Device for limiting grid-side reverse power supply of self-contained power station

Abstract

The utility model discloses a device for limiting reverse power supply at the network side of a self-contained power station, which comprises a line protection measurement and control screen, a four-circuit tripping unit TS4 is arranged in the line protection measurement and control screen, and the outlet end of the four-circuit tripping unit is connected with a first protection line, a second protection line, a third protection line and a fourth protection line; the first protection circuit is connected to the high-voltage side of the 1 # main transformer and is connected with the 301 circuit breaker control loop; the second protection circuit is connected to the low-voltage side of the 1 # main transformer and is connected with a 107K circuit breaker control loop; a third protection circuit is connected to the high-voltage side of the 2 # main transformer and is connected with a 302 circuit breaker control loop; a fourth protection circuit is connected to the low-voltage side of the 2 # main transformer and is connected with a 208K circuit breaker control loop; when reverse power is monitored by the line protection measurement and control screen, a tripping instruction is sent out, the four-circuit tripping unit is closed, a corresponding protection line tripping circuit is switched on, and a corresponding power supply line is switched off, so that the problem that the electric quantity is absorbed from the self-contained generator when an external network side has a fault is solved, and overload tripping of the self-contained generator is avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of power distribution networks, in particular to a device for limiting reverse power supply on the grid side of a self-provided power station. Background Art

[0002] like Figure 1 As shown, the external power lines of the factory area supply power to the station through two circuit breakers. The external power is sent to the busbar in the station through the parallel 1# main transformer or 2# main transformer, and then supplied to each workshop section. The station is equipped with a generator for independent power supply. The generator generates electricity through the busbar and supplies it to each workshop section. Among them, 85% of the electricity consumption is provided by the independent power generation of the generator.

[0003] When the external power line is switched and the main transformer is switched, a response inrush current will appear on the busbar of the power plant or substation (when two or more transformers are connected to the busbar in the power plant or substation, if one transformer is closed under no-load conditions, an excitation inrush current will appear in the transformer winding. At the same time, a surge current will also appear in the windings of other neutral-grounded transformers running in parallel with it, which is called a response inrush current). This will cause the overcurrent protection of the 107K circuit breaker line protection panel cabinet on the low-voltage side of the 1# main transformer and the overcurrent protection of the 208K circuit breaker line protection panel cabinet on the low-voltage side of the 2# main transformer to be activated, causing the 107K circuit breakers and 208K circuit breakers to trip.

[0004] At present, the conventional method is to avoid the influence of the combined inrush current by increasing the overcurrent protection setting value on the low-voltage side of the main transformer. However, this method cannot 100% solve the combined inrush current problem. In addition, after increasing the setting value, it is bound to cause excessive absorption of electricity when a fault occurs on the external grid side, resulting in the risk of overload tripping of the generator in the station and power outage of the entire plant. Based on this, a device is needed to limit the amount of power supplied back to the external grid by the generator of the self-contained power station after increasing the overcurrent protection setting value on the low-voltage side of the main transformer. Utility Model Content

[0005] In response to the above problems, the utility model provides a device for limiting the reverse power supply on the grid side of a self-contained power station, and then improves the original line protection and control panel. The original four tripping outlet ends are connected to the high-voltage side of the 1# main transformer, the low-voltage side of the 1# main transformer, the high-voltage side of the 2# main transformer, and the low-voltage side of the 2# main transformer through hard pressure plates. The hard pressure plates can flexibly select the start and stop functions. When the external power grid fails and absorbs power from the generator, when the set value is reached, the selected circuit breaker will operate reliably, thereby protecting the safe operation of the internal power grid.

[0006] Specifically, the utility model provides a device for limiting reverse power supply on the grid side of a self-contained power station, comprising a line protection measurement and control panel, wherein the line protection measurement and control panel has four built-in trip units, and the outlet ends of the four trip units are respectively connected to the trip circuits of the first protection line, the second protection line, the third protection line, and the fourth protection line;

[0007] The first protection line is connected to the high voltage side of the 1# main transformer and is connected to the tripping circuit of the 301 circuit breaker;

[0008] The second protection line is connected to the low-voltage side of the 1# main transformer and is connected to the tripping circuit of the 107K circuit breaker;

[0009] The third protection circuit is connected to the high voltage side of the 2# main transformer and is connected to the tripping circuit of the 302 circuit breaker;

[0010] The fourth protection circuit is connected to the low-voltage side of the 2# main transformer and is connected to the tripping circuit of the 208K circuit breaker;

[0011] When the power value monitored by the line protection measurement and control panel reaches the set value, the four-circuit tripping unit closes.

[0012] Furthermore, the first protection circuit includes: a first hard pressure plate and a first circuit breaker, the first hard pressure plate being used for switching the first circuit breaker on and off;

[0013] The second protection circuit includes: a second hard pressure plate and a second circuit breaker, the second hard pressure plate is used for switching the second circuit breaker on and off;

[0014] The third protection circuit includes: a third hard pressure plate and a third circuit breaker, the third hard pressure plate is used for switching the third circuit breaker on and off;

[0015] The fourth protection circuit includes: a fourth hard pressure plate and a fourth circuit breaker, and the fourth hard pressure plate is used for switching on and off the fourth circuit breaker.

[0016] Furthermore, an expansion relay is provided at the outlet end of the four-circuit trip unit, and when the four-circuit trip unit is closed, the expansion relay is energized.

[0017] Working principle:

[0018] Line protection measurement and control panels are primarily used in transmission and distribution stations, providing intelligent, networked measurement and protection control capabilities for various high-voltage equipment within the station. Their principle is to monitor the voltage and current signals on the incoming line (342 or 341 circuit breakers) in real time, and then compare the current amplitude and angle with those during normal operation. When the current amplitude reaches the set value and the current angle is reversed compared to normal operation, the protection device determines that reverse power has occurred and issues a trip command, achieving the desired protection.

[0019] Specifically, in the present invention, when the current amplitude reaches the set value and the current angle is opposite to that in normal operation, the line protection measurement and control panel determines that reverse power has occurred, issues a tripping command, and the selected circuit breaker is actuated, thereby achieving the purpose of limiting reverse power supply.

[0020] For example: when the four-circuit trip unit is closed, the first hard pressure plate is closed and put into operation, the first circuit breaker is actuated, the first protection line trip circuit is connected, the 301 circuit breaker is actuated, the high-voltage side power supply circuit of the 1# main transformer is cut off, the internal power grid is in isolated operation, and the power supply is provided by the self-contained generator to achieve the purpose of limiting reverse power supply.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The device for limiting the reverse power supply on the grid side of the self-contained power station provided by the utility model can effectively solve the problem of absorbing too much electricity when the external grid side fails due to the influence of inrush current by increasing the overcurrent protection setting value on the low-voltage side of the main transformer. Therefore, when the external grid fails and absorbs electricity from the self-contained generator, the reverse power supply is limited, thereby avoiding the overload tripping of the self-contained generator. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the existing power supply system;

[0024] Figure 2 Schematic diagram of the device for limiting reverse power supply on the grid side of a self-provided power station in Example 1. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below through specific implementations in conjunction with the accompanying drawings.

[0026] Example 1

[0027] like Figure 2 As shown, this embodiment provides a device for limiting the reverse power supply on the grid side of a self-contained power station, which is upgraded based on the original line protection and control screen (DCAP-5000) to solve the problem of absorbing power from the self-contained power station generator when an external power grid fails.

[0028] The line protection and control panel has a built-in four-circuit trip unit TS4. The output of the four-circuit trip unit TS4 is connected to the first, second, third, and fourth protection circuits via an expansion relay KA1. The four contacts KA11, KA12, KA13, and KA14 of the expansion relay KA1 are connected to the first, second, third, and fourth protection circuits, respectively. The line protection and control panel monitors the voltage and current signals on the incoming line (342 or 341 circuit breaker) in real time. By comparing the current amplitude and angle with normal operation, if the current amplitude reaches the set value and the current angle is reversed compared to normal operation, the line protection and control panel determines that reverse power is occurring and issues a trip command. The four-circuit trip unit TS4 closes and, based on actual conditions, selects the appropriate protection circuit (one or more of the first, second, third, and fourth protection circuits) to activate, disconnecting the corresponding power supply circuit and isolating the internal power grid, thereby limiting reverse power supply.

[0029] Specifically, the first protection line is connected to the high-voltage side of the 1# main transformer and is connected to the control circuit of the 301 circuit breaker. It includes the first hard pressure plate X1CLP2 and the first circuit breaker KA1-1. The first hard pressure plate X1CLP2 is used to switch the first circuit breaker KA1-1 on and off. The second protection line is connected to the low-voltage side of the 1# main transformer and is connected to the control circuit of the 107K circuit breaker. It includes: the second hard pressure plate X2CLP2 and the second circuit breaker KA1-2. The second hard pressure plate X2CLP2 is used to switch the second circuit breaker KA1-2 on and off. When the external power supply is supplied by the 35KV paper line and the current path passes through the 341 circuit breaker, the 301 circuit breaker, the 1# main transformer, and the 107K circuit breaker to supply power to the intranet, we choose to put the X1CLP2 and X2CLP2 pressure plates into operation. When external power is supplied by a 35kV coiled paper line, and the current path flows through circuit breakers 341 and 301, along with the No. 1 main transformer and the No. 107K circuit breaker, we select the X1CLP2 and X2CLP2 pressure plates for activation. When the line protection and control panel detects reverse power and issues a trip command, the four trip units close, the first circuit breaker, KA1-1, activates the first protection line, the No. 301 circuit breaker activates, disconnecting the No. 1 main transformer's high-voltage side power supply circuit, the second circuit breaker, KA1-2, activates the second protection line, and the No. 107K circuit breaker activates, disconnecting the No. 1 main transformer's low-voltage side power supply circuit, isolating the internal grid and limiting reverse power supply from the captive power station to the external grid.

[0030] Similarly, the third protection line connects to the high-voltage side of the 2# main transformer and is connected to the control circuit of the 302 circuit breaker. The fourth protection line connects to the low-voltage side of the 2# main transformer and is connected to the control circuit of the 208K circuit breaker. When external power is supplied by a 35kV coiled paper line, and the current path passes through the 342 and 302 circuit breakers, the 2# main transformer, and the 208K circuit breaker to supply power to the internal network, we select the X3CLP2 and X4CLP2 pressure plates to be activated.

[0031] The above examples are used to illustrate the present invention, which are only used to help understand the present invention and are not intended to limit the present invention. For those skilled in the art of the present invention, some simple deductions, modifications or substitutions can be made based on the concept of the present invention.

Claims

1. A device for limiting reverse power supply on the grid side of a self-contained power station, comprising a line protection and control panel, wherein the line protection and control panel has a built-in four-circuit trip unit TS4, characterized in that: The outlet ends of the four-circuit trip unit TS4 are respectively connected to the first protection circuit, the second protection circuit, the third protection circuit and the fourth protection circuit; The first protection line is connected to the high voltage side of the 1# main transformer and is connected to the tripping circuit of the 301 circuit breaker; The second protection line is connected to the low-voltage side of the 1# main transformer and is connected to the tripping circuit of the 107K circuit breaker; The third protection circuit is connected to the high voltage side of the 2# main transformer and is connected to the tripping circuit of the 302 circuit breaker; The fourth protection circuit is connected to the low-voltage side of the 2# main transformer and is connected to the tripping circuit of the 208K circuit breaker; When the power value monitored by the line protection measurement and control panel reaches the set value, the four-circuit trip unit TS4 is closed.

2. The device for limiting reverse power supply from the grid side of a self-contained power station according to claim 1, characterized in that: The first protection circuit includes: a first hard pressure plate X1CLP2 and a first circuit breaker KA1-1, the first hard pressure plate X1CLP2 is used for switching the first circuit breaker KA1-1 on and off; The second protection circuit includes: a second hard pressure plate X2CLP2 and a second circuit breaker KA1-2, the second hard pressure plate X2CLP2 is used for switching the second circuit breaker KA1-2 on and off; The third protection circuit includes: a third hard pressure plate X3CLP2 and a third circuit breaker KA1-3, and the third hard pressure plate X3CLP2 is used for switching the third circuit breaker KA1-3 on and off; The fourth protection circuit includes: a fourth hard pressure plate X4CLP2 and a fourth circuit breaker KA1-4. The fourth hard pressure plate X4CLP2 is used for switching the fourth circuit breaker KA1-4 on and off.

3. The device for limiting reverse power supply from the grid side of a self-contained power station according to claim 1 or 2, characterized in that: An expansion relay KA1 is provided at the outlet end of the four-circuit trip unit TS4. When the four-circuit trip unit TS4 is closed, the expansion relay KA1 is energized.

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