JPH0393422A - Multi-output earth leakage relay - Google Patents

Abstract

PURPOSE:To enable system protection, including preventive protection, over a wide range by setting a plurality of earth leakage thresholds for the secondary output of a single zero-phase current transformer independently or in specific relation thereby reducing the relative error between respective outputs. CONSTITUTION:When the leak current is above an operation curve B and below an operation curve A, differential amplifier 31a of earth leakage detecting IC 31 picks up an input signal and triggers a thyristor 34 thus closing the contacts 4B, 41. A threshold setting circuit 2 is set at the operation curve A through the contact 41 and the output remains at 4B. If the leak current is above the operation curve A, a switching circuit 33 is interlocked with the contacts 4B, 41 and switched as shown on the drawing. The differential amplifier 31a. picks up the level A threshold. The output closes the contact 4A through a time delay circuit 32. By such arrangement, preventive protection can be carried out and accidents can be surely prevented.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an earth leakage relay, and more particularly to an earth leakage relay with a predictive function suitable for error countermeasures for general-purpose components that have output means for multiple set values for overload and earth leakage. [Prior Art J] Regarding earth leakage protection, in addition to the viewpoint of preventive maintenance of equipment, the need for more precise protection is increasing. This is also due to the fact that the current JIS standards for earth leakage circuit breakers and earth leakage relays allow a wide error range for the operating sensitivity current setting value. The prior invention disclosed in Japanese Patent Application No. Sho 63-16523 has a plurality of detection units that perform leakage detection based on signals from zero-phase current transformers corresponding to each circuit in order to protect a plurality of electric circuits from leakage. It is configured so that protective devices or alarm devices can be selectively activated by installing them together. [Problem to be solved by the invention] The above prior invention is based on the same circuit (main circuit or branch circuit).
No consideration has been given to setting thresholds for detecting earth leakage at multiple locations in the circuit and emitting multiple outputs according to each set value, and setting, detection, and output of different earth leakage current thresholds in the same circuit is not considered. Since this is not possible, there is a problem in that the selection of output must be limited to, for example, either shutdown or alarm. Also, in order to obtain both cutoff and alarm outputs, for example, even if two zero-phase current transformers are installed and a ground leakage relay is connected to each, the permissible values of sensitivity current and operating time of, for example, JIS C8374 r ground leakage relay. As shown in the shaded area in Figure 4, the relative errors between the two zero-phase current transformers and the earth leakage relay are large, and it is complicated to measure the individual characteristics in advance and correct the relative values. There were also problems such as increased costs due to an increase in the number of installations. An object of the present invention is to provide a multi-output earth leakage relay that enables a wide range of system protection including preventive maintenance by obtaining different independent output values for arbitrary different earth leakage current settings.

[Means to solve the problem]

Structures for achieving the above object are described in the claims. In other words, the first claim provides means for setting a plurality of threshold values for the secondary output of the same zero-phase current transformer, and an output means that operates in accordance with each of the plurality of set values. It is connected to various alarm devices such as electric circuit interrupters, lamps, and buzzers. Further, as described in the second and third sections, the maximum threshold value is determined and the other threshold values are changed at a predetermined ratio with respect to the maximum value,
There is a mode in which the maximum threshold delay time is set, and the operation times corresponding to the other thresholds are set at a predetermined ratio to the delay time. As described in Section 4, the setting operation time for the maximum threshold value among the plurality of threshold values may be set to a longer time, and the others may be set to shorter times. [Function] In the earth leakage relay, multiple earth leakage thresholds for the secondary output of the same zero-phase current transformer are set independently or with a predetermined relative relationship, thereby reducing the relative error of each output. This allows for accurate movement coordination. [Embodiment J] An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 3 is a characteristic diagram showing an example of the operating characteristics of the earth leakage relay to be realized by the present invention. Operating characteristics A to D
The leakage current value showing the sensitivity is gradually decreasing, and the operating characteristics A is of the time-delay type, and the operating characteristics C to D are of the high-speed type. Next, Fig. 2 shows a circuit block diagram, and its configuration consists of the secondary output of the zero-phase current transformer l, the threshold setting circuit 2, the leakage detection section/time delay section 3, the output section 4, and the threshold setting circuit 2. It consists of contacts 4A to 4D corresponding to 2A to 2D of the value setting circuit 2, respectively. The operation shown in this diagram is such that multiple secondary outputs of the zero-phase current transformer 1 are input to each threshold setting circuit 2, and in the earth leakage detection section 3, if the voltage is larger than the set threshold, the output is output after a predetermined time delay. It outputs a signal to the output section 4. At this time, the output contact corresponding to the threshold setting circuit 2: for example, 4A responds to 2A. Next, details of the configuration of this embodiment will be explained with reference to the circuit diagram of FIG. However, the same parts as in FIG. 2 are indicated by the same reference numerals and the explanation will be omitted. A is a switch that can be manually operated from the outside, such as a rotary switch, and the switching contact is a resistor 2 connected in series.
It is connected to each connection point of D to 2A. Further, one end of the series-connected resistors 2D to 2A is connected to the other end of the ZCT via a switch b that can be manually operated from the outside.
Terminal b is used for selection A of a plurality of threshold setting means (not shown). Next, the earth leakage detection part/Tokinobu 3 is a general-purpose! iI electric relay, IC for circuit breaker (example: [stand made 1 {A
I6636, etc.), and its detection output is connected to a subsequent high-speed operation thyristor 34 or a time delay circuit 32 via a high-speed temporary delay switching circuit 33 that is structured around switching elements. On the other hand, the contact 41 interlocking with the output contact 4B is connected to the contact 2
It is connected to the connection point of A and 2B and the non-inverting input screw of IC31. In FIG. 1, only output contacts 4A and 4B are shown for simplicity of explanation. Next, its operation will be explained. Note that each switch a, b
It is assumed that the switch in the switching circuit is set to the position shown in the figure. Now, if the leakage current is above the operating curve B in Figure 3, and the operating curve A is
If it is below, the differential amplifier 31a of the earth leakage detection IC 31 will surprise the input signal, trigger the thyristor 34 within the operating time of the IC 31 (about a few cusp seconds), and the contacts 4B and 41 will close. . At this time, the threshold setting circuit 2 has been changed to the operating curve A level by the contact 4l, and the leakage current is below the surprise value, so the output remains only 4B. Next, we will explain the operation when the leakage current exceeds the operating curve A in Figure 3. The operation up to the closing of the contacts 4B and 4l is as described above, so a description thereof will be omitted. Switching circuit 33 is contact 4B
, 41 to switch to the other shown in the figure. By closing the contact 4l, the threshold setting is changed to the A level of the operating curve in FIG. 3, so the differential amplifier 31a jumps up as the threshold A level. The output then passes through the delay circuit 32 to close the contact 4A. If the current leakage falls below the threshold before this time period, the 4A circuit will not be closed. By the way, general-purpose earth leakage relays and circuit breaker ICs are sold by nearly 10 semiconductor manufacturers, but the big-up values (operating values) all contain an error of 30 to 40%, and earth leakage detection is based on the absolute current. For example, 5mA, 30mA
Therefore, detection of this requires the use of a zero-phase current transformer using a core made of permalloy or the like. In this case, in order to improve the linearity of the secondary output, it is necessary to reduce VA, and the offset voltage of several mV, which is allowable with a general differential amplifier, cannot be ignored. The pick-up voltage of the above-mentioned general-purpose IC is generally 10-odd mV. According to this embodiment, the relative error of each set threshold value is limited to the error of the resistors 2A to 2D shown in FIG. is not included as an operating value error factor, so the operating characteristics shown in FIG. 3 with high accuracy can be achieved, and it is not necessary to use a plurality of expensive ICs 31, so costs can be reduced. Next, another embodiment will be described with reference to FIGS. 5 and 6. FIG. 5 is a circuit block diagram, in which the threshold setting circuit 2
Leakage detection/time delay circuits 3A and 3B are connected to the rear stages of A and 2B, respectively. Next, the details of the circuit will be explained with reference to FIG. However, parts that overlap with those in FIG. 5 are omitted. IC31B and 3! The condition is that both A and B are selected so that the big-up value is within a predetermined relative error range, and the circuit 3B that is constructed around 31B and the circuit 3A that is constructed around 31A are as shown in the figure. It is connected to a threshold setting circuit 2 which is set to the surprise value of the operating characteristics B and A in FIG. Now, if there is a current leakage greater than or equal to B and less than A in the operating curve of FIG. 3, only IC 31B operates and only contact 4B closes. In addition, in case of a leakage exceeding the operating curve A, 4B is closed and IC31A. The time delay circuit 32 operates and the contact 4A
is also closed. According to this embodiment, the operating characteristics shown in FIG. 3 can be reliably realized within the error range allowed for the threshold setting circuit. Another example is the 71st! I will explain. This embodiment shows a threshold setting circuit, in which the third threshold value is set by switch b.
It is possible to set the absolute value of each of the graph movement curves A-D while preserving the relative ratio thereof. Further, the relative ratio between A and B in FIG. 3 can be changed by switch a. FIG. 8 is a schematic diagram of an embodiment of the present invention, in which the maximum threshold setting output is connected to the tripping coil of the molded circuit breaker to interrupt the electric circuit, and the other threshold setting output is connected to the trip coil of the molded circuit breaker. is connected to a load such as a lamp or buzzer for alarm purposes. According to this embodiment, there is an effect that a plurality of absolute setting values and relative setting values can be set independently. [Effects of the Invention] By implementing the present invention, it is possible to set threshold values having arbitrary absolute values and relative values by inputting the secondary output signal of the same zero-phase current transformer, and it is possible to set threshold values with arbitrary absolute values and relative values. Since multiple outputs are possible, preventive maintenance can be carried out and accidents can be prevented reliably and at low cost.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 is a block diagram of Fig. 1, Fig. 3 is an operating characteristic curve to be realized in Figs. 1 and 2, and Fig. 4 is a JIS The operating range regulated by C8374, FIG. 5 is a circuit block diagram of another embodiment of the present invention, FIG. 6 is a circuit diagram of FIG. 5, and FIG. 7 is a threshold setting circuit of another embodiment. FIG. 8 is a schematic diagram of an embodiment of the present invention. l...Zero-phase current transformer 2...Threshold setting circuit 3...Earth leakage detection section/time delay section 4...Output section 3l...Earth leakage relay/IC for circuit breaker

Claims (1)

[Claims] 1. An earth leakage relay that receives a secondary output signal of a zero-sequence current transformer that detects a main circuit zero-sequence current and generates an output when the signal exceeds a predetermined threshold; 1. An earth leakage relay comprising means for setting a threshold value, and output means corresponding to the threshold value. 2. The plurality of threshold setting means are characterized in that the maximum threshold value is independently variable, and the other threshold values are set while changing at a predetermined ratio with respect to the maximum threshold value. An earth leakage relay according to claim 1. 3. In the plurality of threshold setting means, the setting of the maximum threshold delay time is independently variable, and the operation times corresponding to the other thresholds are set at a predetermined ratio to the delay time. The earth leakage relay according to claim 1, characterized in that: 4. In the plurality of threshold setting means, the setting of the delay time of the maximum threshold value is independently variable, and the operation time corresponding to the other threshold values is the operation time corresponding to the maximum threshold value. The earth leakage relay according to claim 1, characterized in that it operates in a shorter time. 5. The earth leakage relay according to claim 1, wherein the output corresponding to the maximum threshold among the plurality of thresholds is connected to a tripping coil of a circuit breaker.