JPH0427775B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a ground fault detector capable of detecting ground faults in ungrounded and high-resistance grounded multiphase single-line power transmission lines with an economical configuration.

BACKGROUND TECHNICAL FIELD In order to detect ground faults in ungrounded and high-resistance grounded polyphase single-line power transmission lines, such as three-phase single-line power transmission lines, conventionally, as shown in Fig. 1, R, S,
Connect capacitors C1, C2, and C3 to each of the T phases, insert a capacitor C4 between their neutral points and the ground, and connect the capacitor C4 in parallel to the transformer T.
1 is connected, and a ground fault is detected based on whether or not the voltage output from the secondary side of the transformer T1 is zero, but this method has the following drawbacks.
That is, since expensive capacitors C1 to C3 with high withstand voltages must be connected to each of the R, S, and T phases, the device becomes expensive, and it is necessary to maintain a balance between the capacitances of each capacitor. Therefore, there was a drawback that installation work, management, etc. were troublesome.

In addition, as shown in Figure 2, R,
One end of the primary side of transformers T2 to T4 is connected to each of the S and T phases, and the other end is grounded.
A method has also been implemented in which the secondary sides of 4 are connected in series and ground faults are detected based on the voltage appearing between terminals A1 and A2, but each phase has a transformer T.
Since it is necessary to connect T2 to T4, there is a drawback that the device becomes expensive.

OBJECTS OF THE INVENTION The present invention is to improve the above-mentioned drawbacks, and its purpose is to have an economical configuration and to be able to reliably detect ground fault detection accidents.

The structure of the present invention is as shown below. That is,
In a ground fault detector that detects ground faults in non-grounded and high-resistance grounded multi-phase single-line power transmission lines, detecting the phase voltage of the phase connected to one phase of the multi-phase single-line power transmission lines. The ground fault detected by the phase voltage detector when one phase of the multi-phase single-line power transmission line has a ground fault. The ground fault detector is characterized in that it combines phase voltages at the time of an accident and obtains a zero-sequence voltage from the difference. Examples will be described in detail below.

Embodiment of the Invention FIG. 3 is a block diagram of an embodiment of the present invention, in which 1 is a phase voltage detector consisting of capacitors C5 and C6 and a transformer T5 and detects the voltage between the T phase and ground; 2 is a synthesis circuit, 3 is a BBD (Bucket Brigade)
4 is an inverting circuit,
5 is a comparator, 6 is a current transformer, 7 is an amplifier, 8 is a phase comparator, and 9 is an AND gate.

The output voltage of transformer T5 in phase voltage detector 1 is applied to a combining circuit 2 and a delay circuit 3. The delay circuit 3 delays the output voltage of the transformer T5 by an integral multiple (N times) of the period t of the phase voltage, that is, tN seconds, and applies it to the inverting circuit 4, and the inverting circuit 4 inverts the output voltage of the delay circuit 3. In addition to combining circuit 2, combining circuit 2 includes transformer T5
and the output voltage of the inverting circuit 4 are combined to output a voltage having the same magnitude and phase as the ground fault voltage. Therefore, if there is no ground fault, transformer T5
Since the output voltage of the inverting circuit 4 and the output voltage of the inverting circuit 4 have the same absolute value and opposite polarity, the output voltage of the combining circuit 2 becomes zero, and if a ground fault occurs, the output voltage of the transformer T5 Since the output voltage and the output voltage of the inverting circuit 4 are different in magnitude and phase, the output voltage of the combining circuit 2 is equal to the ground fault voltage.

The comparator 5 compares a preset threshold with the output voltage of the combining circuit 2 corresponding to the ground fault voltage, and if the output voltage of the combining circuit 2 is higher, it is determined that a ground fault has occurred. The system determines that a ground fault has occurred, sets the output signal a to "1", and sounds an alarm to notify the maintenance personnel that a ground fault has occurred.

Furthermore, the phase comparator 8 determines whether a ground fault is occurring on the power supply side or
Determine where the occurrence occurred on the load side, and if it is determined that the occurrence occurred on the load side, set the output signal b to “1”.
The signal b is applied to the AND gate 9. Therefore, the output signal c of the AND gate 9 to which the signal a is applied to the other input terminal becomes "1" when a ground fault occurs on the load side, and as the signal c becomes "1", the circuit breaker is activated. This is to take measures such as activating the system.

Although a capacitor type detector is shown as the phase voltage detector 1 in this embodiment, the present invention is not limited to this, and it goes without saying that a reactor type detector or the like may also be used. Further, in this embodiment, the output voltage of the delay circuit 3 is applied to the combining circuit 2 via the inverting circuit 4, but if the delay time of the delay circuit 3 is t/2 (2N+1), then the inverting circuit There is no need to use 4. Furthermore, in this embodiment, T
I tried to connect phase voltage detector 1 to the phase, but
Of course, it may be connected to the R and S phases.

FIG. 4 is a circuit diagram showing another embodiment of the present invention. In the embodiment shown in Fig. 3, the output voltage of the normal phase voltage is inverted using a delay circuit, whereas in the embodiment shown in Fig. 4, the R, S, and T phases are all in normal state. The only difference is that an auxiliary power supply is provided which is set to output a voltage equal in magnitude and opposite in polarity to the voltage output from the transformer T5 in the case of the present invention. 16 is this auxiliary power source.

The auxiliary power supply 16 connects the T phase and R phase to the first transformer.
The line voltage between the R phase and the T phase is taken through the PT (if the phase voltage detector 1 is connected to the R phase, the S phase and the R phase). By inverting and adjusting the variable resistor VR2 provided for phase adjustment and the variable resistor VR2 in the capacitor C7, the phase of the line voltage of the T and R phases is changed to the phase voltage phase whose polarity is opposite to that of the T phase. input to the synthesis circuit 2 according to the Note that R1 and VR1 are resistors for voltage level adjustment.

The output voltage of the transformer T5 and the output voltage of the auxiliary power supply 16 are applied to the combining circuit 2. Auxiliary power supply 16
As mentioned above, the output voltage is equal in magnitude to the voltage output from transformer T5 when each phase R, S, and T are healthy, and the polarity is opposite, so there is no ground fault. In this case, the output voltage of the combining circuit 2 becomes zero. Furthermore, if a ground fault occurs, the output voltage of the transformer T5 and the output voltage of the auxiliary power supply 16 will be different in magnitude, so the output voltage of the combining circuit 2 will correspond to the ground fault voltage. Become. Incidentally, in this embodiment as well, a phase comparator or the like may be provided as in the embodiment shown in FIG. 3 to detect whether a ground fault has occurred on the load side or the power supply side. Of course.

Effects of the Invention As explained above, the present invention provides a phase voltage detector, a delay circuit 3, or an auxiliary power supply 1 connected to one phase of an ungrounded and high-resistance grounded multiphase single-line power transmission line.
an output means for outputting a voltage corresponding to the phase voltage of the phase to which the phase voltage detector is connected when the polyphase single-line power transmission line is healthy;
It consists of a comparator 5, etc., and is equipped with a detection means for detecting a ground fault based on the phase voltage detected by the phase voltage detector and the voltage output from the output means. Since it is only necessary to connect the ground faults, there is an advantage that ground faults can be detected with an economical configuration compared to the conventional example.

The present invention is a device for detecting zero-sequence voltage of an ungrounded or high-resistance grounded multiphase single-line power transmission line,
It consists of a phase voltage detector, a delay circuit, an auxiliary power supply, etc. connected to one phase of the multiphase single-line power transmission line, and is cheaper than three circuits of conventional high-voltage capacitors, and can be connected to only one phase. Construction costs are also economical compared to conventional examples. Further, there is no need to worry about the balance of capacitance of each capacitor, and installation work management is easy.

[Brief explanation of drawings]

1 and 2 are block diagrams of different conventional examples, and FIGS. 3 and 4 are block diagrams of different embodiments of the present invention. 1 is a phase voltage detector, 2 is a combining circuit, 3 is a delay circuit, 4 is an inversion circuit, 5 is a comparator, 16 is an auxiliary power supply, 6 is a current transformer, 7 is an amplifier, 8 is a phase comparator,
9 is an AND gate, C1 to C6 are capacitors, T
1 to T5 are transformers.

Claims (1)

[Claims] 1. In a ground fault detector that detects ground faults in ungrounded and high-resistance grounded multiphase single-line power transmission lines, the phase voltage of the phase connected to one of the multiphase single-line power transmission lines is detected. The detection from the phase voltage detector to be detected, or the set phase voltage in a healthy state, and the ground fault detected from the phase voltage detector when one phase of the multi-phase single-line power transmission line has a ground fault. A ground fault detector characterized in that a phase voltage at the time of a fault is synthesized and a zero-sequence voltage is obtained from the difference.