CN101242093A - Integrated relay protection system based on multi-channel transient polarity direction comparison algorithm - Google Patents

Abstract

The invention discloses an integrated relay protection system based on a multi-channel transient polarity direction comparison algorithm. The integrated protective relay is installed in the substation, which is connected to each line through the optical fiber network of the substation through CT. The integrated protective relay protects each line connected to the substation; the integrated protection system uses the high-frequency transient signal generated by line faults Based on detection and extraction, the integrated protection relay detects the transient current signal generated by the fault in the transient detection unit, the multi-channel transient filtering algorithm unit detects transient signals of different frequencies, and the transient polarity identification unit identifies the polarity of the detected signal The fault direction is determined by comparing the signal polarity of each line, and the actual fault line is identified through the polarity direction information processing of each substation. The tripping signal is output to the line switch through the optical network. Compared with the existing relay protection system, it has flexible configuration, convenient use and obvious economic benefits, and has broad application prospects in power systems.

Description

Integrated relay protection system based on multi-channel transient polarity direction comparison algorithm

technical field

The invention relates to a protection system of a power system, in particular to a relay protection system for a power transmission line, which belongs to the technical field of power system transmission line protection.

Background technique

Relay protection plays a vital role in power systems, but most of the existing relay protection is based on the design and installation of independent electrical equipment. With the development of the economy, the scale of the power grid is getting larger and larger, and the security of the power grid is particularly important. Quickly and correctly clearing faults and improving system stability are the development directions of relay protection. In the field of modern power system protection, digital relays have gradually replaced traditional relays. With the continuous development and progress of computer technology, network communication technology and its component manufacturing process, some relay protection systems have integrated some protection functions into one protection device. For example, microcomputer line protection can combine distance or current with different functions The integrated protection can be used as the main protection, and the integration of directional protection and overcurrent protection can also be used as the backup protection. However, the degree of integration is not enough, and the influence of the whole system on the relay protection action is not considered; and various protection principles based on power frequency signals still play a leading role.

Contents of the invention

In order to solve the above-mentioned problems existing in the prior art, so as to quickly and accurately remove faults, the present invention provides an integrated relay protection system based on a multi-channel transient polarity direction comparison algorithm. The system consists of three parts: an interface unit, an optical fiber network communication unit, and an integrated protection relay. The integrated protective relay is installed in the substation, and each line is connected to it through CT, and the integrated protective relay protects each line connected to the substation. As a communication medium, the optical fiber network not only connects the integrated protection relays of each substation, but also connects the integrated protection units, interface units and integrated protection relays, and other devices (such as multi-channel communication units, GPS clocks, man-machine dialogue interfaces, etc.) connected to a fiber optic network. The protocol used is a standard communication protocol.

The integrated protection system of the present invention is based on the detection and extraction of high-frequency transient signals generated by line faults. The integrated protection relay detects transient current signals generated by faults in the transient detection unit, and the multi-channel transient filter algorithm unit detects different frequencies. Transient signal, the transient polarity identification unit identifies the polarity of the detected signal, determines the fault direction by comparing the signal polarity of each line, and identifies the actual fault line by processing the polarity direction information of each substation. The technical scheme of the protection system is:

(1) When a fault occurs in a certain line of a substation, the integrated protection relay of each substation in the system detects the transient current signal generated by the fault.

(2) Compare the polarity of the current signal detected by each substation through optical fiber communication.

(3) Determine which substation's protection zone the line fault is in, and trip the corresponding relay.

The beneficial effects of the present invention are: the integrated protection system not only provides a method for applying transient signal protection to individual transmission lines or electric equipment, but also implements a plurality of protection elements in a substation with an integrated protection system. Compared with the existing relay protection system, it has flexible configuration, convenient use and obvious economic benefits, and has broad application prospects in power systems.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings.

Figure 1 is a schematic structural diagram of an integrated relay protection system based on a multi-channel transient polarity direction comparison algorithm;

Figure 2 is a power transmission system with branches to verify the integrated relay protection system based on the multi-channel transient polarity direction comparison algorithm;

Fig. 3 is a functional block diagram of the relay of the integrated relay protection system based on the multi-channel transient polarity direction comparison algorithm;

Fig. 4 is a protection calculation flow chart.

Detailed ways

The integrated protection system is shown in Figure 1. It is mainly composed of three parts: interface unit, optical fiber network communication unit and integrated protection relay.

The integrated protection relay is installed in the substation, each line is connected to it through CT, and protects each line connected to the substation. As a communication medium, the optical fiber network not only connects the integrated protection relays of each substation, but also connects the integrated protection units, interface units and integrated protection relays, and other devices (such as multi-channel communication units, GPS clocks, man-machine dialogue interfaces, etc.) connected to a fiber optic network. The protocol used is a standard communication protocol.

Interface Unit: This is a measurement and control unit that is connected to various devices through different types of sensors such as traditional CT and PT, optical hybrid sensors, electronic hybrid sensors, etc. The measured analog and digital signals are converted into optical signals and sent to the integrated protection relay through the redundant optical fiber network, and the interface unit simultaneously receives and executes the signals sent by the relay controlled by the control circuit.

Optical fiber network: This communication network is not only connected to the interface unit and relay of the monitoring equipment, but also connected to other devices, such as man-machine dialogue interface, multi-channel communication unit, and GPS clock, etc.; and connected to the integrated protection relay of other substations , using standard network communication protocols.

Integrated protective relay: The integrated protective relay receives measurement information from all over the substation and related substation information through the network. The integrated protective relay then calculates and analyzes whether there is a fault in the substation or other connected lines. If a fault is detected, the integrated protective relay trips the associated circuit breaker via a command returned from the control unit.

Figure 2 shows a one-belt branch transmission system. As shown in the figure, relay units are installed in each substation and connected through communication channels. A network protection and control unit also supports this technology.

When a fault occurs on a line with branches, such as point F2 in Figure 2, the high-frequency transient current signal will reach each busbar from the fault point F2, and the signals will reach the three busbars P, Q, and R respectively. CT on Q and R will simultaneously detect that the polarities of the three transient signals are the same. It is considered to be a fault within the protection interval of P, Q, and S. If the fault occurs at F1, that is, outside the protection interval of P, Q, and R, the transient current signal detected by the CT installed on the line will be different, and the polarity information of the transient current signal generated by the fault detected by each relay Send it to the relay S at the other end related to the protection branch through the communication network, and finally determine that the fault is outside the protection interval of P, Q, and R by comparing the fault polarity.

Then, the polarity information detected by each relay is sent to the network protection and control unit, through which the fault line can be determined. This unit not only acts as a backup protection unit for each line, but also ensures the stability of the network protection and control unit and the main system.

relay design

Figure 3 shows the block diagram of the relay protection system, which mainly includes communication Ethernet and relays.

The communication network fetches the current measurement data from the interface unit of the connection line CT, and these measurement values are either digital signals from the light sensor, or digital signals converted by the interface unit from the traditional CT. The communication network also accepts the trip command from the relay and sends it to the corresponding switch. Another important device connected to the network is the multi-channel communication unit. Its function is to send the polarity signal detected by the relay to the relay at the far end of the protection line, and at the same time receive the polarity signal from the relay at the far end of the protection line. The polarity signal at the local end will also be sent to the central network protection and control unit for system backup protection.

The relay includes fault detection, transient signal extraction, polarity detection, polarity comparison and a trip decision unit.

1) The fault detection unit obtains current measurement information from the CT, once the current exceeds a preset threshold value. The relay starts the protection program immediately. The fault detection unit simultaneously selects the current value measured by the CT on a line for calculation. For the detection of the current polarity required by this technology, knowing the current polarity on one line can lead to the polarity on other related lines.

2) The extraction of fault transient signals, as shown in Figure 3, the extraction of two transient current signals with different frequencies is based on two principles:

a, the extraction of the high-frequency signal band (as shown in A in Figure 3), it includes two steps of modulus conversion and high-frequency band-pass filtering. In this way, an extremely fast response time is provided for system protection.

b. Extraction of fault superposition components (as shown in Figure 3 B), which includes two steps of fault phase selection and fault component extraction. By implanting a superposition component extraction algorithm in the program, that is, the sampling value is delayed for one cycle in the memory, and the delayed sample is subtracted from the latest sample to form the fault current superposition component.

It should be noted here that traditional voltage converters, especially capacitive voltage converters, have bandwidth limitations and cannot be used to extract high-frequency signals. However, with current converters, there is no bandwidth limitation problem.

3) Polarity detection and comparison

Once the fault signal is detected by the transient filtering unit, a digital counter with an adaptive algorithm is used for this signal, if the fault superposition signal level is greater than the adaptive threshold level, after exceeding the limit time determined by the counter, it can Determine the polarity of the transient signal generated by the fault, and then the polarity information is passed to the next stage, and compared with the polarity detected at the other end of the protection unit, only when the relay has received the same polarity as the transmitted signal When the signal is detected, it means that the fault is on the protection line. At the same time, the polarity signal will also be sent to the network protection and control unit for network protection and control. The network protection and control unit can know the faulty line by comparing all the polarity signals of the system through the same principle.

4) Trip decision logic

When the relay has received a signal of the same polarity as the signal it sent, it means that a fault has occurred on the protected line. The trip decision logic unit receives output signals from two channels (high frequency and fault components). This unit has two optional preset working modes:

Mode 1 ("or" mode): one of the output signals of the two channels judges that the fault is on the protection line, that is, the final tripping decision is made.

Mode 2 ("AND" mode): The final tripping decision is made only when one of the output signals of the two channels judges that the fault is on the protection line.

5) Multiple communication unit

Multiple communication units are used in relays for line protection and network protection.

Once the polarity detection device determines the signal polarity, the polarity signal will be sent to the network protection automation device through the communication unit. The network protection automation device receives signals from all relays in the network, compares the obtained signals, and is able to determine the actual faulty line section. The unit is also used to receive commands (eg trip signals) from network protection automation devices.

The communication unit is used to communicate with other individual line protection device relays. The polarity signal measured at the local end is sent to the relay at the other end of the protected line.

Communication here requires only an "on" or "off" communication signal, representing positive or negative polarity, respectively. For example, the same polarity of the signal at both ends of the protected line indicates an internal fault.

The working process of this embodiment

For example, in the transmission network shown in Figure 2, when point F1 fails, the relay P, relay Q and relay R at the three terminals of the 1# line will act, and the action will trip the circuit breaker to cut off the line. Relay S will not act.

The specific working process is as follows:

1. Let point F2 fail.

2. The current flowing through all current transformers (CS, CP1, CP2, CQ1, CQ2, CR) will vary.

3. These current signals will be detected by the interface unit (IU) and sent to the respective substation Ethernet.

4. All relays (Relay S, Relay P, Relay Q and Relay R) connected behind the respective substation Ethernet will get their respective current signals.

5. The relay that detects the fault and starts it calculates its own protection flow chart as shown in Figure 4.

6. Take the relay P as an example. After the fault is detected, the protection algorithm will use the current of the current transformer CP1 or CP2 for the next calculation. Because detecting the current polarity of a current transformer can immediately derive the polarity of another or more lines connected to the busbar. For example, the polarities of CP1 and CP2, CQ1 and CQ2 are opposite.

7. The program then enters two parallel calculation algorithms: (1) extraction of high-frequency quantities and (2) extraction of fault components;

1) The extraction of high-frequency quantities will go through the stages of modulus conversion and high-frequency band-pass filtering;

2) The extraction of fault components will go through two stages of fault phase selection and component extraction.

8. Afterwards, the program will enter the polarity inspection unit, and the algorithm will separately derive the polarity of the two signals of high frequency and fault components, and send them to the remote end of the protected line (line 1, line 2, line 3) through the network Relays (Relay S, Relay Q and Relay R) and network protection and control units. Here the polarity of CP1 is sent to relay S, and the polarity of CP2 is sent to relay Q and relay R.

9. Then the program will enter the polarity comparison unit. At this time, the relay will receive the polarity signals of high frequency and fault components sent from the remote relays (relay S, relay Q and relay R) of the protected line. Here, the polarity of CT1 will be compared with the polarity of CS of relay S. The polarity of CT2 will be compared with the polarity of CQ1 of relay Q and the polarity of CR of relay R. If the polarities are the same, it is an internal fault of the protection circuit, otherwise it is an external fault. In this example, because the fault is at point F2, the polarity of CP2 detected by relay P will be the same as the polarity of CQ1 detected by relay Q and the polarity of CR detected by relay R. The polarity of CT1 detected by relay P will be opposite to the polarity of CS of relay S, so that it can be concluded that the fault is on lines 2 and 3 but not on line 1.

10. Since the high-frequency signal and the fault component are compared separately, the result will produce two results. The results of the two separate comparisons are then output to the trip decision logic unit, which has two preset working modes: mode 1 and 2;

1) Mode 1 requires that one of the two comparison results is an internal fault to make a trip decision;

2) Mode 2 requires both comparison results to be internal faults to make a trip decision; mode 1 has a fast response speed, while mode 2 has high reliability.

11. After tripping, the program will return.

Claims (5)

1. An integrated relay protection system based on a multi-channel transient polarity direction comparison algorithm, which is composed of an interface unit, an optical fiber network communication unit and an integrated protection relay. Its characteristics are: (1) When a fault occurs in a certain line of a substation, the integrated protection relay of each substation in the system detects the transient current signal generated by the fault; (2) compare the polarity of the current signal detected by each substation through optical fiber network communication; (3) Determine which substation's protection zone the line fault is in, and trip the corresponding relay. 2. The integrated relay protection system based on multi-channel transient polarity direction comparison algorithm according to claim 1, characterized in that: as the communication medium, the optical fiber network not only connects the integrated protection relays of each substation, but also integrates the protection Units, interface units and integrated protection relays are connected, and other devices such as multi-channel communication units, GPS clocks or man-machine dialogue interfaces are also connected to the optical fiber network, and the protocols used are standard communication protocols. 3. The integrated relay protection system based on multi-channel transient polarity direction comparison algorithm according to claim 1 or 2, characterized in that: the integrated protection relay is installed in the substation, and receives measurement information and related information from various places in the substation through the network. The information of the substation is used to calculate and analyze whether there is a fault. Each line in the substation or other connected lines is connected to it through CT, and the integrated protection relay protects each line connected to the substation. 4. the integrated relay protection system based on the multi-channel transient polarity direction comparison algorithm according to claim 3, is characterized in that: the integrated protection system is based on the detection and extraction of the high-frequency transient signal that the line fault produces, The integrated protection relay detects the transient current signal generated by the fault in the transient detection unit, the multi-channel transient filter algorithm unit detects transient signals of different frequencies, and the transient polarity identification unit identifies the polarity of the detected signal, and compares the The signal polarity of the line determines the fault direction, and the actual faulty line is identified through the polarity direction information processing of each substation. 5. The integrated relay protection system based on the multi-channel transient polarity direction comparison algorithm according to claim 4, characterized in that: the decision-making trip logic of the multi-channel transient polarity direction comparison algorithm of the protection system has two Two kinds of setting methods: (1) OR logic: when any output is a trip signal, the relay will make a trip decision; (2) AND logic: when both outputs are trip signals at the same time, the relay will make a trip decision.

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