JPS61155870A - Grounding detecting device - Google Patents

Abstract

PURPOSE:To detect the grounding of a system in a hot-line state with small- sized, simple constitution by providing a master cubicle and a slave cubicle and sending the output of a DC power source provided in the master cubicle to the slave cubicle. CONSTITUTION:The master cubicle 10, slave cubicles 11 and 12, clip type measuring instruments M1 and M2, etc., are provided. Current transformers T1 and T2, of the measuring instruments M1 and M2 hold power lines L1 and L2 clipped for respective cubicles 11 and 12. The electric power from a power source ES is supplied to the cubicles 11 and 12 through the line L1 and L2. In this case, the oscillation output of an oscillator OSC is applied to the power source ES as a fine signal. Detection signals of the current transformers T1 and T2, on the other hand, are rectified synchronously by the output Vi of the oscillator OSC. Consequently, the measuring instruments M1 and M2 detects only effective components of the output Vi, which are indicated or displayed and also outputted to the outside as a buzzer signal. Thus, the occurrence of grounding is detected as to the cubicles 11 and 12 individually.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a ground fault detection device suitable for use in detecting ground faults in a live system.

(Conventional technology) The technology for detecting ground faults in live power transmission lines is well established, partly because the transmission lines are simple, but in the case of system systems, the wiring paths are like a network. The reality is that the technology has not yet been established because it involves difficult problems such as the complexity of the signal current and the need to reduce the influence on the signal current because it is small.

(Problems to be Solved by the Invention) The present invention was made to solve these problems, and its purpose is to detect ground faults in live system systems that involve complex problems. This is an extremely small and simple device that can do this.

Means for Solving the Problem c] In order to achieve the above object, the present invention provides an oscillator, a resistor R1, and a capacitor [tCl] connected between a power source arranged in the main cubicle and the ground. a series circuit, a capacitor C2 connected between each slave cubicle and the ground, and a synchronous rectifier circuit that rectifies the output of a transformer that clips the power line for each slave cubicle with the output of the oscillator. and is configured to obtain the output of the synchronous rectifier circuit as a ground fault detection signal. below,
A case will be described in which the present invention is applied to a power monitoring system.

〔Example〕

FIG. 1 is a circuit diagram of an embodiment of the device according to the present invention.
In the figure, 10 is a main cubicle with a built-in power control circuit, etc., 11.12. . . . are slave cubicles in which a control board and the like, which are controlled by the control circuit within the main cubicle 10, are built-in. These cubicles constitute a power monitoring system. Es is a DC power source arranged in the main cubicle 10, and Ll and L2 are power lines that lead the power source E3 to each slave cubicle 11, 12, . . . . In addition, in the figure, two power supply lines L1.
Although L2 is shown, the power supply Hs is actually supplied to each slave cubicle 11, 12, . . . by a plurality of lines.

0'EC is an extremely small value (60
R1 is a resistor 7, C1 is a capacitor, and these are arranged in the main cubicle 10. One end of the oscillator O5C is connected to the negative electrode side of the power source Es, and the other end is grounded via a series circuit of a resistor R1 and a capacitor C1. C2 and C3 indicate capacitors (or noise prevention capacitors) connected between each slave cubicle 11, 12, . . . and the ground.

Ml, M2... are clip-type metamorphic IT1.
T2..., each transformer T1. T2...
. is a power line L1. for each slave cubicle 11, 12... L2 is always clipped. Transformer T1. T2
The output of... is the measuring device M1. The output Vi of the oscillator O5C is used as a synchronous signal to be rectified in the synchronous rectifier circuit provided in the measuring instruments M1. M2
Analog instructions or digital display are given at the , and a buzzer (not shown) is output as output signals 91, S2, etc.
will be sent to.

The operation of the detection device according to the present invention having such a configuration will be explained as follows. In addition, the current measuring device M1 and two current transformers T1. T2... is the secondary cubicle 11, 12...
Power line L1. L2... is held in a clipped state. The power supply voltage E3 is connected to the power supply lines Ll, L2.
.
．． Each control circuit in 12... is in an operating state.

In this case, the oscillation output of the oscillation W O20 is added to the electric W voltage E3 as a minute signal. The equivalent circuit of the ground fault detection part in each slave cubicle 11, 12, etc. in such a power monitoring system is shown in FIG.
Figure (9) shows an equivalent circuit when no ground fault occurs, and Figure 2 shows an equivalent circuit when a ground fault occurs. In addition,
In FIG. 2, the same elements as in FIG. 1 are given the same reference numerals as in FIG. 1. Transformer T1. T2... is the power line L1
．． L2 is clipped.

Transformer T1. The detection signals of T2, . As a result, the measurement WM1,
M2 detects only the effective portion of the signal voltage Vt, and the output of the effective portion is indicated or displayed and is output to the outside as a buzzer signal Sl (FIG. 1). In the case where a ground fault does not occur as shown in the equivalent circuit of Fig. 2 (a), the capacitors ffi C2 (C3,...) connected between each slave cubicle 11, 12... and the ground are Even if the power line L1. L2..., but this current is passed through the measuring device M1. as an imaginary current. M2 does not output this.

If a ground fault occurs in each slave cubicle 11, 12..., the current due to the ground fault! X is the capacity C as shown in the opening of Figure 2.
2 (C3,...) flows to the ground via a ground fault resistor (or short j@) Rx connected in parallel to C3, . . . This ground fault resistance RX
The current flowing through has a real part. This real part is the measuring device M1
．． M2 transformer T1. The detection signals of T2... are extracted by synchronously rectifying them with the output of the oscillator O5C. This synchronously rectified real part output is given an analog indication in the measuring instruments M1 and M2, and is also output as a buzzer signal Sl. As mentioned above, the power supply line L1. L2 actually has a plurality of transformers T1. T2... are the plurality of power supply lines L1. L2 are collectively clipped, but when a buzzer sounds and a signal is detected, the operator removes the collective clip and clips each power line separately, thereby clipping the multiple power lines L1. Check which power supply line of L2 has caused the ground fault. Power line L1
．． Analog instructions at the time of bulk checking of L2 are from measuring instrument M1. M2 operates as a level detector, and the digital indication on each line indicates the value of the ground fault resistance RX.

In this way, it is possible to detect the occurrence of a ground fault in the control system shown in FIG. 1 for each slave cubicle 11, 12, . . . and in which power supply line.

As shown in FIG.
The reason for inserting and connecting the resistor R1 between 3C and the capacitance CI is that the capacitance c2 (c3...) between each secondary cubicle 11, 12...e and the ground is large (as its imaginary number This is to prevent the detection of the resistor Rx from becoming impossible due to the amount of time.The explanation for this is as follows.The equivalent circuit of Fig. 1 in a ground fault state is shown at the beginning of Fig. 2.Here in,
When the oscillation frequency of the oscillator O5C is 750Hz, the impedance of the capacitor C1 is Xl, the capacitor C2 (C3,...
・The impedance of ) is X2, and the ground fault resistance Rx and x2
When the parallel resistance of is R', Rr is expressed by the following formula (1).

Rr= (R1+aX2)+? (X 1 + a Rx)/ (R1+ a X2)
--(1) However, a=RxX2 / (Rx2+X
2''5R1-200, and when the oscillation frequency of the oscillator osc is 750 KHz, and xl-1Ω and X2-10Ω, the relationship between Rx and R' is determined by equation (1) as follows.

RX! When OΩ, Rrm20Ω When Rxw20Ω, Rr-27,40 When Rx=50Ω, Rr=54Ω When Rx=1000, Rr-26-80Rx=200Ω
When Rr-”26.050RX-10000R
r-26-050 Formula (1) means that the limit of R is determined by R1 and xl, but in the above example, R
Maximum r beak (11 is 540 and Rx
It is not preferable because it becomes 260 when the circuit is open (Rx=10000).

x2 to be able to detect IKΩ as Rr is 1000-10+X2 from equation (1) assuming R1■10Ω
/10 x2■Zaidingsei-99,50 C2= 1 /2rf X2-2.22u F Therefore,
Using C2 = 2.2 u F (X2 = 1000), the relationship between Rx and R' is found again using equation (1) as follows.

When Rxm0Ω, 3Rr-IQ, lΩ When Rxm2QΩ, Rr-30-00 When Rxm5QΩ, Rr = 83.60 When Rx = 1000, Rr = 103.350RX-
When Rx=1000Ω, it becomes Rr-1810Ω, and Rr-1000Ω when Rx=1000Ω, and even if the capacitance C2 is large, it is possible to clearly distinguish the value of the ground fault resistance Rx in the open and short states.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to obtain a ground fault detection device which is suitable for detecting ground faults in a system in a live line state and has a small size and simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing an embodiment of the ground fault detection device according to the present invention, and FIG. 2 shows an equivalent circuit of the device shown in FIG. 10... Main cubicle, 11.12... Slave cubicle, Es... Power supply, O20... Oscillator, R1.
...Resistance =, CI. C2 (C3,...) Capacity, Ml, M2... Clip-type measuring device.

Claims (1)

[Claims] Comprising a main cubicle and a plurality of subordinate cubicles,
A ground fault detection device in a system system in which the output of a DC power supply placed in a main cubicle is sent to each slave cubicle via a power line, and an oscillator and a resistor connected between the power supply and the ground. vessel R1
and a capacitor C1, a capacitor C2 connected between each slave cubicle and the ground, and synchronous rectification in which the output of a transformer that clips the power line for each slave cubicle is synchronously rectified with the output of the oscillator. 1. A ground fault detection device, comprising: a measuring device having a circuit, the output of the synchronous rectification circuit being obtained as a ground fault detection signal.