JPS59191419A - Protecting relaying unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protective relay device for a power system.

As is well known, the protective relay device is configured to use analog value electrical information detected from multiple points in the power system as an input signal, and to constantly execute processing for a protective operation.

Conventionally, as this type of device, there have been busbar protection relay devices shown in FIGS. 1, 2, 3, and 4.

In Figure 1, 18 to 1f are power transmission lines, 2 is a bus bar, and 3a
3f is a transformer, and 4 is a bus protection relay device. In FIG. 2, 5 is a filter, 6 is an A/D converter, I is a central processing unit (CPU), 8 is a memory, 9 is a setter, and 10
is the output circuit. In FIG. 3, 11 is a sample and hold circuit, 12 is a multiplexer CMPX), 13 is an analog digital converter (A/DJ converter), and 14 is an input transformer.

Next, the operation will be explained. The bus protection relay device 4 introduces the current transformed by each transformer 3a to 3f of the transmission lines 1a to 1f, that is, the input signal, and calculates the difference current between each terminal. It is used to detect accidents.

The busbar protection device thus has to introduce a large number of inputs, and each of these inputs must be converted correctly. If this conversion is not performed correctly and the error current becomes large (if this happens, it will be mistakenly determined that there has been an accident on the bus 2). Figure 2 shows a block diagram of the bus protection relay device 4. The current converted by the transformer 3 is input and introduced into the transformer 14, where it is converted to a voltage level suitable for the following circuit, and then introduced into the filter 5.The filter 5 converts the harmonics contained in the input signal. The components are removed and supplied to the next A/D converter 6.

The A/D converter 6 converts the input signal from an analog value to a digital value. Next, according to the program recorded in the memory 9, the CPU 7 reads the output signal of the A/D converter 6 and performs arithmetic processing for a predetermined protection operation. In this process, the CPU 7 compares the input signal with a setting reference value (tap value) stored in the regulator 9, and determines whether or not there is an accident on the bus 2. If an accident is detected, the CPU 7 outputs a signal via the output circuit 10. Outputs a signal to shut off a circuit breaker (not shown).

FIG. 3 is a block diagram of the A/D converter 6.

The analog input derived by filter 5 is sample-
The input value is input to the hold unit 11, and the input value at a certain time is sampled and held so as to maintain the simultaneity of each input. Next, each held analog value is input to the multiplexer 12, and is sequentially selected to the A/D converter 1.
3 is input.

Generally, A/D conversion requires 12 pits or more in order to satisfy the performance required for detection sensitivity and accuracy of the protection device. Therefore, if such input is 12
In order to perform A/D conversion for bits or more, a conversion time of several tens of microseconds is required.

In other words, in order to improve the performance of the protection device, it is necessary to use a multi-pit A/
A D converter is required, but on the other hand, the conversion time is long.A bus protection relay device requires many inputs, and the difference current between each input value is calculated to detect the presence or absence of an accident, so each The current must be input correctly.

For example, in the case of an external fault on the busbar, the current phase of all terminals will flow in the faulty line, and a very large current will flow. Therefore, the fault line transformers 3a-3e or 3f become saturated. If the current is not converted correctly, even if no fault current flows, the difference current between the converted input values of all terminals will become a dog.
Causes the relay device to operate unnecessarily. Therefore, the bus protection relay device needs to be determined in a region where the transformer is not saturated. Generally, this time is approximately 60H at an electrical angle of 30° to 45°.
In the z system, it is 1.38 ms to 2 ms. Multi-terminal, ie, multi-input, analog-to-digital conversion must be performed within this time. Moreover, within this time, it is necessary to prepare data for several samples to provide redundancy necessary for protection operation processing.

Therefore, the sampling interval is approximately 300 μs (1.8 ms
÷6=0-3ms). As mentioned earlier, 12
The conversion speed of an A/D converter with a length of 30~30~
It is 40 μs. When configuring a device using this A/O converter, the number of input points for one A/D converter is approximately 7 (300 μs÷40 μ5=−7). In the case of n input points, seven A/D converters are required, and as shown in FIG. 4, six or seven A/D converters are required. A/
D converters are very expensive compared to other logic circuits, etc., so if a large number of D converters are provided, the device 4. becomes expensive.

Since the conventional device is configured as described above, it requires a plurality of A/D converters, which has the drawback of making the device very expensive. In addition, since a plurality of devices are required, a large space is required and the device is bulky.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it requires one person to install a plurality of sample and hold circuits, sample each at a different timing, sequentially switch inputs, The purpose of the present invention is to provide a protective relay device that can be made inexpensive even with multiple terminals and multiple inputs by performing /D conversion.

An embodiment of the present invention will be described below with reference to the drawings. Fifth
In the figure, lla is a sample hold circuit that samples and holds input data at the time of T, 11b is a sample hold circuit that samples and holds input data at 12 o'clock,
11n (n=c, d...) is a sample and hold circuit that samples and holds input data at time Tn. The rest of the structure is the same as the conventional one.

Next, the operation will be explained. At T□, the sample and hold circuit 11a samples the sample, at the next 12 o'clock, the sample and hold circuit 11b holds the sample, and at Tn, the sample and hold circuit 11n holds the sample. In this way, the sample and hold section 11 connects a plurality of sample and hold circuits 11a to 11n in parallel to one input terminal, and sequentially performs sample and hold.

Note that since the sample hold section 11 is constituted by an operational underifier, it can be used in a filter circuit, and the unit price can be obtained at a very low price due to recent advances in integrated circuit manufacturing technology. The fault detection time of a protective relay device is generally about several tens of milliseconds, and even at high speeds it may be about 10 m5. On the other hand, the time of input data that can be determined is about 2 mS, and the remaining 8 ms (1
0ms - 2m5), the CPU 7 may perform the accident determination.

Also, compared to the A/D converter, the CPU 7 is extremely fast, running in several hundred ns.
It works. The input values held by the sample hold section 11 are sequentially switched and derived by the multiplexer 12, and the A/D
The analog input signal is introduced into the converter 13, and the analog input is converted into a digital value, and the CPU 7 calculates and makes a determination. The other input terminals are installed and operated in the same manner.

Further, in the above embodiments, a busbar protection device has been described, but other power transmission line protection devices may be used. Also, although a low-speed A/D converter is used, a high-speed one may be used. Also, although the differential method has been described, the same effect can be obtained even if the method is not differential (or multi-terminal input phase, product, or quotient).

As described above, according to the present invention, the sample and hold circuits are connected in parallel and there is no need to add each card, so the device can be made inexpensive, compact, and highly reliable and accurate. There is an effect that can be obtained.

[Brief explanation of the drawing]

Figure 1 is a power system system diagram 1, Figure 82 is a configuration diagram of a digital protective relay device, Figure 3 is a detailed block diagram of an A/D converter, and Figure 4 is a conventional multi-terminal multi-input A FIG. 5 is a block diagram of an A/D converter in a digital protective relay device according to an embodiment of the present invention. 13~1f...Power transmission line, 2...Bus bar, 33~3f・
- Transformer, 4... Bus bar protection relay device, 5... Filter, 6... A/D conversion unit, 7... CPU,
8... Memory, 9... Setter, 10... Output circuit, 11... Sample and hold section, 12... Multiplexer, 13... A/D converter. In addition, the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 'In a protective relay device that sequentially samples and inputs electrical quantity signals from multiple points in a power system, converts them from analog to digital, and performs digital calculation processing for protective operation,
It is equipped with multiple sample-and-hold circuits whose sample times are sequentially shifted for each input, and a multiplexer that multiplexes the outputs of these sample-and-hold circuits, and the output of this multiplexer is converted from analog to digital. Protective relay device.