JPH0125294B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a carrier protection relay device that can transmit a plurality of current information through a single transmission channel using a frequency modulation transmission method.

[Prior Art] Conventionally, this type of device has been developed and applied for the purpose of multi-terminal protection for ultra-high voltage systems and above, and is described in Electric Cooperative Research No. 32, published in September 1975.
There are some items described in Volume 3, ``Multi-terminal Power Transmission Line Protection Relay'' (Electricity Cooperative Research Association). According to pages 88 to 89 of the said document, the current at each terminal is converted to voltage, the instantaneous voltage value is frequency modulated and transmitted to the other end, and at the same time, the frequency modulated signal from the other end is demodulated and the difference is generated along with the own end information. The system is configured to use a dynamic circuit to determine whether the failure point is internal or external.

[Problem that the invention seeks to solve]

However, the configuration of the device has an independent function for each electrical quantity, that is, each phase current, and a circuit is configured for each phase, and a signal transmission channel is also required for each phase, but in the main system of ultra-high voltage or higher, Communication lines are well-developed, and it is relatively easy to secure multiple transmission channels.

On the other hand, in a high-resistance grounding system, the fault current in the case of a single-wire ground fault is much smaller than the fault current in the case of a fault in two or more wires, so for a fault in two or more wires, the positive sequence current I ₁ , Zero-sequence current for single-line ground fault
Since it is possible to perform the differential protection by introducing I ₀ , a transmission channel is required for two electrical quantities, the positive sequence current I ₁ and the zero-sequence current I ₀ .

However, in general high-resistance grounding systems, it is often difficult to provide a transmission channel for each quantity of electricity.

This invention was made to solve this problem, and it is possible to easily transmit two types of electrical quantities, the positive sequence current I ₁ and the zero-sequence current I ₀ , without providing a transmission channel for each electrical quantity. The object of the present invention is to obtain a transport protection relay device that can transmit each of the above amounts of electricity through one transmission channel.

[Means for solving problems]

The carrier protection relay device according to the present invention is provided with means for superimposing a sideband signal outside the signal band in which current information is modulated and transmitted, and detects the presence or absence of the sideband signal and converts it into first current information. This is provided with means for determining and transmitting the second current information.

[Effect]

In this invention, a sideband signal is superimposed on current information according to the failure state of the power transmission line, the current information is transmitted to the other end, and the presence or absence of the sideband signal is detected at the other end, and then the current information is Sends current information to the determination circuit for Therefore, multiple pieces of current information can be switched and transmitted through a single transmission channel depending on the presence or absence of sideband signals.

〔Example〕

FIG. 1 shows an embodiment of the present invention, showing the configuration of a device installed at one terminal of an electric power system, and the same device is installed at other terminals. In Fig. 1, 1 is a positive sequence current I ₁ by introducing each phase current from a current converter CT.
The current that outputs the voltage at the predetermined conversion ratio −
Voltage converter, 2 is zero-sequence current I ₀ from current transformer CT
A current that outputs a voltage at a predetermined conversion ratio by introducing -
A voltage converter, 3 is a voltage-frequency converter that frequency modulates the output of the current-voltage converter 1, 4 is a current-frequency converter that frequency modulates the output of the current-voltage converter 2, and 5 is a voltage-frequency converter. 6 is a short-circuit fault detection relay that detects faults in two or more wires by introducing each phase voltage from the voltage transformer PT, 7 8 is an inhibit circuit, 9 is an energizing circuit for the switch 5, and 10 is the output of the inhibit circuit 8. 11 is a general operational amplifier that combines the sideband signal output from the oscillation circuit 10 with current information having a predetermined frequency band, which is the output of the voltage-frequency converter 3 or 4. The circuit configuration is an adder, 12 is an attenuator for adjusting the level of the signal to be transmitted, 13 is an isolation transformer for signal transmission, 14 is an isolation transformer for receiving the signal from the other end, and 15 is an attenuator for adjusting the level of the signal to be transmitted. an attenuator for adjusting the level; 16 a bandpass filter for deriving only the signal for current information from the received signal; 17 a frequency-voltage converter for demodulating the output of the bandpass filter 16 into a voltage signal; 18 19 is a level detector that detects the presence or absence of the output of the low-pass filter 18; 20 is an energizer that outputs an output when the output of the level detector 19 is generated; circuit, 21 is an energizing circuit 20
22 is a positive sequence current
Judgment circuit that makes differential judgment based on I ₁ , 23 is zero-sequence current
This is a judgment circuit that makes a differential judgment based on I ₀ . Although FIG. 1 does not show a transmission delay compensation circuit and a noise detection circuit that are essential to this type of device, they are omitted because they are not directly related to the purpose of the present invention.

FIG. 2 shows the delay time characteristics of the transmission line in a microwave line, and shows that the delay characteristics are flat in the center even in the voice band (0 to 4 KHz). Therefore, as shown in Figure 3, when frequency modulating current information, it is common to set the center frequency _f0 to around 2000Hz and the maximum modulation width Δf to about 1000Hz, that is, the current "zero" point is the center frequency f0. ₀ , and the upper and lower limits of the maximum current amplitude are modulated to f ₀ ±Δf. Therefore, by placing the sideband f outside the band, signals other than current information can be superimposed.

The detailed operation of this embodiment will be explained using the following FIGS. 1 and 3.

When a fault occurs in one or more lines in the power system, the short-circuit fault detection relay 6 responds and energizes the negative gate of the inhibit circuit 8. Therefore, regardless of the operation of the ground fault detection relay 7, the output of the inhibit circuit 8 is does not occur, therefore, the switch 5 remains in the state shown in Figure 1, and the frequency modulation signal corresponding to the positive sequence current _I1 is transmitted to the other end, but since the energizing circuit 9 is inoperative, The oscillation circuit 10 is not activated and the third
The sideband wave f in the figure remains unincluded. Since the other end responds in the same way, the received signal does not contain sideband waves, no output is generated in the low-pass filter 18 and level detector 19, and the switch 21 remains in the state shown in FIG. 1. A positive sequence current at the own end and a positive sequence current at the opposite end are introduced into the determination circuit 22 to perform differential determination.

If a single line ground fault occurs in the power system,
Since the short circuit failure detection relay 6 does not respond and only the ground fault detection relay 7 responds, the inhibit circuit 8
An output is generated, and the energizing circuit 9 responds to switch the switch 5, and at the same time, the sideband signal transmitting means 1-1
The oscillating circuit 10 that constitutes the circuit operates to generate a sideband f, and the adder 11, which is a component of the sideband signal superimposing means 1-2, combines the frequency modulated signal corresponding to the zero-sequence current _I0 and the sideband wave. f is combined and transmitted to the other end. Since the signal from the other end also contains the sideband f, the bandpass filter 16 constituting the current information discriminating means 1-3 determines f ₀ ± from the current information.
The zero-phase current information modulated to the Δf (2000Hz±1000Hz) band frequency is filtered out, while the low-pass filter 18 also filters out a sideband signal having a frequency component lower than the band frequency than the current information. As a result, the low pass filter 1
The output of No. 8 is detected by the level detector 19, and the detection output activates the energizing circuit 20, which activates the switch 21.
is switched to the determination circuit 23 side. This judgment circuit 2
A zero-sequence current that has been voltage-converted by a frequency-voltage converter 17 is input to the switch 3 through a switch 21 . As a result, the determination circuit 23 performs a differential determination between the zero-sequence current at its own end and the zero-sequence current at the opposite end.

In addition, in the above explanation, the presence of sideband waves is treated as a one-line ground fault,
Although the absence of sideband waves is defined as a failure of two or more lines, the effects of the present invention are the same even if this relationship is reversed.

In addition, current information can be expressed as positive sequence current I ₁ and negative sequence current I ₂ , etc.
It goes without saying that the present invention is applicable to transmitting different current or voltage information.

〔Effect of the invention〕

As described above, according to the present invention, first current information modulated with a predetermined frequency bandwidth,
Alternatively, a sideband signal is superimposed on any of the second current information, and each current information is discriminated and transmitted based on the presence or absence of the sideband signal, so multiple pieces of current information can be switched using a single transmission channel. transmission. For this reason, the current information transmission line is simplified and inexpensive, and since there is no need to add additional transmission channels, it is possible to provide current information for many types of fault conditions without worrying about economic efficiency. Since the current information can be selectively output to a single transmission channel according to the current information, it is possible to accurately determine the failure point of the power transmission system according to the failure details.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a carrier protection relay device according to an embodiment of the present invention, FIG. 2 is a diagram showing delay time characteristics of a transmission path, and FIG. 3 is a diagram showing frequency bandwidth and frequency modulated current information. FIG. 3 is a characteristic diagram showing the characteristics of a sideband signal. 1, 2... Current-voltage converter, 3, 4... Voltage-frequency converter, 22, 23... Judgment circuit, 1-
0...Current information output means, 1-1...Sideband signal transmission means, 1-2...Sideband signal superimposition means, 1-
3... Current information discrimination means.

Claims (1)

[Claims] 1. Current information at one end and the other end of a power transmission line in a protected area is modulated as appropriate and transmitted between terminals,
In a carrier protection relay device that determines whether a fault point is inside or outside based on the current differential protection principle by determining the difference in current information between the own end and the opposite end, the above-mentioned transmission line short-circuit fault is communicated. Current information output means for outputting first current information and second current information for conveying a ground fault, sideband signal transmitting means for emitting a sideband signal, and detecting the type of failure in the power transmission line. and sideband signal superimposing means for switching and selecting one of the current information from the current information output means and superimposing it on the sideband signal based on the detection result, and current information transmitted from the other end to the own end side. A carrier protection system that includes current information discriminating means that detects the presence or absence of a sideband signal and discriminates between first current information and second current information, and enables transmission of a plurality of current information through a single transmission channel. Relay device. 2. Claim 1, characterized in that the first current information is a positive sequence current at the time of a short-circuit fault of two or more wires, and the second current information is a zero-sequence current at the time of a one-line ground fault. Transport protection relay device as described.