JPS6223316A - Digital type current differential protective relay - 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 [Field of Industrial Application] The present invention relates to a digital current differential protection relay device for protecting power transmission lines.

[Conventional technology]

Figure 2, for example, is from the proceedings of the National Conference of the Institute of Electrical Engineers of Japan in 1982.
1084 is a system configuration diagram showing a conventional digital type 11ER differential protection relay device shown in FIG. In the figure, 1 is the power transmission line to be protected, 2 is the transmission line'r! A current transformer (CT; CU) that detects the current flowing in L line 1
(referred to as RRENT TRANSFORMER).

3 is the above C'! 5 is an input converter that converts the current of the power transmission i1 outputted from the input converter 3 into a signal level; 5 is an A/D converter that converts all the analog 'Iji flow signals input from the input converter 3 into digital signals; (A/D i
ANALOG/DIGITAL), 6 a central processing unit (hereinafter referred to as CPU) that performs protection calculations using the output signal of the FiA/D converter 5; It is a vessel.

4 is a control circuit section having an A/D conversion section 5 and a CPU 6.

Next, the operation will be explained. Before going into details, the performance of the A/D converter 5 will be briefly described. First, recent A/D conversion elements come in various types as the number of bits when converted into a digital signal, such as 8 bits, 10 bits, and 12 bits. However, with digital protective relay devices, the cost, reliability, resolution, etc. of 12-bit A/L are all considered.
Conversion elements are often used. Therefore, a case will be considered here in which a 12-bit A/D conversion element is employed. 1
Even though it is 2 bits, 1 bit is a positive or negative sign, so only 11 bits can be used as data. Since the master analog section uses an operational amplifier, etc., the maximum input voltage is ±I.
OV is common. That is, +10V (or -10V
) is input, the output of the A/D converter 5 becomes maximum.

Therefore, when the current flowing through the power transmission line reaches its maximum, A/
It is necessary to design the input converter 3 so that the voltage input to the D converter 5 does not exceed ±10V. for example.

The maximum current flowing through power transmission line 1 is 30KA, and the CT ratio is 3.
At the time of 000A15A, the maximum input terminal to the input conversion device 3 is . Therefore, the input conversion device 3 needs to be designed to output ±10V when there is an input of 50A.

At this time, when A/D i is converted, since 5OA is converted by 11 bits, the current value of one bit shift (referred to as the weight of one bit) becomes 50 A x -=0.0244 A2I+, -1.

[Problem that the invention seeks to solve]

The input conversion device of the conventional digital current differential protection relay device is configured as described above, so if this device is installed on a power transmission line where the CT ratio of the current transformer 2 is small (
For example, if a device designed with a CT ratio of 3000A15A is
In the case of installation on a power transmission line with a T ratio of 2000A and 15A), or in the case where the maximum current becomes even larger, the input to the A/D converter 3 will exceed ±10V.

At this time, since the A/D conversion is not performed correctly, the CPU 5 may perform calculations using incorrect data, resulting in problems such as the possibility of unnecessary responses.

This invention was made to solve the above-mentioned problems, and it ensures that the input to the A/D converter does not exceed the maximum value even if various conditions such as the CT ratio and maximum current of the power system change. The object of the present invention is to obtain a digital current differential protective relay device that converts the current value of a CT into an analog value.

[Means for solving problems]

In the input conversion device of the digital type tN differential amnestic relay device according to the present invention, when the current value output from the CT is maximum, the output of the input conversion device is ± the input limit of the A/D conversion section. A tag is provided in the input conversion transformer in the input conversion device so that the IOV is not exceeded.

[For production]

The input conversion device according to the present invention samples the current flowing through the power transmission line, and measures the system current by switching the taps of the input transformer within the input conversion device depending on the magnitude of the current at that time.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same parts as in FIG. 2 have the same reference numerals. In FIG. It is a panel.

Next, the operation will be explained. First, set the feed to the maximum of the line [flow 7
) When f30KA and CT ratio are 3000A15A,
That is, the maximum output current of CT2 is 30KAx3ooo=5O
Assume that the design is such that when the tap 8 of the transformer of the input converter 3 is short-circuited at the time of A, the output becomes ±IOV at the maximum input level of the A/D converter 5. and,
If the CT ratio is 2000A15A, CT2
Of course, the maximum output current is 30 K A x 2ooo=
It becomes 75 A, which is larger than the above-mentioned 5OA. If you leave tap 8 as is, the output of the input conversion transformer will be ±IO.
Since it exceeds V, switch tap 8 to connect tap 9 to this rib. If tap 9 is designed so that the input is 75A and the output is ±IOV, the output will be ±IOV.
A/D conversion will be performed correctly without exceeding V. Similarly tap 10. Similarly, if you set tap 11 etc. so that the maximum current does not exceed the possible maximum current, even if the maximum current changes due to fluctuations in system conditions, correct A/D conversion can be achieved by using the corresponding taps. can do. However, when the input conversion device 3 switches the taps, the output current of the CT2 becomes a value corresponding to each tag and is input to the CPU 5, so the CPU 6 can know the output voltage of the input conversion device 3, but The output flow becomes unknown. In addition, since the protection device manages the system using the output current of CT2, by inputting which tap is currently used to the CPU 5 in advance from the setting panel 12, etc., the conversion value corresponding to that tap can be set. becomes clear, and the correct output current of CT2 can be calculated.

Further, in the above embodiment, a tap is provided on the primary side of the transformer in the input conversion device, but the tap may be provided on the secondary side. Furthermore, the input conversion device of the present invention is applicable to protection relays other than current differential relays.

〔Effect of the invention〕

As described above, according to the present invention, the device is configured so that the tap of the transformer in the input converter can be selected in accordance with the maximum current of the power system, so that the current value of the power transmission line changes significantly. Even in such a case, the measurement conditions can be changed immediately, resulting in a highly accurate protective relay device.

[Brief explanation of drawings]

FIG. 1 is a system configuration block diagram of a digital type current differential protective relay device according to an embodiment of the present invention, and FIG. 2 is a system configuration block diagram of a conventional digital type squirrel current differential protective relay device. In the figure, 1 is a power transmission line, 2 is a CT, 3 is an input conversion device, 5 is an A/D conversion unit, 6 is a central processing unit, 8 to 11
is a tap. Patent applicant Mitsubishi Electric Corporation Agent Patent attorney 1) Hiroshi Sawa (2 others)

Claims (1)

[Claims] To protect multi-terminal power transmission lines in power systems, digital current differential protection measures the current at each terminal at a predetermined cycle, converts it with an A/D converter, and then inputs it to the central processing unit to protect the system. In the relay device, an input transformer with a tap that switches according to the magnitude of the current flowing through the power system is provided in the input conversion device, and the position of the tap is input to the central processing unit from a setting panel. A digital current differential protection relay device characterized by the following.