JPH0152978B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protective relay device that protects a power system, and in particular to an overvoltage protective relay that protects a power transformer in a power system when it is continuously in an overvoltage state. Regarding equipment.

When voltage is applied to a transformer, an excitation current determined by the excitation characteristics of the transformer flows, but since this excitation characteristic is nonlinear, when the transformer is exposed to overvoltage, the overvoltage ratio increases. The excitation current increases at a much larger rate than the current. Excitation current is originally related to both iron loss and copper loss of a transformer, and is more severe for transformers than reductions such as overload, which have a large effect on copper loss.

On the other hand, for ratio differential relays commonly used to protect transformers, the excitation current appears as a differential current, so the increase in excitation current due to overvoltage described above is a phenomenon in the area where ratio differential relays can operate. However, ratio differential relays are generally high-speed and trip very quickly compared to the overvoltage withstand capacity of the transformer. In some cases, measures are taken to prevent the device from operating under the excitation current during overvoltage.

When taking such measures, it is essential to provide overvoltage protection that matches the overvoltage withstand capacity of the transformer. That is,
Since the overvoltage withstand capacity of a transformer is determined by the excitation loss of the transformer, it is optimal to provide overvoltage protection with strong reaction time characteristics.

The voltage versus operating time characteristics required for overvoltage protection of transformers in power systems are as shown in FIG. In Figure 1, a is a graph showing the voltage vs. operating time characteristic, b is a graph showing the voltage vs. operating time characteristic expressed in semi-logarithm, and the one-dot chain line and the two-dot chain line represent the changes when the operating value fluctuates. It shows the characteristics.

Conventionally, this type of protection device has included an electromagnetic induction disk relay or a static timed relay with a built-in timer. However, electromagnetic induction disc relays have large errors in operating values. For this reason, the conventional device has a drawback that, in the case of ultra-strong reversal time-limited characteristics, the error in the operating time becomes large as shown by the one-dot chain line and the two-dot chain line in FIG. 1b. In addition, conventional devices using static fixed-time relays have drawbacks such as slow operation time even in large input ranges, if long-time setting is used to avoid malfunctions in transient overvoltage conditions that are not caused by transformer failure. It was hot.

Therefore, if the desired protection characteristics are desired, it would be ideal to have strong reaction time characteristics in the entire voltage range, but in reality, it would be better to obtain strong reaction time characteristics in the long-time characteristic portion (low voltage range). This is very difficult due to the voltage value generated by H/W, the integral characteristic error, the error and stability of the test equipment used to confirm the characteristic.

In the short-time characteristic part (high voltage range), there is a final relay calculation delay time, and the only characteristic that can realistically be achieved is that the speed does not drop below a constant speed. There is a possibility that the relay may react to inputs such as surges, which may cause malfunctions as a relay.Inputs above a certain level may be responded to using a general circuit instead of an integrating circuit. Overvoltage detection must be detected by a level detection circuit and a time element.

In addition, the above-mentioned very short-time (surge-like) inputs include overvoltage caused by fero-resonance of the PD during grid charging (no overvoltage occurs on the grid side), overvoltage caused by lightning surges, switching surges, etc. The device has a certain amount of resistance to the surge, and
Systematic measures against such surges (installation of arresters, etc.) are being taken. ), and these are outside the scope of the overvoltage protection of this invention.

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional products. It is an object of the present invention to provide an overvoltage protection device that can easily settle a low voltage region without malfunctioning due to transient overvoltage that is not due to a transformer failure, by making the region have an inverse time limit characteristic.

An embodiment of the present invention will be described below with reference to the drawings. In Fig. 2, in the order of connection, 1 is an operating value setting mechanism, 2 is a rectifying and smoothing circuit, 3 is a level detection circuit, and 4 is a rectifying and smoothing circuit.
5 is a time-limiting element, and 5 is a low voltage detection element composed of 1 to 4 described above.

6 is an operating value setting mechanism, 7 is a rectifying and smoothing circuit, 8 is a function conversion circuit, 9 is an integrating circuit, 10 is a level detection circuit, 11 is an inverse time circuit composed of the above-mentioned 8 to 10, and 12 is the above-mentioned 6, 7. , 11 is a voltage-dependent time limit circuit.

13 is an operating value setting mechanism, 14 is a rectifying and smoothing circuit,
15 is a level detection circuit; 16 is an AND circuit that is open when the output of the time limit circuit 12 is not energized and the output of the level detection circuit 15 is energized; 17 is a time limit element; 18 is above 13-17
This is a high voltage detection element composed of

Reference numeral 19 denotes an OR circuit that performs an OR operation on the low voltage detection element 5, the time limit circuit 12, and the high voltage detection element 18 to obtain a protection output.

FIG. 3 is a voltage vs. operating time characteristic diagram showing a combination of the elements shown in FIG. 2. In the figure, a indicates the operating characteristics of the low voltage detection element 5, b indicates the time limit circuit 12, and c indicates the operating characteristics of the high voltage detection element 18, respectively.

Next, the operation will be explained. Low voltage detection element 5
starts the time-limiting element 4 by the output of the level detection circuit 3, which is energized when the input voltage is in a relatively low voltage range (a shown in FIG. 3), and after counting the time, the OR circuit 19 is activated. supply the output to. In this case, the low voltage detection element 5 needs to have highly accurate and stable operating value versus operating time characteristics.

On the other hand, the function conversion circuit 8 of the time limit circuit 12 has an inverse function characteristic of the time limit characteristic, thereby converting the magnitude of the input voltage and obtaining a time limit by the integrating circuit 9.
Therefore, the inverse timer circuit 1 of the voltage-dependent timer circuit 12
1 has a voltage vs. operating time characteristic that is approximately inversely proportional to, for example, the square of the input voltage.

Note that the integration circuit 9 is reset when the output of the AND circuit 16 of the high voltage detection element 18 is activated. As a result, in the operation region of the high voltage detection element 18, the operation of the high voltage detection element 18 has priority over the operation of the time limit circuit 12. Conversely, in the operating range of the voltage-dependent time limit circuit 12, the output of the time limit circuit inhibits the AND circuit 16 of the high voltage detection element 18, so the high voltage detection element 18 does not energize its output. .

If the characteristics of the high voltage region are lower than the intermediate region, there is no need to reset, but as mentioned above, if the input is a sudden surge type input, the characteristics of the intermediate region are better than those of the high voltage region. As a countermeasure to this problem, the integrating circuit 9 of the time limit circuit 12 is reset in the high voltage region to eliminate the operating range in the intermediate region.

As mentioned above, when the input is in the high voltage range, the integration circuit 9 is reset by the output of the logic circuit 16, that is, the output of the level detection circuit 15.

However, with only the above configuration, the time limit circuit 1
When the input rises at the output point of step 2 and enters the high voltage region, the level detection circuit 15 of the high voltage detection element 18 operates to reset the integration circuit 9, so the output of the time limit element 12 is restored and the final output is will return instantly. This phenomenon itself is
Considering that this originally occurs near the boundary between the intermediate region and the high voltage region, and the final output leads to a tripping operation, there is a possibility of burnout of the output relay, and when measuring the relay characteristics, the output If the voltage becomes unstable and the output is reached by the time limit circuit 12, the logic circuit 16 is required to stop the output of the high voltage element 18.

The reason why the above measures are not taken between the time limit circuit 12 and the low voltage detection element 5 is because the operating time of the low voltage detection element 5 is sufficiently slow and does not require as much detailed emphasis as the high voltage detection element. It is.

With such a configuration, for example, the input voltage rises very slowly and eventually reaches the high voltage sensing element 1.
8, the output of the level detection circuit 15 of the high voltage detection element 18 resets the integration circuit 9 of the time limit circuit 12, thereby preventing the output of the time limit circuit 12 from being reset. I'm here.

Incidentally, in order to determine the so-called priority of the operating region, it is also possible to lock the AND circuit 16 of the high voltage detection element 18 using the output obtained by detecting the level of the output of the rectifying and smoothing circuit 7 of the time limit circuit 12. (not shown), and in this way, priority over operating time is no longer maintained (the high voltage sensing element 18 is always locked by the voltage dependent time limit circuit 12 when the input voltage changes slowly). ).

The combined characteristics of the low voltage detection element 5, the voltage-dependent time limit circuit 12, and the high voltage detection element 18 are as shown in the graph shown in FIG. In other words, the low voltage region is handled by the low voltage detection element 5 which can easily obtain high accuracy, the intermediate region is handled by the time limit circuit 12 with strong reversal timing characteristics that do not malfunction due to transient overvoltage, and the high voltage region is determined by the stable high-speed constant voltage detection element 5. It can be protected by a high voltage sensing element of time-limited nature.

In the above embodiment, in order to increase versatility, an operation value setting mechanism is provided in the circuit of each region, but these are not necessarily necessary, and are unnecessary when one operation time characteristic is sufficient.

As described above, according to the present invention, by combining a low voltage detection element, a high voltage detection element, and a voltage-dependent time-limiting circuit, stable high-speed time-limiting characteristics can be realized in a wide input voltage range, and high reliability can be achieved. An overvoltage protection relay device can be obtained.

[Brief explanation of drawings]

FIG. 1 is a voltage versus operating time characteristic diagram necessary for overvoltage protection, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a voltage versus operating time characteristic diagram according to the present invention. 1, 6, 13...Operating value setting mechanism, 2, 7, 1
4... Rectifier smoothing circuit, 3, 10, 15... Level detection circuit, 4... Time limit element, 5... Low voltage detection element, 8... Function conversion circuit, 9... Integrating circuit, 11
... Anti-time circuit, 12 ... Time limit circuit, 16 ... AND circuit, 17 ... Time limit element, 18 ... High voltage detection element, 19 ... OR circuit.

Claims (1)

[Claims] 1. A low voltage detection element that activates a time element when it detects that the input voltage detected from the protected object has entered a predetermined first setting voltage range and outputs an output after a predetermined time limit, and the first setting described above. A function conversion circuit that converts an input voltage included in a second set voltage range higher than the voltage range by a predetermined function, an integration circuit that integrates the output of the function conversion circuit, and an output of the integration circuit that is equal to or higher than a predetermined level. a time limit circuit having a detection circuit that outputs an output when the input power is equal to or higher than a third set voltage range higher than the second set voltage range, and the output of the time limit circuit is not energized; a high-voltage detection element that activates a time-limiting element, resets the integration circuit, and outputs after a predetermined time; a logic circuit that obtains an overvoltage protection output by a logical sum of the low-voltage detection element, the time-limiting circuit, and the high-voltage detection element; Overvoltage protection relay device with