JPH10253680A - Test method for short-time withstand current of switchgear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible that a current ratio as the ratio of the maximum peak value of a first wave after the turning-in operation of a current flowing in a switchgear to be tested to the effective value of a sustained current is made largeer than that of a case in which three phases are turned on simultaneously by a conventional turning-on device. SOLUTION: In respective phases of a three-phase power supply generated by a generator 1 for short circuit, the voltage of a phase which is used as a basis is designated as a phase R, the phase of a voltage whose phase is delayed by 120 deg. from a phase voltage at the phase R is designated as a phase S, and the phase of a voltage whose phase is advanced by 120 deg. from the voltage at the phase R is designated as a phase T. Then, the voltage at the phase R and that at the phase S are started to flow simultaneously at prescribed phases by operaitng respective turning-on devices 3, they are delayed by the prescribed phases, and they are started to flow by turning on a turning-on device 3 at the phase T. Thereby, a current ratio becomes large as compared with a case in which three phases are turned on simultaneously. Consequently, even when the current ratio of a standard value does not become 2.5 or higher when three phases are turned on simultaneously in conventional cases, the current ratio becomes 2.5 of higher without increasing a sustained current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switchgear having a relatively large capacity such as a gas-insulated switchgear, for example, a switchgear for verifying the thermal strength and proof strength against electromagnetic mechanical force of a gas-insulated switchgear. The present invention relates to a short-time withstand current test method.

[0002]

2. Description of the Related Art In a switching device such as a gas-insulated switchgear, a rated short-time withstand current for guaranteeing short-circuit current resistance is set in accordance with a rated voltage and a current, which corresponds to the short-time withstand current. A short-time withstand current test is performed as a test for verifying that a current is actually passed through a gas-insulated switchgear to be subjected to the current and endured.

There are two rules regarding short-time withstand current.
The effective value of the current that lasts for 2 seconds and the maximum crest value of the first wave generated immediately after the current flows. The maximum crest value of the first wave is specified to be at least 2.5 times the effective value of the rated short-time withstand current (for example, JEC-2350 "Gas insulated switchgear" of the Institute of Electrical Engineers of Japan). Have been.

[0004] There are two effects of short-circuit current on equipment, one of which is thermal effect. To verify this, a current that lasts for 2 seconds (hereinafter referred to as "continuous current") is applied. It is. The other is for electromagnetic force, which is determined by the maximum current instantaneous value,
The peak value generated in the first wave immediately after the current flow corresponds to this.
The maximum value of the peak value is twice the peak value of the sustained current, ignoring the attenuation due to the resistance component, and the condition is when the voltage is applied at the zero point of the applied voltage. This is because a DC component that transiently occurs immediately after the input is superimposed. The value of the DC component changes depending on the input phase, and becomes maximum when the input is applied at the zero point of the applied voltage.

When the maximum value of the peak value of the first wave is twice the peak value of the continuous current, the ratio of the continuous current to the effective value is about 2.8 because it is a square root of 2 times this value. Such a magnification of the current is hereinafter referred to as a current ratio. FIG. 1 shows a short-time withstand current application circuit in a short-time withstand current test of a switchgear, which is used for explaining an embodiment of the present invention. The short-time withstand current test method will be described.

In FIG. 1, a short-time withstand current test circuit includes a short-circuit generator 1 as a three-phase current supply power supply, a protection circuit breaker 2, a closing device 3R, a closing device 3S, and a closing device 3T for each phase.
, A current limiting reactor 4, a transformer 5, a test switchgear 6 and a shunt resistor 7 as a current measuring device are connected in series. The right end is shorted.

The protection circuit breaker 2 is "closed" unless an abnormality occurs during the test. When any abnormality occurs, the short-circuit generator 1 is immediately disconnected from the test circuit, and the short-circuit generator 1 It has the role of protecting the entire circuit. The thrower 3 can be set and thrown in at the time of throwing, and a current flows through the test circuit only after the thrower 3 is thrown.
This current is measured for each phase by the shunt resistor 7. Of course, the test switchgear 6 is in the "closed" state when the charging device 3 is turned on.

When the three phases are named R phase, S phase, and T phase, the thrower 3 is simultaneously thrown in each of these phases, that is, the thrower 3R, thrower 3S, and thrower 3T for each phase. The time of input is the same. In the figure, the input of the closing command signal for each phase of the thrower 3 is indicated by an arrow, but this is the case of an embodiment of the present invention described later. One input signal is input commonly to the input devices 3R, 3S, and 3T. The input signal is output by a control device of a test device (not shown) in accordance with the phase of the voltage applied by the short-circuit generator 1 and input to the input device 3.

FIG. 4 is a waveform diagram showing a temporal change in current for each of the R, S, and T phases in a test performed by a conventional test method. In this figure, the horizontal axis is one division 1 at time t.
Scaled at 0 ms, the origin at t = 0 is R phase and S
This is the zero point of the line voltage V _RS between the phases. Since the frequency of the applied voltage is 50 Hz, one cycle is 20 milliseconds. Therefore, one graduation in the figure has a half cycle and a phase angle of 180 °. The vertical axis is the current (kiloamps). This current value differs depending on the rating of the test switchgear 6 such as voltage and current.

The time point t ₀ at which the voltage is applied by the thrower 3 is approximately 1.7 milliseconds from the origin. At this point, the phase angle is 30
°, which is a phase difference between the phase voltage VR of the _R phase and the above-described line voltage _VRS , and the line voltage _VRS is more advanced.
The first peak value of the R-phase current I _R becomes maximum at the voltage V _R
This is the case where the input is made at the zero point. In other words, the actuation phase of the diagram the peak value of the first wave of R-phase current I _R is most larger conditions. As can be seen from the figure, the phase current I _R is 0 at time t ₀ , which is limited by the inductance of the current limiting reactor 4 and the current gradually increases from 0 immediately after being turned on. Thereafter, the peak value of the first wave further rises to about 20 kA, and thereafter, the whole wave falls down while repeating the vibration. The amplitude of this vibration component is about 10.4 kA in one-sided amplitude and about 7.4 kA in effective value. Therefore, the ratio of the maximum peak value to the effective value, that is, the current ratio is 2.7 as described above.

As described above, when it is assumed that the input phase is optimum and there is no attenuation of the DC component, the current ratio is about 2.8.
become. In an actual power system, the phase in which a short circuit occurs is arbitrary, and there is also the attenuation of the DC component due to the resistance of the circuit.
Taking these factors into consideration, a current ratio of 2.5 is set in the standard as described above. In the short-time withstand current test, if the current ratio is too large, the electromagnetic mechanical force becomes excessively large, and the test becomes severe. Therefore, the current ratio is set to a value close to 2.5. If the value exceeds 2.5 under optimum conditions, the input phase by the input device 3 is shifted to a value close to 2.5.

[0012]

By the way, when the magnification of the maximum peak value of the first wave to the effective value of the continuous current does not exceed 2.5 even if the phase is applied at the optimum closing phase, the applied voltage is increased to increase the continuous current. Is made larger than the rated short-time withstand current value so that the current ratio of the maximum peak value of the first wave to the effective value of the rated short-time withstand current becomes 2.5 or more. At this time, the sustained current actually passed through the switchgear 6 becomes larger than the rated short-time withstand current value determined by the standard. Problem.

An object of the present invention is to solve such a problem, and when a voltage is applied by three-phase simultaneous application and a current flows through the switchgear 6 under test, even if the applied phase is the optimum phase, When the current ratio of the maximum peak value of one wave to the effective value of the continuous current is 2.5 or less, the current ratio to the effective value of the rated short-time withstand current is increased to 2.5 or more without increasing the continuous current. It is an object of the present invention to provide a short-time withstand current test method for a switchgear capable of performing a test.

[0014]

According to the present invention, there is provided a switchgear for supplying a short-time current having a peak value of a first wave of a predetermined magnitude in a short-time withstand current test of a switchgear. In the short-time withstand current test method of the device, each phase of the three-phase power supply is set to an R phase as a basic phase, an S phase and a R phase voltage delayed by 120 ° from the R phase voltage. When a phase having a phase advanced by 120 ° is called a T phase, the R phase and the S phase are simultaneously turned on at a predetermined phase and the respective phase input devices are turned on at the same time. When the phase starter is turned on to start current flow, the polarity of the T-phase current immediately after turning on is the same as that of the R-phase at the time of conventional three-phase simultaneous input, so that the R-phase current is reduced. Since the operation is delayed, the action is lost, and the speed of the current increase in the R phase is increased. When the polarity of the voltage of the T phase is reversed, T
When the phase is turned on, the current of the T phase becomes opposite in polarity to that of the R phase together with the S phase, so that the current of the R phase is further increased. After the injection, the peak value of the first wave becomes larger.

In the short-time withstand current test method for the switchgear described above, instead of simultaneously turning on the R-phase and S-phase throwers, one phase thrower is thrown in advance. When the thrower of the other phase is turned on at a predetermined phase, the current flows only after the thrower of the two phases is turned on.
Even if the phase and the S phase are injected at different points in time, the input point of the subsequent phase is substantially the same as the input point of the two phases phenomena substantially. Can be made larger than that in the conventional three-phase simultaneous injection.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. FIG. 1 is a circuit diagram of a test apparatus for a short-time withstand current test of a switchgear according to an embodiment of the present invention, and the description of the above items will not be repeated. In this figure, the thrower 3 is comprised of throwers 3R, 3S, 3T for each phase, and each thrower 3R, 3S, 3T has a drive mechanism for each, and has the function of throwing independently for each phase. It has a different point from the conventional one. A control device (not shown) independently issues a closing signal to a driving mechanism (not shown) of each phase of the thrower 3, and when the throwers 3 </ b> R, 3 </ b> S, and 3 </ b> T of each phase receive this signal receive a signal. As a starting point, a closing operation is performed, and the contact is closed to be in a “closed” state.
It should be noted that there is already an input device capable of inputting each phase independently, and a detailed description thereof will be omitted.

FIG. 2 shows the test of FIG. 1 showing an embodiment of the present invention.
Each phase in the short-time withstand current test performed by the device
FIG. 5 is a waveform diagram showing a current waveform, which is similar to FIG.
Description is omitted. 4 in that the T-phase current i
_TTime t_TIs the time t when the R and S phases are charged₀Slower than
At that point. Other conditions are shown in FIGS. 2 and 4.
Is the same as As can be seen from FIG. 2, the R-phase current i_R
Are larger than those of FIG. Thus, the T phase
Delay of the input time of the R-phase current i _RIs large
The reason can be explained as follows.

As can be seen from FIG.₀Immediately after
Is the T-phase current i_TIs the phase current I_RIncreases to the same positive as
You. Since the sum of these three phase currents is 0, this phase current
Style I_TIf there is no phase current i_RIs larger than in Fig. 4.
Can be assumed. The result in Figure 2 proves that
is there. However, the phase current I that increases in the negative direction_SThe value of
2 is smaller than that in FIG._TGana
The phase current i _RHas led to an increase in
There is no. Fig. 3 shows the results of the current ratio obtained under various conditions.
The horizontal axis is the injection time (millisecond) and the origin
The conditions are the same as in FIGS. 2 and 4, and the vertical axis is the current ratio.
Curve G1 is about 0.7 ms after the origin of the time axis.
When the R and S phases are input at the time, the curve G2 is based on the time axis.
When the R and S phases are supplied at about 1.7 ms after the point
In this case, curve G3 is about 2.7 ms after the origin of the time axis.
This is the case where the R and S phases are injected at the point,
The starting point on the left side is the case where three phases are simultaneously input together with the T phase at this time.
The curve on the right after that is the time when the T-phase was injected
In this case. Curve G1 is a diamond, curve G2
Is a square, curve G3 is a triangle and marked in the middle of each curve
The measurement points are shown. The curve G with a white circle
4 is a case of simultaneous injection.

The phase voltage V _R of the R phase is delayed by 30 ° from the line voltage V _{RS in} phase, but this phase difference of 30 ° corresponds to about 1.7 milliseconds in time (20 cycles per cycle). Millisecond × 30 ° / 360 ° = 1.67 millisecond). Therefore,
Left of the starting point of the curve G2 is not a zero point of the phase voltage V _R, the after introduction of R phase if this time is of the three-phase simultaneous-on 1
As described above, the peak value of the wave becomes maximum. This indicates that the curve G4 has the maximum value at this point.

The curve G1 is for the case where the input point of 1 millisecond is advanced from the start point of the curve G2, and the curve G3 is for the case where it is delayed for 1 millisecond. Note that the waveform diagram of FIG. 2 shows a case where the injection point of the T phase of the curve G2 is 5.7 milliseconds, that is, a case where G2 is the rightmost end. The current ratio at this time is about 2.75, which is much higher than the standard value of 2.5. Incidentally, the starting point on the left side of the curve G2, that is, the current ratio in the case of three-phase simultaneous input is 2.48, which is below the standard value of 2.5. That is, by delaying the T phase and feeding,
Even in the case where the conventional three-phase simultaneous injection test method does not satisfy the standard value, it is possible to obtain a current ratio that can sufficiently satisfy the standard value by delaying the time when one phase is applied compared to the other phase even under conditions where the standard value cannot be satisfied. . Of course, it is not necessary to employ a current ratio that greatly exceeds 2.5, so that in an actual short-time withstand current test, appropriate conditions are set such that the current ratio is 2.5 or more. As is clear from FIG. 3, the condition under which the maximum current ratio is obtained does not depend on the curve G2, but a larger current ratio can be obtained, for example, with the curve G1 in which the R and S phases are turned on earlier. .

A method for setting appropriate conditions in a short-time withstand current test method of an actual switchgear is to apply a low current, for example, half of the applied voltage necessary to obtain a current of a standard value in advance. Measure the current and select appropriate conditions from the results. Also, since the circuit constants of the test circuit shown in FIG. 1 including the short-circuit generator 1 can be accurately determined by referring to the past test results, it is also possible to select an appropriate value by circuit calculation based on this. It is possible.

In addition to charging the charging devices 3R and 3S simultaneously,
For example, it is also possible to adopt an input method in which the input device 3R is input in advance, the input device 3S is input at a predetermined time, and then the input device 3T is input at a time after a predetermined time delay. This is because the current does not flow even when the input device of one phase is turned on, and the current flows only after the input device of the second phase is turned on. Which of the input methods is to be adopted may be the one that is more appropriate based on the control method at the time of input of the input device 3 or the like.

[0023]

As described above, according to the present invention, each phase of the three-phase power supply is divided into an R phase as a basic phase, an S phase delayed by 120 ° from the R phase, and a T phase shifted 120 ° from the R phase as T phase. When the phases are named, the R-phase and the S-phase are simultaneously supplied with a predetermined phase at the same time, and each phase is turned on at the same time. When the power supply is started simultaneously, the polarity of the T-phase current immediately after the power-on is the same as that of the R-phase, so that the R-phase current is reduced. When the T phase is turned on when the polarity of the voltage of the T phase is reversed, the current of the T phase becomes opposite in polarity to the R phase together with the S phase. When the peak value of the first wave after simultaneous injection of the R phase is simultaneous injection compared to the case of simultaneous injection Larger than. Therefore, since the value of the current ratio does not become 2.5 or more as in the case of the conventional three-phase simultaneous input, the maximum current of the first wave after the input is set by setting the sustained current to be larger than the rated short-time withstand current. Since the high value does not need to be 2.5 times or more the effective value of the rated short-time withstand current value, increasing the continuous current causes the switchgear under test to be subjected to severe thermal test conditions. Is obtained.

In the short-time withstand current test method for the switchgear described above, instead of simultaneously turning on the R-phase and S-phase throwers, the thrower of one phase is thrown beforehand. When the thrower of the other phase is turned on at a predetermined phase, the current flows only after the thrower of the two phases is turned on.
Even if the phase and the S phase are introduced at different points in time, the same point as that of the above-described test method can be obtained since the point of introduction of the later phase is substantially the point of simultaneous introduction of the two phases.

[Brief description of the drawings]

FIG. 1 shows a test circuit used for a short-time withstand current test of a switchgear according to an embodiment of the present invention.

FIG. 2 is a waveform chart showing current waveforms of respective phases in a short-time withstand current test performed by the test apparatus of FIG. 1;

3 is a graph showing a peak value of a first wave after application of a phase current under various conditions in a short-time withstand current test performed by the test apparatus of FIG.

FIG. 4 is a waveform diagram showing a current waveform of each phase in a short-time withstand current test performed by a conventional test apparatus.

[Explanation of Signs] 1 ... Short-circuit generator, 2 ... Protection breaker, 3, 3R, 3S,
3T ... thrower, 4 ... current limiting reactor, 5 ... transformer, 6 ...
Test switchgear, 7 Shunt resistor

Claims (2)

[Claims] In a short-time withstand current test method for a switchgear, in which a short-time current having a peak value of a first wave of a predetermined magnitude is applied in a short-time withstand current test for a switchgear, each phase of a three-phase power supply is , The basic phase is R phase, and the phase voltage of this R phase is 120
° The phase of the delayed phase voltage is 120
° When the advanced phase is named T-phase, the R-phase and S-phase are simultaneously turned on at a predetermined phase, the respective phase input devices are turned on at the same time, and after starting the flow, the T-phase is delayed by a predetermined phase. A short-time withstand current test method for a switchgear, characterized in that a charging device is turned on to start flowing. 2. The short-time withstand current test method for a switchgear according to claim 1, wherein instead of simultaneously turning on the R-phase and S-phase throwers, one phase thrower is thrown in advance. A short-time withstand current test method for a switchgear, characterized in that the input device of the other phase is input at a predetermined phase.