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Discussion on distribution automation system with closed-loop operation mode
Keywords automation system
Discussion on distribution automation system with closed-loop operation mode
0 overview?
As the last link of power generation, transformation, transmission and distribution, power distribution plays a very important role in power production. Due to historical reasons, the past has not received enough attention. With the development of economy and the improvement of living standards, higher requirements are put forward for the quality and reliability of power supply. After the large-scale transformation of the two networks, the distribution network layout has been optimized, but to further improve the reliability of the distribution network, a high level of distribution network automation must be fully realized. ?
In fact, in recent years, many areas in China have carried out pilot work of distribution network automation at different levels and scales, and achieved certain results. However, because almost all systems are in open-loop operation mode [1], the recovery time is 30? S even a few minutes, users who can't meet the higher requirements of power supply reliability can only take high-cost ways such as double-circuit power supply, self-provided power generation and large-capacity UPS to make up for it. In this context, the author cooperated with relevant power enterprises to equip a closed-loop distribution automation system in a national development zone. After more than two years of operation, it is proved that the system functions and indicators meet the design requirements, greatly improving the reliability of distribution network operation, which is of pioneering significance. ?
1 general situation of distribution network in power supply area and the function and goal of distribution network automation planning
Region *** 10? Km2, area 1 10? 1 kV substation, the current investment is 3 1.5? 2 MVA transformers. 1 10? KV incoming lines are connected by two internal bridges, which are from the superior 500? The outlet of kilovolt substation is 35? kV？ 10, 10? kV？ 14 circuit, before the transformation, overhead lines and cable outlets were mixed, and the neutral point was not grounded; After the transformation, all of them are led out by cable tube arrangement and grounded with small resistance. The secondary equipment adopts conventional relay protection and telecontrol, and only telemetry and telecontrol signals are sent to the superior dispatching center. Communication channels are carrier and spread spectrum, and commercial telephones are available. ?
It is planned to fully realize the automation of distribution network in two stages. The main objectives of the plan are:
(1) Fully closed-loop operation realizes regional distribution network automation. ?
(2) Improve the reliability of power supply, reaching the "N- 1" power supply safety criterion, and the power supply reliability rate is 99.99%. ?
(3) Establish a distribution monitoring system to improve the quality of power supply, and the voltage qualification rate is 98%. ?
(4) When the line has a permanent fault, it can automatically identify, isolate and restore power supply. ?
(5) Realize the load management functions such as remote monitoring and meter reading of client equipment. ?
(6) At the same time, adapt to the open-loop operation mode. This distribution automation system mainly realizes the following functions:?
1)SCADA functions include data acquisition and processing, man-machine contact and tabulation and printing; ?
2) Feeder automation functions are mainly fault identification, isolation and automatic power supply recovery; ?
3) GIS geographic information system function; ?
4) Load side management functions include remote automatic meter reading function; ?
5) Communication functions with RTU of substation and superior dispatching center include sending telemetry, telecommunications and receiving control and dispatching commands. For voltage and reactive power control, this system only transmits the voltage operation value to the substation/superior dispatching center, and does not carry out voltage regulation operation in this system, but provides an interface to access the user-side voltage regulator, and can also convey and execute the voltage regulation instruction of the superior distribution center, and reserve space for function expansion. ?
What are the main contents of the transformation of the original distribution network?
2. 1 substation integrated automation transformation?
Because of this 1 10? The original protection telecontrol of kV substation adopts conventional devices, which does not have the function of networking and communication with user substations. Therefore, firstly, the substation is reformed, and all of them adopt microcomputer telecontrol and protection system. The reformed system has perfect "four remote" function and microcomputer protection function, and can communicate with dispatching center, superior dispatching center, local hierarchical dispatching center and customer RTU/FTU. ?
2.2 Transformation of some users' distribution rooms?
Because the automatic planning and design of distribution network in this development zone adopts the cable ring network mode, the substation rooms involved are all wired in the form of secondary loop after transformation, which is connected with the upper and lower enterprises into a ring network, and the outgoing lines are equipped with remote-controlled switches. ?
DEP-900 FTU is installed in the step-down transformers of various enterprises, and connected into a ring with optical fiber as the channel. The whole distribution network in the area adopts hand-in-hand loop network scheme, which can automatically trip the nearest circuit breaker when the line fails, with short action time and no influence on the system without relying on the main station, thus avoiding the disadvantages caused by the need for multiple switches to trip and judge the fault in the open-loop system. ?
2.3 Change of grounding mode and selection of grounding resistance value?
After the transformation, all of them are changed to cable outlets, and the capacitance current is much higher than that of overhead lines. It is necessary to change the original small current grounding mode into large current grounding mode through small resistance grounding. Starting from the situation of single-phase grounding fault, several neutral grounding resistance values are tried to calculate the steady and instantaneous state of the system, and the changed single-phase grounding fault current value, single-phase grounding fault sound phase voltage value, arc grounding overvoltage value and ferromagnetic resonance overvoltage value are compared and analyzed, and the grounding resistance value is determined by comprehensive calculation considering the total capacitance current of the system, fault current during single-phase grounding fault, power frequency overvoltage, relay protection coordination and communication interference limitation. ?
2.4 Adjustment of protection setting value?
After changing the system grounding mode and installing FTU with longitudinal differential protection function in fault state, the original 1 10? Various protection settings of feeder, bus, main transformer and standby automatic switching in kV substation have been adjusted according to the new system structure and operation mode, and the upper layer is 500? The protection setting value of the corresponding outgoing line of kV substation has also been fine-tuned. ?
2.5 others?
A few enterprises originally used overhead lines, and this time they arranged pipes and cables in a unified way. In addition, the multi-mode fiber ring network channel is laid in the residential area, which not only provides high-speed and reliable digital channels for distribution automation, but also reserves communication means for meter reading, MIS system networking and multimedia data transmission. ?
Because FTU and switching operation must have a reliable uninterrupted power supply to ensure that FTU working power supply, communication power supply and switching operation power supply can still be provided when a line fault occurs in the distribution network, resulting in protection action, outlet switch tripping, complete power failure of the fault circuit or equipment maintenance, so each user transformer is equipped with a dedicated small 220VDC high-frequency switching DC operation power supply. ?
Discussion on closed-loop operation mode of distribution automation system Key words Overview of automation system Discussion on closed-loop operation mode of distribution automation system 0 Overview? As the last link of power generation, transformation, transmission and distribution, power distribution plays a very important role in power production. Due to historical reasons, the past has not received enough attention. With the development of economy and the improvement of living standards, higher requirements are put forward for the quality and reliability of power supply. After the large-scale transformation of the two networks,
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Discussion on distribution automation system with closed-loop operation mode
Keywords automation system
Discussion on distribution automation system with closed-loop operation mode
0 overview?
As the last link of power generation, transformation, transmission and distribution, power distribution plays a very important role in power production. Due to historical reasons, the past has not received enough attention. With the development of economy and the improvement of living standards, higher requirements are put forward for the quality and reliability of power supply. After the large-scale transformation of the two networks, the distribution network layout has been optimized, but to further improve the reliability of the distribution network, a high level of distribution network automation must be fully realized. ?
In fact, in recent years, many areas in China have carried out pilot work of distribution network automation at different levels and scales, and achieved certain results. However, because almost all systems are in open-loop operation mode [1], the recovery time is 30? S even a few minutes, users who can't meet the higher requirements of power supply reliability can only take high-cost ways such as double-circuit power supply, self-provided power generation and large-capacity UPS to make up for it. In this context, the author cooperated with relevant power enterprises to equip a closed-loop distribution automation system in a national development zone. After more than two years of operation, it is proved that the system functions and indicators meet the design requirements, greatly improving the reliability of distribution network operation, which is of pioneering significance. ?
1 general situation of distribution network in power supply area and the function and goal of distribution network automation planning
Region *** 10? Km2, area 1 10? 1 kV substation, the current investment is 3 1.5? 2 MVA transformers. 1 10? KV incoming lines are connected by two internal bridges, which are from the superior 500? The outlet of kilovolt substation is 35? kV？ 10, 10? kV？ 14 circuit, before the transformation, overhead lines and cable outlets were mixed, and the neutral point was not grounded; After the transformation, all of them are led out by cable tube arrangement and grounded with small resistance. The secondary equipment adopts conventional relay protection and telecontrol, and only telemetry and telecontrol signals are sent to the superior dispatching center. Communication channels are carrier and spread spectrum, and commercial telephones are available. ?
It is planned to fully realize the automation of distribution network in two stages. The main objectives of the plan are:
(1) Fully closed-loop operation realizes regional distribution network automation. ?
(2) Improve the reliability of power supply, reaching the "N- 1" power supply safety criterion, and the power supply reliability rate is 99.99%. ?
(3) Establish a distribution monitoring system to improve the quality of power supply, and the voltage qualification rate is 98%. ?
(4) When the line has a permanent fault, it can automatically identify, isolate and restore power supply. ?
(5) Realize the load management functions such as remote monitoring and meter reading of client equipment. ?
(6) At the same time, adapt to the open-loop operation mode. This distribution automation system mainly realizes the following functions:?
1)SCADA functions include data acquisition and processing, man-machine contact and tabulation and printing; ?
2) Feeder automation functions are mainly fault identification, isolation and automatic power supply recovery; ?
3) GIS geographic information system function; ?
4) Load side management functions include remote automatic meter reading function; ?
5) Communication functions with RTU of substation and superior dispatching center include sending telemetry, telecommunications and receiving control and dispatching commands. For voltage and reactive power control, this system only transmits the voltage operation value to the substation/superior dispatching center, and does not carry out voltage regulation operation in this system, but provides an interface to access the user-side voltage regulator, and can also convey and execute the voltage regulation instruction of the superior distribution center, and reserve space for function expansion. ?
What are the main contents of the transformation of the original distribution network?
2. 1 substation integrated automation transformation?
Because of this 1 10? The original protection telecontrol of kV substation adopts conventional devices, which does not have the function of networking and communication with user substations. Therefore, firstly, the substation is reformed, and all of them adopt microcomputer telecontrol and protection system. The reformed system has perfect "four remote" function and microcomputer protection function, and can communicate with dispatching center, superior dispatching center, local hierarchical dispatching center and customer RTU/FTU. ?
2.2 Transformation of some users' distribution rooms?
Because the automatic planning and design of distribution network in this development zone adopts the cable ring network mode, the substation rooms involved are all wired in the form of secondary loop after transformation, which is connected with the upper and lower enterprises into a ring network, and the outgoing lines are equipped with remote-controlled switches. ?
DEP-900 FTU is installed in the step-down transformers of various enterprises, and connected into a ring with optical fiber as the channel. The whole distribution network in the area adopts hand-in-hand loop network scheme, which can automatically trip the nearest circuit breaker when the line fails, with short action time and no influence on the system without relying on the main station, thus avoiding the disadvantages caused by the need for multiple switches to trip and judge the fault in the open-loop system. ?
2.3 Change of grounding mode and selection of grounding resistance value?
After the transformation, all of them are changed to cable outlets, and the capacitance current is much higher than that of overhead lines. It is necessary to change the original small current grounding mode into large current grounding mode through small resistance grounding. Starting from the situation of single-phase grounding fault, several neutral grounding resistance values are tried to calculate the steady and instantaneous state of the system, and the changed single-phase grounding fault current value, single-phase grounding fault sound phase voltage value, arc grounding overvoltage value and ferromagnetic resonance overvoltage value are compared and analyzed, and the grounding resistance value is determined by comprehensive calculation considering the total capacitance current of the system, fault current during single-phase grounding fault, power frequency overvoltage, relay protection coordination and communication interference limitation. ?
2.4 Adjustment of protection setting value?
After changing the system grounding mode and installing FTU with longitudinal differential protection function in fault state, the original 1 10? Various protection settings of feeder, bus, main transformer and standby automatic switching in kV substation have been adjusted according to the new system structure and operation mode, and the upper layer is 500? The protection setting value of the corresponding outgoing line of kV substation has also been fine-tuned. ?
2.5 others?
A few enterprises originally used overhead lines, and this time they arranged pipes and cables in a unified way. In addition, the multi-mode fiber ring network channel is laid in the residential area, which not only provides high-speed and reliable digital channels for distribution automation, but also reserves communication means for meter reading, MIS system networking and multimedia data transmission. ?
Because FTU and switching operation must have a reliable uninterrupted power supply to ensure that FTU working power supply, communication power supply and switching operation power supply can still be provided when a line fault occurs in the distribution network, resulting in protection action, outlet switch tripping, complete power failure of the fault circuit or equipment maintenance, so each user transformer is equipped with a dedicated small 220VDC high-frequency switching DC operation power supply. ?
Discussion on closed-loop operation mode of distribution automation system Key words Overview of automation system Discussion on closed-loop operation mode of distribution automation system 0 Overview? As the last link of power generation, transformation, transmission and distribution, power distribution plays a very important role in power production. Due to historical reasons, the past has not received enough attention. With the development of economy and the improvement of living standards, higher requirements are put forward for the quality and reliability of power supply. After the large-scale transformation of the two networks,