Effective information identification and application of distribution network line fault tripping

introduction

Under the background of the rapid development of distribution network automation technology, the widespread application of automatic switches plays a vital role in isolating line faults and minimizing the scope of power outages. The correct and rapid acquisition of distribution network line fault tripping information plays a positive role in quickly determining the fault type and fault area, and is conducive to rapid power restoration after line fault tripping. However, at present, distribution network operation and maintenance personnel are generally unable to correctly identify the effective information of fault tripping, so there is an urgent need to scientifically analyze the effectiveness of tripping information.

1. Effective information identification of fault tripping

Under the premise of the application of distribution network automation, the effective information for fault tripping analysis includes basic information, master station "three remote" information, terminal device records, etc. They are a unified whole, and each part has different advantages and disadvantages. They need to be used in combination to ensure the accurate identification of fault type and fault area, so as to effectively guide the rapid power restoration work after line fault.

1.1 Basic line information

The basic information is the main configuration of the line, which is the basis for fault tripping analysis. It mainly includes feeder single-line diagram, setting list, equipment manual, etc. The feeder single-line diagram shows the line grid structure, the setting list shows the switch tripping strategy, and the equipment manual can help personnel familiarize themselves with the equipment characteristics. When a fault trip occurs, these basic information will be involved in the accident event analysis.

The single-line diagram of the feeder contains 10KV electrical primary equipment on the outgoing line, describing the equipment network connection of a single feeder. It is an important platform and basis for calculation and analysis by power operators. The 10KV feeder facilities mainly include distribution transformers, circuit breakers, disconnectors, distribution lines, lightning arresters, etc. The single-line diagram of the feeder focuses on the logical connection of the network, which is suitable for the analysis and decision-making of operators and dispatchers. It plays a great role in fault tripping analysis, can clearly reflect the line grid structure and equipment conditions, and make preliminary judgments on possible fault types and fault areas.

The setting list is the carrier for the approval and execution of terminal setting parameters, which generally includes the manufacturer model of the protection device, CT ratio, setting item parameters, etc. Relay protection is an important measure to detect faults or abnormal conditions in the power system, thereby issuing an alarm signal, or directly isolating and removing the faulty part. Through the setting list, you can understand the type of protection (such as overcurrent, zero sequence, voltage protection, etc.) and parameter settings of the switch, which is the principle basis for fault tripping analysis.

1.2 Master station "three remote" information

"Three remote" information refers to the information that the automation terminal interacts with the master station system through communication technology, including telemetry, telesignaling, and remote control. Among them, telemetry is the measurement value of the terminal, such as current, voltage, etc.; telesignaling is the equipment status information, which is a SOE message fed back in the form of action or reset event; remote control refers to the master station sending a command to the terminal to change the equipment status. The "three remote" information of the master station is an important means of monitoring distribution equipment and an important basis for tripping fault analysis. It can help distribution operation and maintenance personnel quickly obtain fault information, such as switch position information, alarm signals, sudden changes in telemetry, etc., to grasp the abnormal situation of the equipment in a timely manner, so as to quickly locate the fault area. Its disadvantage is that it is highly dependent on communication. When the communication is unstable or interrupted, the terminal information cannot be fully received.

1.3 Terminal device records

Terminal device information that is helpful for fault analysis includes recording information, fixed value parameters, telemetry, input, etc. Fault recording information reflects the changes in the equipment analog quantity and state quantity before and after the fault occurs, and can intuitively analyze the fault situation: accurate setting of fixed value parameters is the basis for accurate action of relay protection: terminal telemetry and input conditions reflect the real-time operating conditions of the equipment, which can analyze the possible abnormalities of the terminal and guide fault tripping analysis more effectively. Due to the decentralized distribution of distribution network switches, most of them use wireless communication, which has unstable factors, and the frequency and flow of message upload are limited. The master station may not receive complete information, and the judgment of the fault is prone to deviation. At this time, it can only rely on the automation terminal itself. Its disadvantage is that it can only be viewed on the spot, which consumes manpower and time.

2 Application of line fault information

The following uses a typical fault tripping event to analyze the effective application of fault information, thereby completely eliminating safety hazards in equipment operation and ensuring power supply reliability.

2.1 Fault phenomenon

2020-08-12T16:41, the 601 switch of the 10KV Bijia B line Huanjin public distribution station of a power supply bureau lost power and opened, but the power-on closing function was not started after the power was restored on the power supply side: about 54 minutes later, after checking that there was no abnormality in the line behind the switch, the trial power supply was successful.

2.2 Effective Information Collection

In view of the abnormal protection of the 601 switch of the 10KV Bijia B line Huanjin public distribution station, the following information needs to be collected:

(1) Feeder single-line diagram. According to the single-line diagram of Bijia B Line, the 601 switch of the 10KV Bijia B Line Huanjin Public Distribution Station is the incoming switch, the front side is the substation switch, and the back side has 5 distribution transformers, which are respectively controlled by load switches.

(2) Protection setting configuration. According to the setting list, the following information is obtained: the protection device is Changyuan Shenrui PRS-3342AE, version number is SV03.110, voltage time type logic protection function is activated, conventional protection is exited, and zero sequence alarm and overcurrent alarm functions are retained. The main protection setting items are as follows: power failure trip time limit 3.5s, power on closing (x) time limit 42s, closing confirmation (Y) time limit 5s, power failure trip throw 1 (activated), power on closing throw 1 (activated), fault current detection throw 0 (exited).

(3) Manufacturer's manual. In the case that the switch was not energized and closed, the manufacturer's "10KV Vacuum Circuit Breaker Complete Equipment Technical Instructions" was consulted. "Voltage and current type/time type energization and charging are good" is the prerequisite for "energization and closing action", while "no pressure on both sides of the switch" and "switch jump" are necessary conditions for "voltage and current type/time type energization and charging are good".

(4) "Three remote" information of the master station. Checking the master station system, the messages before and after the switch tripped due to fault are shown in Figure 1. The voltage loss protection of the switch 601 of Huanjin Public Distribution Station was activated, the switch was opened, and the logic function was activated to lock the closing: about 54 minutes later, the switch was closed manually.

(5) Terminal device records. The switch protection terminal of 601 of Huanjin Public Distribution Station was inspected on site, and the SOE records, protection records, fault recording records, and fixed value parameter settings of the terminal were retrieved. Checking the device SOE records, as shown in Figure 2, the terminal records are consistent with the information of the main station, but there is an abnormal situation, that is, after the device lost power and opened, there was no record of the power-on closing and charging good remote signal (power-on closing allowed) being set to 1: Checking the device protection action records, as shown in Figure 3, at 16:41:49.023 on the same day, the voltage and current type power-off opening action: Using the manufacturer's supporting program, the device fault recording diagram was retrieved, as shown in Figure 4, the power-off opening of both sides of the 601 interval of Huanjin Public Distribution Station was started, and the power-off opening action was taken 3.5s later. The abnormal situation was that there was a short-term voltage on both sides of the interval, and the bus side Ua1=81.405V, Uc1=82.559V: After checking the terminal fixed value parameters, they were consistent with the fixed value single settings, eliminating the fixed value setting problem.

Figure 2 Device SOE record

Figure 3 Device protection action record

2.3 Process Analysis

According to Figures 2 and 3, it is confirmed that the "three remote" information of the master station is correct, and it is found that there is no record of the remote signal setting 1 after the switch is opened. Checking the waveform record in Figure 4, the power-off opening of both sides of the Huanjin 601 switch interval is started, and the power-off opening action is performed after 3.5s, which is consistent with the setting value of the fixed value sheet: the bus PT has a short-term pressure (the pressure value is 70V) before the switch trips, indicating that the PT on the incoming line side of the switch may have recovered the power-on state at this time. Combined with the above-mentioned manual information, it is speculated that after the 601 switch tripped, the line side has been in a single-side pressure state, so it cannot meet the power-on closing charging logic, which leads to the inability to execute the power-on closing action of this interval device. Check the variable The power station switch setting sheet shows that the reclosing time is exactly 3.5s: after checking the master station information, the substation switch tripped due to an instantaneous fault, and the reclosing action was successful. Therefore, it is judged that the power-off opening time limit of the 601 switch is the same as the reclosing time of the front side, and the 601 switch is slower than the substation switch. These two factors cause the 601 switch to refuse to close. Later, the power-off opening time of the series of devices was adjusted to be different from the reclosing time of the front power supply. After one year of operation, it has been shown that the operation is normal, which verifies the correctness of the analysis results and also proves the validity of the single-line diagram, setting sheet, manufacturer's manual, master station "three remote" information, terminal device records and other information.