Regarding the busbar protection, in the first two phases (busbar protection1, busbar protection II), the busbar protection is mainly introduced. In this issue, another new busbar protection-busbar arc protection is introduced. The arc protection is mainly used for 35kV and 10kV. And 6kV and other medium and low voltage grade busbars.
Arc protection is a new type of protection developed in recent years with the development of optoelectronic technology. The traditional protection is mainly based on the electrical quantity such as voltage, current, impedance and power. The arc protection is mainly based on current and arc. The criterion is that the criterion of arc (light intensity) is increased compared to conventional protection.
The following briefly introduces the application of special bus protection for medium and low voltage at home and abroad.
In foreign countries, due to the attention of governments in the protection of medium and low voltage busbars, it has been stipulated in the regulations that special busbar protection must be installed for medium and low voltage busbars, and the ratio of various special busbar protections for medium voltage switches in Europe, North America, Russia and Commonwealth countries. Has exceeded 95%.
Domestic medium and low voltage busbars are generally not equipped with dedicated fast busbar protection, but this also meets the requirements of the national standard "Design rules for relay protection and automatic devices for electrical installations" (GB50062-92) and current power industry regulations. Since the domestic medium and low voltage busbars do not have special busbar protection, how is the protection of the medium and low voltage busbars achieved? Solving this problem is mainly achieved in the following three ways:
1 transformer backup overcurrent protection, typical protection action time is 1.2s ~ 2.0s;
2 Transformer backup overcurrent protection with feeder quick-break protection and blocking, the typical protection action time is 0.3s~0.5s;
3 As with the voltage level busbar above 110kV, the busbar differential protection is configured, and the typical protection action time is 15ms;
The shortcomings of these three kinds of protection are also obvious. The protection of 1 and 2 is too long for the total resection time less than 100ms. When the fault is removed, most of the equipment is damaged and cannot be used. The degree of damage of the arc light fault depends on the magnitude of the arc photocurrent and the length of the ablation time. The energy generated by the arc light and the cut-off time T increase exponentially and rapidly as shown in the following figure:
To ensure that the equipment is not structurally damaged, the cutting time must be minimized.
The following is an estimate of the length of various arcing times and the degree of damage to the equipment introduced by foreign materials:
| Arcing time | Equipment damage |
| 35 ms | No significant damage, generally can be put into use after testing the insulation resistance |
| 100ms | Less damage, cleaning or some minor repairs before the switchgear is put into operation again |
| 500ms | The damage to the equipment is very serious, and the personnel at the site are also seriously injured. Some equipment must be replaced before it can be put into operation. |
3 will be limited by the location of the CT installation, the wiring is complex and the investment cost is high, can not be universally promoted, but only used in some substations with high requirements for busbar protection.
As the frequency of short-circuit faults in the medium and low voltage busbars is getting higher and higher, the special busbar protection for medium and low voltage busbars is becoming more and more inevitable. The appearance of arc protection has just made up for the above three kinds of protection. At present, there are many manufacturers of arc light protection, there are domestic and foreign, and there are mainly VAMP in foreign countries. The main domestic ones are Nanjing Hongyi Electric and Guodian Nanrui.
Regarding the arc protection device, although the manufacturers have different configurations, they are generally similar. We take the DCR360ARC series of Nanjing Hongyi Electric as an example to illustrate the protection principle of arc protection.
1. Arc protection logic diagram
The DPR360ARC arc protection is grouped on the basis of a current acquisition unit. A total of 272 arc probes can be correlated to any set of current signals. When the arc unit transmits the arc signal from the arc sensor to the main control unit or the arc unit, the current element starts to act and the arc light protects. The current starting component is divided into a sudden starting component and a constant starting component, and the two components take logic or logic; the device can also select only the arc signal single criterion as the action logic criterion. The specific logic criteria are as follows:
2. Arc sensor
The arc sensor of DPR360ARC arc protection system has spectrum identification function, which can accurately identify the characteristic spectrum of arc light, effectively distinguish various kinds of light sources such as reflected sunlight, illumination light, and maintenance of hand-light and light in daily working environment, avoiding other light source to arc protection system. Interference, improve the sensitivity and reliability of protection actions. These arc sensors are purely lenticular and can absorb visible light and retain ultraviolet light. The sensor transmits the optical signal to the main control unit or the arc unit through the analog optical fiber, and the photoelectric conversion is realized by the main control unit or the arc unit.
3. Protection of export quickness
Two outlets of electromagnetic relay and solid state relay can be selected. The exit time of the electromagnetic relay does not exceed 8ms, and the exit time of the solid state relay does not exceed 4ms, which is much faster than the traditional busbar protection.
4.100% fast protection
The DPR362ARC model in the DPR360ARC arc protection system provides 100% protection for medium and low voltage busbars, cable compartments, and breaker room faults. In other words, the DPR362ARC arc protection system not only protects the busbar, but also protects other faults inside the switchgear. The protection is selective. For example, if an outgoing cable room has an arc short circuit fault, the arc protection can only cut off the outgoing line, and other fault-free equipment can continue to operate without being affected.
5. Busbar arc protection system typical application
Typical application example of bus arc protection system
System composition: 2 power supply lines, 2 main transformers, two busbars, single busbar segmentation structure, I mother and II mother are 7 interval units.
System Configuration:
The arc protection system is equipped with one DPR361ARC main control unit. The main control unit is equipped with three sets of current acquisition modules. It is equipped with 16 arc sensors, including one sensor at Q2 and Q4, and two sensors at Q5. I mother and mother II. Each of the 6 sensors in the bay unit is equipped with 5 trip outlets.
There is 1 sensor at Q2, 1 sensor at Q5, and 6 sensors for I bus spacer unit are connected to sensor interfaces 1 to 8 of the 4X position arc expansion plug of the device. One sensor at Q4, one sensor at Q5, and six sensors at the II female spacer unit are connected to sensor interfaces 1 to 8 of the 2X position arc expansion plug of the device.
At Q2, TA is connected to the three-phase current of device L1, TA is connected to device L2 three-phase current at Q4, and TA is connected to device L3 three-phase current at Q5.
Device exit 1 hops Q1, exit 2 hops Q2, exit 3 hops Q3, exit 4 hops Q4, exit 5 hops Q5, and exit 6 acts as a failure to initiate the exit.
Action process analysis
1 When the I mother and the II mother are running in a row, if the busbar short circuit fault occurs in a certain interval unit of the I mother, the corresponding interval arc sensor acts, and the I mother incoming current changes suddenly, the arc protection action, jump Q1, Q2, Q5 switch; The II mother continues to operate without failure.
2 When the I mother and the II mother are running in the column, if the busbar short circuit fault occurs in a certain interval unit of the mother mother, the corresponding interval arc sensor operates, and the II mother incoming line current changes suddenly, the arc protection action, jump Q3, Q4, Q5 switch; I mother has no faults to continue to run.
3 When the I mother and the II mother are running in parallel (Q5 switch is closed, the I female input line is put into operation, and the II female incoming line is taken out of operation). If the busbar short circuit fault occurs in a certain interval unit of the mother mother, the corresponding interval arc sensor acts, the mother couplet The current is abrupt, the arc protection action, the Q5 switch is skipped, and the I mother does not continue to operate. If a mother bus short circuit fault occurs in a certain interval unit of the mother, the corresponding interval arc sensor operates, and the I mother line current changes suddenly, the arc protection action, the Q1 and Q2 switches, and the fault is removed.
4 When I mother and II mother are running in parallel (Q5 switch is closed, II female incoming line is put into operation, I female incoming line is out of operation), the fault action is similar to 3, and will not be described here.
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