JPH0367183A - Ground-fault-phase detecting circuit - Google Patents

Abstract

PURPOSE:To easily decide a ground fault phase without continuous visual observation by providing auxiliary relays which turn on corresponding to pilot lamps according to the operations of voltage sensors connected to the respective phases of tertiary winding and hold themselves. CONSTITUTION:A DC circuit for holding a detection signal combines operation points 5a-7a and nonoperation points 5b-7b of the voltage sensors connected to the respective phases of the tertiary winding to detect the ground fault phase by the auxiliary relays 8-10, and a self-holding circuit consists of self-contacts a1-10a1, a diode 11, and a return push-button switch 12; and turn-on circuits for the pilot lamps 13-15 are composed of auxiliary relay contacts 8a2-10a2, which are used as fault warning contacts for ground-fault detection. In case of a ground fault, a phase which is 120 deg. precedent to the ground-fault phase becomes a high voltage and the sensor operates, but the sensor of the ground-fault phase does not operate. For example, when a T phase is in operation and an R phase is not in operation, an R-phase ground fault is decided. Then the ground-fault point of the detected ground-fault phase is separated from the system and the tertiary voltage becomes normal, but a ground-fault display is left by the self-holding circuit and the fault warning contact are offered continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a ground fault phase detection circuit for a power receiving and distribution system.

(Conventional technology) An example of a conventional ground fault phase detection circuit is shown in FIG.

Conventionally, as shown in Fig. 4, transparent globe bulb-type indicator lights 2, 3.4 are connected to each phase of the tertiary winding of a grounded instrument transformer 1 installed in the main circuit system of power receiving and distribution equipment. By visually observing the tertiary winding voltage of the grounded instrument transformer, which changes when a ground fault occurs, using the brightness of the filament of the transparent globe bulb-type indicator light, the presence or absence of a ground fault and the ground fault phase can be determined. There is.

In other words, if the brightness of the three filaments is equal, it is a normal state, and if there is a change in brightness, for example, the T-phase filament is the brightest and the R-phase filament is the darkest, then the brightest phase, 120' slow phase. Since it is a ground fault phase, it is determined that it is an R phase ground fault.

(Problem to be Solved by the Invention) However, the voltage of each phase of the tertiary winding of a grounded potential transformer, which changes when a ground fault occurs, is limited by the time when the ground fault point is separated from the grid by the operation of the grid protection device ( Since the voltage returns to normal after a few seconds), it is necessary to visually observe the filament at all times in order to determine whether there is a ground fault, which is impractical in terms of maintenance management. It is an object of the present invention to provide a ground fault phase detection circuit that enables ground fault phase discrimination even after point separation.

[Structure of the invention]

(Means and Effects for Solving the Problems) The present invention provides a voltage sensor connected to each phase of a tertiary winding of a grounded instrument transformer connected to the main circuit system of power receiving and distribution equipment, and It is equipped with an auxiliary relay for each phase that operates in accordance with the operation of the phase voltage sensor to light the corresponding phase indicator light and is self-holding, and a return button switch that releases the self-holding, thereby ensuring continuity of human operations. This makes it possible to easily identify the ground fault phase without using visual inspection.

(Example) An embodiment of the present invention is shown in FIGS. 1, 2, and 3.

Figure 1 shows an AC circuit for voltage detection, in which voltage sensors 5, 6, and 7 are connected to each phase of the tertiary winding of a grounded instrument transformer 1 installed in the main circuit system for power reception and distribution. ing.

Fig. 2 shows a DC circuit for holding detection signals, in which operating contacts 5a, 6b, 7a and non-operating contacts 5b, 6b, 7b of each phase voltage sensor are combined to connect the ground fault phase to an auxiliary relay 8, 9. Detected in 10, and furthermore, the self-contacts 8al, 9a, 10a of the auxiliary relay and the diode 11. The return pushbutton switch 12 constitutes a self-holding circuit, and
Indicator light 13 at auxiliary relay contacts 8az, 9az, 10az
．． 14. Configures the lighting circuit of 15, and connects the auxiliary relay contact 8a.
2.9azp10a2 is provided externally as a fault alarm contact for ground fault detection.

Figure 3 is a block diagram showing the operation of the voltage sensor when detecting a ground fault phase and the combination of non-operating contacts. In the case of a ground fault, the 120° advanced phase of the ground fault phase becomes a high voltage, and the corresponding voltage sensor is activated, the ground fault phase is low voltage and the voltage sensor remains inactive, for example, voltage sensor T phase is activated and voltage sensor R
When a phase is not operating, it is determined that there is an R phase ground fault.

When a ground fault phase is detected according to the ground fault phase detection block diagram shown in Figure 3, the ground fault point is separated from the system by the operation of the system protection device, and the tertiary voltage of the ground fault voltage transformer returns to normal.
Even after that, the ground fault phase display remains due to the self-holding circuit, so
A fault alarm contact for ground fault detection continues to be provided externally.

Furthermore, in the past, it was necessary for humans to visually determine that the phase that was delayed by 120° from the brightest light bulb was the ground fault phase, but with the present invention, the ground fault phase itself is continuously displayed. Judgment becomes unnecessary.

〔Effect of the invention〕

As explained above, according to the ground fault phase detection circuit of the present invention,
Since the ground fault phase display remains even after the ground fault point is separated from the system, continuous visual inspection by one person is not required, and maintenance management and ground fault monitoring of the power receiving and distribution system are extremely facilitated.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the AC circuit section of the ground fault phase detection circuit according to the present invention, FIG. 2 is a diagram showing the DC circuit section, and FIG. 3 is a block diagram showing the combination of contacts when detecting the ground fault phase. , 4th
The figure shows a conventional ground fault phase detection circuit. Engineering... Grounding instrument transformer 5.6.7... Voltage sensor 11... Diode 13.14, 15... Indicator light (8733)

Claims (1)

[Claims] A voltage sensor connected to each phase of the tertiary winding of a grounded instrument transformer connected to the main circuit system of the power receiving and distribution equipment, and a corresponding phase What is claimed is: 1. A ground fault phase detection circuit comprising: an auxiliary relay for each phase that lights up an indicator light and is self-held; and a return button switch that releases the self-holding.