On the power system neutral point grounding

1、 on the power system neutral point groundingpaper keywords neutral-grounded systems abstract for the distribution system neutral grounding involving the safe operation of power grid, power supply reliability, over-voltage and insulation co-ordination, relay protection, grounding design, a number of

2、factors, but also for communications and electronic equipment electronic jamming, personal security, etc. have a major impact. now available for distribution systems are mainly neutral point grounding method is not grounded, the neutral point directly to ground, neutral ground and the neutral point

3、by the resistance by the four kinds of arc suppression coil grounding, this paper these four kinds of neutral grounding were analyzed and compared. power systems neutral grounding refers to the power system in the generator and transformer neutral point and ground connections. ground current system

4、can be divided into large and small ground current system, the former that is directly grounded neutral point current system, which in turn is divided into non-grounded neutral system and the neutral point arc suppression coil or resistance grounding system. the choice of neutral grounding related t

5、o technical, economic, security and other aspects, is a comprehensive issue, due to the level of national electric power technology, and conditions, factors such as operating experience different countries approach to this question exactly the same master in what levels of power system grounding, is

6、 critical for students to learn knowledge of power systems and power system, the staff are very important. a large earth current system large ground current system will soon be directly grounded neutral point. the system is running in the event of a-phase ground fault on the formation of single-phas

7、e ground fault, the line will flow through a great short-circuit current, so that prompt action line protection devices, circuit breakers trip excision failure. high-current grounding system in the event of single-phase ground fault, the neutral point potential is still zero, a relatively non-fault

8、voltage basically unchanged, that is its greatest strength. therefore, in such a system of power transmission equipment insulation level only need to press the grid phase voltage considerations, the more the economy (110kv and above, chinas power grid more to adopt the method). in addition, the syst

9、em single-phase ground fault, it will not produce intermittent arcing caused by over-voltage, will not be cause equipment damage. large earth-current system is not the installation of insulation monitoring device. direct grounding the neutral point are also many shortcomings, first, single-phase gro

10、und fault occurs when the power grid are not allowed to continue running, preventing short-circuit current can cause greater damage, so the reliability is better than a ground current system. second, the direct ground neutral system in the event of operation of single-phase ground fault, its locatio

11、n would then have a greater step voltage and contact voltage. at this point, if the staff posted under false or mistaken touch live conductors are prone to electric shock injuries. this need to strengthen safety education and proper configuration relay protection and strict security measures to avoi

12、d accidents. third, the neutral point grounding directly to single-phase ground fault ground current generated when a larger impact on the communication system the interference is also big, especially when the power lines and communication lines parallel to trends, due to coupling produces induced v

13、oltage on the communication disruptive. 2, small earth current system small current grounding system, that is ungrounded or arc suppression coil or resistance grounding system. little earth current system can be divided into non-grounded neutral system, neutral grounding via arc or resistance ground

14、ing system. (a) ungrounded system neutral point ungrounded system, that is, the neutral-point-to-ground insulation. this grounding structure is simple, convenient, without any additional equipment, invest in the economy. lokv overhead lines for the radiation-based or tree-shaped shaped power supply

15、network. neutral point ungrounded system, the advantage of single-phase ground fault occurs, due to ground current is small, if the transient fault, the general can automatically extinction, non-fault phase voltage is not increased and will not destroy the symmetry of the system, according to an reg

16、ulatory requirements, the system single-phase ground fault occurs can be allowed to continue to run after no more than two hours, to gain troubleshooting time, relatively higher power supply reliability. grounding the neutral point does not disadvantage is that because of where sex is insulated, pow

17、er-to-ground capacitance is not the release of stored energy path. ground in the event of arc, the arc flame and renewed repeatedly, but also to the capacitor charging process repeated. since the energy-to-ground capacitance can not be released, resulting in higher voltage, resulting in over-voltage

18、 or resonant grounding arc over voltage, and its value up to a very high multiples of the equipment insulation threat. (b) the neutral-point arc suppression coil grounding neutral arc-suppression coil grounding system, that is, the neutral point through a petersen coil inductance grounding. since th

19、e 1916 invention of the arc-suppression coil present, the neutral point arc suppression coil grounding system has more than 80 years of history. resonant neutral grounding advantage lies in its speedy compensation for non-grounded neutral system generated when single-phase ground capacitive current,

20、 reduced the occurrence of over-voltage arc. although the non-grounded neutral system has a single-phase ground fault occurs can continue to supply the outstanding advantages, but there are also produced intermittent arcing caused by over-voltage dangers. when the ground current is greater than 30a,

21、 the resulting arc often can not self-extinguishing, resulting in increased probability of over-voltage arc ground is not conducive to safe operation of power grid. the arc-suppression coil is a adjustable core inductor, ground fault occurs when the power grid, the grounding current through the arc-

22、suppression coil inductor current when the was on the ground to compensate for capacitive current, the current passing through the point of failure can be reduced to self-quenching arc range. when the current zero and the arc flame, the arc-suppression coil can still reduce the fault phase voltage r

23、ecovery rate, thereby reducing the possibility of renewed arc is conducive to the elimination of single-phase ground fault. in addition, pairs of arc-suppression coil no-load tap-operation, so that it can be achieved within a certain range of compensation had to run to achieve the reduced ground cur

24、rent. this allows the network up and running for some time, the relatively improved supply reliability. reposted elsewhere in the paper for free download resonant neutral point grounding system is the main disadvantage of the zero sequence ground fault protection circuit can not be detected. when th

25、e system grounding occurs when the residual current due to take place is very small, and the procedures required under the arc-suppression coil must be in the state over compensation, grounding lines and non-grounding line of zero-sequence current flowing in the same direction, so zero-sequence over

26、-current, zero-sequence the direction of the protection can not detect the fault line has been grounded. second, the arc-suppression coil itself is emotional component, and constitute a resonant circuit-to-ground capacitance, the resonance can occur under certain conditions, over-voltage. third, the

27、 neutral grounding via arc suppression coil can only reduce the probability of over-voltage arc grounding or not grounding the complete elimination of over-voltage arc, we can not reduce the amplitude of over-voltage arc grounding. (c) neutral grounding resistor neutral grounding resistance, which i

28、s the neutral point between the earth and access to a certain resistance value of the resistor. the resistance and system-to-ground capacitance constitutes a parallel loop, since resistance is energy-consuming devices, but also the release of components and resonant capacitor charge pressure of the

29、resistance components to prevent resonance over-voltage and intermittent arcing ground over-voltage. have certain advantages. resistance grounding method uses an additional event of a substation grounding metallic phase after the phase voltage increased to improve the system voltage, grounding jump-

30、start, three-phase voltage is quickly restored to normal, then place current value by the system capacitive current size of the and the neutral point resistor value common decision. ground in the event of non-metallic nature, the subject then places the impact resistance, flow through the neutral po

31、int of access locations and the current when compared with metallic grounded significantly decreased at the same time, a sound phase voltage rise in a significant reduction in the zero sequence voltage value of approximately single-phase metallic grounding half. thus, using the resistance grounding method can be generated when a single-phase ground fault current limiting antihypertensive effect on the equipment insulation levels that require lower levels of the pressure phase voltage can be chosen. neutral grounding system