CN115589016A - A Detection and Judgment Method for Island System Formation - Google Patents

Abstract

The invention discloses a detection and judgment method for formation of an island system, and relates to the technical field of electric power. When the phase angle difference, the frequency and the voltage have larger load for the waste heat power station after the mains supply disappears, the detection speed is higher and more accurate. When the reverse power approaches the waste heat power station and the load after the mains supply disappears, the fact that the mains supply disappears is identified more accurately by returning power to the power grid. When an LC3 upper-level switch in a cement plant trips, a waste heat power station and a power grid are disconnected, and the state of the circuit breakers is led to an island system screen to identify the disappearance of commercial power. In order to prevent that the reverse power is difficult to identify when being small, the state of the circuit breaker of the transformer substation which is always descended to the upper level is led to an island system screen, so that the island can be judged by identifying the fact that the mains supply disappears in one of the above modes, and dead-angle-free detection and judgment are achieved.

Description

A Detection and Judgment Method for Island System Formation

technical field

The invention relates to the technical field of the electric power field, in particular to a method for detecting and judging the formation of an island system.

Background technique

Cement plant waste heat power station refers to the use of heat from the grate cooler or waste gas at the kiln tail of the cement plant (referred to as the cement plant firing system) to heat the water in the waste heat boiler to a superheated state, and then send the water steam to the turbine generator set for Power generation (hereinafter referred to as waste heat power station), the power generated by the waste heat power station is used for the load of the cement plant after removing the part of the power used by the plant. No internet access" connection method. Under normal circumstances, the cement plant is powered by two power sources, one is the waste heat power station, and the other is the city power. If the city power disappears due to various reasons, the waste heat unit cannot bear the power load of the entire cement plant, and the waste heat The unit will be forced to shut down and stop generating power.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a detection and judgment method for the formation of an isolated island system, which can provide a detection and judgment method for the formation of an isolated island system after the mains power disappears.

In order to achieve the above object, the present invention is realized through the following technical solutions: a method for detecting and judging the formation of an isolated island system includes the following steps:

S1: The waste heat power generation of the plant has been calculated in the previous stage;

S2: All loads of the firing system are moved to the LC3 distribution station of the cement plant;

S3: The waste heat power station will be connected to the LC3 distribution station of the cement plant through the QF11 contact circuit breaker, and run in parallel with the mains to supply power to the load of the cement plant;

S4: When the mains power disappears, use the island detection device to judge the operation status of the power grid to determine whether the island operation condition is met. If it is satisfied, it is necessary to issue a command to disconnect the connection with the grid from @1, and issue a load reduction command to disconnect Coal mill load at @2, thus forming an island operation mode of waste heat power station with LC3 distribution station.

Preferably, in S1, the calculation of waste heat power generation of the plant can meet the full-load operation of the firing system, and the plant meets the conditions of island operation.

Preferably, in S2, the LC3 power distribution station includes the load of the cement plant firing system when the waste heat power station operates in an island.

Preferably, judging the change rate of the voltage phase angle at the switch of LC3 distribution station @1 to determine the island state where waste heat power generation needs to carry a large amount of grid load after the mains disappears. In the above state, waste heat power generation needs to carry a large amount of power grid load. The power generation suddenly brings a large amount of grid load. The change rate of the voltage phase angle at the @1 switch is obvious. From this, it can be judged that the waste heat power generation has entered the island state. The device sends a trip command to trip the @1 switch, and the waste heat power generation brings the load of the island part of the LC3 distribution station run.

Preferably, the reverse power is used to detect the island state in which the generated power can meet the power consumption of the load after the mains power disappears. In the above-mentioned state, the voltage and frequency do not change significantly, and the traditional method for detecting sudden changes in voltage and frequency cannot For identification, we can use the characteristics of waste heat power generation connected to the grid and not connected to the grid to detect the power direction of the interval between F1 and F2 at the main step-down station of the cement plant. From this, it can be judged that the waste heat power generation has entered an island state, and the device issues a trip command to trip the @1 switch. The load operation of waste heat power generation with the island part of LC3 substation.

Preferably, the feeder switch contacts of the main step-down station of the cement plant and the feeder switch contacts of the upper distribution station are introduced into the reverse power screen. When the reverse power is too small to be recognized by the detection device, the state of the switch contacts can Turn on the @1 switch, and the waste heat power generation will run with the load of the island part of the LC3 distribution station.

Preferably, through the switch contacts (F9, F1, F2, F3) between the island part LC3 distribution station and the grid to judge the island state caused by fault or other reasons, when the switches F9, F1, F2, F3 trip, The isolated island state of the waste heat power station is formed. At this time, the power generation can meet the load power consumption. The reverse power at F1 and F2 cannot identify the island state. The phase angle mutation of the voltage and frequency at the @1 switch is insufficient, and no island cannot be identified. At this time, it can only be judged that the waste heat power generation has entered the island state by disconnecting the switch contacts (F9, F1, F2, F3), and then the device sends a trip command to trip the @1 switch, and the waste heat power generation takes the island part of the LC3 distribution station load operation.

Preferably, the island load is placed on a section of the busbar of the LC3 distribution station. If the mains power disappears, you only need to jump off the @1 switch and @2 switch, and the waste heat power station can bring the burning system load island of the cement plant Compared with the traditional method of not dividing the island load into sections, the island is formed directly through load shedding is faster. In addition, a synchronous device is installed at @1, which can perform reverse synchronous closing.

The invention provides a method for detecting and judging the formation of an isolated island system. Has the following beneficial effects:

The phase angle difference, frequency, and voltage are faster and more accurate when the waste heat power station has a large load after the mains disappears. Reverse power is more accurate to identify the disappearance of mains power by sending power back to the grid when the waste heat power station is close to the load after the mains power disappears. After the LC3 upper-level switch in the cement plant tripped, the waste heat power station was disconnected from the power grid. The status of these circuit breakers was used to lead to the island system screen to identify the disappearance of the mains power. In order to prevent the reverse power from being difficult to identify when the reverse power is small, the state of the circuit breaker in the upper-level substation of the general downgrade is led to the island system screen to identify the disappearance of the mains power. judge.

Description of drawings

Fig. 1 is a wiring diagram of the whole plant of the present invention

Fig. 2 is a table of screen components of an island system of the present invention

Fig. 3 is the screen layout diagram of the island system of the present invention

Fig. 4 is a table of components of a reverse power screen of the present invention

Figure 5 is a layout diagram of the reverse power screen of the present invention

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention.

Examples of the described embodiments are shown in the drawings, wherein like or similar reference numerals designate like or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

In order to make the technical means adopted by the present invention, the purpose achieved and the effects easy to understand, the present invention will be further described in conjunction with the accompanying drawings and embodiments.

The implementation steps of this method are as follows:

According to previous calculations, the waste heat power generation of the plant can meet the full-load operation of the firing system, and the plant meets the conditions for island operation, so we moved all the load of the firing system to the LC3 distribution station of the cement plant, and the waste heat power station will pass The QF11 contact breaker is connected to the LC3 distribution station of the cement plant, and runs in parallel with the mains to supply power to the load of the cement plant. The LC3 distribution station includes the load of the cement plant's firing system when the waste heat power station is running in an isolated island. When the mains disappears , judge the operating state of the power grid through the island detection device, and determine whether the island operation condition is satisfied. If it is satisfied, it is necessary to issue a command to disconnect the connection with the grid from @1, and issue a load reduction command to disconnect the coal mill load at @2 , thus forming an island operation mode of waste heat power station with LC3 distribution station. see picture 1. When the utility power is restored, the @1 switch is turned on by the synchronous detection device, and the waste heat power station and the utility power enter into parallel operation again.

Judging the change rate of the voltage phase angle at the switch of LC3 distribution station @1 to judge the island state where waste heat power generation needs to carry a large amount of grid load after the mains disappears. In the above state, waste heat power generation needs to carry a large amount of power grid load. The change rate of the voltage phase angle at the @1 switch of a large number of grid loads is obvious. From this, it can be judged that the waste heat power generation has entered the island state. The device issued a trip command to trip the @1 switch, and the waste heat power generation belt LC3 The load operation of the island part of the distribution station.

Use inverse power to detect the island state where the power generation can meet the load consumption after the mains power disappears. In the above state, the voltage and frequency do not change significantly. The traditional detection method of voltage frequency mutation cannot be identified, and waste heat can be used The power generation is connected to the grid and not connected to the grid. By detecting the power direction of the interval between F1 and F2 at the main step-down station of the cement plant, it can be judged that the waste heat power generation has entered an island state. Load operation of the island part of the power station.

Introduce the incoming line switch of the main step-down station of the cement plant and the feeder switch contact of the upper distribution station into the reverse power screen. When the reverse power is too small to be recognized by the detection device, it can be opened and tripped by the state of the switch contact@1 Switching, waste heat power generation with load operation of the island part of LC3 distribution station.

Use the switch contacts (F9, F1, F2, F3) between the island part LC3 distribution station and the power grid to judge the island state caused by faults or other reasons. When the switches F9, F1, F2, and F3 trip, a residual In the island state of the thermal power station, the power generation can meet the power consumption of the load at this time, the reverse power at F1 and F2 cannot identify the island state, and the phase angle mutation of the voltage and frequency at the @1 switch is insufficient, and the island state cannot be identified without. At this time, it can only be judged that the waste heat power generation has entered the island state by disconnecting the switch contacts (F9, F1, F2, F3), and then the device sends a trip command to trip the @1 switch, and the waste heat power generation takes the load of the island part of the LC3 distribution station to run .

Place the island load on a section of the busbar of the LC3 distribution station. If the mains power disappears, you only need to jump off the @1 switch and the @2 switch, and the waste heat power station can operate in an isolated island with the load of the firing system of the cement plant. Compared with the tradition, the isolated island load is not divided into sections, and the isolated island formed directly by the method of load shedding is faster. In addition, a synchronous device is installed at @1, which can perform reverse synchronous closing.

When LC-3 bus low frequency (48.5Hz), low voltage (75V) and angle change (2°) appear, delay 0.1 second to start the island signal

When the upper power supply switch on the LC-3 bus is arbitrarily cut off (logically determines the continuous power supply circuit) to determine the island

When the contact switch protection 7SD61 load exceeds 1.2 times - less than 1.3 times the rated power of the generator, a signal is sent to @1 switch protection, and the island signal is judged to start.

When the reverse power of F1/F2 points detects the signal, it sends a signal to the @1 switch to start the island operation.

When the contact switch between LC-3 and the generator is opened or the GCB is opened or the generator protection fault is blocked, the island signal output.

In the non-islanding state, the islanding monitoring device is always in the closed state, and the generator runs in the non-islanding state. Once the island is detected, the island detection device outputs a signal to the excitation adjustment screen and the turbine DEH screen, activates the island mode of the excitation adjustment screen and the turbine DEH screen, and at the same time sends a signal to notify the staff that the generator is running in an island state.

After the island system screen is put into operation, the @1 switch is only allowed to be closed simultaneously on the island system screen, and the @1 switch cabinet can only be closed experimentally.

When the island detection device detects that there is pressure on the line side of the @1 switch and the LC-3 busbar, and the @1 switch is successfully closed synchronously, it will exit the islanding operation state.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Any equivalent replacement or change of the inventive concepts thereof shall fall within the protection scope of the present invention.

Claims (8)

1. A detection and judgment method for the formation of an isolated island system, characterized in that, comprising the following steps: S1: The waste heat power generation of the plant has been calculated in the previous stage; S2: All loads of the firing system are moved to the LC3 distribution station of the cement plant; S3: The waste heat power station will be connected to the LC3 distribution station of the cement plant through the QF11 contact circuit breaker, and run in parallel with the mains to supply power to the load of the cement plant; S4: When the mains power disappears, use the island detection device to judge the operation status of the power grid to determine whether the island operation condition is met. If it is satisfied, it is necessary to issue a command to disconnect the connection with the grid from @1, and issue a load reduction command to disconnect Coal mill load at @2, thus forming an island operation mode of waste heat power station with LC3 distribution station. 2. The method for detecting and judging the formation of an isolated island system according to claim 1, characterized in that: in S1, the calculation of the waste heat power generation of the plant can meet the full-load operation of the firing system, and the plant meets the requirements of island operation condition. 3. A method for detecting and judging the formation of an island system according to claim 1, characterized in that: in S2, the LC3 power distribution station includes the load of the cement plant firing system when the waste heat power station operates in an island. 4. The method for detecting and judging the formation of an island system according to claim 1, characterized in that: judging the change rate of the voltage phase angle at the switch of LC3 distribution station @1 to judge that waste heat power generation needs to bring a large number of power grids after the mains disappears In the island state of the load, the waste heat power generation needs to carry a large amount of grid load in the above state. At this time, the waste heat power generation suddenly takes a large amount of grid load @1 The change rate of the voltage phase angle at the switch is obvious, so it can be judged that the waste heat power generation has entered the island state, and the device Issue a trip command to trip the @1 switch, and the waste heat power generation will run with the load of the island part of the LC3 distribution station. 5. The method for detecting and judging the formation of an island system according to claim 1, characterized in that: the reverse power is used to detect the island state in which the power generation can meet the load power consumption after the mains disappears, and the voltage in the above state The frequency and frequency have not changed significantly, and the traditional detection method of voltage frequency mutation cannot be identified. By virtue of the characteristics of waste heat power generation connected to the grid and not connected to the grid, the power direction of the interval between F1 and F2 at the total step-down station of the cement plant can be detected. It is judged that the waste heat power generation has entered the island state, and the device issues a trip command to trip the @1 switch, and the waste heat power generation will run with the load of the island part of the LC3 distribution station. 6. The detection and judgment method for the formation of a kind of isolated island system according to claim 1, characterized in that: the feeder switch contacts of the total step-down station of the cement plant and the feeder switch contacts of the upper distribution station are introduced into the reverse power panel, when When the reverse power is too small and the detection device cannot identify it, the @1 switch can be opened and tripped according to the state of the switch contact, and the waste heat power generation belt runs under the load of the island part of the LC3 distribution station. 7. The detection and judgment method for the formation of a kind of isolated island system according to claim 1, characterized in that: the fault is judged by the switch contacts (F9, F1, F2, F3) between the island part LC3 distribution station and the power grid Or the island state caused by other reasons. When the switches F9, F1, F2, and F3 trip, the island state of the waste heat power plant is formed. At this time, the power generation can meet the load power consumption, and the reverse power at F1 and F2 cannot identify the island. state, the phase angle mutation of the voltage and frequency at the @1 switch is insufficient, and the islanding state cannot be identified. At this time, it can only be judged that the waste heat power generation has entered the islanding state by disconnecting the switch contacts (F9, F1, F2, F3). Then the device sends out a trip command to trip the @1 switch, and the waste heat power generation runs with the load of the island part of the LC3 distribution station. 8. The method for detecting and judging the formation of an island system according to claim 1, characterized in that: the island load is placed on a section of the busbar of the LC3 distribution station, and if the mains power disappears, only the @1 switch needs to be tripped , and @2 switch, the waste heat power station can operate with the burning system load of the cement plant in an isolated island, which is faster than the traditional island load that is not divided into segments and directly formed by load shedding. In addition, @1 is installed With the synchronous device, reverse synchronous closing can be performed.

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