of these current transformers. A zero-phase current transformer for detecting ground fault current is disposed in the neutral wire on the secondary side of the When the ground fault current detected by the phase current transformer and the overcurrent detected by the detection means exceed their respective set values and exceed their respective set times, the tripping coil is driven to intervene in each phase of the main circuit. It is characterized by a configuration with a static trip circuit that opens the breaker contact.
The DC power supply from the DC power supply circuit is intended to be supplied to the tripping coil and the static type tripping circuit.

[Embodiments of the invention]

A first embodiment of the present invention will be described below with reference to FIG.

33 is a main circuit that supplies three-phase AC power from a three-phase AC power supply to a load such as a three-phase AC motor, and its R, S and T phase conductors 33R, 33S and 33
T is provided with breaker contacts 34, 35 and 36. And each R, S and T phase conductor 33
AC generators 37, 38, and 39 for detecting load current are provided at R, 33S, and 33T. 40 is a full-wave rectifier circuit formed by bridge-connecting eight diodes 40 ₁ to 40 ₈ , and a common connection point of diodes 40 ₁ and 40 ₅ and a common connection point of diodes 40 ₂ and 40 _{6 are} AC input terminals. One end of each of the secondary coils of the alternating current generators 37, 38 and 39 is connected to the common connection point of the diodes 40 ₃ and 40 ₇ , and the other ends of the secondary coils are connected in common. A neutral line 41 serving as a common connection line is connected to a common connection point of diodes 40 ₄ and 40 ₈ . 42 is a stabilized power supply circuit connected to the DC output terminal of the full-wave rectifier circuit 40, which together with the full-wave rectifier circuit 40 constitutes a DC power supply circuit 43. 44 is the current transformer 3
7, 38, and 39, and both ends of the secondary coils thereof are connected to input terminals of a ground fault current detection circuit 45. This ground fault current detection circuit 45 is supplied with a stabilized DC power from the stabilized power supply circuit 42, and this ground fault current detection circuit 45 receives the detected current of the zero-phase converter 44. (ground fault current)
When the current exceeds a predetermined ground fault current setting value and exceeds the set time, a ground fault current tripping signal _S45 is output.
46, 47 and 48 are each R and S of the main circuit 33.
and a current transformer serving as a detection means for detecting overcurrent arranged on the T-phase conductors 33R, 33S, and 33T; 49 is a full-wave rectifier circuit formed by bridge-connecting eight diodes 49 ₁ to 49 ₈ ; One end of each secondary coil of the current transformers 46, 47 and 48 is an AC input terminal, which is a common connection point of diodes 49 ₁ and 49 ₅ , a common connection point of diodes 49 ₂ and 49 ₆ , and a common connection point of diodes 49 ₃ and 49. _The other ends of the secondary coils are connected in common, and the common connection point is connected to the common connection point of diodes 49 ₄ and 49 ₈ . 50 is an overcurrent detection circuit whose input terminal is connected to the DC output terminal of the full-wave rectifier circuit 49; When the current (current) exceeds a predetermined overcurrent setting value and exceeds a set time, an overcurrent trip signal _S50 is output. Incidentally, the overcurrent detection circuit 50 is also supplied with stabilized DC power from the stabilized power supply circuit 42. Reference numeral 51 denotes a tripping signal circuit to which stabilized DC power is supplied from the stabilized power supply circuit 42, and this has an input terminal supplied with an earth fault current tripping signal S ₄₅ and an overcurrent tripping signal S ₅₀ . Then, the tripping coil 52 is energized and driven by the stabilized DC power supply from the stabilized power supply circuit 42, thereby opening (tripping) the shield breaker connection points 34, 35, and 36. The above ground fault current detection circuit 45, overcurrent detection circuit 50, and tripping signal circuit 51 are combined into a static type tripping circuit 53.
It consists of

Therefore, with the above configuration, current transformers 37 and 38
and 39 is 90% of the minimum setting value of earth fault current.
The stabilized power supply circuit 42 may be established at a certain point to drive the tripping coil 52;
Since a proportional characteristic of the secondary output with respect to the overcurrent of the main circuit 33 is not required, a small one is sufficient.
Furthermore, the current transformers 46, 47, and 48 output a secondary output linearly proportional to the overcurrent flowing in the main circuit 33 up to at least 10 times the maximum rated current of the circuit breaker. However, since very high output is not required, the core area can be small, and if necessary, saturation can be prevented in areas with large overcurrent by using a gapped core. , Therefore, a small one is sufficient. The zero-phase current transformer 44 includes current transformers 37 and 38.
Since the arrangement is such that the ground fault current is detected from the neutral wire 41 on the secondary side of 39, only a maximum of several amperes flows through the neutral wire 41 even momentarily, so a small one is sufficient.

In this way, according to this embodiment, the tripping coil 5
Current transformers 37, 38 and 39 for supplying DC power to 2 and static trip circuit 53, current transformers 46, 47 and 48 for overcurrent detection of main circuit 33, and current transformers 37, 38 and a zero-phase current transformer 44 for ground fault current detection arranged in the secondary side neutral wire 41 of 39, so the overall size can be reduced and the installation space can be reduced. Therefore, it has the advantage of increasing the degree of freedom in design.

FIG. 2 shows a second embodiment of the present invention, and the same parts as in FIG. 1 are denoted by the same reference numerals, and only the different parts will be explained below.

That is, 54, 55 and 56 are current transformers for control current arranged in each R, S and T phase conductor 33R, 33S and 33T of the main circuit 33, and these are current transformers 37, 38 and 39. It has the same rating. 57 is a full-wave rectifier circuit formed by bridge-connecting eight diodes 57 ₁ to 57 ₈ , and the common connection point of diodes 57 ₁ and 57 ₅ and the common connection point of diodes 57 ₂ and 57 _{6 are} AC input terminals. One end of each of the secondary coils of the current transformers 54, 55 and 56 is connected to the common connection point of the diodes 57 ₃ and 57 ₇ , and the other ends of each of the secondary coils are connected in common. The common connection point is the diode 57 ₄ ,
57 Connected to ₈ common connection points. 58 is a control current circuit whose input terminal is connected to the DC output terminal of the full-wave rectifier circuit 57. 5
Reference numerals 9, 60 and 61 are Hall elements serving as detection means disposed on the R, S and T phase conductors 33R, 33S and 33T of the main circuit 33, and these current terminals are connected in series and Current circuit 58
, and each output terminal is connected to an input terminal of an overcurrent detection circuit 62 to which stabilized DC power is supplied from the stabilized power supply circuit 42 . This overcurrent detection circuit 62 constitutes a static type tripping circuit 63 together with the ground fault current detection circuit 45 and the tripping signal circuit 51.

Therefore, the Hall elements 59, 60 and 61 are R,
By detecting the flux generated by the current flowing through the S and T phase conductors 33R, 33S, and 33T, a detection voltage corresponding to the current is generated, and the overcurrent detection circuit 62 detects the detection voltage according to the predetermined overcurrent setting. When the value exceeds the set time, the overcurrent trip signal S ₆₂ is output and the trip signal circuit 5
1 input terminal.

Therefore, even in this second embodiment, the first
The same effects as in the embodiment can be obtained.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but can of course be implemented with appropriate modifications within the scope of the gist.

〔Effect of the invention〕

As explained above, the present invention includes a current transformer for detecting the load current of the main circuit to obtain DC power, and a zero-phase current transformer for detecting the ground fault current from the secondary side neutral wire of the current transformer. Since a current transformer is provided and a detection means for detecting overcurrent in the main circuit is provided, the device can be made smaller as a whole and has the excellent effect of reducing the installation space. .

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 show the first and second embodiments of the present invention, respectively.
FIG. 3 is an electric circuit diagram showing an embodiment of the present invention, and FIGS. 3 and 4 are electric circuit diagrams showing conventional examples. In the drawing, 33 is the main circuit, 37 to 39 are current transformers,
41 is a neutral wire, 43 is a DC power supply circuit, 44 is a zero-phase current transformer, 45 is a ground fault current detection circuit, 46 to 49 are current transformers (detection means), 50 is an overcurrent detection circuit, 5
1 is a trip signal circuit, 52 is a trip coil, 53
59-61 are Hall elements (detection means), 62 is an overcurrent detection circuit, and 63 is a static type tripping circuit.

Claims (1)

[Claims] 1. A loop breaker contact interposed in each phase of the main circuit and a tripping coil for opening the loop breaker contact;
a current transformer arranged in each phase of the main circuit to detect the load current; a DC power supply circuit that rectifies the secondary outputs of these current transformers to obtain a DC power source; and a secondary side of the current transformer. a zero-phase current transformer disposed in the neutral line to detect ground fault current; a detection means disposed in each phase of the main circuit for detecting overcurrent; and the zero-phase current transformer A circuit comprising a static tripping circuit that drives the tripping coil when the ground fault current detected by the detection means and the overcurrent detected by the detection means exceed the respective set values and exceed the respective set times. Shiya disconnector.