JP3641567B2 - Ground fault protection device for distribution substation - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ground fault protection device for a distribution substation, and more particularly to a device suitable for loop fault normally open type ground fault protection.
[0002]
[Prior art]
The looping of high-voltage trunk lines has been adopted mainly for large-scale buildings and intelligent buildings as power supply systems for distribution substations, minimizing power outage times and power outage ranges in the event of accidents, and improving supply reliability Yes.
[0003]
There are two types of system configurations of the high-voltage loop trunk line: a normally closed loop type and a normally open loop type depending on whether the loop section switch is normally closed or open.
[0004]
The normally closed loop type has advantages such as interchange of loads between high-voltage systems, voltage improvement, utilization improvement, etc., but malfunction of direction ground fault relay due to constant circulating current, decrease in ground fault detection sensitivity, and ground fault accident Sometimes ground fault current flows from both systems into the ground fault point, causing problems such as both systems are shut off and the entire section or power distribution station is stopped.
[0005]
On the other hand, the normally open loop type always opens the connection point of the high-voltage loop trunk line electrically, and automatically reverses from the healthy circuit side to the terminal healthy section of the fault line only at the time of failure. The technical problem of the closed loop type can be solved.
[0006]
2 and 3 are conventional examples of the ground fault protection method in the normally open loop type, and FIG. 2 shows a case where the ground fault detection protection is performed collectively at the power receiving side substation in the A high voltage main line and the B high voltage main line. Is the case of ground fault detection protection at each distribution substation.
[0007]
In FIG. 2, reference numeral 10 denotes a power receiving side substation that supplies power to a plurality of distribution substations by two circuits of an A high voltage main line and a B high voltage main line. Reference numeral 11 denotes a transformer, 12 denotes a power receiving side bus, and GPT denotes a grounded instrument transformer. Power receiving stations 10A and 10B of the A high voltage main line and the B high voltage main line are connected to the power receiving side bus 12.
[0008]
These power stations 10A and 10B are respectively provided with feed-off circuit breakers 13a and 13b and ground fault direction relays 14a and 14b connected to the zero-phase current transformer ZCT. The ground fault direction relays 14a and 14b are normally used and operate by detecting the zero phase current and the zero phase voltage with the zero phase current transformer ZCT and the zero phase voltage detector ZPD to determine the directionality. is there.
[0009]
20A and 30A are distribution substations connected to the A high-voltage trunk line, 20B and 30B are distribution substations connected to the B high-voltage trunk line, and each distribution substation is composed of the same equipment and the same circuit. Has been.
[0010]
Taking the distribution substation 20A as an example, the distribution substation 20A has an input side (power supply side) high voltage trunk line BUi and an output side (load side) high voltage trunk line BUo. These input side and output side Are connected to each other via an input-side switch 21a and an output-side switch 22a provided on each of the high-voltage trunk lines, and the load is fed to a load via a distribution transformer 23a and a distribution line 24a. The In addition, 25a in the figure has shown the earth capacitance which the electric circuit between switch 21a and 22a has. The connection cables 1a and 1b also have a ground capacitance, but are omitted.
[0011]
Since the other distribution substations 30A, 20B and 30B are configured in the same manner, the same number as the distribution substation 20 is set to the same one-digit number of each distribution substation, and thereafter A for the A high-voltage trunk line and b for the B high-voltage trunk line will be denoted with a detailed description thereof.
[0012]
The input-side switch 21a of the distribution substation 20A is connected to the A-high-voltage trunk power supply station 10A via the A-high-voltage trunk-side connection cable 1a, and the output-side switch 22a is connected to the input side of the adjacent distribution substation 30A. The output switch 32a of the distribution substation 30A is connected to the loop point section switch LLS by the connection cable 3a.
[0013]
Similarly, the distribution substations 20B and 30B are connected to the B high-voltage main line power supply station 10B via the connection cable 1b on the B line side, and the output side switch 22b is connected to the distribution substation 30B via the connection cable 2b. The output side switch 32b of the distribution substation 30B is connected to the loop point division switch LLS via the connection cable 3b. As described above, the A high voltage main line and the B high voltage main line are connected in a loop via the loop point section switch LLS, and the loop point section switch LLS is always open.
[0014]
Ground fault protection in such normally open loop, for example, when the ground fault occurs at F ₁ point of distribution substations 30A which is connected to the A high pressure mains, provided the feeding stations within 10A of A high pressure mains A certain zero-phase current transformer ZCT and a zero-phase voltage detector ZPD detect this, and the ground fault direction relay 14a is operated to shut off the sending circuit breaker 13a. On the B high voltage main line side, the loop point section switch LLS is open, but a charging current flows through the ground capacitance represented by the ground capacitances 35b and 25b, and this current is detected as a zero-phase current. However, since the operating current phase is 180 ° different, the ground fault direction relay 14b does not operate.
[0015]
FIG. 3 shows a case where each distribution substation is provided with a ground fault detection protection means. The same or corresponding parts as in FIG. In addition, C1-C5 in the figure has shown the grounding capacitor provided in each distribution substation in order to detect a zero phase current reliably.
[0016]
Each distribution substation is provided with a ground fault direction relay corresponding to power supply from the A high voltage main line side and power supply from the B high voltage main line side. Taking the distribution substation 20A as an example, reference numerals 26a and 27a denote ground fault direction relays that operate by detecting a ground fault current flowing to the load side with respect to the ground fault of the power supply from the A high voltage main line side, 66b and 67b. B is a ground fault direction relay that operates by detecting the ground fault current that flows to the load side accident point against the ground fault at the time of power supply from the high voltage main line side, and the local fault direction relay is connected to each zero-phase current transformer ZCT. And connected to a zero-phase voltage detector ZPD.
[0017]
Note that the ground fault direction relays 66b and 67b may operate by detecting the charging current flowing from the power source side fault point with respect to the ground fault of the power feeding from the A high voltage main line side. Similarly, the ground fault direction relays 26a and 27a may operate by detecting a charging current flowing from the power source side fault point with respect to the ground fault of power feeding from the B high voltage main line side.
[0018]
Then, when a ground fault occurs in the substation, a ground fault direction relay 26a that operates by detecting a ground fault current flowing at the fault point, and a ground fault direction relay 66b that operates by detecting a charging current flowing from the fault point. Are operated simultaneously (when the AND condition is satisfied), the input-side and output-side switches 21a and 22a are simultaneously shut off.
[0019]
In addition, when a ground fault occurs in the connection cable 2a that connects the distribution substation 20A and the distribution substation 30A, a ground fault direction relay 27a that operates by detecting a ground fault current flowing at the fault point, When both 57b of the distribution substation 30A that operates by detecting the charging current flowing from are operated simultaneously, the output-side and input-side switches 22a, 31a are simultaneously shut off.
[0020]
The ground fault direction relays 67b, 27a, 57b, 37a, 47b, 47a, 56a, 36b, 66a, and 26b are ground fault direction relays corresponding to the ground fault of the connection cable connecting the distribution substations. Omitted.
[0021]
The distribution substation 20A has been described above, but the other distribution substations 30A, 40A and 20B, 30B are also configured in the same manner, and the same part as the distribution substation 20 includes the number of the distribution substation. The same one-digit number is omitted, and the description is omitted.
[0022]
Since the loop point section switch LLS is normally opened, the ground fault protection of the distribution substations 20A, 30A and 40A on the A high-voltage main line side is protected by the respective ground fault direction relays 26a, 36a, 46a and 46b, 56b. , 66b.
[0023]
If a ground fault occurs at point F _{2 of} the distribution substation 30A, a ground fault current (zero phase current) Ig flows. At this time, the zero-phase current transformers of the ground fault direction relays 26a and 36a operate by detecting the zero-phase currents of (Ig-Ic1-Ic2-Ic3) and (Ig-Ic2-Ic3), respectively.
[0024]
Further, the charging current flowing from the power point side fault point is detected, and the ground fault direction relays 56b (Ic3) and 27b (Ic4) operate if they detect the zero-phase current in the parentheses and exceed the sensitivity set value.
[0025]
In the ground fault direction relays 46b and 37b, the loop point section switch LLS is open, and only the ground capacitance of the connection cable is considered to be inoperative. Other ground fault relays do not operate because the current phase is opposite to the operating phase.
[0026]
In this case, since only the distribution substation 30A operates the ground fault direction relays 36a and 56b and the AND condition is established, the input / output side circuit breakers 31a and 32a are simultaneously disconnected.
[0027]
When the circuit breakers 31a and 32a are cut off, one voltage of the loop point section switch LLS disappears, so that the loop point section switch LLS is turned on after a certain time, and the distribution substation 40A has the B high voltage main line side. Is supplied with power.
[0028]
[Problems to be solved by the invention]
The ground fault protection method shown in Fig. 2 has the advantage that only one ground fault direction relay is required for each circuit. However, when a ground fault occurs at one distribution substation in the A high voltage trunk line. , All distribution substations connected to the high-voltage trunk line were out of power, and after searching for and disconnecting the substation where the accident occurred, power was supplied again from the A line, and at the same time, the loop point switch was turned on. Power is supplied also from the B high-voltage trunk line, but during that time, the healthy distribution substation connected to the A high-voltage trunk line continues to be in a power failure state. Especially in recent years, distribution substations have been distributed on each floor of high-rise buildings and intelligent buildings, and several distribution substations have been installed on one high-voltage trunk line. There is a problem that it takes a considerable amount of time to discover a substation, disconnect it, and supply power again.
[0029]
In addition, the ground fault protection method shown in FIG. 3 completely eliminates the above problem by minimizing the number of power outages because the distribution substation that caused the ground fault detects and disconnects it in its own substation. However, a ground fault direction relay including a number of zero-phase current transformers in one distribution substation is required.
[0030]
Moreover, it is necessary to install grounding capacitors C1 to C5 in order to operate these ground fault direction relays with certainty. That is, the zero-phase current of the ground fault direction relay 56b is equal to the ground capacitance as in the case of the ground fault direction relay 46b that does not operate because the loop point section switch LLS of FIG. 3 is open and has no ground capacitance. Since only Ic3 flows, the relay will not operate unless Ic3 is equal to or higher than the sensitivity setting value, and normal judgment cannot be made. In order to avoid this, it is necessary to provide a grounding capacitor to forcibly increase the ground capacitance, to allow a zero-phase current greater than the sensitivity set value to flow, and to ensure the operation of the ground fault direction relay. In particular, in the normally open loop type, it is not specified where to install the loop point class switch, and once a ground fault has occurred, each switch is opened to release the switch and change the feeding direction. It is necessary to install a grounding capacitor with a capacitance that can flow a zero-phase current greater than the sensitivity current value at each separation point.
[0031]
Switch 31a at ground fault F ₂ points, the monitoring state after the worked 32a and then its LLS, can similarly protected when a ground fault accident at the power distribution substation 30B. However, when a ground fault occurs in the distribution substation 40A, the zero-phase current of the ground fault direction relay 46a flows only to the ground capacitance of the cable as in the case of the ground fault direction relay 37b before the accident. Operation is not possible, and the AND condition of the ground fault direction relays 46b and 46a is an uncertain protection method. (Capacity to ground required to flow 200 mA of zero-phase current with 10% zero-phase voltage sensitivity of a complete ground fault in a 6.6 kV circuit is 1.4 μF, and 2.5 km is required when the CV cable is 150 mm ^2. (If the cable is shorter than this, the ground fault relay 46a cannot operate normally and cannot be reliably protected.)
In view of the above points, the present invention provides a ground fault protection device for a distribution substation that does not require a grounding capacitor, as long as one ground fault detection protection means is provided in one distribution substation. The purpose is to provide.
[0032]
[Means for Solving the Problems]
In the distribution substation, the load current and the zero-phase current flowing from the input high-voltage trunk line normally flow out of the output high-voltage trunk line as it is, and in addition, a ground fault in the distribution substation In this case, the inflow side and the outflow side become unbalanced, and this phenomenon does not change even when the current flow direction changes from the output-side high-voltage main line to the input-side high-voltage main line like the normally open loop type. The zero-phase current is smaller than the load current (about 30 A).
[0033]
In the embodiment of the specific means, the input-side high-voltage trunk line and the output-side high-voltage trunk line of the distribution substation are connected via the input-side switch and the output-side switch provided in each high-voltage trunk line, and the connection In a ground fault protection device for a distribution substation that supplies power to a load by a branch line from a line, the input side high-voltage trunk line and the output-side high-voltage trunk line are bundled so that current flow directions are opposite to each other. Through the iron core window of the zero-phase current transformer, the zero-phase current transformer cancels the zero-phase current in the case of a ground fault outside the protection range, and the zero-phase current due to the ground fault in the protection range And a ground fault detection protection means that operates when the zero-phase current exceeds a preset value, and the input side and output side switches are shut off by the operation of the ground fault detection protection means. It is characterized by doing so.
[0034]
By configuring as described above, even if power is supplied from either the A high-voltage main line side or the B high-voltage main line side as in the normally open loop type in the loop power distribution system, protection is provided by one ground fault detection protection means. In addition, it is possible to reliably detect a ground fault within the protection range without a grounding capacitor.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0036]
FIG. 1 shows an embodiment of the present invention, and shows one distribution substation among the plurality of distribution substations shown in FIG. 3, (A) is a circuit configuration diagram by single wire connection, and (B) is a ground fault. It is explanatory drawing of detection protection.
[0037]
In FIG. 1, 1 is an input side (power supply side) high voltage main line, 2 is an output side (load side) high voltage main line, and these high voltage main lines are connected via an input side switch 1a and an output side switch 2a. Branching from the connection line 3a and connecting the transformer 3 to supply power to the load is the same as in the case of FIG. The present invention is characterized by the installation means of the zero-phase current transformer 4. That is, as shown in FIG. 1, both the input-side high-voltage main line 1 and the output-side high-voltage main line 2 (six in the case of three phases) are used as the primary conductors of the zero-phase current transformer 4 and penetrate the iron core window. The induced voltage of the next winding is detected by the ground fault detection protection means 5.
[0038]
The ground fault detection protection means 5 simply detects a zero-phase current and outputs an operation signal when the zero-phase current exceeds a preset value, like a ground fault relay having no directionality. Anything is acceptable. Then, the input side and output side switches 1a and 2a are simultaneously shut off by the operation signal of the ground fault detection protection means 5.
[0039]
By configuring in this way, the zero-phase current IoA flowing through the input side high-voltage trunk line 1 from the point F other than the normal load current and its own distribution substation (outside the protection range) and the output-side high voltage trunk line 2 It is equal to the output zero-phase current IoB, the sum of the primary current passing through the zero-phase current transformer 4 is 0, and the detection signal from the zero-phase current transformer input to the ground fault detection protection means 5 is also 0, The ground fault detection protection means 5 does not operate. (Fig. 1 (A))
However, as shown in FIG. 1 (B), the self-power distribution substation (the protection scope), ground fault occurs at _three points F, ground fault current (zero-phase current) when Ig flows, input The zero-phase currents IoC and IoD flowing to the output side and the output side normally satisfy IoC> IoD, and the ground fault detection protection means 5 detects this difference signal and outputs an operation signal to output the input side and output side switches 1a. And 2a are shut off simultaneously.
[0040]
The above is the case where power is supplied from the input high-voltage main line to the output high-voltage main line. On the contrary, even if the power supply direction changes from the output high-voltage main line to the input high-voltage main line, there is no effect. Thus, the protection operation can be surely realized.
[0041]
Although only one distribution substation has been described above, a plurality of distribution substations are looped through normally-open loop point division switches as shown in FIG. It is installed and used in the shape.
[0042]
When installing, place each distribution substation equipment in the switchboard and use it as a row board configuration, and connect adjacent switchboards in a loop using a well-known joint method using cables. Is desirable.
[0043]
Although the above has described the case of a loop line provided with a loop section switch LLS, the loop section switch LLS can also serve as an input / output side switch of an adjacent distribution substation. For example, the loop section opening / closing LLS becomes unnecessary by always opening the output side switch 42a of the distribution substation 40A and the output side switch 31b of 30B in FIG. In this way, when the entire monitoring system is a central monitoring system and each input / output switch also serves as a loop point division switch, the loop division point can be changed at any point, and each distribution can be performed while distributing power according to power demand. It will be a ground fault protection device that protects against ground faults in substations.
[0044]
In addition, the earth fault protection of the connection conductor between switchboards is protected by the method of installing a protective relay in the cable shield earth line currently performed normally.
[0045]
【The invention's effect】
As described above, the present invention can provide ground fault protection by providing a single ground fault detection protection means in each distribution substation, and can be used in a normally open loop system in the loop system of the A high voltage main line and the B high voltage main line. Thus, even when the high-voltage main line is switched, the ground fault detection protection means does not operate outside the protection range, and can operate reliably only within the protection range. In addition, since this ground fault detection protection means does not need to have directionality, a zero-phase voltage detector is also unnecessary.
[0046]
Therefore, the present invention eliminates the need for four sets of zero-phase current transformers and ground fault direction relays and a zero-phase voltage signal from the zero-phase voltage detector. Furthermore, since no grounding capacitor is required, the reliability of power supply can be improved, the installation area of the distribution substation can be reduced, and the cost can be reduced. In particular, when the distribution substation has a distribution board configuration and is applied to a distribution system in which the distribution substations are connected in a loop shape, the effect is remarkable as the number of connection boards increases.
[Brief description of the drawings]
1A and 1B are a circuit configuration diagram and an operation explanatory diagram of single-wire connection according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram of a conventional loop-type ground fault protection method.
FIG. 3 is an explanatory diagram of another ground fault protection method of the conventional loop method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Input side high voltage main line 2 ... Output side high voltage main line 1a ... Input side switch 2a ... Output side switch 3 ... Transformer 4 ... Zero phase current transformer 5 ... Ground fault detection protection means

Claims (1)

Connect the input high-voltage trunk line and the output high-voltage trunk line of the distribution substation via the input-side switch and output-side switch provided on each high-voltage trunk line, and supply power to the load from the connection line via the branch line In the ground fault protection device for distribution substations,
The input-side high-voltage trunk line and the output-side high-voltage trunk line are collectively penetrated through the iron core window of the zero-phase current transformer so that the current flow directions are opposite to each other. Zero-phase currents cancel each other out in the case of a ground fault, and the zero-phase current caused by a ground fault within the protection range is detected, and when this zero-phase current exceeds a preset value, a ground fault detection protection means is activated. And a ground fault protection device for a distribution substation characterized in that the input side and output side switches are shut off by the operation of the ground fault detection protection means.

Images