KR20090119058A - The determination and autonomous isolation method of fault zone based on intelligent frtu in distribustion system - Google Patents

Abstract

PURPOSE: A method for determining and separating a fault section based on a feeder remote terminal unit in a distribution system is provided to enhance reliability of power supply by accurately determining a fault section. CONSTITUTION: A voltage sensor is installed in each phase of both ends of a switch(10). Three phase voltage signals and three phase current signals pass a surge protector(20) for protecting a circuit from a surge, and are transmitted to a measuring part(30). A DSP(40) reads the three phase voltage signals and the three phase current signals from an A/D converter inside the measuring part, and determines a fault. The DSP monitors a current state, a voltage state, and a current direction from the signals. An EEPROM(50) records a fault current waveform, a voltage waveform, and fault information. A circuit breaker separates a fault section.

Description

The Determination and Autonomous Isolation Method of Fault Zone based on Intelligent FRTU in Distribustion System

The present invention is an intelligent FRTU-based fault zone determination and autonomous separation method in the distribution system, more specifically, three-phase voltage measured from the current sensor by the FRTU (Feeder Remote Terminal Unit) installed in the switchgear of the overhead distribution line, After determining the fault / inrush / HIF (High Impedance Fault) from the current waveform, it collects 3-phase voltage and current information by 1: 1 communication with FRTU elements of NAVER ZONE under ubiquitous distribution system. Determining whether a breakdown occurs in the protection section, and distributing the breakdown section autonomously before the circuit breaker (CB) or recloser is permanently opened, thereby reducing the area of failure and the blackout time to minimize the effect of accidents. In the FRFR based fault section determination and autonomous separation method.

In general, the distribution system consists of dozens of distribution lines passing through load areas such as urban areas, trees, salt fields, etc. to supply power to widely distributed electricity consumers. Since these distribution lines pass directly through various load areas, they are exposed to natural disasters, car collisions, and tree contact accidents.

To solve these problems, utilities have designed and operated a distribution system that divides the distribution system into multiple divisions so that fault sections can be separated and load fused.However, when the distribution lines are long-distance lines, they can be divided into several tens of kilometers. It required a lot of time and effort to operate the recloser or switchgear for load balancing.

Therefore, a distribution automation system (DAS) was introduced to check the fault section remotely and to control the switch on the track. As a result, the reliability of the power supply was greatly improved.

In the event of any fault in the distribution system, the fault handling procedure consists of fault determination, fault section determination, fault section isolation, re-entry of breaker (CB) or recloser, fault section recovery and system repair. These troubleshooting procedures are performed sequentially by the DAS. The DAS consists of a FRTU (Feeder Remote Terminal Unit) attached to the central control unit, recloser and switch.

Once instantaneous or permanent failure occurs, the FRTUs determine the system failure from the fault current and if it is determined to be faulty, set the FI (Fault Indicator) state and set a, b, c phase voltage, a, b, c, n Send fault information such as phase current to the central controller. In case of permanent failure, the central control unit judges the fault range from the fault information provided from the FRTUs, creates a load fusion table, and then gives the switch operation commands to the FRTUs sequentially in the order presented. The fault handling procedure is executed by sending the result to the central control unit. At this time, fault determination, fault section determination, and fault segmentation strategies based on the existing FRTU include the following serious problems.

Fault determination is a key function of FRTU. However, since the existing FRTUs judge fault determination only by the magnitude of fault current, accurate fault determination was difficult. In the case of general failure, it is easy to determine the failure because a low fault impedance circuit is formed and the fault current flows largely and exceeds the set value. However, if a ground fault occurs in the areas such as asphalt, wood and gravel on the road, a high impedance circuit is formed, and it is difficult to determine the fault because the current change is weak, and it is not possible to remove the fault from the track and also fail to check the fault section. Serious accidents such as human injury and fire may occur. This is commonly referred to as a High Impedance Fault (HIF). In addition, if the fault / ground current suppression device of the recloser is not set under an urgent situation during load transfer, the inrush current may exceed the set value and may cause a malfunction and malfunction. On the other hand, even when the recloser fault / ground current suppression device is set or when the fault is caused by the inrush current suppression function of the FRTU, the fault determination is delayed and it malfunctions for a certain period of time, resulting in serious accidents such as loss of life, fire and poor supply reliability. Ripple effects may occur.

In case of failure section determination, after failure of CB or recloser is permanently opened, the failure section is checked from the failure information of FRTU provided by the central control unit. Will increase.

1 is a configuration diagram of a general distribution system, a distribution line may be formed of a mixture of overhead lines and underground lines, and frequent breakdowns occur through various load areas. The system is operated in a multi-slice structure to minimize accidental spillovers from these various accident events. Distribution switches start from the line protection CB for the line accidents and work interruption on the tracks, and link switches for load consolidation are installed at the link points with other lines. It shows a disconnection diagram.

In FIG. 1, CB denotes a line protection circuit breaker, R / C denotes a recloser, S _i denotes an i-th processing switch, and P _{i, j} denotes a j-th circuit of an i-th multi-circuit switch. In particular, the process switches S ₂ , S ₄ , S ₁₀ and the multi-circuit switches P _{9 , 4} , P _{8 , 4} denote linkage switches. The symbols ■, □ indicate the opening and closing state of breaker or recloser switch, and ●, ○ indicate the opening and closing state of switchgear, respectively.

The distribution system is exposed to various structural and environmental failures. The distribution system can be classified into line short circuit, three phase short circuit, 1 line ground fault, 2 line ground fault, and disconnection according to the fault type. In particular, HIF is defined as the case of disconnection or ground fault which has a very large impedance that cannot be detected by the existing phase and ground overcurrent protection mechanism. Table 1 below shows representative types of faults and fault currents in the distribution system.

Distribution system fault classification Action type Failure Type Surface Current (A) Characteristic Re./Fl operation  Normal operation Short circuit failure Line ㅡ The fault current is greater than the OCR operating current. ○ 3 phase ㅡ Ground fault 1 line ㅡ Fault current is greater than OCGR operating current ○ 2-wire ㅡ     Minor action     HIF monorail ㅡ Fault current does not flow ×     HIGF Dry asphalt 0     Fault current is less than OCGR operating current     × (Non-reinforced) concrete 0 Dry sand 0 Wet sand 15 Dry mud 20 Dry grass 25 Wet mud 40 Wet grass 50 (Reinforcement) concrete 70 Oh action Inrush Current ㅡ The switching current is greater than the OCR operating current. ○

In Table 1, the inrush current is not a fault current, but a momentary current at the time of load switching or after the work is completed, and a current larger than the operating current of the relay flows, causing the breaker to malfunction. Therefore, when injecting a CB or recloser, the inrush current suppressor increases the operating current of the relay and then makes it possible to succeed. However, care should be taken in the case of multiple faults, since the section where the fault has not been eliminated may be put on the track and the CB may trip. In case of Re (Recloser) / FI (Fault Indicator) operation of Table 1, ○ indicates that the fault is larger than the relay or FI operating current, so that the fault is accurately detected so that the Recloser operates or the FRTU sets the FI state. × indicates the opposite case.

As the conventional FRTU-based fault determination method determines the fault based only on the magnitude of the fault current, as shown in Table 1, the FRTUs fail correctly because the fault current flows largely and exceeds the set value in the case of a general short circuit or ground fault. In the case of HIF where ground faults occur in areas such as asphalt, wood and gravel on the road, a high impedance circuit is constructed and the recloser or FRTUs are determined to be faulty because the fault current is very small, such as 0-70A. Will fail. As a result, serious accidents such as human injury and fire can occur.

In general, when switching loads, a fault / ground current suppression device is set in the case of a recloser in the load sharing line, and the FRTU prevents malfunction due to the inrush current by the inrush current suppression function. However, under an emergency situation, the recloser failure / ground current suppression device may not be set. In this case, the inrush current may exceed the set value and may be regarded as a failure and malfunction. On the other hand, if the fault / ground fault current suppressor of the recloser is set in the case of a real fault, the fault / ground fault suppression function of the recloser and the judgment of the fault are delayed, which may cause injuries, fire, etc. In the case of FRTU, the inrush current suppression function makes it difficult to determine the fault and determine the fault section, which may cause serious accident ripple effects such as lower supply reliability.

As a failure section determination and separation technique based on the conventional FRTU, it is assumed that any accident occurred in the section {S ₆ , P _{7 , 1} } as shown in FIG. 1. Because the fault current exceeds the pick-up current of the protective device, the recloser will instantaneously and delay to eliminate the fault. In general, 2F2D operation is performed. In case of permanent failure, the recloser is permanently opened, and the area A, the failure area, and the B area that receive power from the recloser all experience power failure. At this time, because the FRTUs of CB, R / C, S ₁ and S ₆ experience fault current, the fault indicator state is set. On the other hand, the FRTUs of S ₂ , S ₃ , S ₄ , S ₅ , P ₇ , P ₈ , and P ₉ cannot experience the fault current, so the fault indicator remains in Reset.

First of all, FEP receives CB, R / C (recloser), S ₁ , S ₂ , S ₃ , S ₆ , S ₄ , S ₅ , Collect fault indicator states from FRTUs for P ₇ , P ₈ , and P ₉ . The following inference process confirms that the fault zone occurred at {S ₆ , P _7,1 }. The central control unit issues an open command to the switch {S ₆ , P _{7 , 1} } to isolate the fault area, re-close the recloser, and resume supplying power to area A. In addition _, load balancing is attempted to receive electric power from other lines using the link switches P _{8 , 4} , P _{9 and 4} in the area B.

In this case, even though the area A is a healthy load area, it experiences a power outage, and after a permanent failure, the outage time is prolonged by searching the fault section by the polling method of the central control unit. Therefore, it is necessary to reduce the blackout area and blackout time by autonomously detecting and separating the fault section before the recloser is permanently opened, thereby minimizing the accident spillover effect and improving supply reliability. In addition, if the fault indicator does not operate even though a fault current flows through the switch S ₁ , it may be inferred that a fault has occurred in the load section {R / C, S ₁ }. At this time, since the accident propagation effect can be seriously enlarged, a methodology that accurately infers the fault section from the malfunction of the fault indicator is required.

The present invention has been invented in view of the problems caused by the error of fault determination and the error of judgment and failure of the power outage region and the delay of the power outage in the conventional distribution automation system as described above. 3-phase voltage RMS value collected through 1: 1 communication with neighboring FRTUs based on 3-phase fault current RMS value, 3-phase fault current waveform, voltage RMS value, current direction, and NAVER map information In power distribution system that can improve reliability of power supply by determining fault / inrush / HIF from 3 phase current RMS value, 3 phase current 1 cycle waveform, and quick and accurate fault section and autonomous separation It provides intelligent FRTU based fault section determination and autonomous separation method.

In order to achieve the above object, the present invention provides a fault / inrush / HIF (High Impedance Fault) from a voltage, a three-phase voltage measured by a current sensor, and a current waveform by a FRTU (Feeder Remote Terminal Unit) installed in a switchgear of a overhead distribution line. After determining whether there is a failure in the self-protection section by collecting three-phase voltage and current information through 1: 1 communication with FRTU elements of Naver Zone in the ubiquitous-based distribution system environment, The circuit breaker (CB; circuit breaker) is characterized in that the failure section is autonomously separated before the recloser is permanently opened.

By applying intelligent FRTU based fault section determination and autonomous separation method in the distribution system of the present invention, it is possible to minimize fault spreading effect by reducing fault area and blackout time, and improve fault reliability by improving operation reliability of fault indicator. Accurate reasoning has the effect of preventing accidental damage.

Hereinafter, the intelligent FRTU based fault interval determination and autonomous separation method in the distribution system of the present invention will be described with reference to the accompanying drawings.

Figure 2 is a block diagram of the intelligent FRTU of the present invention, the voltage sensor VS is installed on each end of the switch 10, the current sensor CT is installed on each side of one end. The three-phase voltage and three-phase current signals provided from the voltage sensor installed at both ends of the switch and the current sensor installed at one end pass through the surge protector 20 configured to protect the circuit from the surge and then to the measurement unit 30. Is sent. The DSP 40 reads the three-phase voltage and current signals of the multi-circuit from the A / D converter in the measurement unit to determine whether there is a failure, calculates the distance of failure, and establishes a corresponding strategy.

The DSP 40 monitors the current, the voltage state, and the current direction from the measured signal. When a failure occurs, the fault current waveform, voltage waveform, and fault information for several cycles before and after the fault are recorded in the EEPROM 50. The LAN port 60 is a communication port for communication between the FRTU as well as the central control unit (DSP). The LAN port 60 plays a very important role in any FRTU exchanging information with other FRTUs or central controllers at high speed for fault determination, fault distance calculation, fault zone determination and autonomous separation.

FIG. 3 is a schematic diagram of an intelligent FRTU-based ubiquitous distribution system according to the present invention. Recently, due to the development of sensors and IT technology, a distribution system (DAS) is rapidly evolving into a ubiquitous environment. The present invention enables free wired / wireless connection based on a redundant Internet optical line as shown in FIG. 3, enabling free optical connection and high reliability communication between distribution facilities, and free 1: 1 communication between FRTUs on a line. And high-speed processing of a large amount of data.

The operation control strategy of the intelligent FRTU proposed in the present invention calculates the current effective value every half cycle, checks the starting point of the LIF (Low Impedance Fault) by comparing with the pickup value, and calculates the effective value of the voltage half cycle value, and calculates the low voltage reference value. It is determined whether to start HIF by comparing with. Record one cycle three-phase current waveform before failure, the first, second, and third three-phase current, three-phase voltage waveforms at maximum current after failure. And through Digital Fourier Transformation (DFT), harmonic magnitudes are obtained for the first and second one-cycle waveforms at the maximum current after failure, and the ANN is used to determine whether the failure / entry is in progress. For one cycle waveform, the fundamental wave component is obtained and the fault distance is calculated. When failure determination is made, it is designed as a flowchart showing the operation control strategy of FIG. 4 so that failure section determination and autonomous separation are performed through 1: 1 communication with neighboring FRTUs.

<Step 1>

Unlike the existing FRTU, the intelligent FRTU of the present invention is designed to communicate with neighboring FRTUs so that basic data is initialized at the initial stage of operation and neighboring zone data created based on electrical connectivity from the central control unit. Store in a buffer. The event triggering (ET) state, fault starting (FS), indicates the fault starting state. i and j indicate the circuit number and the number of measurements, respectively. Set the event triggering state ET _p of each phase and the current starting state FS _p of each phase to Reset.

The neighbor zone data is defined as shown in FIG. 5. For convenience, the NAVER Zone element (FRTU) name is indicated by the switch number and is electrically aligned from the power supply side to the load side. NAVER zone has attribute and element attribute data.

First, each switch is associated with two neighbor zones. The attribute of the power-side neighbor zone is defined as "Source Zone" and the load-side neighbor zone is defined as "Sink Zone". In case of S ₆ , the attribute of power side neighbor zone SET {S ₁ , S ₂ , S ₃ , S ₄ , S ₆ } is set to "Source Zone", and the load side NAVER zone SET {S ₆ , P _{7 , 1} , P _{9 , 1} } property is defined as "Sink Zone". Next, each element of NAVER ZONE SET has an element attribute to identify a power switch. For example, element properties are displayed for all elements of source neighbor zone SET {S ₁ , S ₂ , S ₃ , S ₄ , S ₆ } of switch S ₆ , where S ₁ is the "Source" property. , All elements of the remaining elements {S ₂ , S ₃ , S ₄ , S ₆ } have a "Load" attribute as the element attribute. On the other hand, of Sink Naver Zone SET's {S ₆ , P _{7 , 1} , P _{9 , 1} } elements, S ₄ has a "Source" attribute and the remaining elements have a "Load" attribute. The load zones in the blackout zones are switched to other lines to avoid blackouts during an accidental power outage or work outage. At this time, the zones and element properties of the zones change because the load zones undergo a current change.

In FIG. 5, "□" at both ends of the switch indicates a voltage detector, and the voltage detector for each phase (A, B, C phase) is displayed as a single detector. On the other hand, "○" in "□" indicates a current detector, which indicates a fault current detector for each phase (A, B, C, N phase) as a single fault current detector. Detect steady or no voltage condition from the voltage detector. On the other hand, current detectors detect forward, reverse, no current, and fault current conditions.

<Step 2>

Three-phase voltage, current data I _{i, a, j} , I _{i, b, j} , I _{i, c, j} , I _{i, n, j} , V _{i, a, j} , V _i from the AD converter to multiple circuits Read _{b, j} , V _{i, c, j} for n circuits. Here, _{i i, p, j} , V _{i, p, j} denote sample current and voltage data measured for the j-th on the i-th circuit and p-phase, respectively. N is the maximum number of circuits and can be displayed up to 4 for a multi-circuit switch.

<Step 3>

Set the current phase p to a.

<Step 4>

Check ET _p . If ET _p is SET, go directly to step 5 because the p-phase is a triggering event with a possible fault current. On the other hand, if ET _p is RESET, the absolute value abs (I _{i, p, j} -I _{i, p, j-1} ) of the current difference between samples is determined to determine whether there is a fault current. Check if it is greater than TV (Triggering Value). If it is large, the event is triggered, set ET _p to SET, and then go to step 5.

<Step 5>

Sample values are stored sequentially in I _p and V _p . Where I _p and V _p represent the p-phase current and voltage waveforms, respectively.

<Step 6>

Check for zero crossing on p. If zero crossing, go to step 7.

<Step 7>

If ET _p is SET, go to step 8. On the other hand, if RESET, check whether p = n. If p ≠ n, set p to the next phase and go back to step 4. On the other hand, if p = n, since the processing for the a, b, c, n phase current sample values is completed, go to ⓑ of FIG. 7 to check whether there is no voltage in step 12 described below, and determine HIF.

<Step 8>

If FS _p is SET, go to step 10 below. If RESET, find the effective value I _{p , RMS} for the half-period waveform I _p and go to step 9.

<9 levels>

If I _{p , RMS} > P _pickup (phase pickup current), it is considered as p phase fault and set FS _p to SET and go to step 10. On the other hand, if I _{p , RMS} <= P _pickup , check whether p = n. If p ≠ n, set ET _p to RESET, p to the next phase, and return to step 4. On the other hand, if p = n, since the processing for the a, b, c, n phase current sample values is completed, go to ⓑ of FIG. 7 to check whether there is no voltage in step 12, and determine HIF.

<Step 10>

Obtain ZC _p ++. Then go to ⓓ of Figure 6 and starts step 11.

<Step 11>

If ZC = 2, record one cycle fault current waveform I _p1 of the first cycle after failure, and if p = n, go to ⓐ of FIG. 4 and execute step 2. On the other hand, if p ≠ n, go to step 4 after setting p to the next phase. If ZC = 4, record the second 1st cycle fault current waveform I _p2 after the fault. If p = n, go to fault determination step and execute the procedure of ⓔ of FIG. If ZC = 6, record the third one-cycle fault current waveforms I _a1 ^* , I _b1 ^* , I _c1 ^* , I _a3 , I _b3 , I _c3 , V _a3 , V _b3 and V _c3 after the fault. If p = n, the fault distance determination step is executed. On the other hand, if p ≠ n, go to step 4 after setting p to the next phase. Where I _pc ^* and I _pc are the c-th cycle of the first cycle current waveform before and after the fault on p, respectively, and V _pc is the c-th cycle of the voltage waveform after the failure. Consider the case of phase-to-phase or three-phase short circuit fault and I _p1 ^*, I _p3 for the a, b, c is, the V _p3 is obtained.

<Step 12>

To determine whether HIF is checked, there is no voltage on each voltage. First set phase p to a, then go to step 13.

<Step 13>

After storing the voltage sample data, check for zero crossing of the p-phase voltage. If p phase is not zero crossing and p ≠ n, then set p to the next phase and repeat step 13, but if p = n, go to step 2. On the other hand, if p-phase succeeds in zero crossing, go to step 14.

<Step 14>

If no voltage start state NS _p = SET, go to step 15. On the other hand, if NS _p ≠ SET, the half-cycle voltage rms V _{p and RMS} values are calculated. If V _{p , RMS} > V _min and p ≠ n, then set p to the next phase, then go to step 13 or go to step 2 if p = n. On the other hand, if V _{p , RMS} <V _{min, the} no-voltage start state NS _p is set to SET. Then go to step 15.

<Step 15>

If p ≠ n, set p to the next phase and go to step 13. On the other hand, if p = n, the number of voltageless phases NVC is calculated from the NS _p information, and if NVC <3, the HIF is determined, and then HIF section determination and autonomous failure section separation procedure are performed as the HIF fault section determination step. On the other hand, if NVC = 3, the switch or the breaker is in the open state.

The fault determination step of the present invention is as follows.

In the present invention, a fault determination method using two-cycle data on the maximum fault current is proposed. 8 shows a fault determination procedure proposed in the present invention. The first and second one-cycle waveform data I _p1 , I _p2 after the phase failure with the maximum fault phase current are obtained from the failure start state FS _p information.

Then, the digital Fourier transform (DFT) for each of them obtains harmonic magnitudes of 1-5 harmonics, i ₁ (j) and i ₂ (j). Here, i ₁ (j) denotes the j harmonic magnitude of the first one period. Based on this, the input pattern p of ANN is defined as {i ₁ (0) / i ₁ (1), i ₁ (2) / i ₁ (1), i ₁ (3) / i ₁ (1), i ₁ (4 ) / i ₁ (1), i ₁ (5) / i ₁ (1), i ₂ (0) / i ₁ (1), i ₂ (2) / i ₁ (1), i ₂ (3) / i ₁ (1), i ₂ (4) / i ₁ (1), i ₂ (5) / i ₁ (1)}. Then enter the ANN to check the inference result. At this time, when the output of the ANN is 0, the inrush current goes to ⓐ of FIG. 4. On the other hand, if the output is 1, it is a line fault, so go to the LIF fault section judgment step and perform the fault section determination and autonomous fault section separation procedure.

The following relates to the LIF failure section determination step of the present invention.

1) FRTU based LIF interval search method

In the present invention, the fault current triggering current direction based independent search based on 1: 1 communication between FRTUs is referred to as a LIF interval determination method. The FRTU may not operate even after experiencing a fault current for functional or various reasons. This includes procedures to verify the authenticity of the fault zone. 9 shows a search method for determining a LIF failure section based on the FRTU.

Suppose a one-line ground fault occurs in zone {S ₆ , P _{7 , 1} } in FIG. 9 and the FRTU fault indicator of S ₄ is inoperative. Breakers (CB), reclosers (R / C), S ₁ , S ₄ , and S ₆ FRTUs experience fault currents. Therefore, these FRTUs are triggered by the fault current and independently try 1: 1 communication with the FRTU elements of their Sink NAVER ZONE SET to check the Sink Zone for faults. At this time, the CB and R / Cs fail to detect the fault section because one of the magnetic sink zone elements experiences a fault current. However, since S ₁ and S ₆ do not experience any fault currents in all elements of the magnetic sink zone set, HR 1-2 determines the magnetic sink zone as the failure section. In particular, in case of S ₁ , a false fault section is inferred due to the operation of the FRTU fault indicator of S ₄ . This problem can be solved by each FRTU inferring the fault interval by checking all the FRTUs of the self sink NAVER ZONE SET to detect the fault current of the magnetic sink NAONE elements. For example, in the case of S ₁ FRTU, the FRTUs of S ₂ , S ₃ , and S ₄ check and report whether the fault current is sensed by their Sink Zone Set elements. At this time, the S ₄ FRTU check whether the fault current detection S _6, by reporting to the S ₁ S ₁ can determine that the fault lies. On the other hand FRTU of S ₆ it is finally confirmed that a magnetic Sink ZONE SET P element _7, by receiving the report did not detect any fault current from the _first magnetic Sink ZONE the fault section.

2) FRTU-based LIF interval autonomous separation procedure

In case of general failure, the recloser repeats the instantaneous (F) and delayed (D) operation, and a large number of failures naturally disappear during this operation. However, in the case of permanent failure, this operation is repeated to accumulate fatigue in the power plant and ultimately to extend the blackout period. Under this situation, the switch zone is open to all FRTUs of the fault zone in the no-voltage state of the no-voltage detection number, and the fault zone is separated autonomously and the momentary fault is removed. It succeeds to minimize the blackout period. In this case, the CB-recloser cooperative line as well as the CB single line are mixed. Therefore, the separation point of fault section should be decided according to the type of system.

FIG. 10 illustrates a step-by-step failure zone check and autonomous separation strategy for a failure for any FRTU ₀ , and step 1 may be omitted since it may be repeated if not executed independently.

<Step 1>

If the IP and the pick-up currents for the setting FRTU _{0, 0} FRTU downloads the information of SRZS (Source Zone Set) and SZS (Sink Zone Set) from the central control unit of the ADS.

<Step 2>

FRTU ₀ monitors the current and when the current exceeds the set pickup current and the ANN output determines a fault, it switches to fault current detection.

<Step 3>

FRTU ₀ determines SZS1 (Sink Zone Set 1) based on the current direction. If the line is reconstructed due to a line accident or work outage, SRZS is determined to be SZS1. Next, FID (Fault Information Data) information is collected through 1: 1 communication with each element of SZS1 FRTU _i . If there are FRTUs with a, b or c phase faults and have a fault current sensing state, or FCSS (Fault Current Sensing Status), or elements that have experienced n-phase faults and have experienced a no-voltage sensing state, or NVSS (Nil-Voltage Sensing Status), If not present, based on HR 1-2, SZS1 is determined to be a health zone and goes to step 2. On the other hand, if all the elements do not experience fault current or have no voltage, SCSS1 is designated as a preliminary zone for failure zone based on HR 1-2 and FCS is applied to each element FRTU1 _i of SZS1 to determine whether there is a real fault. Give the collection order and go to step 4.

<Step 4>

FRTU _i determines SZS2. In addition, each element of FRTU2 _i is issued a FID collection command through 1: 1 communication. If a, b or c phase failure and all elements of SZS2 have not experienced a fault current, or if n phase failure and any element of SZS2 experiences no voltage in any phase, FRTU ₀ is HR 1- Based on 2, the SZS1 is finally determined to be a fault zone from these information, and the process goes to step 5. On the other hand, if there is a fault current detection state, FRTU ₀ determines that FRTU _i is inoperative and determines SZS1 as normal zone, and proceeds to step 2.

<Step 5>

FRTU ₀ is set by HR 2 and when the preset no-voltage number is reached, all switch units of SZS1 are commanded to open or close the switch.

HR 1: If a, b or c phase failure and FCES = {}, FRTU sets its sink neighbor zone to the failure zone. Here, FCES (Fault Current Element Set) is a set of elements that have experienced fault current among elements of SINK NAVER ZONE SET.

HR 2: If n-phase fault and NVES = {}, FRTU sets its sink neighbor zone to fault zone. In this case, the NVES (Nil-Voltage Element Set) is a set of elements that have experienced no voltage among the elements of the Sink NAVER ZONE SET.

HR 3: If the fault current is experienced and PNVC = CNVC, FRTU is the point of fault separation. Where PNVC is the preset no-voltage count in FRTU0 and CVNC is the current no-voltage sense count.

The following relates to the HIF interval determination step of the present invention.

1) FRTU based HIF section search method

In the present invention, an independent search method for a voltage-free triggering current direction considering a voltage sensor error based on 1: 1 communication between FRTUs is a HIF interval determination method. Voltage sensor errors can occur in the actual distribution system management process, which can be embarrassing to the operator and can cause significant reliability problems in determining the HIF. Therefore, since the probability of occurrence of two consecutive voltage sensors is very low, a strategy considering one voltage sensor error is proposed.

 First, the FRTU, which has experienced no voltage on any phase, checks the voltage on the same phase for any of the elements of the Sink Naver ZONE. If no voltage is encountered, it is determined by HIF. Otherwise, it is checked by voltage sensor error. Once it is determined as HIF, check whether there is no voltage on the same phase of the power attribute elements among the elements of the source neighbor zone. If the voltage is normal, the Sourec Naver Zone is the fault zone. Otherwise, the fault zone search fails and the original voltage monitoring service continues.

FIG. 11 shows a case where HIF in the form of a one-wire ground fault occurs on b of the S ₁ load stage. First, the switches S ₂ , S ₃ , and S ₄ all experience a no-voltage that satisfies HR 1, but the search process is described centering on S ₄ . Since switch S ₄ experiences no voltage on phase b, FRTU checks the voltage of phase b on the basis of 1: 1 communication to FRTU of switch S ₆ among elements of Sink NAVER ZONE. At this time, if S ₆ does not experience no voltage, it returns to the normal state determined by the voltage sensor error. On the other hand, when experiencing no voltage, it is determined as HIF and checks whether there is no voltage for the same phase to S1 FRTU of the power property among the elements of the source neighbor zone. At this time, since the FRTU of the power property shows a normal voltage state, the source neighbor zone is determined as the fault zone.

2) FRTU based HIF interval autonomous separation

HIF failure zone identification and autonomous separation strategies for any FRTU ₀ on the distribution line are described in five steps as shown in FIG. However, step 1 may be omitted since it may be repeated unless it is executed independently.

<Step 1>

If the IP and the pick-up currents for the setting FRTU _{0, 0} FRTU downloads the information of SRZS (Source Zone Set) and SZS (Sink Zone Set) from the central control unit of the ADS.

<Step 2>

FRTU ₀ monitors the voltage in the state of the end switch and transitions to the HIF detection state when the set no-voltage condition is met and the HIF condition HR 4 is satisfied. On the other hand, if all three phases are in the normal voltage state, repeat step 2.

<Step 3>

FRTU ₀ determines the SZS (Sink Zone Set) based on the current direction. NVS (Nil Voltage State) information is collected through 1: 1 communication with the first FRTU1 ₁ of the following elements of SZS. If HR 4 is satisfied from the NVS information, it is determined as an actual HIF, and the process goes to step 4 to find a fault section. Otherwise, go to step 2 and continue monitoring voltage because the voltage sensor is an error.

<Step 4>

FRTU ₀ determines SRZS (Source Zone Set) based on the current direction. If the line is reconstructed due to a line accident or work outage, the SZS is determined as SRZS. The elements of the following SRZS FRTU1 _i with 1: 1 through the communication collects each FRTU1 current value _i and NVS (Nil Voltage State) information. Based on HR 6, FRTU _i having the maximum current is determined as SOURCE FRTU. If the NVS of SOURCE FRTU is RESET, determine SRZS1 as HIF fault zone based on HR 5 and go to step 5. On the other hand, if it is in the SET state, the SRZS is regarded as a healthy power failure section and the flow goes to step 2.

<Step 5>

FRTU ₀ autonomously opens the switchgear to isolate the HIF fault section and transmits the HIF fault information to the central control unit of the distribution automation system. At this time, the FRTU of the Source attribute of the SOURCE NAVER Zone, which provides voltage and current value information through 1: 1 communication, also automatically isolates the fault section by opening the switch.

HR 4: When two or less of three phases experience a voltage-free condition, it is determined as HIF. It is difficult to identify the possibility of HIF with no voltage because any FRTU ₀ experiences no voltage due to HIF on the line, operation of the CB or recloser for fault elimination, operation of the recloser and power failure. This rule is the rule for checking HIF in this case. In general, the distribution line accident is more than 90% of ground fault, there is little probability of three-phase ground fault or three-phase disconnection accident. When all three phases experience no voltage, it is mainly the case of operation or work interruption by opening and closing the CB or recloser. Therefore, since HIF shows the form of a 1-wire or 2-wire ground fault or disconnection, it can be judged as HIF if 1-phase or 2-phase experiences no voltage. In other words, if all three phases experience no voltage, it can be determined as HIF.

HR 5: If the voltage state of the power supply FRTU is normal and the fault current is not experienced, the source neighbor zone set is regarded as the HIF zone.

HR 6: The element with the maximum current is defined as FRTU of the power property. This rule is due to the fact that the current of the supply line is greater than the branch line current, and it is a rule to check the FRTU supplying power.

The fault distance determination step for the fault section of the present invention is as follows.

In the present invention, the fault distance determination procedure is composed of fault determination, fault type determination, fault path determination, and fault distance estimation procedure. FIG. 13 shows a FRTU-based fault distance estimation procedure. Is done. However, steps 1 and 3 may be omitted since they may be repeated unless they are executed independently.

<Step 1>

The FRTU monitors current sample data input in real time to determine whether there is a failure. If the half-cycle current RMS value exceeds the pickup value and the ANN output is marked as fault, go to step 2.

<Step 2>

FRTU determines the type of failure. At this time, one of ground fault, phase short fault, two-line fault or three-phase short fault is decided according to whether RMS values of I _a , I _b , I _c , and I _n exceed the set value. 14 shows the failure type determination process. Go to the next three steps.

<Step 3>

The FRTU collects one cycle waveforms of three phase voltages V _a , V _b , V _c , three phase currents I _a , I _b , I _c after failure. The fundamental wave frequency component is obtained by applying DFT (Digital Fourier Transformation) to these data. Then go to step 4.

<Step 4>

The FRTU collects the effective value V _RMS for each FRTU through 1: 1 communication with Load Area Switch FRTUs (LASFs), and then proceeds to step 5.

<Step 5>

FRTU determines the fault zone based on rule 1. The fault path is determined based on rules 2-6. Go to the next six steps.

RULE 1: FRTU judges its own load zone as a fault zone when experiencing a fault current and when one or more elements of the load side FRTUs experience no voltage.

15 shows a case where a ground fault occurs at the point F. FIG. At this time, the power supply side S ₁ experiences a fault current, but S ₂ and S ₃ show a normal load voltage and a normal load current. On the other hand, since one wire is grounded at point F, S ₄ and S ₅ are voltage-free in the phase of the accident. I.e., experiencing two elements S _4, S ₅ of a non-voltage-side power FRTU S ₁ of the failure ZONE is experiencing a fault current in its load-side elements _{{S 2, S 3, S} 4, S 5}. Therefore, by using this rule, the FRTU experiencing the fault current can check whether the magnetic load zone has failed through 1: 1 communication with the load side FRTUs.

After the fault zone is confirmed, the fault path should be checked. Each FRTU keeps the switch zone information set of the load zone aligned with the main line from the power side to the load side. In the case of FIG. 3, the FRTU of S ₁ stores the switch set of the load zone as {S ₂ , S ₃ , S _{4 ,} S ₅ }. At this time, the fault location is a combination of the paths composed of the switch S ₁ and {S ₂ , S ₃ , S _{4 ,} S ₅ } {S ₁ , S ₂ }, {S ₁ , S ₃ }, {S ₁ , S ₄ }, {S ₁ , S ₅ }, {S ₂ , S ₃ }... Can be one of This problem can be determined by the following RULE 2-4 with voltage information collected from FRTUs in the load area by 1: 1 communication.

RULE 2: FRTU determines the path of failure by the last switch that satisfies the voltage condition and the first switch that satisfies the no-voltage condition.

RULE 3: FRTU determines the main line from the last switch which does not satisfy the no-voltage as the starting point of the fault when there is more than one switch that satisfies the voltage condition.

RULE 4: FRTU decides the main line to the first switch that satisfies the voltage as the end point of the failure path when there are two or more switches that satisfy the voltage-free condition.

RULE 5: FRTU decides the fault path from the branch point to the switch in view of the electrical connection when there is more than one switch that satisfies the voltage condition on the load side of the switch that satisfies the no-voltage condition.

RULE 6: FRTU decides fault path as branch line connected to fault when there is no switch that satisfies no voltage condition.

In the case where a failure occurs at point F in FIG. 3, the switches S ₂ and S ₃ on the power supply side of the point F do not experience no voltage. Thus, paths {S ₁ , S ₂ }, {S ₁ , S ₃ } cannot be fault paths. On the other hand, the switches S _{4 and} S ₅ on the load side of the fault occurrence point (point F) structurally satisfy the no-voltage condition. Therefore, it can be inferred that the path from the power switch to the last switch that satisfies the voltage condition and the first switch that satisfies the no-voltage condition is the fault path. That is, it can be confirmed that the fault path is the main line of {S ₂ , S ₄ } from the switch S ₂ satisfying the voltage condition and the switch S ₄ satisfying the no voltage condition. Thus, based on these structural characteristics, RULE 2 is obtained.

In particular, if two or more paths satisfy voltage or no-voltage conditions, it can be inferred that the common main line is a failure path. Since the switch S ₃ satisfy the voltage condition shown in Figure fault path starts from point A, and the switch S ₄ Since S ₅ satisfies the no-voltage condition, a fault path exists on the path to point C. Therefore, it can be seen that the main line sections {A, B} of the sections {S ₂ , S ₄ } are fault routes. This is defined by RULE 3-4.

If a fault occurs at point E, there is no switch that satisfies the no-voltage condition. Therefore, it can be inferred that a failure has occurred in the branch line in which the switch is not installed, and in particular, the branch line connected to the failure of the switch S ₁ in the branch line can be inferred as a failure path. This principle is represented as RULE 6. To apply this rule, the end of the line must be marked as a dummy switch and added to the FRTU's load stage switch information set.

<Step 6>

Apply the following equation (1) to estimate the fault distance. When the work is completed, go to step 1 and repeat the failure distance estimation procedure.

As a method of estimating fault distance, a relatively practical algorithm that does not require fault resistance is adopted. At this time, the calculation of the fault distance is determined differently according to the fault type, which can be largely classified into a one-line ground fault or a short circuit fault between lines. Equation (1) shows the failure distance estimation equation for ground fault failure.

(1)

(One)

의 실수부와 허수부를 표시하는데, I_p3 는 고장 p상의 3번째 1주기 전류파형의 기본파 성분이다. 특히 I_{p (L),i} 는 부하 측의 i번째 개폐기의 1주기 전류파형의 기본파 성분으로써 FRTU간 1:1 통신에 의해서 수집되며, n은 부하 개폐기들의 수를 표시한다. R_I, X₁은 단위 길이당 정상 임피던스의 실수부와 허수부를 표시한다. 그리고 I_kR, I_kX는 I_k=I_p3 + {(Z₀-Z₁)/ Z₁}I₀ 의 실수부와 허수부를 표시하는데, I_p3, I₀, Z_O, Z₁은 고장 상 의 3번째 1주기 전류파형의 기본파 성분, 영상 전류, 단위 길이당 영상 및 정상 임피던스를 표시한다. In Equation (1), V _P3 , _R , V _P3 , and _X represent the real part and the imaginary part of the third one-cycle voltage waveform on the fault. Especially I _mR , I _mX Is fault current

Real and imaginary parts of I _p3 Is the fundamental wave component of the third one-cycle current waveform on fault p. In particular, I _{p (L), i} is the fundamental wave component of the 1-cycle current waveform of the i-th switch on the load side and is collected by 1: 1 communication between FRTUs, and n denotes the number of load switches. R _I , X ₁ represent the real and imaginary parts of normal impedance per unit length. I _kR and I _kX represent the real and imaginary parts of I _k = I _p3 + {(Z ₀ -Z ₁ ) / Z ₁ } I ₀ , where I _p3 , I ₀ , Z _O , and Z ₁ indicate fault conditions. The fundamental wave component, image current, image per unit length, and normal impedance of the 3rd 1-cycle current waveform of.

In case of short-circuit fault, 2-wire ground fault or 3-phase short fault, V _p3 , I _k and I _c are the corresponding values, V _p3 -V _q3 , I _p3 -I _q3 , {(I _p3- ) I _p3 ^* )-(I _q3 -I _q3 ^* )}.

Where p and q represent phases experiencing short or ground faults, and * means before failure.

1 is a schematic view showing a distribution system in a form in which a general overhead line and a ground line are mixed;

2 is a block diagram of an intelligent FRTU based fault interval determination and autonomous separation method in a distribution system of the present invention;

3 is a schematic diagram of a ubiquitous environment for intelligent FRTU based fault interval determination and autonomous separation in a distribution system of the present invention;

4 is a flowchart illustrating an operation control strategy of an intelligent FRTU of the present invention;

5 is a plan view overview of the Naver Zone (Zone) modeling of the present invention,

6 is a flowchart showing an arbitrary step in the operation control strategy of the intelligent FRTU,

7 is a flowchart illustrating a voltage-free HIF determination processing procedure in the operation control strategy of the intelligent FRTU;

8 is a flowchart showing a fault determination procedure proposed in the present invention;

9 is a schematic diagram showing a search method for determining a LIF failure section based on the FRTU of the present invention;

10 is a flowchart showing step-by-step confirmation and autonomous separation for any FRTU ₀ based on the FRTU of the present invention;

11 is a schematic diagram showing an independent search method for the voltage-free triggering current direction based on the FRTU angle 1: 1 communication of the present invention;

12 is a flowchart illustrating an autonomous separation step of an HIF interval based on the FRTU of the present invention;

13 is a flowchart showing a fault distance estimation procedure based on the FRTU of the present invention;

14 is a flowchart showing a failure type determination process based on the FRTU of the present invention;

15 is a schematic diagram showing an example of the determination of a failure zone according to the present invention.

<Description of Symbols for Major Parts of Drawings>

10: switchgear 20: surge protector

30: measuring unit 40: DSP (central control unit)

50: EEPROM 60: LAN port

Claims (5)

Distribution automation consisting of a central control unit, a recloser, and a FRTU installed in the switchgear to remotely check for any faults occurring in the distribution system and control the fault handling procedure during the construction and operation of the distribution line over a long distance. In the system, A voltage sensor VS is installed on each end of the switch 10, and a current sensor CT is installed on each side of one end, and the voltage sensor 3 is provided from a voltage sensor installed at both ends of the switch and a current sensor installed at one end. Phase voltage and three-phase current signals are passed to the measuring unit 30 after passing through the surge protector 20 is configured to protect the circuit from the surge, the DSP 40 receiving the signal from the measuring unit 30 is in the measuring unit Read the three-phase voltage and current signal of the multi-circuit from the A / D converter to determine the fault, calculate the fault distance and establish a corresponding strategy, the fault generated in the wiring system detected by the DSP (40) Various information such as fault current waveforms and voltage waveforms for several cycles before and after faults are recorded in the EEPROM 50, and various kinds of information randomly generated in the wiring system are connected to the central controller (LAN) through the LAN port 60. DSP) of course Intelligent FRTU based fault section determination and autonomous separation method in a distribution system characterized by communicating between different FRTUs, allowing any FRTU to exchange information for fault determination, fault distance calculation, fault zone determination, and autonomous separation . The method of claim 1, wherein the operation of the FRTU calculates the current effective value every half cycle, checks the LIF (Low Impedance Fault) starting point by comparing with the pickup value, calculates the effective value of the voltage half-cycle value, and compares with the low voltage reference value Determine whether to start High Impedance Fault (HIF), record 1 cycle 3-phase current waveform before fault, 1st, 2nd, and 3rd 3-phase current waveform, and 3-phase voltage waveform on maximum current after fault Through the Digital Fourier Transformation (DFT), harmonic magnitudes are obtained for the first and second one-cycle waveforms at the maximum current after failure, and the ANN is used to determine whether the failure / entry is performed, and the third three-phase voltage before and after the failure. For the current 1 cycle waveform, calculate the fault distance by obtaining the fundamental wave component, and when fault determination is made, determine the fault section and perform autonomous separation through 1: 1 communication with surrounding FRTUs. The intelligent FRTU based fault in the power distribution grid, characterized in that the configuration control section determination and self-separation method. The method according to claim 2, wherein for the determination of the failure section and the autonomous separation in case of LIF failure for any FRTU ₀ on the distribution line, If the IP and the pick-up currents for the setting FRTU FRTU _{0 0} is the first step to download information of SRZS (Source Zone Set) and SZS (Sink Zone Set) from the central control unit of the ADS; The FRTU ₀ is the second phase to be monitored and the current exceeds the pick-up current and the current is set if the ANN output judging the failure transition to fault current detection state; To the FRTU ₀ determines the SZS1 (Sink Zone Set 1) on the basis of the current direction, and if the line is reconfigured track accidents or work power failure if the backhaul conditions are SRZS decided SZS1, the elements of the following SZS1 FRTU _i and FID (Fault Information Data) information is collected through 1: 1 communication, so if there is a, b or c phase fault and there is a FRTU with fault current sensing status (FCSS (Fault Current Sensing Status) or n phase fault and no voltage) If there are no elements that have experienced a sensing state, or NVSS (Nil-Voltage Sensing Status), then SZS1 determines that it is a health zone and goes to step 2, while all elements do not experience a fault current or have experienced no voltage. A third step of making SZS1 a candidate candidate for failure zone and issuing an FCS collection command to each element FRTU1 _i of SZS1 to determine whether or not the actual failure occurs; FRTU _i determines SZS2 and 1 to each element of FRTU2 _i: if degrees with the FID gather instruction via the first communication, a, b, or c-phase fault, and if all elements of SZS2 they did not experience the fault current, or the n-phase If the failure and any element of SZS2 experiences voltage free in any phase, the fourth step of FRTU ₀ finally determining SZS1 as the failure zone from the collected information; The FRTU ₀ is a fifth step of issuing a switch open command to all FRTUs of SZS1 when the preset no-voltage count is reached. Intelligent FRTU based fault interval determination and autonomous separation method in a distribution system. The method according to claim 2, wherein for the determination of the failure section and the autonomous separation in case of HIF failure for any FRTU ₀ on the distribution line, A first step for downloading the information on when the IP and the pick-up current is set FRTU is ₀ (Source Zone Set) SRZS from the central control unit of the ADS and SZS (Sink Zone Set) for the FRTU _0; The second step of the FRTU ₀ is to monitor the voltage in the terminal switch state, the transition to the HIF detection state when the set voltage-free condition is satisfied; The FRTU ₀ determines the sink zone set (SZS) based on the current direction, collects NVS (Nil Voltage State) information through 1: 1 communication with the first FRTU1 ₁ of the elements of the next SZS, and from the NVS information to the actual HIF. Determining and searching for a fault section; The FRTU ₀ by determining the SRZS (Source Zone Set) on the basis of the current direction if the line is reconfigured track accidents or work power failure if the backhaul conditions are SZS is determined SRZS, the elements of the following SRZS FRTU1 _i and 1: through the first communication collect current and NVS (Nil Voltage State) information of each FRTU1 _i to determine a FRTU _i with the maximum current to the SOURCE FRTU, if in determining the SRZS1 if the SOURCE FRTU NVS is RESET by HIF failure ZONE The fourth step; The FRTU ₀ autonomously opens the switchgear to separate the HIF fault section and transmits the HIF fault information to the central control unit of the distribution automation system.In this case, SOURCE NAVER Zone provides voltage and current value information by 1: 1 communication. The FRTU of the source attribute of the intelligent FRTU based fault interval determination and autonomous separation method of the distribution system, characterized in that the fifth step to completely separate the failure section by opening the switch autonomously. According to claim 1, In order to determine the fault distance on the distribution line based on the FRTU, FRTU monitors the current sample data input in real time to determine whether there is a failure, if the half-cycle current RMS value exceeds the pickup value and the ANN output is displayed as a failure; FRTU decides the type of failure and at this time, depending on whether the RMS values of I _a , I _b , I _c , and I _n exceed the set values, 1-line ground fault, phase short circuit fault, 2-wire ground fault or 3-phase short circuit fault Determining a second one; FRTU collects one-cycle waveforms of three-phase voltages V _a , V _b , V _c , three phase currents I _a , I _b , I _c after failure, and applies digital fourier transform (DFT) to these data, Obtaining a third step; FRTU, the fourth step of collecting the effective value V _RMS for each FRTU through 1: 1 communication with the load area switch FRTU (LASF: Load Area Switch FRTU); FRTU determines a fault zone; a fifth step of determining a fault path; Intelligent FRTU-based failure section determination and autonomous separation method in a distribution system characterized in that the sixth step of estimating the failure distance by applying the following equation (1).

(One)

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