JP3109633B2 - Insulation degradation detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a bus connected to a power supply.
Connected to multiple distribution lines each having a load electrical device
The present invention relates to an insulation deterioration detection device for detecting insulation deterioration of a system at an early stage of deterioration.

[0002]

2. Description of the Related Art In general, as shown in FIG.
In a system in which a plurality of distribution lines are connected to a bus 3 connected to the power supply, a grounded-type instrument transformer GPT is connected to the bus 3, and the third-order zero-phase voltage E of the grounded-type instrument transformer GPT is connected.
_0, has been detected ground fault to determine the earth絡回line and sound circuit by comparing the phases of the secondary of the zero-phase current I ₀ of the zero-phase current transformer ZCT provided in each distribution line Was. Further, as described in JP-A-4-42726, the line voltage and
By comparing the phase with the secondary zero-phase current of the zero-phase current transformer ZCT provided in each distribution line, the ground fault phase and the ground fault point in the same distribution line are specified. Things are known.

[0003]

However, the above-mentioned conventional ground fault detecting device is for detecting, for example, a case in which the deterioration of the insulator progresses and leads to a ground fault. In order to detect the initial state of deterioration of the device, a detection device with higher sensitivity is required. That is, in order to perform such high-sensitivity detection, a voltage in a minute level region equal to or smaller than the residual value of the zero-phase voltage E ₀ constantly generated in the tertiary of the ground-type instrument transformer GPT is detected. Since it is necessary to perform phase comparison, the third-order zero-phase voltage E ₀ of the ground-type instrument transformer GPT cannot be used. As shown in FIG. 1, when a single-line ground fault occurs in a power supply system having a plurality of distribution lines, a healthy line having a large capacitance to ground such as a cable 8 and a motor 9 serving as load electric devices is connected to the ground. Zero-phase current flows due to the unbalance of the capacitance,
As described in Japanese Patent Application Laid-Open No. 4-42726, comparing the phase of the line voltage with the phase of the secondary zero-phase current of the zero-phase current transformer ZCT, this healthy line also looks like a ground fault. As a result, the accident line cannot be specified.

It is an object of the present invention to provide an insulation deterioration detecting device capable of accurately detecting an initial stage of insulation deterioration on the bus side .

[0005]

According to one aspect of the present invention, a plurality of distribution lines each having a load electric device are connected to a bus connected to a power supply. A phase voltage conversion circuit for generating a reference phase voltage from the line voltage of the bus, and a reference voltage and the zero phase current for each phase. Detecting means for detecting that the phase difference between the secondary zero-phase current of the current transformer and the secondary zero-phase current of the current transformer falls within a predetermined range and that the secondary zero-phase current of the zero-phase current transformer exceeds a predetermined set value. And each distribution
At least two of the first detection means for each phase of the line
Detection signals from the first detection means of the same phase
Second detecting means for detecting that the
When a detection signal is obtained from the detection means of
A determination means for determining insulation breakdown is provided.

[0006]

According to the insulation deterioration detecting device of the present invention, when the neutral point potential of the grounded type transformer changes, the secondary phase voltage of the grounded type transformer also fluctuates. Note that the reference phase voltage E1 with an absolute value of 1 / √3 and a phase delay of 30 degrees is created using the line voltage that does not fluctuate as described above. Each of the reference phase voltages E2 and E3 of the phase difference is generated. On the other hand, when the dielectric strength is normal, the surface leakage current flowing through the insulator of the load electric device is small and almost the ground charging current. Therefore, the secondary zero-phase current of the zero-phase current transformer has a leading phase closer to 90 degrees than each reference phase voltage, but when the dielectric strength decreases, the surface leakage current increases to the ground leakage current, and the zero-phase current Note that the secondary zero-phase current of the detector approaches the same phase as each reference phase voltage And, since the phase difference as detected by the first detecting means that enters the predetermined range, and the secondary of the zero-phase current of the zero-phase current transformer exceeds a predetermined value, the load electric it can be accurately detected in the early stages of the insulation degradation of degradation of equipment and busbar-side electrical equipment of the insulator has progressed further, the field ground fault accident occurs at bus side
The phase of the ground leakage current flowing through each distribution line is the same
Notice that the same phase of at least two distribution lines
That the detection signals were simultaneously obtained from the first detection means
Since the detection is performed by the second detection means, the insulation
It can be determined that the progress of deterioration has occurred on the bus side
You.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a system employing an insulation deterioration detecting device according to one embodiment of the present invention.

A power supply transformer 1 as a power supply has a power receiving breaker 2
The bus 3 is connected via a power distribution circuit breaker 5 to the bus 3. Each distribution line includes a distribution circuit breaker 5, a current transformer CT, a zero-phase current transformer ZCT, and a load electric device including a motor 9 and the like connected via a cable 8. . A bus 3 has a ground-type instrument transformer GPT for voltage measurement.
Are connected, and the line voltage E ₁₂ of the ground-type instrument transformer GPT is taken into the insulation deterioration detecting device 6.

[0010] The insulation deterioration detection device 6, the phase voltage conversion circuit line voltage E ₁₂ each reference phase voltage E ₁ from the 11,
A reference phase voltage E composed of E ₂ and E ₃ is generated, and a phase comparison circuit 1
3 has been entered. Further, the secondary zero-phase current I ₀ of the zero-phase current transformer ZCT of each distribution line is taken, and the commercial frequency zero-phase current passed through the commercial frequency bandpass filter 12 is converted into a phase comparison circuit 13.
And an effective value calculating circuit 14. The phase comparing circuit 13 compares the phase of the reference phase voltage E with the phase of the commercial frequency zero-phase current for each phase, and the effective value calculating circuit 14 calculates the effective value of the commercial frequency zero-phase current. And whether the value has exceeded a predetermined set value _Ior . When the phase difference falls within the predetermined range θ in each phase, a signal indicating the phase difference is input to the deterioration determination circuit 15 for each phase. On the other hand, when the effective value of the commercial frequency zero-phase current exceeds the set value _Ior , the value becomes
Is input to the maximum value comparison circuit 16. Deterioration determination circuit 15
When there is an input from each of the phase comparison circuit 13 and the effective value calculation circuit 14, that is, in any one of the phases, the phase difference between the reference phase voltage E and the commercial frequency zero-phase current is within a predetermined range. enters the theta, and the effective value of the commercial frequency zero-phase current exceeds the set value I _or, to determine that line degradation line, and sends the determination signal to the maximum value comparator circuit 16. The maximum value comparison circuit 16 turns on a built-in switch for each line according to the determination signal to capture the effective value of the commercial frequency zero-phase current, and indicates the maximum value among the effective values of the lines determined to be deteriorated lines. The line is finally displayed on the display 19 as a deteriorated line.

Furthermore, the deterioration determination circuit 15, for each phase of the line, the phase difference is entered within a predetermined range theta, and to see if the effective value exceeds the set value I _or, for each phase The deterioration is determined. Therefore, by inputting the determination signal for each phase and the signal indicating the line determined to be the deteriorated line by the maximum value comparing circuit 16 to the all line deteriorated phase common output circuit 17, which phase of the deteriorated line is It can be determined whether or not it has deteriorated, and this is displayed on the display 19.

FIG. 2 shows a detailed block diagram of such an insulation deterioration detecting device 6.

The phase voltage conversion circuit 11 takes in the line voltage E ₁₂ of the bus 3 taken out by using the grounding type transformer GPT, and uses this line voltage E ₁₂ to obtain 1 / √ in absolute value.
3. A reference phase voltage E composed of a reference phase voltage E ₁ delayed by 30 degrees in phase and reference phase voltages E ₂ and E ₃ having a phase difference of 120 degrees with respect to each other, and a phase comparison circuit is provided for each phase. 13 has been entered. Further, the secondary frequency zero-phase current I ₀ of the zero-phase current transformer ZCT of each distribution line is taken in and the commercial frequency bandpass filter 1
The commercial frequency zero-phase current passing through the phase comparison circuit 2
3, the phase of the reference phase voltage E and the phase of the commercial frequency zero-phase current are compared. When the phase difference falls within a predetermined range θ, the comparison circuit 13 outputs a signal indicating the phase difference to the AND circuit 15a of each phase of the deterioration determination circuit 15 as described later in detail.
Is input to one of the input terminals. The effective value calculating circuit 14 inputs the commercial frequency zero-phase current through the bandpass filter 12 and calculates the effective value. When the effective value exceeds a predetermined set value _Ior , the effective value is calculated for each phase. AND circuit 15
a is input to the other input terminal. Thus, in any of the phases, the phase difference is entered within a predetermined range theta, and when the effective value exceeds the set value I _or, a signal indicative thereof from the AND circuit 15a of the phase is output, It is input to the maximum value comparison circuit 16 via the OR circuit 15b. The maximum value comparison circuit 16 inputs the effective value and the output of the OR circuit 15b from each line, turns on a built-in switch for each line at the output of the OR circuit 15b, captures the effective value, and compares these with each other. By comparison, the line indicating the maximum value among the effective values of the respective lines is selected, and this is finally displayed on the display 19 as a deteriorated line.

The output of the AND circuit 15a of each phase is directly input to one input terminal of the AND circuit 17a of the common output circuit 17 for all lines, without passing through the OR circuit 15b, and is input to the other input terminal. The output of the maximum value comparison circuit 16 is input. Therefore, in the deteriorated line selected by the maximum value comparing circuit 16, the AND circuit 17 of the phase in which the phase difference falls within the predetermined range θ and the effective value exceeds the set value I _or
The signal indicating the deteriorated phase is input to the display 19 via the OR circuit 17b, and the deteriorated phase is displayed. OR circuit 17
Since the signal indicating the degraded phase from each line is input to b, the degraded phase of each line can be displayed on the display 19 in common.

The maximum value comparing circuit 16 and the AND circuit 1
7a is omitted, and only in the output of the OR circuit 15b of the deterioration determination circuit 15, that is, in any phase of the line, the phase difference falls within a predetermined range θ, and the effective value exceeds the set value _Ior . The line is judged to be degraded only under the conditions
A signal indicating the degraded phase of the AND circuit 15a of each phase can be directly input to the OR circuit 17b without passing through the AND circuit 17a. Since the signal indicating the phase may be output, the maximum value comparing circuit 16 and the AND circuit 1
7a is provided to improve the reliability of the determination.

Next, in order to understand the function of the insulation deterioration detecting device 6, the configuration of the load electric equipment shown in FIG. 3 will be described.

Power is supplied from the power transformer 1 to the load electric equipment including the cable 8 and the motor 9 via the distribution circuit breaker 5 and the zero-phase current transformer ZCT. Cable 8 is a load electric device, the electric motor 9 has the ground electrostatic capacitance C _c to the insulation between the center conductor 7 and the cover fabric ground layer, also a load electric equipment, each phase stator and a ground electrostatic capacitance C _m in insulation between the winding 10 and the ground layer.

The ground capacitance C _{c of the} above-described load electric device
And ground capacitance C _m , a ground leakage current I _0f flows as shown in FIG. That is, the ground leakage current I _0f flowing through the zero-phase current transformer ZCT is supplied to the cable 8 and the electric motor 9, and the ground leakage current I _oc in the cable 8 is a combination of the ground charging current I _cc and the surface leakage current I _sc. On the other hand, the ground leakage current I _om of the motor 9 is a composite current of the stator winding charging current I _cm of the stator winding and the surface leakage current I _sm, and the ground leakage current I _0f flowing through this distribution line is a cable. 8
Of becomes ground leakage current I _oc and the resultant current of ground leakage current I _om the motor 9, corresponding to the commercial frequency zero-phase current detected by the zero-phase current transformer ZCT. In the following description, it is assumed that the ground leakage current I _0f is equal to the commercial frequency zero-phase current.

FIGS. 5A and 5B show the current vector of the leakage current to the ground and the phase relationship of each phase when the insulator is normal.

The ground charging current I _cc (I _cm ) due to the ground capacitance of the insulator is 90 degrees ahead of the reference phase voltage E, and the surface leakage current Is _c (I _sm ) of the insulator is the reference phase voltage. And the same phase. However, their size is a surface leakage current I _sc (I _sm) is substantially zero in the normal state, therefore, the ground leakage current I _0F1 of the distribution _line, I 0f2, I 0f3 each phase reference voltages E _1, The leading phases of each of E ₂ and E ₃ are close to 90 degrees, and the three-phase sum of the current vectors is always zero. On the other hand, if the insulation of the cable 8 or the motor 9 as the load electric equipment deteriorates, the surface leakage current _Isc (I
_sm ) increases, and the ground leakage current I _oc (I _om ), which is a combined current with the ground charging current I _cc (I _cm ), approaches the phase of the reference phase voltage E as shown in FIG. Therefore, the ground leakage current I _0f of the distribution line is, as shown in FIG. 6B, the ground leakage current I _{0f1 of the} deteriorated phase and the ground leakage current I _0f of the other healthy phases.
_0F2, becomes a combined current of _I 0f3, surface leakage current due to the deterioration is increased by increment alpha.

FIGS. 7A to 7C _show ground leakage currents I _0f1 , I _0f2 , and primary current flowing through the primary of the zero-phase current transformer ZCT of each distribution line.
The phase relationship between I _0f3 and the reference phase voltages E ₁ , E ₂ , E ₃ is shown. FIG. 7A shows the deteriorated line, and FIGS. 7B and 7C show healthy lines.

As can be seen from the figure, the ground leakage current I _0f1 due to the deterioration of the insulator connected to the first phase of the deteriorated circuit affects the sound circuit and _causes the phase near the second phase to change. _Appear as ground leakage currents I _0f2 and I _0f3 . However, the current values of the ground leakage currents I _0f2 and I _0f3 themselves are small.

The insulation deterioration detecting device 6 will be described based on the above analysis results. Since the reference phase voltages E ₁ , E ₂ , and E ₃ are obtained from the line voltage E ₁₂ of the bus 3, the transformer for the ground-type instrument is obtained. When the neutral point potential of the detector GPT changes, the secondary phase voltage of the ground-type instrument transformer GPT does not fluctuate as in the prior art, thereby improving the accuracy and reliability of detection. Can be. Moreover, as in the past, the grounding type transformer GP
Since the third-order zero-phase voltage E ₀ of T is not used, malfunction due to the zero-phase voltage E ₀ can be prevented, and detection can be performed with high sensitivity equal to or less than the residual value. Phase comparison circuit 13 shown in FIG.
Is the ground leakage current I of the deteriorated line as shown in FIG.
And _0F1, the phase difference between the reference phase voltage E ₁ of the degradation line detects that the is in the range θ set in advance, is inputted to the maximum value comparator circuit 15. As shown in FIG. 8, when the ground leakage current I _of1 becomes equal to _{or larger} than the set value I _or , the value is input from the effective value calculation circuit 14 to the deterioration determination circuit 15 and the maximum value comparison circuit 16. Leakage of other lines to ground I _of2 , I
_{Although of3} occurs near the second phase, the effective value is not output from the effective value calculation circuit 14 because it is equal to _or less than the set value _Ior . Therefore, it is determined that the first phase is the deteriorated phase, and the line including the deteriorated phase is the deteriorated line. Note that the range θ that is the set value of the phase difference between the ground leakage current I _0f1 and the reference phase voltage E ₁ may be set at least to the _leading side. Each set range θ is defined.

Next, detection of a ground fault occurring on the bus 3 will be described.

When a ground fault occurs on the bus 3 side, the difference between the charging current to the ground based on the capacitance of the insulator as a three-phase unbalanced component due to the change in the phase voltage is the primary of the zero-phase current transformer ZCT. And the leakage currents I _0f1 , I _0f2 , and I _0f3 of each distribution line to the ground are detected with the phase relationships shown in _FIGS . The current values of the ground leakage currents I _0f1 , I _0f2 , and I _0f3 greatly change in phase voltage and phase depending on the degree of ground fault as shown in FIG. As the ground leakage current based on the ground fault increases, the detection level becomes all I _or more, and the phase difference between the ground fault phase and a phase voltage different from the ground fault phase falls within the set range θ. However, in this case, as shown in FIG. 10, _since the phases of the ground leakage currents I _of1 , I _of2 and I _of3 of each line are all in phase, this is detected by the multiple line phase simultaneous comparison circuit 18 of FIG. By doing so, it is determined that there is an accident on the bus side, and this is displayed on the display 19. It should be noted that the multiple line phase simultaneous comparison circuit 18
Inputs a deterioration determination signal from the AND circuit 15a for each phase in each line, as shown in detail in FIG.
An arithmetic circuit 18a or more circuits and an OR circuit 18b are provided, and two or more arithmetic circuits 18a detect that degradation determination signals are simultaneously input from the same phase of at least two of the lines, and OR the detected signals. The signal is output to the display 19 via the circuit 18b, that is, for each phase in common, to indicate a bus ground fault.

In the above-described embodiment, the line voltage of the bus 3 is obtained from the grounded-type instrument transformer GPT provided on the bus 3. However, another method, for example, the instrument transformer is connected to the bus 3. Then, the line voltage of the bus 3 may be obtained from the instrument transformer.

[0027]

As described above, according to the insulation deterioration detecting apparatus of the present invention, the secondary zero-phase current of the zero-phase current transformer of the distribution line and the reference phase voltage converted from the bus line voltage are used. The first
Since the phase comparison is made by the detection means, the insulation is degraded at a voltage lower than the tertiary zero-phase voltage of the ground-type instrument transformer generated in use as in the past, and ignoring the effect of the phase voltage change. can be performed in the detection, it is possible to accurately detect the insulation deterioration from the initial stage with high sensitive output Kendo. Furthermore, the first of the same phase of at least two distribution lines
The second detection indicates that the detection signals have been simultaneously obtained from the detection means.
The insulation deterioration is detected by the bus
Can be determined to have occurred.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a system using an insulation deterioration detecting device according to an embodiment of the present invention.

FIG. 2 is a detailed block diagram of the insulation deterioration detecting device shown in FIG.

FIG. 3 is a schematic configuration diagram of the load electric device shown in FIG. 1;

FIG. 4 is an equivalent circuit diagram of the load electric device shown in FIG.

FIG. 5 is a vector diagram of a reference phase voltage and a ground leakage current in a normal state.

FIG. 6 is a vector diagram of a reference phase voltage and a ground leakage current in an insulation deterioration state.

FIG. 7 is a vector diagram of each ground leakage current and each reference phase voltage of a plurality of distribution lines.

8 is an operation characteristic diagram of the deterioration determination circuit shown in FIG.

FIG. 9 is a vector diagram of each ground leakage current and each reference phase voltage at the time of a bus-side ground fault.

FIG. 10 is an operation characteristic diagram of the multiple line phase comparison circuit shown in FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Power transformer 3 Bus 6 Insulation deterioration detection device 8 Cable 9 Motor 11 Phase voltage conversion circuit 13 Phase comparison circuit 14 Effective value calculation circuit 15 Deterioration judgment circuit 16 Maximum value comparison circuit 17 All line deterioration phase common output circuit 18 Multiple line phase Simultaneous comparison circuit 19 Indicator GPT Transformer for grounded type instrument ZCT Zero-phase current transformer _I0 Zero-phase current _I0f1 , _I0f2 , _I0f3 Ground leakage current

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ Identification code FI H02H 7/26 H02H 7/26 CF (72) Inventor Hironobu Abe 3-7-1, Ichibancho, Aoba-ku, Sendai City, Miyagi Prefecture Tohoku Electric Power Co., Inc. (56) References JP-A-4-42726 (JP, A) JP-A-57-97326 (JP, A) JP-A-4-331417 (JP, A) JP-A-59-169326 (JP JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02H 3/00 H02H 7/26 H02H 3/34

Claims (1)

(57) [Claims] 1. An insulation deterioration detecting apparatus comprising: a plurality of distribution lines each having a load electric device connected to a bus connected to a power supply; and a zero-phase current transformer provided in each distribution line. A phase voltage conversion circuit that generates a reference phase voltage from the line voltage, and for each phase, a phase difference between the reference phase voltage and the secondary zero-phase current of the zero-phase current transformer falls within a predetermined range, First detecting means for detecting that the secondary zero-phase current of the zero-phase current transformer has exceeded a predetermined set value; and at least two of the first detecting means for each phase of each distribution line. Power distribution
The detection signals are simultaneously obtained from the first detection means of the same phase of the line.
Second detecting means for detecting the occurrence of the insulation failure, and judging means for judging the bus-side dielectric breakdown when a detection signal is obtained from the second detecting means. Insulation deterioration detection device.