CN103560512A - High-reliability closed loop wiring method of medium voltage distribution network - Google Patents

Abstract

The invention relates to a high-reliability closed-loop wiring method for a medium-voltage distribution network, which is characterized in that it includes the following steps: step S01: lead out two independent busbars from the 10 kV side of each transformer in the substation; step S02: connect the The two sections of bus bars are respectively connected by a ring network unit to form a closed-loop ring network structure. At least one circuit breaker is arranged in the ring network unit as a tie switch, and the closed-loop ring network structure formed by each transformer passes through the tie switch and The tie line is connected to the closed-loop ring network structure formed by another transformer; when the transformer is in normal operation, the circuit breakers at both ends of the tie line are turned on, and the tie line is in a standby state; and the power supply load on each ring network does not exceed two feeder lines. 40% of the stable limit power supply load. The method of the invention has the advantages of high power supply reliability, and the closed-loop operation of the same transformer will not increase the short-circuit current of the distribution network, so the transformation amount is small, the construction cost is low, and the feasibility is high.

Description

A high-reliability closed-loop wiring method for medium-voltage distribution network

technical field

The invention relates to the technical field of power supply, in particular to a high-reliability closed-loop wiring method for a medium-voltage distribution network. the

Background technique

The medium-voltage distribution network in high-reliability power supply areas at home and abroad generally adopts a ring network structure, and its operation mode is divided into two types: open-loop operation and closed-loop operation. my country's medium-voltage 10 kV distribution network adopts the "open-loop operation + distribution automation" method, that is, the contact switch between each 10 kV feeder is opened during normal operation, and the 10 kV feeder uses radiation power supply; when the feeder fails, Fault location and isolation are implemented through the distribution automation system, and the contact switch is closed to realize power supply to the non-fault segment. The disadvantage is that it takes a long time to restore power supply after a fault, and it takes several minutes to tens of minutes. The medium-voltage 20 kV distribution network in Singapore, Hong Kong and other regions adopts the "closed-loop operation + differential protection" method, that is, the two 10 kV feeders are connected through circuit breakers and other equipment during normal operation to form a ring network; When the feeder fails, the fault location and isolation can be implemented quickly through the relay protection equipment, which only takes tens to hundreds of milliseconds. Compared with the open-loop operation mode, the advantage of closed-loop operation is that it takes a short time to restore power supply after a fault, and the disadvantage is that the short-circuit current value is large and the construction cost is high.

However, in the closed-loop operation mode adopted by the medium-voltage 20 kV distribution network in Singapore, Hong Kong and other regions, the two 20 kV feeders come from 20 kV buses of different transformers. In the case of the same short-circuit capacity, the short-circuit current of the 10 kV distribution network is twice that of the 20 kV distribution network. If this wiring mode is directly applied to my country's 10 kV distribution network, the short-circuit current of my country's 10 kV distribution network will greatly exceed the rated value of existing equipment (generally 25 kA or 31.5 kA) , a large number of transformations are required, which not only requires a large investment, but also may affect the normal power supply of users during the transformation period.

Contents of the invention

The purpose of the present invention is to provide a high-reliability closed-loop wiring method for a medium-voltage distribution network, which can realize the closed-loop operation of the same transformer without increasing the short-circuit current of the distribution network.

The present invention is realized by the following scheme: a high-reliability closed-loop wiring method for a medium-voltage distribution network, which is characterized in that it includes the following steps:

Step S01: Lead out the 10 kV side of each transformer in the substation to two separate busbars;

Step S02: Connect the two sections of busbars through a ring network unit to form a closed-loop ring network structure. At least one circuit breaker is set in the ring network unit as a tie switch, and the closed-loop ring network structure formed by each transformer is uniform. The tie switch and the tie line are connected to the closed-loop ring network structure formed by another transformer; when the transformer is in normal operation, the circuit breakers at both ends of the tie line are turned on, and the tie line is in a standby state; and the power supply load on each ring network is not 40% of the power supply load exceeding the thermal stability limit of the two feeder lines.

In one embodiment of the present invention, when both feeder lines of a certain ring network are faulty and out of service, the tie circuit breaker is closed, and the tie line changes from the standby state to the running state; the load on the faulty feeder line is connected by the non-faulty ring network Line powered.

In an embodiment of the present invention, a differential relay protection is configured on the circuit breaker.

The method of the present invention adopts the method of "closed-loop operation + differential protection" and is applied to the 10 kV distribution network. When a feedback line fails, the fault location and isolation are quickly implemented through the relay protection equipment, and the power supply is quickly restored; when the two feedback lines After a failure, support can be realized through the tie line, and the power supply can be restored quickly. It is suitable for power supply areas with high reliability requirements. In this method, the two feeders forming the ring network come from different busbars of the same transformer, and only one transformer supplies short-circuit current to the ring network, and the level of the short-circuit current is no different from that of conventional open-loop operation.

Description of drawings

Figure 1 is a schematic diagram of the closed-loop wiring of the 10kV feeder of the substation with three main transformers (the dotted line box is the current wiring mode).

Figure 2 is a schematic diagram of the state changes of the circuit breakers on both sides of the fault point after a fault occurs on a single-circuit 10kV feeder.

Figure 3 is a schematic diagram of the state changes of the circuit breakers on both sides of the fault point and the tie line circuit breaker after the double-circuit 10kV feeder of the same transformer fails.

Detailed ways

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

This embodiment provides a high-reliability closed-loop wiring method for a medium-voltage distribution network, which is characterized in that it includes the following steps:

Step S01: Lead out the 10 kV side of each transformer in the substation to two separate busbars;

Step S02: Connect the two sections of busbars through a ring network unit to form a closed-loop ring network structure. At least one circuit breaker is set in the ring network unit as a tie switch, and the closed-loop ring network structure formed by each transformer is uniform. The tie switch and the tie line are connected to the closed-loop ring network structure formed by another transformer; when the transformer is in normal operation, the circuit breakers at both ends of the tie line are turned on, and the tie line is in a standby state; and the power supply load on each ring network is not 40% of the power supply load exceeding the thermal stability limit of the two feeder lines.

Please refer to accompanying drawings 1, 2 and 3. In this embodiment, there are three main transformers in the substation, namely main transformer 1, main transformer 2 and main transformer 3, and each main transformer forms a closed-loop network structure , taking the main transformer 1 as an example, its 10kV side leads to two independent busbars, namely busbar 11 and busbar 12, and each busbar feeds out a 10kV feeder, corresponding to feeder 11 and feeder 12, The feeder 11 is connected to the two ring network units HW11 and HW12 through the circuit breaker 11, and the feeder 12 is connected to the two ring network units HW14 and HW13 through the circuit breaker 12, and finally connected to form a closed-loop ring network structure. The ring network unit is either a power distribution station, or a ring network cabinet, or a switching station, and a circuit breaker is used as a connecting element inside each ring network unit. A differential protection device is installed in the closed-loop ring network structure formed by each transformer (not shown in the figure, and an existing commercially available differential protection device can be used). Under normal operating conditions, the power supply load on each closed-loop network structure shall not exceed 40% of the thermal stability limit power supply load of the two feedback lines.

In the closed-loop ring network structure of the main transformer 1 , the ring network unit HW13 is provided with a tie switch, which is connected to the closed-loop ring network structure of the main transformer 2 through the tie line 12 . In the figure, the solid block structure is the circuit breaker in the closed state under normal operation, and the hollow block structure is the circuit breaker in the open state under normal operation.

Similarly, both the bus bar 21 and the bus bar 22 come from the 10 kV side of the main transformer 2 , and both the bus bar 31 and the bus bar 32 come from the 10 kV side of the main transformer 3 . HW11, HW12...HW33, HW34 in the figure represent ring network cabinets, distribution stations (rooms) and other connection units that can form a ring network. Each connection unit uses a 10 kV circuit breaker as a connection device. The connection unit is connected to the electric load through the closed circuit breaker, and the substation supplies power to the electric load through the feeder and the ring network connection unit. The tie line 12 and the tie line 23 are connected to different connecting units inside the closed loop network. Normally, the circuit breakers on both sides of the tie line are in the off state, that is, the tie line is not connected and is in a standby state.

When any feeder (such as feeder 11) fails, the following actions will occur in sequence:

The differential protection detects a fault; an action command is issued, the circuit breakers on both sides of the fault point are opened (for example, circuit breaker 11 and circuit breaker A in the ring network HW11 are opened), and the faulty line section on the feeder 11 is isolated; HW11, HW12 , HW13, and HW14 are all powered by the feeder 12.

When two feeders from the same transformer (e.g. feeder 11 and feeder 12) fail, the following actions take place in sequence:

The differential protection detects a fault; an action command is issued, and the circuit breakers on both sides of the fault point are opened (for example, circuit breaker 11 and circuit breaker A in the ring network HW11 are opened, circuit breaker 12 and circuit breaker B in the ring network HW14 are opened), The faulty line section on the feeder 11 and the feeder 12 is isolated; the circuit breakers on both sides of the tie line 12 are closed, and the tie line 12 changes from the standby state to the running state. The loads on HW11 , HW12 , HW13 and HW14 are all powered by the feeder 21 and the feeder 22 .

The main transformer mentioned above can be the main transformer of a 220 kV substation or a 110 kV substation, but the low voltage side of the transformer is 10 kV.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention. the

Claims (3)

1. a medium voltage distribution network high reliability closed loop mode of connection, is characterized in that comprising the following steps:

Step S01: 10 kilovolts of sides of every transformer of transformer station are drawn to independently two sections of buses;

Step S02: described two sections of buses ring-main unit of respectively hanging oneself is connected, to form closed loop ring network structure, a circuit breaker is at least set as interconnection switch in described ring-main unit, every formed closed loop ring network structure of transformer is all connected on the formed closed loop ring network structure of another transformer by this interconnection switch and interconnection; When transformer normally moves, the circuit breaker at interconnection two ends is all opened, and interconnection is in stand-by state; And the load of powering on each looped network is no more than 40% of the thermally-stabilised limit supply load of two feedback line.

2. medium voltage distribution network high reliability closed loop mode of connection according to claim 1, is characterized in that: when the equal fault of two feedback line of certain looped network is stopped transport, network interconnecting circuit is closed, and interconnection transfers running status to by stand-by state; Load on fault feeder is powered by interconnection by non-fault looped network.

3. medium voltage distribution network high reliability closed loop mode of connection according to claim 1, is characterized in that: on described circuit breaker, configure differential type relaying protection.

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