JPH08227639A - Simulation method for multiple reignition surge - Google Patents

Abstract

PURPOSE: To enable a faithful simulation of spiking voltage, which is frequently generated in the actually measured waveform, so as to simulate the multiple reignition by turning off a switch, which equivalently operates a breaker, when the high frequency current passes through the zero pint. CONSTITUTION: The condition for turning ON (generation of multiple reignition) and OFF a switch for simulating a breaker is set as follows. Intensity of the electric field between electrodes is obtained on the basis of the voltage of both ends of a switch per each computing step. When this electric field intensity exceeds the flash-over level, the flash-over condition is generated, and the switch-on signal is generated in the switch control signal so as to obtain the switch closing signal. At this stage, the processing for deciding the flash-over level is decided on the basis of the static withstand voltage, which depends on the gap length of a breaker, and the withstand voltage restoring characteristic, which depends on the passing time after the current is cut-off. High frequency current is cut-off when it passes through the zero point independently of the di/dt value. The current flowing in the switch is monitored, and the cut-off signal is generated on the basis of the detection of passing of the current through the zero point, and the control signal for opening the switch is thereby obtained. The restoring signal of the cut-off signal is obtained by the generation of the flash-over level from the flash-over level deciding process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for simulating multiple re-ignition surges generated in a vacuum circuit breaker, and more particularly to a simulation method using a general-purpose transient analysis program EMTP.

[0002]

2. Description of the Related Art When an inductive load current is interrupted by a vacuum circuit breaker, multiple re-ignition surges occur in which arcing and interruption are repeated under appropriate conditions, and voltage buildup occurs. This will be described in detail below.

FIG. 4 shows voltage and current waveforms when an arcing surge occurs. Normally, the breaking command to the switch is output regardless of the phase of the breaking current, so the time (arc time) from the moment when the electrodes of the switch start to mechanically separate to the breaking of the current has various values. Will be taken.

When the arc time is long, as in the case of the open contact point a in the figure, the voltage between the electrodes after the interruption is sufficient because the electrodes are sufficiently open before the current is actually interrupted. Can withstand.

However, if the arc time is short as in the open contact point b, the generated voltage exceeds the withstand voltage between the electrodes before the electrode interval is sufficiently widened, and the electrodes are flashed and connected again by the arc ( (Point c in the figure). This phenomenon is called an arc surge, and a high frequency current (arc current) flowing through the circuit around the switch and a commercial frequency current from the power source flow between the electrodes.

Since the arcing current creates a current zero point, the arcing current that has started to flow is interrupted again (point d in the figure), and a voltage is generated between the electrodes. This voltage causes a flashover between the poles again (point e in the figure), and the generated voltage rises while repeating the same process. This is called a multiple recurrence surge.

FIG. 5 and FIG. 6 show a circuit diagram and a waveform diagram for explaining the voltage rise due to multiple re-ignition surges. Inductance L which is a load from the commercial power source via switch SW
In the circuit for passing a current to the load side, the load side voltage is generated by the oscillating current in the loop of LC formed by the load side capacitance C and the inductance L. This fluctuation is similar to the cutting surge generation mechanism and is called a cutting loop.

When an arc occurs at point a in FIG. 6, an arc current flows through the loop of capacitor C _S -SW-C (referred to as an arc loop) in FIG. 5, and this arc current flows for several cycles and is cut off. In many cases, the electrodes are connected by an arc while the arcing current is flowing, and the current flows not only in the arcing loop but also in the loop of the power supply-SW-L (main loop).

A commercial frequency current flows from the power source to L through this main loop, and energy is injected into L. The change in the current flowing through L is such that energy is injected into L through the main loop during the period T1, the arcing current is cut off during the period T2 and energy is transferred from C to L through the cutting loop, and the current flowing through L during the period T3. Energy reaches from L to C after the peak of the peak and before the next arc occurs.

The increment of the energy of L during one cycle from these periods T1 to T3 is the energy received in the periods T1 and T2 minus the energy released in the period T3.

The voltage generated by the multiple re-ignition surge rises because the energy (current) of L increases as the above cycle is repeated and the energy can be changed to voltage during the period T3. Is increased, and this and the breakdown voltage between the electrodes due to the increase in the gap length of the switch increase the generated voltage.

As described above, the arcing surge is a complicated phenomenon, and it is difficult to analytically obtain various circuit configurations. Therefore, simulation methods are being developed.

Simulation of the arcing surge requires modeling of the withstand voltage characteristic of the circuit breaker, the high frequency current (arcing surge) interruption characteristic, and the circuit.

Of these, a general-purpose transient analysis program EMT
When performing an arcing surge simulation using P, the circuit breaker is replaced with a switch, and the state of firing is simulated by closing the switch and the state of breaking is simulated by opening the switch.

FIG. 7 shows a block diagram of conventional switch control signal generation processing. With the switch open,
The electric field strength between the electrodes is obtained from the voltage across the switch for each calculation step (S1), and when the electric field strength exceeds the flashing level obtained by the experiment, a flashing state is generated (S1).
2) As a result, a switch ON signal is generated as a switch control signal (S3), and a control signal for closing the switch is obtained.

When the switch is closed, the high-frequency current cannot be cut off unless it is at the zero point. Therefore, the current flowing through the switch is monitored to detect whether it has passed the zero point (S4), and the current change rate di / It is detected that dt is below the set level (S5), a cutoff signal is generated by simultaneous establishment of both detections (S6), and a control signal for opening the switch is obtained. The cutoff signal is restored when the set cutoff level is exceeded.

[0017]

8 [SUMMARY OF THE INVENTION] shows an example of arcing surge test circuit, simulating the commercial frequency by discharging through the reactor L ₁ from the capacitor C ₁ which is charged with on of the main switch MS, the In this state, the circuit breaker CBt is opened and its phase is controlled to cause a re-ignition surge. C ₂ and L ₂ are the frequency (high frequency) of the arcing surge current
To adjust.

When multiple re-ignition surges are measured using the above test circuit, a voltage including a spike-like voltage is generated between the firing and the interruption as shown in FIG. In this voltage waveform, V ₀ is the initial flashing voltage that first flashes after the voltage is applied, V _SP is the spike-like voltage that occurs during current application, and V _R is the flashing voltage that occurs after the high-frequency current is interrupted. It is the re-ignition voltage.

Since the spike-like voltage V _SP corresponds to the zero point of the arcing current, it is considered that the high-frequency surge voltage immediately after the interruption of the current could not withstand the high voltage surge voltage and immediately ignited. .

However, in the switch control signal generating process according to the conventional simulation method, the interruption is determined depending on whether the di / dt value at the zero point of the arcing current is less than or equal to the set level, so that it actually occurs frequently. Unable to simulate spike voltage.

Also, the equivalent circuit of the circuit breaker is replaced by a switch SW as shown in FIG. 10, and the CR is connected to the ground.
However, the spike-like voltage rises in the calculation time interval (1 step). This means that when L is connected in series to the switch (when dealing with high frequency such as multiple recurrence, it is necessary to consider the residual conductance), Ldi / dt
This is because a voltage shift corresponding to is generated between the electrodes.

The actual spike-like voltage shows a waveform that rises with a certain time constant, whereas in the conventional equivalent circuit, it rises with a fixed time constant determined by the vibration preventing CR circuit or the like when the switch is turned off. , It is not possible to exactly simulate the rise of spike voltage.

The initial flashover voltage V ₀ and the re-ignition voltage V _R
Similarly to the rise of the spike-shaped voltage, the initial rise of is not strictly simulated.

It is an object of the present invention to provide a simulation method for obtaining a simulation waveform faithfully simulating an actually measured waveform in the simulation of multiple re-ignition surges of a vacuum circuit breaker using a general-purpose transient analysis program EMTP.

[0025]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a general-purpose transient analysis program EMTP for detecting multiple recurrence surges that occur when a load is cut off by a vacuum circuit breaker.
In the simulation using, the equivalent circuit of the circuit breaker sets a series circuit of a capacitor and a resistor in parallel with the switch, the capacitance of the capacitor is adjusted to the gap capacitance of the circuit breaker, and the resistance value of the resistor is Matching the time constant with the capacitor to the initial flashover voltage of multiple re-ignition and the rising time constant of re-ignition voltage, the multiple re-ignition ignition is simulated by turning on the switch, and the static breakdown voltage and current applied to the circuit breaker The flashover level is determined by the withstand voltage recovery characteristic that depends on the elapsed time after the cutoff, and when the inter-electrode voltage of the switch exceeds the flashover level, the ON signal of the switch is obtained, and the multiple re-ignition is cut off. This is simulated by turning off the switch, and an off signal of the switch is obtained when a current flowing through the switch passes through a zero point.

[0026]

In order to simulate multiple re-ignitions, the switch equivalent to the circuit breaker must be turned off when the high-frequency current passes through the zero point, so that the spiked voltage that frequently occurs in the measured waveform can be faithfully reproduced. To be able to simulate.

The flashover level which is the condition for turning on the switch is
By determining the static breakdown voltage depending on the gap length of the circuit breaker and the breakdown voltage recovery characteristic depending on the elapsed time after current interruption, the flashover of the circuit breaker can be faithfully simulated.

A CR series circuit is provided in parallel with the switch constituting the equivalent circuit of the circuit breaker, the capacity of the capacitor is adjusted to the gap capacitance of the circuit breaker, and the time constant with the resistor is set to the initial flash voltage and the re-ignition. By adjusting the rising time constant of the voltage, it is possible to faithfully simulate the initial waveform of the spike-like voltage generated after the current interruption.

[0029]

1 is a block diagram of a switch control signal generation process showing an embodiment of the present invention. In the figure, the same processes as those in FIG.

In the present embodiment, the conditions for turning on the switch simulating the circuit breaker (ignition of multiple re-ignitions) and off (breaking multiple re-ignitions) are as follows.

(1) Switch on condition The electric field strength between the electrodes is obtained from the voltage across the switch at each calculation step (S1), and when the electric field strength exceeds the flashover level, a flashover state is generated. (S2), which generates a switch ON signal in the switch control signal (S2).
3) Get the control signal to close the switch.

Here, the process of determining the flashover level (S
7) is determined by the static withstand voltage that depends on the gap length of the circuit breaker and the withstand voltage recovery characteristic that depends on the elapsed time after current interruption. The flashover level V _SPK can be determined, for example, by the following equation.

[0033]

[ _Formula ] V _SPK = V ₀ × exp (-Δt / τ) V ₀ : Static breakdown voltage τ: Time constant of breakdown voltage increase Δt: Elapsed time from current 0 (2) Switch off condition High frequency current is di / dt value Regardless, it always shuts off when passing through the zero point. Therefore, the current flowing through the switch is monitored to detect whether it has passed the zero point (S
4) Generates a cutoff signal upon detection of this zero point passage (S
6) Get the control signal to open the switch. The return signal of the cutoff signal is obtained by the occurrence of the flashover level from the flashover level determination process (S7).

As described above, by determining the on / off condition of the switch, the switch is turned on when the inter-electrode voltage exceeds the flashover level, and the switch is turned off at the current zero point after turning on. The current is always cut off, and a spike-like voltage can be generated at this timing.

In the conventional simulation method,
The di / dt value at the current zero point is obtained, and the cutoff level is set from this. Since this di / dt value depends on the frequency of the high frequency current, it is affected by the circuit constant around the circuit breaker. That is, in the conventional method, di /
It is necessary to change the interruption level of the dt value, and for this purpose it is necessary to obtain the interruption level in advance by a test or the like.

On the other hand, in the present embodiment, the di / dt value can be ignored depending on the cutoff determination condition, which is simplified.

Next, in this embodiment, as shown in FIG. 2, an equivalent circuit of the circuit breaker is connected in parallel with the switch SW and the capacitor C.
A series circuit of ₀ and resistance R ₀ is set. Of these, the capacitance of the capacitor C ₀ is determined in association with the value of the gap capacitance, and the resistance value of the resistor R ₀ has a time constant with the capacitor C ₀ that is the initial flashover voltage V ₀ and the re-ignition voltage. determined in accordance with the time constant for the rise of V _R.

As a result, in this embodiment, the rising of the initial flash voltage V ₀ and the re-ignition voltage V _R can be simulated, and the actual multiple re-ignition surge phenomenon can be strictly simulated.

FIG. 3 shows an example of multiple re-ignition surge waveforms calculated by EMTP based on the present embodiment, and a waveform well simulating the actually measured waveform of FIG. 9 could be obtained.

[0040]

As described above, according to the present invention, the switch equivalent to the circuit breaker always turns off the switch when the high-frequency current passes through the zero point, so that the flashover level which is the on condition of the switch is cut off. Determined by the static breakdown voltage that depends on the gap length of the circuit breaker and the breakdown voltage recovery characteristics that depend on the elapsed time after the current is cut off, a CR series circuit is installed in parallel with the switch, and the capacitance of the capacitor is the capacitance between the gaps of the circuit breaker. Together,
Since the time constant with the resistor is adapted to the rising time constants of the initial flashover voltage V ₀ and the re-ignition voltage V _R , the following effects are obtained.

(1) It is possible to faithfully simulate the spike-like voltage that frequently occurs in the actually measured waveform.

(2) The flashover of the circuit breaker can be faithfully simulated.

(3) The initial waveforms of the initial flash voltage V ₀ and the re-ignition voltage V _R generated after the current interruption can be faithfully simulated.

(4) The di / dt value for generating the cutoff signal is unnecessary, and the test for determining the cutoff level is unnecessary.

[Brief description of drawings]

FIG. 1 is a block diagram of switch control signal generation processing according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit of a circuit breaker according to an embodiment.

FIG. 3 shows an example of multiple re-arcing calculation waveforms by simulation based on the embodiment.

FIG. 4 is an explanatory diagram of an arcing surge.

FIG. 5 is a circuit diagram accompanied by the occurrence of arcing surge.

FIG. 6 shows a voltage / current waveform when the voltage rises due to an arcing surge.

FIG. 7 is a block diagram of conventional switch control signal generation processing.

FIG. 8 is an arc surge test circuit diagram.

FIG. 9 shows an example of an actually measured waveform of multiple re-ignition surges.

FIG. 10 is an equivalent circuit of a conventional circuit breaker.

[Explanation of symbols]

Switch C to simulate the SW ... breaker, C ₀ ... capacitor R, R ₀ ... resistance L ... inductive load

Claims (1)

[Claims] 1. A general-purpose transient analysis program EMTP to detect multiple re-ignition surges that occur when a load is cut off by a vacuum circuit breaker.
In the simulation using, the equivalent circuit of the circuit breaker sets a series circuit of a capacitor and a resistor in parallel with the switch, the capacitance of the capacitor is adjusted to the gap capacitance of the circuit breaker, and the resistance value of the resistor is Matching the time constant with the capacitor to the initial flashover voltage of multiple re-ignition and the rising time constant of the re-ignition voltage, the multiple re-ignition ignition is simulated by turning on the switch, and the static breakdown voltage and the current applied to the circuit breaker. The flashover level is determined by the withstand voltage recovery characteristic that depends on the elapsed time after the cutoff, and when the inter-electrode voltage of the switch exceeds the flashover level, the ON signal of the switch is obtained, A method for simulating multiple re-ignition surges, which is simulated by turning off the switch and obtains an off signal of the switch when a current flowing through the switch passes through a zero point.