JP4050714B2 - Ground fault detection relay device - Google Patents

Description

  The present invention relates to a ground fault detection relay device for a system composed of two sets of quadrature single-phase power sources converted from a three-phase AC power source by a transformer.

  Generally, an AC feeding load is a single-phase load, and an AC feeding system using a single-phase power source is configured as a power supply system. This AC feeding system is composed of two sets of single-phase power supplies of quadrature phase obtained by using a three-phase to two-phase conversion transformer in order to balance a single-phase load on the three-phase power supply side (for example, Patent Document 1).

  Such an AC feeder system is shown in FIG. The electric power of the customer is supplied from the power transmission facility 2 of the electric power company and is received by a three-phase power source. The received three-phase power is converted into two sets of A-phase power and B-seat power having two phases orthogonal to each other and supplied to the load by the feeding transformer 3 of the customer.

  On the other hand, ground fault detection protection in an AC feeder system has conventionally been designed to open a power supply system by determining a ground fault according to the magnitude of the voltage difference between the potentials at both ends and ground potential of both sets of single-phase power supplies. Was configured. In order to perform such ground fault protection, the voltages of the two sets of single-phase power supplies A and B are respectively secondary voltages obtained by dividing the midpoint of the two instrument transformers 5 and 6 with the ground potential. VA1, VA2, VB1, and VB2 are input to the ground fault detection relay device 1.

  FIG. 3 shows steady voltage vectors of the received three-phase and two sets of single-phase conversion voltages. The primary power receiving three-phase vectors a, b, and c in the feeding transformer 3 are 120 ° phase balanced vectors, and are indicated by respective interphase voltages V. Assuming that the transformation ratio is 1: 1, one single-phase power source A seat of the transformer secondary is in phase with the three-phase power source bc phase and has a voltage value V. Further, the other single-phase power source B of the transformer secondary has the voltage value V / √3 in the same phase as the three-phase power source a-phase, but the feeder circuit voltage V by the step-up transformer 4 having a transformation ratio 1: √3. Is supplied. The two sets of single-phase power supply voltages V are equally divided as secondary voltages VA1, VA2, VB1, and VB2 by the above-described instrument transformer 5 by the ground potential at the midpoint, and input to the ground fault detection relay device 1 Has been.

  Here, VA1 and VA2 are the first potential and the second potential of one set A seat, and VB1 and VB2 are the first potential and the second potential of the other set B seat. These are equal in value and their phase angles are orthogonal to each other, and the phase difference angles φ1 to φ4 are each 90 °. Further, the inter-phase voltages V1 to V4 in a steady state are regular quadrilateral outer peripheral oblique voltages with two sets of orthogonal single-phase power supplies V of A and B seats as diagonal lines, and the value thereof is V / √2.

  Conventionally, the ground fault detection relay device 1 receives the electric potentials VA1, VA2, VB1, and VB2 of the A seat and B seat from the transformers 5 and 6 as described above. These input voltages are sampled and held every arbitrary electrical angular velocity time of the system frequency, converted into digital values, and stored in the data storage means. This stored data is updated every arbitrary electrical angular velocity time as time-series stored data for a predetermined number of sampling times.

  In detecting the ground fault, the difference voltages Δva and Δvb between the potentials at both ends of the two sets of single-phase power supply A and B and the ground potential are calculated from the values of the respective potentials VA1, VA2, VB1, and VB2. The difference voltage is compared with a predetermined motion detection value kv, and the difference voltages Δva and Δvb of the two sets of single-phase power supply A seat and B seat or both exceed the motion detection value kv. Execute operation output in case.

  That is, as described with reference to FIG. 3, the feeding voltage vector in the steady state is a pair of single-phase power supply A-seat and B-seat voltages, each of which is a regular quadrilateral diagonal, and the center of the regular quadrilateral is the ground potential. It is. Therefore, the difference voltage between the potentials at both ends and the ground potential is equal for the two sets of single-phase power sources A and B. Therefore, Δva = VA1-VA2 = 0v and Δvb = VB1-VB2 = 0v, and it is determined that no ground fault has occurred.

  On the other hand, when a ground fault occurs on the single-phase power supply side, the feeding voltage vector is deformed into a shape in which the ground potential moves from the center of the quadrilateral to the ground fault side as shown in FIG. For this reason, when a difference occurs between VB1 and VB2 and Δvb which is the difference exceeds the operation detection value, it is determined as a ground fault and an operation output is executed.

  Thus, in the conventional ground fault detection method, it is possible to detect a ground fault accident on the single-phase power supply side. Nevertheless, it is erroneously detected as a ground fault.

  That is, when a contact accident occurs, the potential between both ends of the two sets of single-phase voltages is displaced toward the middle point between the contact phases. FIG. 7 shows an example of contact of the interphase voltage V1. A fault current flows through the two sets of single-phase power supplies A and B due to a mixed accident, and the fault current flowing through the A seat returns to the three-phase side bc phase. On the other hand, 1/2 of the a-phase current flows back to the a-phase on the three-phase side, and the b- and c-phases respectively. Due to this current and the impedance of the feeding transformer 3, a voltage drop that is related to the voltage value and the phase displacement occurs, and the quadrilateral formed by the feeding voltage vector of two sets of single phase is reduced, and the outer peripheral voltages V 1 to V 4 are reduced. The voltage also drops. In addition, the mixed current between the different-phase power sources circulates through the midpoint grounding of the auto-transformer provided in each of the single-phase two sets of feeder circuits.

  As a result, as shown in the figure, the ground potential is displaced toward the both-end potential side of the mixed phase, so that the ground sharing voltage differences Δva and Δvb between the two sets of single-phase power supply A seat and B seat are generated.

That is, due to the voltage drop with respect to the ground potential due to the mixed current and the system impedance or the fault point impedance, the balance between the potentials at both ends and the ground potential of each of the two sets of single-phase power supply A and B seats is lost, and the difference voltage Δva, Δvb occurs, erroneously detecting a ground fault and leading to unnecessary operation. In order to prevent this unnecessary operation, time cooperation with the subordinate system is required, and the high speed is hindered.
Japanese Patent Laid-Open No. 3-132436

  As described above, in the conventional method of detecting the ground fault on the single-phase power source side based on the differential voltage between the both-end potential of each of the two single-phase power sources A and B and the ground potential, the mixed-phase accident on the single-phase power source side is detected. Even if a fault occurs, the operation is unnecessary, and it is erroneously detected as a ground fault despite a heterogeneous accident.

  It is an object of the present invention to provide a ground fault relay device that can reliably detect a ground fault on the single-phase power supply side and that does not needlessly operate against a mixed-phase accident on the single-phase power supply side. .

The ground fault detection relay device of the present invention is a ground fault detection relay device of a system constituted by two sets of quadrature phase single phase power sources converted from a three-phase AC power source by a transformer. a single-phase power supply each set of the first potential equally divided on each potential across the ground potential of VA1, VB1, input means for inputting second potential VA2, VB2 respectively, in each of these respective sets, later According to the equations (1) and (2), the first potential VA1 (VB1) of the self set, the first potential VB1 (VA1) and the second potential VB2 (VA2) of the other set, the self set The first effective component is obtained from the phase difference angle φ1 between the first potential VA1 (VB1) of the second and the first potential VB1 (VA1) of the other set, and the second potential VA2 (VB2) of the own set is obtained. The first potential VB1 (VA1) and the second potential VB2 (VA2) of the set, the phase difference angle φ3 between the second potential VA2 (VB2) of the self set and the second potential VB2 (VA2) of the other set To obtain the second active ingredient from Phase calculation means for obtaining the difference between the first effective component and the second effective component as effective component differences Δwa and Δwb for each set, and the motion detection value in which the obtained effective component differences Δwa and Δwb are set in advance. And a comparison determination means for determining that a ground fault has occurred when any of them exceeds the motion detection value.

  According to the present invention, the first and second potentials of each set obtained by equally dividing the potentials at both ends of the two sets of single-phase power sources with the ground potential are input, respectively. From the value of the potential and the phase difference angle thereof, the difference in the effective component for each set that occurs at the time of the ground fault on the single-phase power supply side is obtained, and if any of them exceeds this motion detection value, Since it determines, it can detect a ground fault accident reliably, without performing unnecessary operation | movement with respect to a heterogeneous accident.

  Hereinafter, an embodiment of a ground fault detection relay device according to the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 2, the AC feeder system itself receives power from a power company's power transmission equipment 2 with a three-phase power supply, and then a single phase two sets of A-phases orthogonal to each other by a customer feeder transformer 3. Convert to power supply, B seat power supply and supply to load. In order to protect the earth fault of such AC feeding system, the voltage of the two sets of single-phase power supply A seat and B seat is divided by the midpoint of the two instrument transformers 5 and 6, respectively, with ground potential. The secondary voltages VA1, VA2, VB1, and VB2 are input to the ground fault detection relay device 1.

  The processing means block configuration of the ground fault detection relay device 1 will be described with reference to FIG. In FIG. 1, 21 is an input means, and two sets of single-phase power supply voltages VA1, VA2, VB1, and VB2 are input from the instrument transformers 5 and 6 shown in FIG. That is, VA1 is a first potential obtained by dividing the voltage V across one single-phase power source A by the ground potential at the midpoint, and VA2 is the second potential. VB1 is a first potential obtained by dividing the voltage V across the other single-phase power source B by a ground potential at the midpoint, and VB2 is the second potential.

  These input voltages are converted by the input means 21 at a predetermined ratio, passed through an analog filter, and then sampled and held by the input sampling and holding means 22 for every electrical angular velocity time of the system frequency. This sample hold value is converted into a digital value by the A / D conversion means 23. In this way, each input voltage data converted into a digital value every arbitrary electrical angular velocity time is stored in the data storage means 24. This stored data is updated every arbitrary electrical angular velocity time as time-series stored data for a predetermined number of sampling times.

  25 is a phase calculation means, and each set generated at the time of a ground fault on the single-phase power source side from the values of the first and second potentials VA1, VA2, VB1, and VB2 of each set of A seat and B seat and their phase difference. Find the active ingredient difference for each. That is, the effective component differences Δwa and Δwb between the two sets of single-phase voltages are calculated from the sampling data of the input voltages VA1, VA2, VB1, and VB2 by the following expression.

Δwa = VA1 × (VB1 + VB2) × cosφ1-VA2 × (VB1 + VB2) × cosφ3
= VA1 × VB1 × (1 + 1 / kvb) × (cosφ1-cosφ3 / kva) (1)
Δwb = VB1 × (VA1 + VA2) × cos φ1-VB2 × (VA1 + VA2) × cos φ3
= VA1 × VB1 × (1 + 1 / kva) × (cosφ1-cosφ3 / kvb) (2)
Here, kva is a voltage ratio between VA1 and VA2, and kvb is a voltage ratio between VB1 and VB2.

  That is, the phase calculation means 25 first has the first potential VA1 (VB1) of its own set A seat (B seat) and the first of the other set B seat (A seat) for each set of A seat and B seat. The potential VB1 (VA1) and the second potential VB2 (VA2), the first potential VA1 (VB1) of its own set A seat (B seat) and the first potential VB1 (VA1) of the other set B seat (A seat) The first effective component is obtained from the phase difference angle φ1. Next, the second potential VA2 (VB2) of the own set A seat (B seat), the first potential VB1 (VA1) and the second potential VB2 (VA2) of the other set B seat (A seat), A second effective component is obtained from the phase angle φ3 between the second potential VA2 (VB2) of the set A seat (B seat) and the second potential VB2 (VA2) of the other set B seat (A seat). Then, the difference between the first effective component and the second effective component is obtained as effective component differences Δwa and Δwb for each of the A seat and B seat groups.

  Reference numeral 26 denotes a comparison / determination means, which compares the effective component differences Δwa and Δwb obtained by the phase difference calculation means 25 with a preset motion detection value Kw, and if any of these exceeds the motion detection value Kw, Judged as an accident. The motion detection result determined as a ground fault is output to the outside by the output processing means 27.

  In the above configuration, a consumer such as an electric railway company receives the three-phase power supplied from the power transmission facility 2 of the power company as shown in FIG. The received three-phase power is converted into a single-phase two-set A-phase power source and a B-seat power source having orthogonal phases by the feeding transformer 3 of the customer and supplied to the load.

  The voltage of the two sets of single-phase power supplies A and B are the secondary voltages VA1, VA2, VB1, and VB2, which are divided by the ground potential at the midpoint of the two instrument transformers 5 and 6, respectively. Input to the fault detection relay device 1.

  As shown in FIG. 3, the voltage vectors in the steady state of these three phases of power reception and two single-phase conversion voltages are primary power reception three-phase vectors a, b, and c, which are 120 ° phase balanced vectors, respectively. This is indicated by the interphase voltage V. When the transformation ratio is 1: 1, one single-phase power source A seat of the transformer secondary is in phase with the three-phase power source b-c phase and has a voltage value V. The other single-phase power source B seat is in phase with the three-phase power source a phase and has a voltage value V / √3, but the feeder circuit voltage V is supplied by the step-up transformer 4 having a transformation ratio of 1: √3. Two sets of single-phase power supply voltages V are equally divided as secondary voltages VA1, VA2, VB1, and VB2 by a ground potential at the midpoint in the instrument transformer 5 and input to the ground fault detection relay device 1. .

  These input values VA1, VA2, VB1, and VB2 have the same value and the phase angles thereof are orthogonal to each other, and the phase difference angles φ1 to φ4 are each 90 °. Further, the inter-phase voltages V1 to V4 in a steady state are regular quadrilateral outer peripheral oblique voltages with two sets of orthogonal single-phase power supplies V of A and B seats as diagonal lines, and the value thereof is V / √2. These values and phase angles are sampled and held, then A / D converted, and stored in the data storage means 24 as digital data.

  The phase calculation means 25 performs calculations according to the above equations (1) and (2) using these data, and obtains the effective component differences Δwa and Δwb for each of the A seat and B seat groups.

  Here, when a ground fault occurs on the single-phase power supply side, the feeding voltage vector is deformed into a shape in which the ground potential moves from the center of the quadrilateral to the ground fault side, as shown in FIG. Therefore, in the example of FIG. 6, a difference is generated between the potentials VB1 and VB2, and a difference is also generated in the phase difference angles φ1 and φ3. For this reason, when the active component differences Δwa and Δwb calculated by the equations (1) and (2) are generated and the magnitude exceeds the motion detection value Kw, it is determined that a ground fault has occurred.

  On the other hand, when a single-phase power supply side different-phase contact accident occurs, the potential between both ends of the two sets of single-phase voltages is displaced toward the middle point between the contact phases. For example, when the cross-phase voltage V1 is mixed, as shown in FIG. 7, the quadrilateral formed by the single-phase two sets of feeding voltage vectors is reduced, and the voltages of the outer peripheral voltages V1 to V4 are also lowered. . In addition, since the ground potential is displaced to the both-end potential side of the mixed phase, the difference in ground voltage Δva (= VA1-VA2) and Δvb (= VB1-VB2) between the two sets of single-phase power supply A and B seats are generated. To do.

  However, since the phase difference angles φ1 and φ3 are equal to each other, the effective component differences Δwa and Δwb calculated by the equations (1) and (2) are substantially zero. That is, it does not operate in a mixed-phase accident, and therefore, as in the conventional case, a ground fault is erroneously detected in a mixed-phase accident and no unnecessary operation is performed.

  When an accident occurs on the three-phase power supply side, the voltage vectors of VA1, VA2, VB1, and VB2 input to the ground fault detection relay device 1 are deformed as shown in FIG. Further, when a short circuit accident occurs on the single-phase power supply side, the voltage vectors of VA1, VA2, VB1, and VB2 are deformed as shown in FIG.

  However, in any of these cases, since the phase difference angles φ1 and φ3 are equal to each other, the effective component differences Δwa and Δwb calculated by the equations (1) and (2) are substantially zero. That is, it does not operate in the case of a three-phase power supply side accident or a single-phase power supply side short-circuit accident, and therefore, it is not erroneously detected as a ground fault at the time of these accidents and no unnecessary operation is performed.

  In this way, the ground potential of the two sets of single phase intersecting each other becomes the same potential at the intersection, and the difference between the effective components of the voltage on one side of the two sets of single-phase power supplies and the voltage shared on both ends on the other side is obtained. Therefore, in the vectors due to the three-phase power supply system fault and the single-homogeneous system short-circuit fault shown in FIGS. 4 and 5, the active component difference is extremely small, and the detection operation is suppressed. On the other hand, in the ground fault accident shown in FIG. 6, the value of one of the two effective component differences is large and the difference in the other effective component is very small. Further, in the heterogeneous color mixture vector of the single homologous system shown in FIG. 7, the ground potential difference occurs in both of the two sets of single-phase voltages, but the phase difference angles φ1 and φ3 are equal to each other. Becomes extremely small and the detection operation is suppressed.

  As a result, it can operate only on the ground fault accident that is the original detection target accident, without unnecessary operation for the accident on the three-phase power supply side outside the detection section or the short circuit / contact accident of the single homologous system that is not the detection target. . This eliminates the need for detection coordination and time coordination with other equipment and devices, enables high-speed protection, and simplifies on-site adjustment tests and maintenance inspections and improves workability.

It is a processing block diagram explaining one embodiment of a ground fault detection relay device according to the present invention. It is a figure explaining the electric power grid | system to which one embodiment same as the above is applied. It is a voltage vector figure at the time of steady state inputted into one embodiment same as the above. It is a voltage vector figure at the time of the three-phase power supply side accident input into one Embodiment same as the above. It is a voltage vector figure at the time of the single phase power supply side short circuit accident input into one Embodiment same as the above. It is a voltage vector figure at the time of the single phase power supply side ground fault accident input into one Embodiment same as the above. It is a voltage vector figure at the time of the single phase power supply side different phase infringement accident input into one embodiment same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground fault detection relay device 3 Transformer 5,6 Instrument transformer 21 Input means 25 Phase calculation means 26 Comparison determination means

Claims (1)

A ground fault detection relay device of a system composed of two sets of quadrature phase single phase power source converted from a three phase AC power source by a transformer,
Input means for inputting the first potentials VA1 and VB1 and the second potentials VA2 and VB2 of the respective sets obtained by equally dividing the potentials at both ends of the two sets of single-phase power sources with the ground potential;
For each of these sets, according to the following equations (1) and (2), the first potential VA1 (VB1) of the self set, the first potential VB1 (VA1) and the second potential VB2 ( VA2), the first effective component is obtained from the phase difference angle φ1 between the first potential VA1 (VB1) of the self set and the first potential VB1 (VA1) of the other set, and the second potential of the self set is obtained. VA2 (VB2), the first potential VB1 (VA1) and the second potential VB2 (VA2) of the other set, the second potential VA2 (VB2) of the self set and the second potential VB2 (VA2) of the other set Phase calculating means for obtaining the second effective component from the phase difference angle φ3 and the difference between the first effective component and the second effective component as effective component differences Δwa and Δwb for each group ,
Comparison determination means for comparing these determined effective component differences Δwa, Δwb with a preset motion detection value and determining a ground fault when any of them exceeds the motion detection value;
A ground fault detection relay device comprising:
Δwa = VA1 × (VB1 + VB2) × cosφ1-VA2 × (VB1 + VB2) × cosφ3
= VA1 × VB1 × (1 + 1 / kvb) × (cosφ1-cosφ3 / kva) (1)
Δwb = VB1 × (VA1 + VA2) × cos φ1-VB2 × (VA1 + VA2) × cos φ3
= VA1 × VB1 × (1 + 1 / kva) × (cosφ1-cosφ3 / kvb) (2)
Here, kva is a voltage ratio between VA1 and VA2, and kvb is a voltage ratio between VB1 and VB2.

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