JPH02237421A - Ground detector in solar battery circuit - Google Patents

Abstract

PURPOSE:To materialize an inexpensive ground detector circuit by connecting resistances whose neutral point is grounded between the positive and negative electrodes of a solar battery and by monitoring the balance of voltage of the resistances connected to positive and negative sides. CONSTITUTION:Resistances R1P, R2P, R1N and R2N are connected in series into between a positive pole P and a negative pole Q of a solar battery 1. With R1P=R1N and R2P=R2N, its neutral point C is grounded. The difference in voltage between a connecting point A of the resistances R2P and R1P and a connecting point B of the resistances R1N and R2N is found by a voltage differences absolute value detection circuit 5, which is compared with set voltage of a voltage level setter 7 by a ground detection circuit 6 and if it exceeds the set value, it is to be a ground detection output.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ground fault detection device for a solar cell circuit, and particularly to a ground fault detection device that does not require a ground fault detection relay.

[Conventional technology]

FIG. 6 is a circuit diagram of a solar cell circuit and a conventional ground fault detection device shown in, for example, Japanese Utility Model Application No. 65-16464 or No. 56-58875.
] is a solar cell module, and usually a plurality of such solar cell modules (1) are connected in series and parallel. (2)
is a battery, which is connected in parallel with the solar cell module (1), the positive electrodes P of both of which are connected to each other, and the negative electrodes N of both of them are also connected to each other. (3) is Patte! J-
(2) is a load connected in parallel to These solar cell module (1), battery (2), and load (phantom) constitute a solar cell circuit. Conventionally, ground fault detection has been used to prevent electric shock and protect circuits in the event a ground fault occurs in this solar cell circuit. This ground fault detection device includes voltage dividing resistors (R11) and (R12) connected in series with each other between the positive pole P and the negative pole N of Patute 9-(2J) and having equal resistance values. , these voltage dividing resistors (R1
It consists of a current limiting resistor (R1) and a ground fault detection relay (4) connected in series between the connection point C of 1) and (R12) and the ground G.

The conventional ground fault detection device is configured as described above. If the positive pole P of the DC circuit has a ground fault, the connection point C
becomes a negative potential with respect to the ground G, and the current limiting resistor (R16
) and the ground fault detection relay (4), and this causes the ground fault detection relay (4) to operate. When the negative electrode N has a ground fault, the connection point C becomes a positive potential with respect to the ground 9, a detection current 12 flows, the ground fault detection relay operates, and an upward ground fault is detected.

[Problem to be solved by the invention]

Conventional ground fault detection devices require a current detection type ground fault detection relay for ground fault detection, and have the problem of being expensive.

The present invention was made to solve these problems, and an object of the present invention is to provide an inexpensive and simple voltage-based ground fault detection device that does not require a ground fault detection relay.

[Means for solving confusing problems]

In the solar cell circuit according to the present invention, the positive and negative electrodes of the solar cell circuit are connected in series, and their neutral point is connected to the ground, and the neutral point is connected to the ground. A plurality of voltage dividing resistors each have two voltage detection points that generate equal voltages on the positive and negative sides in the event of a ground fault. The circuit is equipped with a circuit for detecting faults.

[For production]

In this invention, when a ground fault occurs in a DC circuit, the voltages generated at two voltage detection points are no longer equal, and this is detected by a voltage detection circuit, thereby detecting a ground fault.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention, where (6) is exactly the same as that in the conventional device.
2p, Rap. R+x and R2N are voltage dividing resistors connected in series between the positive pole P and the negative pole N of the DC circuit. Furthermore, the connection point C between the voltage dividing resistor R+p and RIN
is connected to the ground G, and the resistance value of the voltage dividing resistor R+p and Ray
The resistance values of are chosen equally. Also, the voltage dividing resistors Ryp and R
A connection point A of +p and a connection point B of voltage dividing resistors RTM and R2N are voltage detection points. (5) These voltage detection points (
This is an absolute value voltage difference detection circuit connected to A) and CB), which detects the absolute value IVA+ of the voltage at the voltage detection point (A) and the absolute value Val of the voltage at the voltage detection point (B) with respect to the ground (G).
Detect the difference ΔVa between the two. (No. 6 is a ground fault determination circuit connected to the output side of this absolute value voltage difference detection circuit (5), (7)
) is a voltage level setter connected to the other input terminal of the ground fault determination circuit (6), and provides the reference voltage VR to the ground fault determination circuit (6). In addition, the voltage difference absolute value detection circuit (5)
The ground fault determination circuit (6) can be constructed from a general-purpose integrated circuit.

Next, the operation of the solar cell circuit and its ground fault detection device shown in FIG. 1 will be explained. As an example, consider a case where the positive electrode P of the DC circuit is grounded.

E: DC voltage (VJ R+p, R2p, R-N, R2N: Resistance f of voltage dividing resistor
lX (Ω) RG: Resistance of ground fault resistance [(Ω) Δ■G: Voltage detection point (A) and (B
), the combined resistance Rp between the positive electrode P and the neutral point C is expressed by the following equation (1), and the combined resistance RN between the negative electrode N and the neutral point C is expressed by the following equation It is expressed as (2).

FIG. 2 (If) is a circuit diagram when the positive electrode P is grounded, and FIG.

The voltage Vp of the positive electrode P with respect to the neutral point C is expressed by the following equation (6), and the voltage VN of the negative electrode N is expressed by the following equation (4).

The voltage VA at the voltage detection point A and the voltage Vs at the voltage detection point B with respect to the neutral point 0 are expressed by the following equations (1), (2),
(33, (4)) and the following equation (5) and equation (6
It is requested like ノ.

From equations (5) and (6), the absolute value ΔVG of the voltage difference between voltage detection points A and B with respect to neutral point C is ΔWG = l VB − V person 1 (VJ

(7) becomes. In addition, in the event of a non-ground fault, voltage detection points A and B (+1 voltage
Select N). That is, R+p == R+N(=
Rt ) (8) R2P =
R2N (= Rj ) − t9) Substituting equations (5), (r+ (8), and (9) into equation (7) and summarizing it gives equation (10).

RG For example, ground fault resistance Ro=-10 (KΩ}, voltage division resistance R+
= 5. 9 (KΩ, R2: 200 (KΩ), DC voltage m = 200 (V), voltage difference ΔV
a=5.48(V). However, the ground fault resistance Ra
= 1 0 0 (KΩ), and assuming that the other conditions are the same as above, the voltage difference ΔVo = 1.9 3ff). As can be seen from this example, as the ground fault resistance Ro increases, the voltage difference ΔVo decreases. Such a decrease in detection sensitivity can be solved by providing an amplifier circuit in the detection circuit. In addition, even in the case of a negative electrode ground fault, the voltage difference ΔVc
is expressed by the above equation (10). The output ΔMe of the voltage difference absolute value detection circuit (5) is compared with the output 'VR of the voltage level setter (7) in the ground fault determination circuit (6), and ΔVo
) When the voltage becomes vn, the ground fault determination circuit (6) operates and detects a ground fault.

〔Effect of the invention〕

As explained above, the present invention has a positive electrode and a negative electrode of a solar cell circuit connected in series with each other, and their neutral point is connected to the ground, and furthermore, when a non-ground fault occurs, the positive electrode side of the solar cell circuit is connected to the ground. and a circuit that detects a ground fault by comparing the difference in voltage from the voltage detection points with a predetermined set value. Therefore, the ground fault detection device can be constructed from a voltage dividing resistor and a general-purpose integrated circuit, which has the effect that it is simple, inexpensive, and highly accurate.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, Fig. 2 is a circuit diagram when the positive electrode is grounded in Fig.
Figure 2 is an equivalent circuit diagram of a composite resistor derived from InnoYoku, and Figure 3 is a circuit diagram showing a solar cell circuit and a conventional ground fault detection device. Module, (5)...
Voltage difference absolute value detection circuit, (6)...Ground fault determination circuit, (7
)...Voltage level setter, A, B, voltage detection point, C--
Neutral point, Rap, R2P, RIM, R2N・
It is a voltage dividing resistor. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Figure 1 P 7: Fu Lebeno Lz standard Figure 2 Buried person Teru So Ga Do

Claims (1)

[Claims] (1) In a solar cell circuit including multiple solar cell modules connected in series and parallel, the positive and negative electrodes are connected in series with each other, and the neutral point where the voltage is halved is connected to the ground. , and a plurality of voltage dividing resistors each having two voltage detection points that generate equal voltages on the positive and negative sides in the event of a non-ground fault with respect to this neutral point, and a voltage difference between the voltage detection points and a predetermined value. 1. A ground fault detection device for a solar cell circuit, comprising: a circuit for detecting a ground fault by comparing the set value of .