KR20040079743A - A switching method and apparatus for ground current by condencer - Google Patents

Abstract

PURPOSE: An apparatus and a method for blocking ground using a capacitor are provided to block a ground current by configuring a path on which the ground current flows by a Y-connected capacitor. CONSTITUTION: A ground blocking capacitor(300) comprises a first capacitor(310), a second capacitor(320), and a third capacitor(330). An end of the respective first, second, and third capacitors is connected to each of 440V(Volt)-lines(l,m,n). The 440V-lines are coupled to a secondary of a distribution transformer(100). The other ends of the first, second, and third capacitors are coupled in a Y-connection and a neutral point(P) of the Y-connection is grounded. An earth leakage breaker(400) is connected between the ground blocking capacitor and a load(500) and blocks a distribution line upon detecting a ground current.

Description

Ground fault interrupting device and method by capacitor {A switching method and apparatus for ground current by condencer}

The present invention forms a passage through which a ground current can flow by a three-phase Y-connected capacitor when a ground fault occurs in an ungrounded wire path of 440V, and operates a ground fault breaker by the fault current flowing through the capacitor to block the ground current. As described in more detail,

In order to supply 440V of power, three ground fault current sensing capacitors are Y-connected to each line of the secondary side of the distribution transformer connected in a Δ method, and then the neutral point of the ground fault current sensing capacitors connected Y is grounded. By installing an earth leakage breaker between the ground fault current sensing capacitor and the load,

If a ground fault occurs in any one of the distribution lines, a circuit is constructed so that the ground current flows through the ground current sensing capacitor, and when the ground current is detected, the ground fault breaker that detects the flow of the ground current cuts off the ground line. It relates to a ground fault interrupter and method of 440V characterized in that.

A ground fault breaker is installed in a facility that is concerned about the contact of a contraction in order to prevent an electric shock due to an electric shock caused by a ground fault in a high or low voltage line. It is a device that cuts off the power supplied by separating facilities from the cable line.

Article 45 of the Electrical Equipment Technical Standards

A low voltage mechanical device with a metal enclosure with a voltage of more than 60 V, which is required to be equipped with a device that automatically cuts off the converter when electricity is supplied to the converter that supplies electricity to facilities where people may be easily contacted. According to this clause, a ground fault breaker must be installed on a low voltage line to prevent a ground fault.

In this case, 220V or 380V that we usually use is output from the transformer which is connected to V or Y by the secondary side, and their wiring method is grounding current by neutral ground at low voltage side (220V, 380V) Can be detected. In other words, if a ground fault current flows through the neutral point when a ground fault occurs, the ground fault breaker detects this and operates the circuit breaker.

However, AC power of 440V is used for the ground power supply (railway inspection power supply) of railway, and most of the 440V power supply to these devices is supplied by the non-grounding method of connecting the secondary of the distribution transformer. Therefore, even if a ground fault occurs, there is no passage for the ground current to pass through, so it is impossible to cut off the ground current by the earth leakage breaker alone.

Therefore, a facility using 440V as a power source must have a ground fault blocking device of GPT (Ground Potential Transfomer) method, which is an inevitable ground fault breaker even though its voltage is low. It was.

However, the ground fault blocking device of the GPT method, which is a ground fault blocking method for the high pressure, as can be seen in FIG.

A grounding type transformer (GPT) 30 for detecting an image voltage (polarity voltage) and operating a ground fault relay in case of a ground fault of the system; A current limiting resistor (CLR) 40 connected to the secondary side of the transformer for grounding type and passing only an active component of the ground current; An overvoltage ground relay (OVGR) 50 connected to the ground type transformer and operated by a magnitude of an image voltage generated in a ground fault event; A circuit breaker (MCCB) for interrupting power supplied to the low voltage facility in response to a ground fault detected by the overvoltage ground relay; As it is constructed, not only the structure is very complicated, but also the periodic and precise inspection of the device is required, so that the cost of installing the ground fault interrupter and the time and cost of maintaining the device are excessive. .

Here, the ground fault breaking method of the conventional GPT method used in the non-grounding type 440V low voltage will be described with reference to FIG. 1.

First, when one of the secondary circuits (l, m, n) of the secondary side of the power distribution transformer 100 is grounded, the ground current is a ground type transformer (GPT) 30 detects the image voltage and the overvoltage ground relay 50 To operate. When the image voltage is out of a predetermined range, the overvoltage ground relay 50 operates to supply an operating power for operating the circuit breaker 60 to the power distribution circuit breaker, and when the power is supplied, the power distribution circuit breaker 60 responds thereto. To break the converter by operating the breaker.

However, the ground fault blocking method of the GPT method, which operates through the above process, has a complicated structure as mentioned above, which not only increases installation and maintenance costs, but also causes many obstacles in operating it, thereby making it more frequent inspection and repair. It causes a lot of problems, such as the need for it.

An object of the present invention is to provide an apparatus and method for safely and reliably cutting off an electric wire in the event of a grounding accident by three ground fault interrupting capacitors connected with a ground fault circuit breaker and Y-connected.

In addition, it aims to contribute to the improvement of railway management by reducing the cost of new facilities investment and maintenance, and to drastically improve customer service by rapid maintenance.

1 is a block diagram of a ground fault interrupting device using a conventional GPT method

2 is a block diagram of a ground fault interrupting device using a capacitor of the present invention.

Figure 3 is a comparison diagram of the secondary wiring method of the transformer for distribution

<Explanation of symbols on main parts of the drawings>

10: transformer for distribution 20: contact prevention plate

30: transformer for grounding type 40: current-limiting resistor

50: overvoltage ground relay 60: circuit breaker

70: load

100: power distribution transformer 200: contact prevention plate

300: ground fault blocking capacitor 310: the first capacitor

320: second capacitor 330: third capacitor

400: earth leakage breaker 500: load

l, m, n: distribution line

Looking at the configuration of the present invention for achieving the above object with reference to FIG.

First, the configuration of the ground fault interrupting device according to the present invention

One end is coupled to each of the 440V lines (l, m, n) of the secondary side of the power distribution transformer 100 and is configured to ground (G) the Y-connected neutral point (P) after the other end is coupled in a Y-connection manner. Ground fault blocking capacitors 300, that is, the first capacitor 310, the second capacitor 320, the third capacitor 330 and;

It is connected between the rear end of the ground fault blocking capacitor 300 and the load 500, when a ground fault current flows through the ground fault blocking capacitor when one of the secondary lines (l, m, n) is grounded. A circuit breaker (ELB) 400 that senses and cuts the distribution line; Characterized in that configured.

Configuration 200 is not described here is a contact prevention plate for preventing the contact of high and low pressure.

Referring to Figures 6 and 7 the operation of the present invention configured as described above,

First, when a ground accident occurs, a passage for flowing the ground current I through the ground (G) of the neutral point (P) of each capacitor (310, 320, 330) is configured. When the ground current flows along the passage, the ground current flow is detected by a ZCT (not shown) mounted inside the ground fault circuit breaker, and the ZCT sensing the flow of the ground current is a tripping part (not shown) of the ground fault breaker. The circuit breaker is opened by operating the earth leakage breaker by flowing a current.

Here, the reason why the ground fault circuit breaker does not open the circuit by itself in the non-grounded 440V power supply by Δ connection will be further explained with reference to FIG. 3.

The voltage we usually use is 220V or 380V as mentioned above, which is obtained by the V connection or Y connection method with the 1st ground of the secondary side of the transformer as shown in FIGS. 3A and 3B. Therefore, when a ground accident occurs, a ground current flow path is formed through the ground side to operate the earth leakage breaker.

3A and 3B show a V connection method and a Y connection method having the secondary side grounded.

However, in the case of 440V, although the use voltage is high, the effect on the drawing in case of a ground accident is large, and thus it is formed by the non-grounding method by the Δ connection as shown in FIG. 3c, thereby preventing the formation of a passage for the ground current. Therefore, the grounding state cannot be detected without opening the ground fault circuit breaker unless a passage for the separate ground current is formed.

In the present invention, the three capacitors 310, 320 and 330 coupled by the Y-connection method are coupled to the secondary side, and a ground fault current flows to the ground (G) part of the neutral point P of the Y-connected capacitor 300. By forming a string passage, a tripping block (not shown) of the ground fault circuit breaker (ELB) that detects the ground fault is blocked by blocking the ground fault circuit breaker (ELB).

Here, the capacitor capacity of the present invention constituting the ground fault interrupter of 440V is

Calculated by the formula C = I / 2πfE,

This equation is for the ground current

I = 2πfCE.

Capacitor capacity applicable in the present invention calculated by the above formula is about 0.6 kV to 0.8 kV of 250V rating.

According to the experiment results of the applicant, when the ground fault blocking device is made by the above method, the structure of the ground fault blocking device is simpler than the conventional ground fault blocking method. It takes about 1/6 times, and the installation cost is about 200,000 won per place, which is about 1/10 of the conventional facilities, and the incidence of obstacles is reduced by about 1/5 compared with the prior art.

This is shown in the table below.

Installation device rescue Inspection time (minutes) Installation fee (KRW 10,000) Failure Factors (%) G P T Complex 6 0 2 0 0 5 0 Condenser simple 1 0 2 0 1 0 Benefit Easy to work △ 5 0 △ 1 8 0 △ 4 0

When the ground fault is blocked by the present invention configured as described above,

Due to the relatively low cost, it is effective to safely install and maintain ground fault blocking equipment.

In addition, it greatly reduces manpower for maintenance of ground fault blocking devices, and greatly reduces the incidence of failures, thereby improving railroad management and improving customer service.

Claims (3)

In constructing a ground fault interrupting device for a non-grounded 440V distribution line, One end is coupled to each of the 440V lines (l, m, n) of the secondary side of the power distribution transformer 100 and is configured to ground (G) the Y-connected neutral point (P) after the other end is coupled in a Y-connection manner. Ground fault blocking capacitors 300, that is, the first capacitor 310, the second capacitor 320, the third capacitor 330 and; It is connected between the rear end of the ground fault blocking capacitor 300 and the load 500, when a ground fault current flows through the ground fault blocking capacitor when one of the secondary lines (l, m, n) is grounded. A circuit breaker (ELB) 400 that senses and cuts the distribution line; Ground circuit breaker by the capacitor, characterized in that the configuration. The method of claim 1, The ground fault blocking device 300, the capacity of the ground fault blocking device by a capacitor, characterized in that the 250V rating 0.6 ~ 0.8㎌. In blocking the ground current of the ungrounded 440V distribution line, When a ground accident occurs, a passage for flowing the ground current (I) through the ground (G) of the neutral point (P) of each capacitor (310, 320, 330); When the ground current flows along the passage, the flow of the ground current is sensed by the ZCT mounted inside the earth leakage breaker; ZCT detecting the flow of the ground current flows the current to the tripping part of the circuit breaker to operate the circuit breaker to open the converter, characterized in that to open the converter.